A Microscope Repair.

[Pete W.]

Hi there, all,

Here is one of my first projects of 2015.

Several years ago, a friend gave me a Cooke, Troughton & Simms polarising/petrological microscope.  It was in need of a repair to the substage cluster, which should look like this:



At the very top, immediately beneath the stage, the condenser and its iris diaphragm sits a filter holder and beneath that the polariser (the component with the 0 to 360 degree graduations).  Next down is one of the two lugs that support the entire swing-out sub-stage cluster, followed by another filter holder.  The lowest swing-out component is a supplementary condenser lens beneath which is a second support lug.  The threaded portion of the spindle next to the major diameter of the tapered section screws into the hole in the upper mounting lug and the lower end of the plain section is secured in the lower mounting lug with a tiny grub-screw.  The polariser unit is retained by a nut that fits the other threaded section of the spindle.  The assembly is interspersed with several plain and one spring washers.  Oh, and I forgot to say that the upper filter holder, swinging on the plain section of the spindle, is retained by a collar and grub-screw.

However, some previous owner (not he who gave the microscope to me!) had modified (butchered!!!) it.  I presume that the polariser unit had suffered damage to its polarising material and so had been removed, complete with the upper filter holder.  In the process, the spindle on which all the swing-out components pivot was sawn in two.  When the microscope came to me, the empty polariser unit and upper filter holder came separately, complete with half the spindle!

I had put off doing this repair for far too long despite having acquired a complete polariser unit via that well-known on-line auction site but I've decided to make it one of my first workshop projects for 2015.  The first step was to strip out the part of the spindle that was still mounted on the microscope and to have a measuring session.  The two sections of the spindle, arranged to simulate a new spindle, look like this:



To give an idea of the size of this part, the threaded sections are ¼" by 40 tpi ME thread (i.e. Whitworth form) and the overall length of the entire spindle will be roughly 1½ inches.

The polariser unit swings on the tapered section of the spindle.  I could measure the length and maximum diameter of that tapered section easily but could only get an approximate measurement of the minor diameter.  I plan to set over the top-slide of my lathe and machine a dummy spindle with just the tapered section then check the taper in the polariser with engineers' blue.  Then adjust the set-over until I get a good enough fit and machine the tapered section of the replacement spindle at that setting.

The original part was probably drawn with dimensions referenced to some particular point on the spindle - I have no way to retrieve the original manufacturers' dimensions.  So I just have to measure each feature of the spindle sections, compare them with measurements of the mounting lugs and proceed as best I can.  If the first attempt doesn't work, I'll try again - I just need to avoid resetting the top-slide setting until I'm sure I don't need it again!!

I'm going to machine the new spindle from EN1A material. 

Watch this space!!        

[awemawson]

Hi Pete, glad to see you active in the workshop 

Being a lazy sod, I'd just face up those two parts, bore them, and either hold them together with a stud and loctite, or a pin and silver solder. If much material has been removed between them then a suitably shaped pin would make up for it I would think.

[vtsteam]

Looking forward to this...  

[Jonny]

Good one Pete, if a jobs worth doing, do it it right or not at all.

Have both studs to be cock on inline, most likely. If so machine in one from bigger dia bar to avoid flex, I do it all the time.

[BaronJ]

Hi Pete,

One way of getting a very close idea of the diameter of the small end of that taper would be to cut a hole in some thin card and press the small end into it.  I would use my drill press to get enough pressure without doing any damage to the part. Then measure the diameter of the depression in the card.

[Pete W.]

Hi there, all,

Thank you all for your replies and suggestions.

Andrew, the approach you suggested was the same as the advice from a couple of posters on the Yahoo Microscopy list.  While that might be a good approach in a commercial environment or if I were busting to get the microscope working for some urgent observation, I've decided not to go that way, not at first anyway.

Please don't be offended.          

The thing is that I want to know if I can master all the processes required to make a complete replacement spindle - I'll never know that unless I try it.  Another reason is that I've been carting my Myford around with me for forty-four years now and I can't justify that if I only use it as a drilling machine!          

Another reason is that Graham, the now deceased microscopist who gave me the microscope (and lots of other help, advice and assistance) wasn't a 'quick fix' kind of guy and I'd feel shivers down my spine while standing at the lathe if I took an easy way out!          

So I say again, please don't feel offended, guys, I'll go for the complete replacement spindle and hope you don't have reason to say 'we told you so' if I make a pig's ear instead!!
                   

[awemawson]

Pete I quite understand where you are coming from, and after all, you still have the possibility of doing it that way if the taper turns out wrong.

Of course if you take the "Conservationist Approach" you have to preserve as much of the original as possible and make a clear distinction between the old and the new. So in your case you must use a contrasting material that obviously isn't original. Not an approach I agree with, where in old buildings you see new oak scarfed into the old, but not dressed to match, and glass monstrosities attached to Grade 1 listed cottages 

[Pete W.]

Hi there, all,

Andrew, this microscope is venerable but I don't think it's listed!            

So my intention is to make a spindle that is a F³ replacement (you know, 'Form, Fit & Function) for the original one.  As to material, I already stated it's EN1A.  It seems to be free-turning.

I'm not using oak but I have been given four nice pieces of mahogany which I plan to use to make the accessory drawers that fit inside the microscope case to hold the spare objectives and eyepieces.

Today's task has been refinement of my taper test piece.  I did attempt to measure the included angle of the original 'stump' using a 'Bevel Box' and standing the 'stump' on a mini surface plate (actually a 3" x 3" sample of granite from a stone merchant's) but it didn't help me much, the degree scale on my top-slide is too coarse and has about a degree of zero error!

So, having made a first attempt two days ago and persevered this afternoon, I achieved this:



My tin of 'Micrometer' engineer's blue has been kidnapped by the shed gremlins so I used a Sharpie, I was quite pleased with that result having arrived at that fit by trial and error.          

So, just to test the result, I removed that piece of rod from the chuck and turned a taper on the end of another piece - it fitted too.         

My next task is to contrive a tool to turn the run-out groove at the ends of the two lengths of ¼" x 40 tpi ME thread, it needs to be quite narrow.  I do have a grooving tool holder that takes TC tips but I only have 2 mm tips, I need more like ½ mm.  I was wondering if I could grind up a piece of hack-saw blade but all my old hacksaw blades are bi-metal.  Then I saw a slitting saw blade being used for parting on Stuart's thread on here.

So, as I'm in no great hurry, I shall go into cogitate mode for a while.          

[Pete W.]

Hi there, all,

I've been pottering-on with this project.  It's all quite simple stuff compared with most of you other guys' posts but it means that I'm getting some workshop time,
so share my joy!!          

The new spindle will have each end turned down to 0.150" diameter and then a section of ¼" x 40 tpi ME thread each side of the tapered section.  So I have to machine one end, then remove it from the chuck or collet and turn it round.  The initially machined end will be a bit awkward to hold.  So, today's task has been to make a fixture to hold the spindle while I perform that second set of operations.

Starting with a short piece of ⅜" EN1A rod, I faced both ends and centre drilled one.  Then I through-drilled a pilot hole and opened it up with a #24 drill:



Then I opened about half the length of the hole with a #1 drill (tapping size for ¼" x 40 tpi ME thread according to G.H.Thomas):



I then tapped the enlarged section of the hole ¼" x 40 tpi ME thread, starting with the taper tap held in the tail-stock drill chuck and pulling the vee-belt by hand to turn the job.  When I'd got enough thread to locate the tap, I finished the operation with the second and then the plug taps in a hand tap-wrench:



I completed the fixture by turning it round in the collet and cleaning up the drill exit hole with a centre drill.

I've found that my ¼" x 40 tpi ME thread die has a pronounced lead so I don't think it will thread as close to a shoulder as the Cooke, Troughton & Simms original part!  I do have a 40 tpi Whitworth form chaser but it's too deep to fit in the Dickson quick-change tool-holder. 
So I've had to dig out the original ML7 tool-clamp with its elephant-foot screw - just one snag with that, the shed gremlins have kidnapped the spherical washer!!           so finding that is going to be Saturday morning's first job!

I held the work in the collet today, for better concentricity and to minimise overhang, but I found that it's sometimes difficult to get the tool near the work-piece - the three-jaw gets the work-piece within reach of the tooling.   

[philf]

Pete,

A bit late to suggest something different perhaps but couldn't you make the spindle with the two plain ends and a threaded centre portion. The taper section could be tapped and then be 'loctited' on to the threaded portion. The threads would then be complete right up to the taper.

Phil.

[Pete W.]

Hi there, Phil,

Thank you for your suggestion.  I did actually consider that approach but I concluded that turning the tapered section to length with clean ends would be tricky.  Difficult to hold the part.  Also, any slackness in the thread might put the polariser unit out of square.

It is a problem that I shall have to solve sometime, though.  I'm thinking my next project after this one ought to be a mandrel handle and that needs a tapered plug with a threaded through hole to act as an expander.  The thread probably won't be ¼" x 40 tpi ME though, more likely ¼" BSF. 

[vtsteam]

I've found that my ¼" x 40 tpi ME thread die has a pronounced lead so I don't think it will thread as close to a shoulder as the Cooke, Troughton & Simms original part!  I do have a 40 tpi Whitworth form chaser but it's too deep to fit in the Dickson quick-change tool-holder.

Pate, I usually just turn the die around backwards after threading the normal way, to thread to a shoulder.

Looks like you're making great (and fun) progress!

[philf]

Hi there, Phil,

Thank you for your suggestion.  I did actually consider that approach but I concluded that turning the tapered section to length with clean ends would be tricky.  Difficult to hold the part.  Also, any slackness in the thread might put the polariser unit out of square.

Pete,

Not if you machined the taper after it had been loctited on.

Phil.

[Pete W.]

Hi there, all,

Put in some more workshop time today.

I'd pondered on the best sequence of operations and realised that, in the later stages of machining, the work-piece was going to be held by a narrow spigot one end while the other spigot, the thread and the tapered section were machined.  To give the job some support, I fitted a piece of brass in the tailstock drill chuck and drilled it from the headstock, drill #24, a running clearance for the diameter of the two spigots.  Here's a photo, sorry the camera auto-focus decided it preferred the background!



I had originally planned to hold the raw material in a ⅜" collet to minimise overhang but, for reasons cited in my earlier post, that didn't allow the tools to reach the job!  So I used my 'Sunday Best' three-jaw instead.  Further thought revealed that I needed to win some clearance between the top-slide handle and the tail-stock body (remember, the tail-stock is set over in preparation for machining the tapered section; I didn't want to disturb that setting.)  So, I extended the tools further out of the QCTP holders than I usually have them.

I started by machining the long spigot, first with a right-hand knife:



Then cleaning the corner with a 'Mini-Thin' tipped grooving tool:



Next, I machined the bar to the diameter of the major diameter of the tapered section and, using the 'Mini-Thin' tipped grooving tool, marked the extent of the threaded portion:



I then reduced the diameter of that section to ¼" and threaded it ¼" x 40 tpi ME using a tail-stock die-holder.  I had to refine the undercut at the end of the thread by repeated applications of the grooving tool.  Before proceeding, I checked that the shape so-far achieved fitted nicely in the sub-stage bracket of the microscope.  Sorry, forgot to take photos of that operation.  I then trimmed the long spigot back to the correct length.

It seemed advisable to remove as much metal as possible with the job still supported on the end of the raw material bar.  So I put in two further grooves to denote the boundaries of the tapered section and the other threaded section.  I next withdrew enough of the bar from the chuck and supported the long spigot using my tail-stock steady while I plunged the sections of the bar whose diameters needed to be reduced.  I reduced what was to become the second threaded section to ¼".



Again, I had to apply the grooving tool to refine the depths of the grooves as this work progressed.  When the short spigot section of the job was finished to the required diameter, I removed the job from the chuck, sawed the work-piece off the raw bar and reversed it in the chuck, holding on the long spigot.  I was relieved to find that it revolved true.

Proceeding carefully, I threaded the appropriate section ¼" x 40 tpi ME using a tail-stock die-holder.  As before, I had to refine the undercut at the end of the thread by repeated applications of the grooving tool.  (The QC tool-post really shows its value when repeatedly swapping tools like this.)  I also used the grooving tool to clean up the shoulder where the short spigot meets the threaded section - if you examine the photo carefully, you'll see that I overdid this a bit!  I then carefully trimmed the short spigot to the correct length.

Because of the ravages of anno domini, I was a bit tired by this time and I should have quit while I was winning!  'Winning'?  Instead, I decided to go for broke and machine the tapered section.  There was just sufficient room at the start of the cut for the right-hand knife tool with the end of the short spigot engaged in the tail-stock steady.

Now, I do know, from folk-lore, from all the books I've read, from all the forums I've browsed and even from some practical experience, that you do have to be very careful turning tapers.  The sharper the taper, the more care is required and this taper is only about 8° included angle.

BUT, I was tired and when it was almost done, I decided to take 'just one more cut'!!!!          



So, this is what I achieved through my day's labours:



Well, that last cut took off about twice the meat that it should have done so the taper protrudes a few thou through the polariser unit rather than being flush.  I might be able to shim it, time will tell.  Also, some of the threads that seemed fine while work was in progress, now seem to have tightened up, maybe some fine swarf in the threads.  So, I plan to sleep on it and do some fitting and fettling and see how things turn out.

Maybe this one will be declared a trial run and I'll machine another - it should be simpler second time around!                   

[Jonny]

Anything accurate you shouldn't keep removing from chuck, it will never line up. Runout at tip may be as good as ok but where held something else and in doing so the taper can be eccentric to the threads plus runout.
That's why I said do it in one from bigger dia to avoid the flex, threads, taper and both ends of shaft all in line. Good bit is can mark all lengths out in situ but retain strength at chuck end doing that last. Doing two things similar now.

Try the mini thin for doing the  start and finish shaft dia on power feed.
Taper best left oversize maybe 2 thou, black up and sand to suit fitment trying often.

Shame you cant try the threaded microscope portion on what your threading. Drill and tap may come out sloppy or tight, see what the old part fits like.

[Pete W.]

Hi there, Jonny,

Thank you for your post.   

I've now had a look at the spindle through a pocket magnifier and tried the fit of some of the threads.  Despite my run-out groove being quite a generous width, the starting lead of the die still results in the very end thread preventing full engagement.  I think one way round that, as I wrote earlier, is to screw-cut the threads using my chaser.  (I have three ¼" x 40 tpi ME dies and they all have a significant lead on both sides so I don't think reversing the die in the holder is going to work.)          

Also, Jonny, I'll machine the next one as you suggested, without removing it from the chuck until the very end.  That means that I shall have to screw-cut the threaded section nearest the chuck so I might as well screw-cut them both.  I don't want to alter the set-over of the top-slide so I shall have to machine the part with the short spigot towards the tail-stock.  Also, in order to be able to try the polariser unit on the taper as I machine it, the taper has to 'point' towards the tail-stock.

I'll machine the short spigot first and then reduce the diameter of the two threaded sections (and what will later become the long spigot) to ¼" and screw-cut them before machining the taper.  Only then will I plunge cut to reduce the diameter for the long spigot (to 0.150") so as to maintain the support for the part for those outer operations.  I'll use my tail-stock steady for all those operations that permit it.  I'll need to be careful to note my cross-slide dial readings while screw-cutting because at that stage only one threaded section will be accessible for checking the fit.

So, what to do next?          

I think the next thing will be to turn another dummy taper or two to check that the set-over of the top-slide hasn't shifted.  Then I think I'll have a practice at screw-cutting with the chaser. 
I bought 4 feet of ⅜" mild steel rod so I think I have enough material!                  

For the record, Jonny, I only removed the job from the chuck once, to saw off the part-machined part and reverse it in the chuck.  I did, at one earlier stage, draw it further out of the chuck but I took care not to turn it wrt the chuck jaws.  Also, I did as stated try the threaded portion in the microscope sub-stage bracket and it did fit then - but it doesn't now!              

[vtsteam]

Pete, did you miss my earlier suggestion to cut the threads once the proper way with your die, then re-cut the same threads with the die reversed so you can cut full depth threads all the way to a shoulder? I did that many times in the construction of my lathe.

[Pete W.]

Hi there, Steve,

Thank you for your post - yes, I did see your suggestion.  I responded to it in my first main paragraph, the sentence in brackets. 

[vtsteam]

Oh, okay, I finally found it (after reading three times through the thread!) I guess I don't understand what you meant by lead in, because all my dies cut to the very edge of the die, and the start end is tapered, while the opposite end is full depth. so if you reverse them they cut full depth to an edge. But I'm guessing that what you have is a die where the cutting edges don't extend to the end of the die -- and maybe there is some kind of coutersunk hole there. Anyway, I trust you know what you have won't work, so apologies for the repetition!

[Pete W.]

Hi there, all,

Well, after a lot of distractions from workshop time, I managed to get to grips with a second attempt.

I'd previously had difficulty getting a good thread right up to the shoulder (see earlier posts).  Thinking this was because of the lead (aka taper) in the mouth of the die, I'd bought a 40 tpi chaser.  So, before starting on a spindle for real, I'd had a few practices with the chaser on some 1/4" free-cutting mild steel rod.



The camera didn't do that thread justice!  Some of my attempts weren't bad.

I started on the spindle by turning the stock material (3/8" free-cutting mild steel) down to the maximum diameter of the spindle, namely 0.350".  That very ordinary process looks like this:



The end of the material shows an earlier 'dummy run' at turning the taper.  That gets removed in subsequent operations.

Then I used the top-slide and the mini-thin grooving tool to define the lengths of each section of the spindle.  I dialled the required dimensions after correcting for the angular offset of the top-slide (1/Cos 4°), pretty small but I did it anyway.  I turned each groove to the appropriate depth.  The tresult looked like this:



(There's a very thin 'extra' section right at the outer end of the job - this is to allow for the centre drilled hole in the end of the stock, to be removed later.)

Then I turned each of the outer sections to the outside diameter of the thread, 1/4" (intending to further reduce the spigot diameter as a later operation), resulting in this:



Then, with the lathe gear-box set to 40 tpi, I presented the chaser to the 1/4" section.  I had the chaser mounted in a rear tool-post, NOT inverted, with the feed set to move the carriage away from the chuck.  Because there wasn't enough room to clear the chaser, I removed the tail-stock and centre.

This, and cutting the grooves at the chuck end of the job, caused my downfall!  The job rode up over the chaser and snapped, resulting in this:



                 

Oh, well, as my dear old mother used to say, 'If at first (and second) you don't succeed, try, try, try again!'.          

I should have left those grooves at the tail-stock end of the job until later.  It would also have helped if I'd had a piece of 0.218" hardened steel rod with a true 60° point ground on one end and its other end set in a 2MT shank - Set in the tail-stock, it would have supported the job against light cuts.     

[Pete W.]

Hi there, all, again,

After the catastrophe of the second attempt, I retired to lick my wounds (figuratively speaking) and to ponder a 'better way'.

This afternoon, I was ready for the third attempt!

I chucked and centred a fresh piece of material and reduced most of its length to a diameter of 0.350".  I then machined a groove sufficiently far in from the outer end of the bar for the threaded section plus the spigot.  I used the mini-thin grooving tool and cut to a root diameter a few thou less than the core diameter of a 1/4" x 40 tpi ME thread.  I then reduced a section of its outer end to 0.250" diameter, temporarily removed the tail-stock centre and used a tailstock die-holder to thread that outer section, resulting in this:



I used a different die from the one I used for my first attempt.  What I replied to Steve back then about 'all my dies' was plainly wrong - this one cut a good thread and I was able to run a nut right up to the shoulder, like this:



I restored the tail-stock centre support and turned the tapered section, like this:



When it was close to size, I tried the polariser unit on the taper and took VERY careful and light cuts.  I stopped when the top surface of the polariser unit lug was as nearly flush with the top of the taper as I could see by eye.

Then I used the mini-thin grooving tool again to define the 'back end' of the tapered section, like this:



The next operation was to turn down the section of the job between the base of the taper and the chuck to, again, 0.250", with this result:



I then further reduced a section of the job immediately in front of the chuck to a diameter of 0.150".  This was looking ahead to having to cut off the job and reverse it in the lathe to allow access for the 1/4" x 40 tpi die to thread the section behind the base of the taper.  I'll then support that short section of spigot on a drilled brass bar-end in the tail-stock chuck.  But that comes later!  Here's what it looks like:



The final operation in today's session was another application of the mini-thin grooving tool to define the length of the threaded section above the taper, like so:



Looking ahead, the next operation will be to turn off the surplus thread at the current tail-stock end and reduce the diameter to 0.150" to form the spigot at that end.  Then to cut off the job at the narrow neck at the chuck end, reverse the job in the lathe and use the tail-stock die-holder to thread the section next to the wide end of the taper, then mini-groove to define the desired length of that thread, then reduce the surplus thread at that end to the spigot diameter, i.e. 0.150".  All of that promises to present some centring challenges!!

Watch this space!!                   

[vtsteam]

That looks pretty!

Fingers crossed.......!

[Pete W.]

Third attempt continued:

At the end of my last post I outlined the next operations and today's workshop session more or less followed that sequence.  First of all I removed the surplus thread and finished the spigot to final diameter on the end nearest the tail-stock (i.e. next to the narrow end of the taper).  I left a bit of thread because the tail-stock centre limited how close to the end I could go.  Here's a photo:



Next, I removed the job from the lathe and removed excess material from each end, using a junior hacksaw.  I then trimmed the spigot to length and reversed the job in the lathe using the fixture shown in my first post in this thread.  I supported the short spigot in a piece of drilled brass bar, held in the tail-stock chuck, like this:



I then realised that I was getting ahead of myself,and swapped the tail-stock chuck for the tail-stock die-holder and cut the thread, like this:



You can see that, as with the other end, this die cut a clean thread right up to the shoulder.  I ran a couple of nuts onto the thread to verify.

Next, I used the mini-thin grooving tool to define the required length of the thread and removed the excess thread, finishing at the desired spigot diameter, 0.150".  For careful light cuts, the mini-thin grooving tool also works well as a right-hand knife tool.  I then defined the required length of the spigot.  Here's a photo:



I then removed the job from the lathe and cut off the excess length from the spigot, using the junior hacksaw.  The torque applied during the latest turning operations had tightened the job in the thread of the fixture and I had quite a tussle to remove it!  The only part I dared to hold in the bench vise (with fibre jaws) was the spigot but it wouldn't grip.  Eventually, I gripped the spigot in the tail-stock chuck and the fixture in another chuck and was able to separate job from fixture.  I returned the job to the lathe and used a Swiss file to break the sharp edges and then used the junior hacksaw to start a screwdriver slot in the end of the longer spigot, finishing the slot with a Swiss file.  That produced this:



I think (and hope!) that this concludes the lathework.  The next step is a trial assembly of the spindle, its mounting bracket and all the optical components that swing on the spindle.  I can already see that I've cut the lower threaded section and the lower spigot a bit shorter than ideal but hopefully they'll be good enough.   

[Pete W.]

                   

I decided that one isn't good enough!

I went out to the workshop this afternoon to clean down the lathe and, sort of 'on autopilot', found myself machining another!          

[awemawson]

Well shelf spares are always handy ! I'm terrible in that if I acquire a useful 'thing' particularly if it contains electronics, I grab any spares that crop up and box and store them. Almost guarantees that they'll never be needed.

Example #1 : I have a complete set of electronics, electrics and servos for my Diesinker EDM rescued from one being scrapped.

Example #2 : pretty much a re-run of the above for my Wire EDM

[vtsteam]

Pete, I know exactly what you mean. Finish up something, and that night, think about how it could have been done better, but still, it's usable........and then a day later, you're making another one. I made five valves and 3 different valve cases for the pipe engine, and 4 pistons. Probably the first pieces would have worked after a fashion.

[Pete W.]

Hi there, all,

I've done some more work and have some photos to post but I can't get in to Photobucket at the moment!                   

[Pete W.]

Well, I don't know how I did it but I did it and now seem to have access to my Photobucket pictures, so here goes:

As I wrote in a previous post, I made another spindle.  Here's the sum of my spindle efforts so far:



The top one is what I received with the microscope, on the next one down I took too much off the tapered section while the next one broke because I didn't support it properly.  (While looking for something else in my chaos department recently, I found a 'miniature centre' that might have avoided that failure.)
The next spindle suffered a dimensional error in length.
The bottom one is, I think, good enough to use, though I was disappointed with having to use a junior hacksaw to make the screwdriver slot in the end!  I deliberately made the lower spigot of that one longer than the original for a reason I'll expalin after the next photo.

This shows the spindle in position in the microscope's sub-stage bracket:



With the original spindle dimensions, the thread below the tapered section and the end of the lower spigot would need to be engaged simultaneously.  This is fiddly and awkward when fitting just the spindle but I felt it would be really difficult when feeding the auxiliary condenser lens, spring washer and filter holder etc on to the spindle during the complete assembly.  With my modified spigot length, that can be well engaged in its bracket hole before trying to start the threaded portion.

You can also see in the photo a washer under the larger end of the tapered section.  Although I made the length of the tapered section the same as that of the original spindle parts, the replacement polariser unit fouled the bracket.  I chucked a length of rod, faced it, drilled an axial hole that just cleared the thread OD and then parted off a 40 thou slice.  The mini-thin grooving tool did this really well - I feared when I bought it that I was being extravagant but it's really performed well for far more operations than I originally thought would use it!  40 thou was thicker than it needed but I was being cautious - I think the mini-thin groover would have easily coped with parting-off a thinner washer.  That first washer was a touch too big on the diameter so I skimmed the bar and took another slice!  Here they are:



It's a bit out of focus but you should be able to see a dimple in the end of the spindle spigot.  My lovely but shy assistant and I added that dimple to avoid the grub screw burring the spigot and making it difficult to dismantle in the future.  We removed the grub screw, fitted the spindle (and washer) fully tight and then LBSA held the bracket while I presented a 1.5 mm drill down the grub screw hole using a hand-brace.  I then enlarged the dimple once the spindle was removed from the bracket.  We seem to have avoided damage to the thread in the grub screw hole.  Refitting the 8 BA grub screw in the bracket was a challenge - despite my interest in microscopy, I regard 8 BA as small!!

The remaining operation on the spindle is to make a flat on the other spigot to take another 8 BA grub screw securing a collar that keeps the upper filter holder on the spigot (see the photo on the initial post). 

But first, I'll make the collar.   

Oh, I did find what was stopping my access to Photobucket - it was a FireFox add-on called Bluhell Firewall 2.5.0.  It's now disabled!!   

[Pete W.]

OK, now, about this collar.

It's just a 3/16" slice off the ⅜" mild steel bar (previously reduced to 0.350" OD, drilled axially 0.150" then cross-drilled and tapped 8 BA.  Doesn't sound difficult, does it?!?!  Still, I bet some of you are thinking 'I know which bit of this goes wrong for him!'.

Well, the first operation mostly went well, like this:



What you see in that photo is raw ⅜" mild steel bar, I omitted to previously reduce it to 0.350" OD!  Mistake #1!!  Not too serious, that one, I can skim the OD just before parting-off the slice.

In weighing up how I would approach this job, the principal difficulty I had anticipated was cross drilling the tapping size hole for the 8 BA grub screw.  If I parted-off the 3/16" slice first, it would be difficult to hold.  I wrote off any idea of cross drilling the hole using my drilling machine (it's only a drilling machine, not a vertical mill, so no tables with graduated lead-screws).  So, how was I going to ensure that the cross hole was accurately on a diameter?  The answer to both of those problems was to drill the cross hole using the lathe and before parting-off the collar from the stock - this would give plenty of material to hold while positioning and drilling.

First thoughts were to use the vertical slide and the little Myford machine vice.  But rigging that seemed to be a cumbersome process.

Then I realised that maybe I had the answer right there in my Dickson pattern quick-change tool-post!  I fitted the length of rod in a boring bar tool-holder, the type with a vee-groove, with a fair length extending out of the holder.  I could then adjust the height of the tool-holder to bring the centre of the rod to the lathe centre height.  The conventional way to set this up would be to use a clock gauge, again a rather fiddly procedure.

Instead of that, I used a Myford accessory comprising a 2 Morse taper shank with a Vee pad.  I fitted this in the lathe mandrel taper and turned the mandrel to level the vee.  Then, having checked that the rod was square to the lathe axis, I offered the rod into the vee groove, adjusting the tool-holder height as necessary.  When I thought that was OK, I turned the lathe mandrel through 180° and checked the alignment again.  It turns out that, on my drill-pad, the vee-groove is slightly off so I 'split the difference'.  I then repositioned the rod in the tool-holder with just enough overhang for the drilling operation.  I then replaced the vee-pad with a drill chuck.

I forgot to take photos of these operations - in the one I did take the camera auto-focus locked-on to the cross-slide rather than on the cross-drilling operation.                     

Next time I get in the workshop, I'll restage these operations and take more photos.

To summarise, the cross-drilling went well, as did the parting-off of the 3/16" slice.  However, catastrophe struck when I tried to tap the cross hole.  Maybe I drilled too small a hole, maybe I was just clumsy.  The bottom line is I have to do it again!  Watch this space. 

[Pete W.]

Another day, more swarf!!

I didn't actually say in my previous post what catastrophe had befallen - not difficult to guess, it was a broken 8 BA tap.  I couldn't remove the broken-off stump of the tap so I started again.  I tried to remember to take more photos this time.

Well, I parted off the end of the ⅜" rod, faced the remaining end and deepened the axial drilled hole, here's a photo:



Then I transferred the ⅜" rod to the boring bar tool-holder, with quite a large overhang, and put the 2 MT vee drill-pad in the lathe mandrel:



Then I offered the rod to the vee in the drill pad, adjusting the tool-holder height to get the rod snugly in the vee, this puts the axis of the rod level with the axis of the lathe, ensuring that the subsequent cross-drilling is through the rod diameter.  Actually, the vee in my drill pad is not quite truly central so I rotated the drill pad through 180° and 'split the difference'.



Next, I reduced the overhang of the rod in the tool-holder and replaced the 2 MT vee drill-pad with the tail-stock drill chuck.  Starting with a small centre drill, I touched the end of the rod against the side of the centre drill, zero'd the cross-slide dial, moved the saddle until the end of the rod cleared the centre drill and then wound the cross-slide forward by ½ the centre drill diameter plus 3/32".  I then centre drilled and cross-drilled the rod (right through) with a #55 drill followed by a #50 drill (GHT's recommended tapping size for 8 BA).



I re-chucked the centre drill and moved the rod back to touch it, loosened the tool-holder screws and carefully turned the rod through (by eye) 90°, maintaining contact between the rod end and the flank of the centre drill.  I then repeated the cross-drilling sequence.  I refitted the 3-jaw chuck to the lathe mandrel and chucked the ⅜" rod and fitted the mini-thin grooving tool to the tool-post.  Having touched off the side of the tool against the end of the rod, I wound the cross-slide out to clear, advanced the saddle past the rod end by the width of the tool plus the desired thickness of the collar and parted-off.

Here's the collar, after tapping the holes 8 BA (by hand):



And here it is, partially assembled on the spindle with the filter holder and bracket:



and



I'm not happy with it, the hand tapping is crooked, the collar is too thick and I forgot (again) to reduce the ⅜" rod OD to 0.350" before parting-off.  I'm hyping myself up to contrive some sort of tapping device - it won't be GHT's Universal Pillar Tool, magnificent though that is!!          

I shall treat this collar as temporary and proceed with assembly of the microscope sub-stage components (see opening post photo).  Because the collar is the last part to be fitted, I can substitute a better version later without having to completely dismantle the microscope. 

[Pete W.]

Hi there, all,

                 

I'm hoping I'm on the home straight with this project now.  I'm ready to try assembling all the sub-stage components onto the new spindle in the sub-stage bracket. 
So today has been a living room dining table session rather than a workshop session.          

Here's the bracket with all the components that have to go on the spindle between the two bracket lugs (see previous post for a picture of just the spindle in the bracket):



Assembling all that lot was tricky - I felt I could have done with two extra hands, round corners vision and no gravity!              

It was a good move to lengthen the lower spigot (I explained that in a previous post).  Still, eventually they were all together.     

Adding the polariser unit with its washer & fixing nut and the upper filter holder and the collar got me to here:



I then fitted the bracket to the microscope and inserted the condenser into its mounting which got me to here:



Compare that photo with the one in the opening post which was of someone else's microscope.

That's all I had time for today.  I do intend to make another collar, the one I showed in these photos is too thick.  I may also make a thinner washer to put under the tapered section of the spindle.

However, I'm planning to attend a microscope club meeting this coming Saturday and the microscope is now sufficiently together to take along and show to the other members. 

[awemawson]

Well done Pete it's coming along nicely

A Microscope Club intrigues me - is the interest in the microscopes or the objects being magnified ?

[Pete W.]

Hi there, Andrew,

I hope that you are well.
Thank you for your post - I was beginning to fear I was talking to myself!       

Well done Pete it's coming along nicely

A Microscope Club intrigues me - is the interest in the microscopes or the objects being magnified ?

There are lots of clubs and societies for microscopists, e.g. http://www.quekett.org/ .  Members' interests range across a wide spectrum (no pun intended!), some are interested in the microscope itself as an instrument, others (including my lovely but shy assistant) in pond life, there's a lot of interest in trying to resolve the finest details on diatoms, many microscopists make their own slides and others collect historic slides made by famous mounters.  Photomicrography is an active interest of many.  Most of us have too many microscopes though not many will admit to being merely 'a collector'!!!

One organisation of interest is the Postal Microscopical Society which has two grades of membership, 'on-circuit' and 'off-circuit'.  For the 'on-circuit' members, a box of slides is launched into their circuit by Post and the members view the slides and then post the box on to the next member of the circuit.  Each box is accompanied by a notebook in which members note their comments.  The Society has several circuits.  Both 'on-circuit' and 'off-circuit' members receive a quarterly magazine published by the Society.

The UK's membership of the EU is having an influence on microscopists.  Historically, microscope illumination was by lamps that employed bulbs with flat mat tungsten filaments.  Rather like slide projector bulbs.  They tend to have short lives.  These have now been outlawed by the EU and are hard to find, consequently their prices have been driven sky-high!  Some more recent microscopes with internal illumination use tungsten halogen bulbs but retro-fitting tungsten halogen into an older lamp can be difficult.  I read that the EU now have tungsten halogen bulbs on their embargo list!  Some microscopists are moving to high power white LEDs but these have a 'bumpy' spectrum and, particularly for polarising microscopes, are not entirely satisfactory; you can't get the full range of colour in the image if it's missing from the illuminator.  LEDs, being semiconductors, don't emit as much heat as a tungsten halogen bulb but they can't tolerate as high a temperature either - the heat-sink can complicate getting the light source to where the optics need it to be!!

[philf]

Hi Pete,

Nice repair.

A long time ago I acquired an Olympus binocular microscope but the entire condenser holder and slide was missing. It was a challenge to make a new dovetail slide including the focussing rack and centering mount for the condenser but very satisfying when it was done.

I have too many microscopes and need to rationalise my collection. I'm watching a Baker Interference on eBay at the moment. I have a complete one sat in its box in our dining room which I regularly get earache about. (I think when they were new in the 1950s they cost something like £400). The analyser needs the polarising element replacing which will be interesting. It is something like a pie with a hole in the middle and then a 90 degree portion taken out. I was thinking of buying a polarised camera filter and modifying it but that will probably mean making a diamond core drill to put the central hole in and a diamond saw to take out the 90 degree slice - hence why I've not got round to doing it!

I have seen the price that some microscope lamps go for. I have several spares for my Wild M20 and M40 which I will hang on to.

What do you use to take photos through the microscope - a digicam, webcam or dedicated adaptor (or even a film camera)? It's something I'd like to have a go at.

I too find pond creatures fascinating.

 

Phil.

[awemawson]

Pete I suspect many have been following your posts, myself included, but not making comments.


I'm interested in your illumination comments - I have just brought into service a 'centring scope' that projects it's image onto a 3" ground glass screen - illumination being a 6v 15 watt 210 lumen microscope bulb. Although there seems to be no problem sourcing spares (quoted life is 100 hours) where I am using it (*) it would be far more convenient were it battery powered and  brighter. To this end I have on order a small LED torch that I hope to modify. Torch is powered by a 3.6 volt 3000 mA /hr Lithium Ion rechargeable Seller claims 2200 lumens, but the LED manufacturer (CREE) seem to imply 220 is nearer the mark !

(* I'm using this device in the Traub lathe to measure tool height to be able to set them on centre, so it goes in a collet in the main spindle)

[dsquire]

Pete I suspect many have been following your posts, myself included, but not making comments.

Pete

I'm guilty the same as Andrew. I definitly am learning something. Maybe I'll even get interested in them yet. 

Cheers 

Don

[vtsteam]

I've also been following along Pete, and enjoying your work and writing! 

[Pete W.]

Hi there, Phil,

Thank you for your post.

Hi Pete,

Nice repair.

A long time ago I acquired an Olympus binocular microscope but the entire condenser holder and slide was missing. It was a challenge to make a new dovetail slide including the focussing rack and centering mount for the condenser but very satisfying when it was done.

I have too many microscopes and need to rationalise my collection. I'm watching a Baker Interference on eBay at the moment. I have a complete one sat in its box in our dining room which I regularly get earache about. (I think when they were new in the 1950s they cost something like £400). The analyser needs the polarising element replacing which will be interesting. It is something like a pie with a hole in the middle and then a 90 degree portion taken out. I was thinking of buying a polarised camera filter and modifying it but that will probably mean making a diamond core drill to put the central hole in and a diamond saw to take out the 90 degree slice - hence why I've not got round to doing it!

I have seen the price that some microscope lamps go for. I have several spares for my Wild M20 and M40 which I will hang on to.

What do you use to take photos through the microscope - a digicam, webcam or dedicated adaptor (or even a film camera)? It's something I'd like to have a go at.

I too find pond creatures fascinating.

 

Phil.

I seem to remember that we've discussed your Baker interference microscope before - was it on a thread of Rob Wilson's?  And I seem to remember that you have a copy of Hallimond's book 'The Polarising Microscope'?

Regarding the analyser for the Baker, you may know that The Quekett have a members' shop and polarising material is one of the items they sell.

I confess that I'm not very clear about the difference between linear polarisers and circular polarisers - a friend who's a photography enthusiast tried to explain the differences and application to me but I must have had something else on my mind at the time!!          

We have a couple of USB eyepiece cameras but we haven't used them very much - not enough space on the dining table for all the paraphernalia, lap-top, mouse etc. etc!!  I can't use those with the CTS polarising microscope because it needs an eyepiece with cross-hairs. 

[Pete W.]

Hi there, Andrew,

Thank you for your post.

Pete I suspect many have been following your posts, myself included, but not making comments.


I'm interested in your illumination comments - I have just brought into service a 'centring scope' that projects it's image onto a 3" ground glass screen - illumination being a 6v 15 watt 210 lumen microscope bulb. Although there seems to be no problem sourcing spares (quoted life is 100 hours) where I am using it (*) it would be far more convenient were it battery powered and  brighter. To this end I have on order a small LED torch that I hope to modify. Torch is powered by a 3.6 volt 3000 mA /hr Lithium Ion rechargeable Seller claims 2200 lumens, but the LED manufacturer (CREE) seem to imply 220 is nearer the mark !

(* I'm using this device in the Traub lathe to measure tool height to be able to set them on centre, so it goes in a collet in the main spindle)

Your centring scope sounds interesting - how about a couple of photos?

I'm also intrigued by what you say about the LED torch - you must have dismantled it to know that the LED is by Cree!!  Does it have a driver board in there?

I have a centring scope, it's made by Isoma and I rescued it from a skip!  It's semi-derelict and I'd like to repair it but there are a few other projects ahead of it in the 'to-do' list!  It has a 12 mm diameter parallel shank about 125 mm long but I anticipate it would be more use to me with a 2 MT shank.

[Pete W.]

Hi there, Don and Steve,

Thank you for your posts.

Steve, I've been following your tiny workshop and your furnace threads.  I don't envy you your weather.  We have a clear blue sky and bright sunshine here this morning.

I was impressed by a YouTube video by Keith Fenner, he's on Cape Cod, see

     

Oops!!           I don't need to explain where Keith Fenner is to readers of MadModders, do I?!?  I must have been thinking I was on a Microscopy forum!!   

[awemawson]

Pete, I've added the Centering 'scope to the Traub lathe thread as that's where it's used:

http://madmodder.net/index.php/topic,8261.600.html

[RobWilson]

Good fix Pete   

What will be your area of  microscopy ? 


Phil ,that microscope I got from you is a godsend at times 


Rob

[philf]

Phil ,that microscope I got from you is a godsend at times 

Hi Rob,

I'm glad you're making good use of it. I couldn't do without one now. 30 years ago I could take a watch apart (and put it back together) without glasses or even a loupe. Now I never take my glasses off and have to use the microscope to do any watch work.

Cheers.

Phil.

[philf]

Hi there, Phil,

Thank you for your post.

I seem to remember that we've discussed your Baker interference microscope before - was it on a thread of Rob Wilson's?  And I seem to remember that you have a copy of Hallimond's book 'The Polarising Microscope'?

Regarding the analyser for the Baker, you may know that The Quekett have a members' shop and polarising material is one of the items they sell.

I confess that I'm not very clear about the difference between linear polarisers and circular polarisers - a friend who's a photography enthusiast tried to explain the differences and application to me but I must have had something else on my mind at the time!!

We have a couple of USB eyepiece cameras but we haven't used them very much - not enough space on the dining table for all the paraphernalia, lap-top, mouse etc. etc!!  I can't use those with the CTS polarising microscope because it needs an eyepiece with cross-hairs.

Hi Pete,

I'd forgotten that I'd mentioned the interference microscope before. I'll take the analyser apart (after I've done the washing up!) and perhaps buy a piece of film from the Queckett Club shop. I'm guessing mine is laminated between pieces of glass. Would it be stuck with Canada Balsam? This might be much easier than modifying a camera filter.

I've heard less than complimentary comments about some of the USB eyepiece cameras. Before getting one I'd like a recommendation from someone who has had good results from one.

I have a camera tube which fits the Wild M20 but it came with a Polaroid camera which I got rid of. It's nice that it can take all the light from the image or 50% to the camera and 50% through the eyepieces.

I have several microscope books but not a copy of "The Polarising Microscope".

Cheers.

Phil.