A Microscope Repair.

[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.