Author Topic: Red lathe woes..or 'The joy of owning a piece of history'  (Read 7736 times)

Offline DavidA

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Red lathe woes..or 'The joy of owning a piece of history'
« on: March 30, 2015, 04:20:56 PM »
Although I've been busy doing other things recently, I managed to settle down to spending some time in the warm outhouse today. It is raining very cold water all over the garden so it seemed the best option.

Now,  as some of you will know,  I have an old lathe of unknown provenance. By the quality of the build it is obvious that it was an expensive bit of kit when it was new.

But it is quirky.  And yes,  it's red.

I'm going to note down some of the odd things as they become apparent. All those of you with (relatively) modern lathes may consider yourselves blessed.

First,  a picture. (not sure where it will appear).

Ok.
For some time I have known that the spindle nose M2 taper socket was damaged. Now was the time to do something about it.

I was watching Doubleboost's video on making a tailstock die holder and more or less followed that method.
Problem was,  as the nose socket is damaged I can't stick a centre in there to support one end of the centre I want to use to set my topslide over.
No problem, fit the three jaw and chuck up a bit of bar.  Create a 60 degree point. use that as the location for one end.
I have a centre that is wide enough at the 'big end' to fit in the hole of the tailstock without going right in,  so that was the other end sorted.

Lots of gentle tapping and the dial guage was finally reading zero over the length of the 'alignment' centre.

Great ! ready to bore out the spindle nose. Remove all the gubbings used to set up; including the chuck.

Ah....
Now you see the disadvantage of a gap bed.

With the saddle fully advanced towards the headstock and the topslide as far forward as possible on the slotted table I can't get the boring tool within three inches of the spindle nose. And that is before any cut is made.

Bugger !!  I'm going to have to make some kind of extension that bolts to the table and bolt the topslide to it.

But not today.

You can see the problem in the (earlier) picture.

For scale,  the slotted table is 5.5" from end to end.  Also note that the saddle is as far forward as it goes and the tailstock is hard up against it.

Dave :bang:



Offline bertie_bassett

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #1 on: April 05, 2015, 07:07:24 AM »
would it be worth fabricating a section of bed to fit the gap? iv seen it done for the tail end before

would take some carefull work to get it accurate but might be better in the long run?

a competent engineer uses the tools and knowledge available, to get a challenging job done.

 An incompetent "engineer" tells his boss that the existing equipment "can't do the job" and to get another machine

Offline vtsteam

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #2 on: April 05, 2015, 08:46:46 AM »
It can be done somewhat tediously (and carefully), with a small boring bar, and a new male taper for a test piece and some blue color -- per scraping. The compound slide angle is set by test and refinement  -- checking of the pattern of the rub. I'll probably be doing it on my lathe building thread at some point in the near future.

In general, you set the angle as close as you can get it. Then take a light cut. If testing with the blued plug shows it is hitting at the front of the cut, the angle is too fine, so tap the compound slightly to compensate. And vice versa if the rub shows it hitting at the back of the cut. You gradually "sight in" on the right angle by successive comparisons, and get to the point where it hits the tapered plug evenly whle you cut. When you have cut all the way from front to back and the taper plug contacting throughout, you're done. As in scraping, the blue is extremely sensitive.


I love it when a Plan B comes together!
Steve
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Offline DavidA

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #3 on: April 05, 2015, 02:28:52 PM »
Bertie,

It would be a major undertaking to do that on this lathe.
Although it is a huge inconvenience,  I'm not stuck for the use of the mt socket. Also I don't want to change the original machine.

VT,

What don't show so well in the picture (must get another one) because the chuck is fitted,  is the huge distance between the Morse taped end of the mandrel and the position of the table (and hence my tool post) even when the table is as close to the mt socket as possible.  I would need to have about eight inch of overhang on the boring tool if it was to get right inside the socket.

Many lathes have an 'H' shaped saddle. My Rufold lathe does. This,  along with the bedways going right up to the headstock (non-gap) allows one to get up close to the mandrel.

As for the procedure,  I have no problems with that. As I mentioned,  I did it before I realised I hadn't allowed for the chuck being there.

So I had my topslide all set over and ready to go.  But couldn't reach the headstock mandrel with the too.

I'll fit up something to do the job. It's not urgent.

Any way, I will be able to use the Denford when I get a PSU for it.

Dave.

Offline Fergus OMore

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #4 on: April 05, 2015, 02:47:17 PM »
I am far from sure what you mean by a damaged No2 MT in the headstock spindle.

I have corrected a 'buggered' tailstock on a Boxford with a finishing No2 MT reamer. Not mine- belonged to Newcastle City Council. Again, I recall another one.

So if the spindle is 'soft' and you can't reach in with a normal length reamer, you can use and extended jumper to bring the reamer forward. I'm assuming the gap is the problem!

However there is construction of a sinebar to cut No2MT. One of my mates did one fr his ML7 by using a the Classic 10" sine made from silver steel and a setover of 0.250" and this was the old No2MT ( until someone arsed it)

I've Colin's sketch if you want it.

Norman

Offline DavidA

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #5 on: April 05, 2015, 03:54:16 PM »
Norman,

I mean that the Morse taper socket in the head stock mandrel (spindle) has been damaged sometime in the past by, apparently, someone trying to bore it out. Maybe in an attempt to true it up. I can only guess what the original problem was.

I suspect a taper reamer would try to follow the damaged bore and would not end up in the right place. I need to bore it out first.

I'll probably make a temporary extension to the slotted table so I can mount the topslide closer to the headstock. A slab of 1/2" steel plate milled flat and bolted on should do it.

As I don't use the Morse taper in my normal work,  it is really just to bring it back to how it should be.  I do mostly three jaw stuff on this machine.

Thanks for the offer though. If I get stuck I'll get in touch.

Dave.

Offline Fergus OMore

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #6 on: April 05, 2015, 04:44:19 PM »
My understanding is that you should initially 'rough it out' again using a roughing reamer but the downside is that the taper may go in TOO far!
So is it possible to remove the spindle and 'Go up' to MT3 using the non functioning lathe?

Failing this, I'd buy a soft No2 MT blank. I think ArcEuros are left soft. Drive it in. Mig it in place and start again.

Frankly, it is fairly straight forward- or seems so.

Cheers

Norman


Offline DavidA

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #7 on: April 20, 2015, 02:32:20 PM »
This picture gives a better impression of the problem.

Dave.


Offline DavidA

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #8 on: April 20, 2015, 02:39:21 PM »
Anyone else using wooden pulleys ?

Dave

 

Offline vtsteam

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #9 on: April 20, 2015, 02:43:55 PM »
David, if it was mine (and I didn't have a Morse taper reamer) I'd make up a boring bar extension out of a heavier shaft -- maybe 5/8" dia, with a hole in the end, and a setscrew to take a thinner boring bar to cut the actual taper. The extension of the smaller bar should be just over the total depth needing boring. That can be set by the depth of the hole you drill in the larger shaft.

I'd also use the largest diameter "tip" boring bar that would fit the back of the taper to be cut. You'll have to go slowly, and several passes to take up the spring of the bar(s) each turn of the carriage handle,  but you should be able to do it, given time and patience.

EDIT:

Actually if the 5/8" bar fits part way into the bore, you can make the tip extension even shorter -- just long enough to cut that part blocked to the 5/8" (or whatever you chose) bar. You could also bevel the end of the longer bar to fit further in.
I love it when a Plan B comes together!
Steve
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Offline PekkaNF

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #10 on: April 20, 2015, 03:03:19 PM »
If I had taper reamer I would try it first. On one Myford 10 copy spindle taper seemed off big time, light - very light touch of MT-reamer cleaned it very well. One adapter I managed to bugger up royal, probably I got oo greedy. I have read of people getting MT reamer stuck on spindle, best to have hole trough spindle.

MT2 taper needs a long slender boring bar - small cuts.

Pekka

Offline vtsteam

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #11 on: April 20, 2015, 04:37:27 PM »
I bored the #1 Morse taper on my Gingery tailstock quill using the blue it, try, then adjust method, and it does indeed take even a slimmer boring bar. But it can be done. I do wonder in this case, if the hole has been machined badly by someone else, as apparently happened, would a morse taper reamer center properly, or just follow the messed up hole? A single point tool bores true.
I love it when a Plan B comes together!
Steve
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Offline DavidA

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #12 on: April 20, 2015, 07:02:42 PM »
I mentioned earlier that I was worried that a reamer would tend to follow the damaged hole instead of truing it up.

I think I will go for a beefy extension to hold a slim boring bar and carefully cut a new taper taking the very minimum I can out of the spindle.
If all else fails I could bore it out parallel, fit a sleeve.  Then cut a new taper in the sleeve.

Dave.

Offline vtsteam

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #13 on: April 20, 2015, 10:40:53 PM »
David if you do that, you can maximize the end size of the main bar if you offset the hole in the end (from center) enough to just allow a small degree of cutting overhang with the cutting bar.

That would be just enough to keep the thicker bar centered in the taper hole while the cutting bar is cutting.

Hope what I just wrote is comprehensible!!
I love it when a Plan B comes together!
Steve
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Offline PekkaNF

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #14 on: April 21, 2015, 09:18:07 AM »
I mentioned earlier that I was worried that a reamer would tend to follow the damaged hole instead of truing it up.

I think I will go for a beefy extension to hold a slim boring bar and carefully cut a new taper taking the very minimum I can out of the spindle.
If all else fails I could bore it out parallel, fit a sleeve.  Then cut a new taper in the sleeve.

Dave.

I realise that, but my point is that if most of the taper is fine and concentric and only the mouth of it excentric, then chances are good of truing it (I had this case). If error is big then you need to true it, I have tried similar and it was not easy to me. To the extent that I'm entertaining idea of small slender ID grinder for the final "lick". Very little, very gently.

Pekka

Offline DavidA

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #15 on: April 21, 2015, 04:11:38 PM »
Pekka,

I see more clearly what you mean now.

Sadly the taper appears to have been messed up by someone trying to machine it in the past.  I'll have another check with the blue before I commit myself to re machining the taper.
Believe me,  if I can get away with a very minimal skimming then that is the route I will take.

Dave.

Offline PekkaNF

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #16 on: April 22, 2015, 02:46:56 AM »
OK. Then you need plan "B" (VT speciality really :D).

I'm interested on this one too, because ofter few projects I'll get back to my pet project and I need to make ER or MT taper there in a spindle.

Luckily you compound looks substantial, it probably has some extra feed as you already tried it.

One daft idea came to my mind: Can you dismantle the top slide from apron and mount that on temporary mount on the gap? If your compound has enough feed you don't need any apron movement and no provision for that.

Gap bed is very useful for model engineer, specially if you have a faceplate. Those removable pieces are always a bit of compromise and I think that they are not that easy to make.

That 8" overhang is hard to work with, even if you make the tool butt end extra large, you still have that nose down tendency because cross slide support is really very far away and narow. You could try to compensate nose dive by mounting a plate with accurate top surface next to spindle like a chisel rest on wood lathe......this time it would be boring bar rest.

Some ideas, hope it is conversational piece.

Pekka

Offline vtsteam

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #17 on: April 22, 2015, 10:29:25 AM »
There will definitely be spring. But with a sharp tool, and in the case of a one-off operation like this, it's usually just a matter of patience while cutting. A few passes per turn of the compound rather than cranking it every pass.

Since you don't want to go too fast and ruin things, a slow cut isn't really a disadvantage. The whole operation isn't going to take a tremendous amount of time. The only thing to avoid is chatter. That's a matter of speed, cutter sharpness, cutter point width, and  point position (should be very slightly above center on an inside cut). Also, be certain your cutter has enougn relief under to avoid rubbing at the narrow end of the bore.

But you'll know how things are going at the start of the first pass. If you get chatter or rubbing, modify whatever is needed and proceed. You will have only taken off a tiny amount of material, anyway.

You could also try all this out on a test piece, if worried. That would set your compound angle ahead of time, and give you practice with everything else.

If you have a fixed steady, put a piece of scrap rod in it, drill out to the narrow diameter, and then practice boring the taper.Maybe you can even use that piece for something afterwards!
I love it when a Plan B comes together!
Steve
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Offline DavidA

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #18 on: May 22, 2015, 06:23:51 AM »
Another quirky aspect of this machine.

The base of the top slide is very nicely engraved with degree marks..  But the fiducial line to use with them is on the opposite side of the top slide and hence won't line up.
I can turn the base through 180 degrees to put it on the same side as the mark,  but then I can't see it .

 :doh:

And why a 6 TPI leadscrew ?
That gives an advance of 166.666 Thou per revolution. Try putting that into your dividing head and making a indicator dial.  I could cut marks at 1 thou on the perimeter , but would have to remember that the last gap in the marks would be odd.  Rather like the system used for the quill on the X1L mill.

Dave.

Offline Fergus OMore

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #19 on: May 23, 2015, 04:01:54 AM »
I'm involved with a more important bit of history which people are trying to mend-me,it happens!
This 6tpi screw is - or was quite normal in the olden days  and the surprise is really that it is graduated. People chalked their settings rather than relied on dials. What you have is is a lathe which 'roughed out' and finishing to precision limits was done on a cylindrical grinder.

My own old Clarkson tool and cutter grinder has only one graduation- for an angle. The rest of things is was on jigs or other devices. It was production machinery whilst my little Stent and Quorn  were made with to do- all things for all men.

Regardless of me 'prattling on'. there was no guarantee that it was a 'dead on' 6TPI on your lathe and going into the realms of 'recurring decimals' was a bit over the top. We can have a scientific calculator for a quid from Poundland and a 'Vernier' not quite from Ornans in the Doubs but Lidl or Aldi.  We had to rely on a slate and pencil or Trachtenburg- if you were a posh kid.

Frankly, I would 'do up' your old mangle my older generation did. For a 20 note you could have a rather nice tool and cutter grinder.

Meanwhile, here's nurse!

Norman

Offline DavidA

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #20 on: May 23, 2015, 06:52:27 AM »
Norman,

I'm relieved to hear the nurse has arrived.  Clearly your meds are beginning to lose efficacy.

You (may) recall I wrote, right at the top of this thread,

...I'm going to note down some of the odd things as they become apparent. All those of you with (relatively) modern lathes may consider yourselves blessed...

And that is all this is about.  The odd quirky things I come across with this machine.

As for t'old meister wi't  weskit an' flat cap,  well, I reckon he would have swapped his bit of chalk for a decent set of calibrated dials given half a chance.

If I really want accuracy I do have a Denford Viceroy 280 Synchro with twelve speeds and more threading options that you could shake a stick at.

Keep taking the tablets.

Dave.

Offline beeshed

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #21 on: June 16, 2015, 05:32:06 PM »
Nothing wrong with a 6tpi leadscrew. It's just less twiddly than 12tpi. 12 inches to the foot, so natural to use 12ths or sixths next. Problem is with those weirdos who want to use thous instead of 864ths or 1728ths.

Offline hopefuldave

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #22 on: June 16, 2015, 06:06:45 PM »
Also in the 6tpi leadscrew's favour, there's the old machinist's tale that you shouldn't cut threads coarser than your leadscrew - although my QCGB goes down to 2 tpi with a 6 tpi leadscrew if I engage the back-gear...

As long as you make the threading dial a whole (preferably even) number of inches per turn, and graduate it at inches/halves/quarters of leadscrew travel you can use it to pick up imperial threads like any other, so a 24-tooth with 8 numbered marks and intermediate ticks lets you pick up pretty much anything you're likely to want to cut on it :)

Now to work out how I can cut a 3 inch-per-turn thread for a mod on the lathe!
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Offline Pete.

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #23 on: June 17, 2015, 03:49:06 AM »
Now to work out how I can cut a 3 inch-per-turn thread for a mod on the lathe!

Add a 1:6 ratio into the 2tpi train and drive the leadscrew, not the spindle :)

Offline hopefuldave

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Re: Red lathe woes..or 'The joy of owning a piece of history'
« Reply #24 on: June 17, 2015, 09:21:34 PM »
I was thinking that, bicycle chain and sprockets would let me get the ratio! It's to cut a DIY ballscrew for an actuator, so I was thinking I'd put a router on the toolpost at the lead angle (45 degrees) and hit the screw-to-be with a carbide endmill...

Better not hijack the thread though ;)
Rules are for the obedience of fools, and the guidance of wise men.