Putting life back into my tailstock

[Bogstandard]

This will hopefully be my last post using my old machinery. It is a long one, with a few ramblings to explain why it was done, and why this way.

My Atlas 10F lathe is now 70 years young, but in the time it has been with me, I have resurrected it from a wreck, to one that will match anything size for size on the market today, with regards to keeping size and precision. All due to loving care and attention, and a few mods that the original manufacturers didn't deem necessary. OK it has a few paint chips and is a bit oily, but paint doesn't do the cutting, it is the ironwork that matters, look after that, the paint can be changed anytime.

So, what am I doing in this post?

This lathe is going to a new owner, and before it goes I want to repair the droop snoot on the tailstock. If you try to put a centre into a part while the ram is towards full extension, the chuck droops at the drill point by about 20 thou. This is caused by 70 years of wear as shown in the sketch. I could have done a quikfix and it wouldn't have been noticed for another few months, but that isn't my way. So as shown on the sketch I will be inserting a bronze bearing in the nose, replacing the worn area, and hopefully it won't need doing for another 70 years, so I don't think I can give a lifetime guarantee.

So, away we go.
I have been mulling this over for a couple of months now, you only get one real go at this, bugger it up and you are into a bigtime rescue operation.
I needed a datum point to work to, and eventually selected the top of the ram bore, I reckoned this would be the least worn point. By use of this datum and the screw under the nose I could get a precision bar locked in there to check if everything I am to do later will be correct.

So a bit of hex brass was chosen to make this test bar out of.

It was machined to exactly 1.125", the optimum size of the ram.

I now needed a method of checking the height of the top surface of the test bar, then be able to use the same setting to check when the bar was eventually mounted into tailstock.
I came up with this idea. A friend had given me some very high precision ball raced sliding ways a while back. I mounted my small mag base with a DTI onto the top of one. The same idea was used with my height gauge. These would bridge the gap over the bed and allow me to very smooooothly move them side to side.

They were duly put onto the cleaned down bed, and the DTI was zeroed on the top part of the bar while it was still in the chuck. This was then taken away very carefully, as it had the datum setting for the bar top, and put somewhere safe, hopefully it will retain its setting.

The same system was used to mark the centre of the bar, for later use on the mill.
After this was done, the bar was parted off, end cleaned up and mounted into the tailstock and locked into position against the top face of the bore by tightening up the screw underneath the nose.

Tailstock was locked down, then the DTI was very carefully reintroduced. The difference in height was 0.0005". I think near enough for what I want to do.

To do a double check, I took a swipe across with the height gauge. No detectable difference. So I now knew my datum was the correct choice. I could continue with renewed confidence. The tailstock was rebuilt to allow it to do its last job with a droop snoot.
A lump of bronze was mounted up in the chuck and the end was machined down to 1.375" diameter, this would give me a bush with a wall thickness of 1/8".

I had to do this shot. This is a 1" blacksmiths drill from a set that I bought at Harrogate show, and got rid of the metal as though it wasn't there. I love drilling big holes.

What a useless picture you might think, but this is one of the major bits of the repair, and I will explain why.
I very accurately bored the hole to fit the ram, job done. It was why it was done in that position that was the main part.
If you notice, all the work on the bush was done OUTSIDE the chuck jaws. If it was bored whilst inside, because of the thin wall thickness, the pressure of the jaws would minutely distort the inner surfaces whilst the boring is carried out. When it is taken out of the jaws, the metal springs back to a circular shape and you end up with a slightly triangular hole. Do all boring work like this OUTSIDE the chuck jaws if you can.
The bush was parted off and cleaned up very carefully, then put to one side.

The t/stock was stripped down and clamped to an angle plate, with the t/stock sitting on a pair of parallels between the t/stock and angle plate.
The ram was locked into place and used as a datum face to get the t/stock into perfect vertical position. It was then checked at 90 deg. to the first and it was spot on.

The ram was replaced with the test bar, and was roughly centred by using a point in the chuck and rough aligning it with centre marks done with the height gauge. Thank goodness for preplanning the whole job.
The DTI was then mounted up, and the test bar was centred up. Table locked up until all cutting was finished. Time to take the plunge, no backing out now.

Really sweating on these cuts now, if anything moved or was banged I would be in deep s**t. The hole was bored to 3/4" deep and to a very nice sliding fit for the bronze bush. Don't want interference fit on the bush, because it is machined to such fine tolerances, it just might make it slightly undersize if it is forced into the hole, again causing anal sphincter twitch.

Boring done and perfect. A fine coat of engineering adhesive (Loctite), and the ram and bush slipped into position. The little clamp bolt was tightened slightly.
The whole lot was left overnight, untouched, to allow the adhesive to reach max strength.

A new day, and the ram anti rotation screw hole was drilled and tapped to penetrate the bush, this also acts as a secondary retention of the bush, to give backup to the Loctite. The t/stock was then reassembled using light lubrication inside and out.
Whilst it was off the machine, I took the opportunity to give the t/stock gib and setover screws a good checkout.

Time to try it out.
Ram out close to max, the ram is slightly tighter that it was before, but that will bed in nicely. No up/down movement detectable.

Using the smallest slocombe (centre) drill I have, I fed it into the test piece.

Job done and dusted.

Did it work?

You betcha, better than I could ever have hoped for.

All the worrying, preplanning and doing now over. With a perfect end result.

Life is good.

John the bodgit man.

 

[Divided He ad]

Doesn't it just give you that warm fuzzy feeling when it all just goes to plan?! ;D

Good result from a job well done I think John. Shame it's going now.... Good for the new owner though

I have been delaying some needed improvements to my existing machinery... I think I should get off my lazy rear and fix them!

Well inspired sir!


Ralph.

 

[CrewCab]

Good post John, I enjoyed reading that, well done ............... you just make it look so easy ??? ;D

I'm sure the new owner will be delighted.

Dave

 

[te_gui]

Just a thought, could you have chucked up the boring head in your lathe and hooked the tailstock to the carriage to feed it into the boring head, seems like that would have put everything spot on. Just another way of looking at the problem.

 

[Bogstandard]

te_gui,

When a lathe like this was made it would be line bored. The head and tailstock would be fixed to the bed and done as a matched pair. It shows how good and accurate old engineering practices were, these aren't a matched pair, the later model headstock was added by myself, but to be only 0.0005" out in height, between bits that were made years apart, is astounding.

I had already thought of your solution, but it would mean somehow getting the tailstock fixed to the leadscrew or saddle, plus making all sorts of fixtures to keep in in tight contact and register with the bed of the lathe (maybe get the wife to sit on the tailstock), and still allow slip movement along the bed (forget wife bit, too heavy, the lathe would stall). Five minutes after thinking about it, it was consigned to the 'not easy to do' bin.

John

 

[te_gui]

I wouldnt recommend it with most of the lathes used in the hobby but back in my job shop days it was pretty common on the larger engine lathes when drilling large holes to tie the tailstock to the carriage, snug up the clamps a little, and kick the long feed in. Saved lots of cranking. That same setup was what came to mind when reading your post. Lots of ways to skin the proverbial cat, out come looks great

 

[Bogstandard]

As you say, there are lots of different ways to do things, this was my way (sounding like Sinatra now).

Not only does it look good, it works good as well.

I am overjoyed at the result, and I am now happy that I am passing my machine on with a clean bill of health.

I hope that people reading this post pick up a few tips from it, not just for tailstock repair, but anywhere that a similar thing is required.

John

 

[BobWarfield]

Nice job!

I had the same reaction as te_gui RE line boring. I think I'd have put the tailstock between carriage and headstock and thence let the carriage push the tailstock along the ways while a boring head in the chuck did it's work. A very slow feed and a light cut would be needed, but it seems doable.

Be that as it may, you've done the job and done it well.

What lathe will replace the venerable Atlas?

Cheers,

BW

 

[Bogstandard]

http://www.chesteruk.net/store/crusader_lathe.htm

 

[BobWarfield]

Very nice replacement indeed!

Nothing quite like a fine lathe. I hope to upgrade my own sometime over the next year.

Best,

BW

 

[Bogstandard]

Bob,

That is in fact an old picture.

It also has a foot operated brake, plus 2 axis. I will be fitting a 3rd and 4th by taking the 2 axis readout off my new mill with new read heads, and upgrading the mill to 3 axis. For the same money that Chester wanted to charge me for upgrading the mill to 3 axis, I can do both, using the same models of readout and scales for the same money.

This is in fact the same as the next model up, which is industrial/school, but has had the module thread cutting removed and instead of an 8 speed gearbox, an 18 speed has been fitted.

If all goes well it should be the last one I buy.

John

 

[nh_eng]

I understand the entire strategy you used - very clever, but why not just mount a boring bar in the headstock and bore the ID of the tailstock for the bearing by sliding the tailstock along the ways. Would this not work? This appraoch assumes that the bottom of the tailstock riding on the ways is in good shape. I am pretty new to machining, and I have the same issue with my tailstock on my vintage Rockwell 11" engine lathe, so I am looking for a solution that I can execute with my limited skills.

thanks in advance for a reply.

 

[Foozer]

Just when I say I cant trust my tailstock alignment, but then. a good idea is a good idea.

Glad this showed up

Robert

 

[Blogwitch]

This is an old post you have resurrected, I had almost forgotten about it.

The very easiest way would have been for me to borrow an auto boring and facing head and mount it into the spindle taper, that would mean the tailstock could have been locked down rigid. But not having that facility to hand, I had to use the datum method.

The main reason I did it like I did was because I could, I was and still am very happy using datum points for machining, whereas, I don't think I could have controlled it tight enough if I had it sliding towards the headstock, the tailstock could have been swinging about almost anywhere.
As it ended up, I am sure it was less than a thou out, which when you consider most tailstocks, even new ones, that is well acceptable.

Bogs