Author Topic: Non adjustable tailstock - how to fix?  (Read 3903 times)

Offline dbendeke

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Non adjustable tailstock - how to fix?
« on: June 25, 2017, 10:09:42 PM »
I have an old lathe - a Lesto Scintilla - that in spite of its small size, really performs wonderfully. The tailstock is placed on two parallel round bars and the MT1 socket no longer ligns up with the chuck. If I place a drill bit, a drill chuck or other items in the tailstock - MT1 - the point of the tool "wanders" by quite a lot.
The Lathe was in bad condition when I got it and I have spend some time fixing it. It works really nice and it is almost fully functional. The worst problem, however, is not having the tailstock ligning up. It makes it very hard to do anything with it.

But how do I fix it?

I have ordered some Morse Taper 1 reamers, in the hope that I can use them to fix/adjust the bad MT1 "hole" in the tailstock. Maybe running it slow in the Lathe Chuck to "drill" the tailstock straight. I have checked the chuck and it runs very very straight. But. I am thinking there must other options. Even better options and I would love suggestions. As there are no available adjustments - vertical or otherwise it will have to be, fix the tailstock or make new parts. However, the tailstock "arbor" is fairly complicated so I am hoping to avoid it.

Lastly - english is NOT my primary language. Please excuse any mistakes or badly explained details.
/dbendeke

Offline b.lindsey

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Re: Non adjustable tailstock - how to fix?
« Reply #1 on: June 26, 2017, 01:28:38 AM »
You say that the tailstock rides on two parallel rods. I am assuming that there is a split base to allow the tailstock to be moved along thes rod as needed. Could it be that resulting channels in the tailstock that ride on the rods have worn in a way that now skews it off axis?

When you put a tool into the tailstock how does it fit? Does it appear to be loose or have and side to side or up and down movement once the tapers (male and female) are engaged?

Maybe some pictures might help as well if possible.

Bill

Online Jo

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Re: Non adjustable tailstock - how to fix?
« Reply #2 on: June 26, 2017, 07:21:20 AM »
 8) Nice Lathe, well worth sorting out.

Yes as Bill says you need to find the route of the problem.

1. Check the alignment of the shaft in the tailstock. Clamp it to the bed, lock the tailstock shaft, mount a lever dial gauge in the lathe chuck and turn the lathe chuck and see if the outside is true. As it is a Swiss lathe I am guessing it will be  ;)

2, Check the fit of the socket: Lightly blue up a suitable 1mt shank and use that to check the fit in the socket.

My guess is someone has damaged the inside of the tailstock shaft. If there is a ridge you may just get away with lightly grinding it down with a dremel. Otherwise, depending on how hard the shaft is, you might be able to set up and taper turn a new taper inside then finish with the reamer/grinder. Worse case is you will need to make a new shaft for the tailstock but it will be worth it  :cartwheel:

Jo
« Last Edit: June 26, 2017, 08:23:09 PM by Jo »
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Online Jasonb

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Re: Non adjustable tailstock - how to fix?
« Reply #3 on: June 26, 2017, 07:51:48 AM »
Could also be wear in the tailstock casting or on the tailstock barrel. If you put some tooling in the socket can you wobble the barrel in the casting or does the tool wobble in the socket.

Online sco

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Re: Non adjustable tailstock - how to fix?
« Reply #4 on: June 26, 2017, 08:15:54 AM »
I had this issue with the Cowells and it was as Jason suggested - wear in one or both of the tailstock casting or barrel.  Tightening the barrel clamp just pulled it out of line further so I gave up with it in the end.

Hope you have better luck,

Simon.
Ars longa, vita brevis.

Offline wagnmkr

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Re: Non adjustable tailstock - how to fix?
« Reply #5 on: June 26, 2017, 01:34:43 PM »
Is this the lathe?

I was cut out to be rich ... but ... I was sewn up all wrong!

Offline dbendeke

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Re: Non adjustable tailstock - how to fix?
« Reply #6 on: June 26, 2017, 09:05:02 PM »
Thank you so much for all the suggestions. I will try and take some pictures and measurements. I don't know why I didn't think of checking the inside/outside of the barrel?! I may have been a little closeminded about the solution :-)
The barrel seems to be a good fit but I haven't checked it with a dial - it just feels pretty solid. Will test tomorrow. What worries me is that the "point" of a drill (or other tools) will move both up, down and mostly right is I twist it in the barrel. I had a hard time figuring out where the error was but I am sure that measurements with a dial will be very helpfull in diagnosing the problem. I will get back with pictures and some numbers.
I am fairly sure that "someone" has abused the lathe and that damage is very possible to the barrel in the tailstock. As the tailstock slides on an steel rails and the tailstock is alu, it could be worn  out. I did toy with an idea to cut the tailstock in two pieces to be able to add/make some sort of adjustments to height and direction. But it would ruin the originality of the lathe and I really don't want to do that.
Making a new barrel is not a huge problem except for the threads - an internal ACME/trapezoidal type thread which I don't have the tooling for.
But as stated, it is a swiss lathe and seems very well made. A little untraditional but very easy to maintain and the two important rods can be made fairly easily - even in stainless a very little cost. The were a little rusty when I got it  so I worry about them damaging the alu carriage.
For now - the barrel/alignment issue is the most urgent problem to solve. Will look into it during the week and report back. I really appreciate all of your inputs! Very gratefull! Thanks :-)
/Dan

Online Jo

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Re: Non adjustable tailstock - how to fix?
« Reply #7 on: June 26, 2017, 09:30:20 PM »
I did not realise that the tailstock was Aluminium but good news you have the original so could have it recast in Iron  :ThumbsUp: I am struggling to understand why a Swiss company would make a tailstock in Ali unless it was a good Dural or one of our special Aluminiums for avionics which are often better than steel :thinking:

Don't cut anything before you have a solution :hellno: And remember that it should only be true with everything clamped solid.

Ignore the threads in the old tailstock, if you make a new one you can use whatever thread is suitable 1.0mm pitch... imperial :-X A new sleeve is easy to make. (keep the original)

If you replace the bars do it in a ground material like silver steel  ;).

Jo
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Offline dbendeke

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Re: Non adjustable tailstock - how to fix?
« Reply #8 on: June 26, 2017, 09:55:33 PM »
Could not wait and tried a few things. I seem to have a problem with adding pictures. Will have to try later.

1: Locking the tailstock etc. make the barrel rock solid. No movement up, down or sideways. A tool in the barrel is sort of solid but will move a little if provoked.

2: Measuring the outside of the barrel shows that it is off by very little, perhaps 0.005mm (sorry, I am a metric guy. The lathe is not, but I am)

3: Measuring  just inside the barrel shows that it is off by at least 0.1mm, so I suspect the problem is inside the barrel

4: Adding "blue" to an MT1 taper and mounting it in the barrel shows it is only minimal supported. The support is in the front (the thick part) - maybe 3-4mm long - at the very front and a very tiny 1mm spot at the end of the taper (not all the way around). Maybe 95% of the taper remains blue so that would be a problem?

Should I make a new barrel or fix the old? Perhaps trying to use a reamer on the old barrel wouldn't hurt anything and if it fails - make a new barrel? And thank you for the point on the threads. A 1mm thread is used on the cross slide, so why not? As for the alu - Most of the structure is steel but a few parts, like the tailstock, is alu. I would not know why they made it this way. To save on weight perhaps? To avoid wear - just replace the alu parts and you would be back in business? Who knows :-)

Offline dbendeke

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Re: Non adjustable tailstock - how to fix?
« Reply #9 on: June 26, 2017, 10:15:14 PM »
That is indeed the lathe. Two parallel rods which holds the moving parts. Works amazingly well except for a few "could have been better" issues :-)

Offline dbendeke

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Re: Non adjustable tailstock - how to fix?
« Reply #10 on: June 26, 2017, 10:16:35 PM »
My lathe :-)

Offline dbendeke

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Re: Non adjustable tailstock - how to fix?
« Reply #11 on: June 26, 2017, 10:23:20 PM »
The lathe was given to me and except for labor, some paint and two SKF bearings I have very little invested in it. I would love to have it working properly. The motor is not the original but very powerfull and is definitely worth the effort. I think.

I will try and see if a reamer can fix the barrel and if not, I will have to make a new barrel and sleeve. I think I even have some silversteel for available. The barrel is straight but the taper seems to be ruined. Thank you all for the comments and suggestions to measure the barrel. I am not a machinist - just a keen amateur - and what might seem obvious to some is not to others. Meaning me :-)

Offline Vixen

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Re: Non adjustable tailstock - how to fix?
« Reply #12 on: June 26, 2017, 10:51:32 PM »
Dan,

If the existing tail stock taper is damaged or out of alignment, there is a risk that a reamer will simply follow the bad taper and not correct the fault or make it 'true'.
You may need to bore out the existing sleeve (or a new sleeve) to get it 'true' and in line with the lathe axis; then use the reamer to finish the tapered bore.

Mike
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Sometimes, it can be a long and winding road

Offline wagnmkr

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Re: Non adjustable tailstock - how to fix?
« Reply #13 on: June 26, 2017, 11:15:41 PM »
I had the exact same problem with my Sherline tailstock. I got a new one under warranty and it too was not quite right ... so

I put a short length of 1/2" drill rod in the head-stock and tightened it down and clocked it for true. Then, I took the drill chuck and tightened it on the drill rod. That left the taper on the drill chuck mandrel facing the tail stock. I used some 600 grit lapping compound on the mt0 taper and SLOWLY brought the tail-stock up to the mandrel and used the mandrel as a reamer. Several gentle goes at it, with a full cleaning of both the inside of the quill and the mandrel. After about an hour of doing this, I now have a very smooth and tight fitting drill chuck, and any other accessory I want to use in the tail stock.

Tom
I was cut out to be rich ... but ... I was sewn up all wrong!

Offline dbendeke

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Re: Non adjustable tailstock - how to fix?
« Reply #14 on: June 27, 2017, 01:48:03 AM »
It has become very clear that the barrel in the tailstock is damaged. I can't see any obvious damage but using the blue marking stuff and the dial  has made it clear that the taper is damaged.  When is was in doubt about the reamers it was because I was unsure of whether it would correct the problem or just make it worse. Thank you for clarifying the problem.

I really like the idea of lapping it and might give that a go.  I will make sure to clean everything before putting it to use again.

Unfortunately, getting spareparts is not an option as the company went under decades ago and the inventory was sold to a scrapdealer. Go figure. But that means parts are really hard to come by. If I need a part, like a barrel or sleeve for the tailstock, I will have to make it myself.

Thanks again  :NotWorthy:

 

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