Author Topic: Fixing you tailstock blues  (Read 5642 times)


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Fixing you tailstock blues
« on: September 02, 2012, 10:26:22 AM »
Here is the one I did about the bain of not just Chinese lathes, but older ones as well. The curse of curses, a rotating tailstock chuck, but not when you need it. How many have drilled a hole and had the chuck start spinning in the tailstock morse taper, when you were just coming to a critical bit. PITA isn't it.

This is a catalogue on how I fixed mine.

This only works with tanged morse tapers, which really is the only type you should be using your tailstock (unless you can't get one). The ones with threads in the end are for machine mounting using a drawbar. But don't be dismayed, screw in tangs are now being made available.

Go down a couple of items and you should see them. I have used them, and they work perfectly.

So the first thing you do is get yourself two morse tapers that fit your tailstock, one with a tang, and one without.

Make sure the tailstock ram is screwed out a bit, just so that the auto eject doesn't come into the equation. then just put each morse taper in turn into the 'spout', and mark on the taper with marker pen, where the ram nose and taper meet. This will show how far into the ram the taper fits. It is now tailstock stripdown time. For the moment, you only need the ram bit, so you should just screw out on the ram and it should disengage from the screw, allowing you to pull the ram all the way out. Inside the tailstock ram bore, there is usually a control pin that stops the ram rotating, make sure you don't lose it, in fact if done correctly, that should just stay in position. If you have trouble getting the ram back in, it is usually caused by the pin being slightly out of alignment and just needs turning slightly to realign it with the groove in the bottom of the tailstock ram.
So, ram on bench, lay the first MT against the side, with your mark from before, lining up with the ram nose. Mark on the side of the ram where the end of the MT comes to. Repeat this exercise using the other MT. It would pay you to do this on the scale side of the ram, I didn't, and ended up with a nice hole right in the middle of the scale. Just below the scale should be perfect, and make sure when you drill, you are as far away from the control groove underneath as possible. The next two pics show what I did.

I haven't told you where to drill yet, so hold your horses. You should have two lines on the ram like in the above pic. Find the centre between the two marks, that is your drilling point, so now you can carry on.

I centered up the bar, and drilled right thru both ram walls, you should only really need to do one. I will be drilling BIG holes with my tailstock (I love drilling big holes in things, it gives me a feeling of power over inanimate materials), so I need to have a bit more stopping power than most lathe users. You can do two or one hole, the choice is totally yours.

So, we come to fitting the actual stops. I drilled and tapped mine 5mm, on a small lathe 4mm (or equivalent) should be ok.

For my stops I used long hex head grub screws, you could just use a bit of threaded rod with a sawn screwdriver slot.

Notice on mine, I gave it a bit of a decent countersink, just to make sure that burrs thrown up are totally removed.

Now for a bit more stripping. The tailstock that is, not clothes, you don't want to scare the cat.

You now need the tailstock leadscrew, and that will be up to you how you get it into your greasy little hands.

Once that is obtained, back out the screw(s) you have fitted, so the leadscrew can be screwed in well past your hole drilling exercise.

Now comes the critical bit, getting the screws to the right length.

What you do is gently screw it (or them) in, until it just touches on the leadscrew inside the ram. This will then give you a guide as to how much to grind or cut off the end of the screw. You should end up with the head of the screw just below the outer surface of the ram, but the screw should not quite touch the leadscrew.
You will now have your screws to the correct length.

What I did then, was to screw out the screws a little, dab on a minute drop of loctite, and screwed them back into position. If you have a screw shear off during use, just apply a little heat onto the ram, just to break down the loctite and then screw the broken screw INTO the centre of the ram. If you try to screw it out, you run the risk of damaging the threads.
Make sure any extra loctite is removed (otherwise you might end up with a bonded ram and tailstock), give it a bit of lube and reassemble.

You should end up with a chuck that doesn't rotate when you put a bit of pressure on.

It has taken me longer to do this post than to actually carry out the mod. An hour should see it easily out of the way.

BTW, lots of people have now done this mod, and from feedback, it has solved the problem completely.