No! Specially not on a Harrison. No idea what's wrong though.

How are you locking the tailstock after alignment? I’m not sure about the exact procedure but there are usually 2 screws 1 on each side of the tailstock which should tighten on to the tenon and prevent any movement. Sorry if you are doing this but it’s the only thing I can think of.
David.

I think there’s one either side and another on the back to lock it all up – typically, I’m nowhere near my L5a at the moment to check !

Mine had quite rough as cast ‘lump’ that the screws made contact with which I machined flat on the mill. I also cut them at an angle and at the same angle setting, milled brass inserts to go inbetween the screws.

The rationale behind this was that the original rough surface tended to twist and lift the upper part of the tailstock, machining it smooth stopped this from happening with the machined angle now effectively pulling the two parts together.

It made adjusting it a lot easier – beforehand, you’d get it spot on, give everything a final tighten and then find you were miles out !

Hope that makes sense !!

W.

I think the Harrison L6 has a V way so that should act to keep the base inline rather than two flat ways

More thoughts,

Is the error completely random, or biased to one side or the other?

It it always present when you are drilling/ Or if you align the two centres to look at each other, move the tailstock away and then back is there a change in position after the movement?

At this stage it is detection work for clues to see what is wrong and why before trying to fix anything.

Regards

Brian

Me thinks something basic is being overlooked here.

These old things are too heavy to constantly slip out of alignment without something being obvious. How do you know its moved, do you use an alignment bar every time? with it clamped down on the bed can you physically move it?

Is it possible that the bore of the barrel may be damadged ? Maybe the female taper has some scoring and is not letting the male taper seat properly ? The last flatbed lathe i used had a bit of wear and we used to push the tail stock hard against the back way and clamp it as that was where we set the tailstock alignment up on . Maybe the clamp is not sitting right and is walking the tailstock around as you clamp it down ?

If it is a vee bed then as stated earlier maybe there is something stopping the tailstock from seating properly on its vee way . It may be a bit out there but i would run the barrel out say 1/2 of its travel and clamp the lock on then lock the tailstock down then grab the barrel end and give it a good wiggle and see if anything moves .

Ian

Hello again Chris,

Now that you have found what was wrong, you still have to re-align the tailstock to get it looking in line down the bed again.

If i the sleeve is properly hardened you won't be able to machine it as Neil suggests and if it were mine I would never trust it again even if I was able to salvage it. Bin it and put it down to experience, it has cost you enough time already. already..

Regards Brian

Hello David,

You may well be right but Neil did talk about adaptor as did Chris when he changied his 3-2 MT sleeve, it wasn't clear in my mind. I have employed that trick on soft shanks as well, certainly on ones I have made that were less than satisfactory.

I would still chuck the faulty item away, soft or otherwise, it has been more trouble than it's worth

As an aside, Chris now has the answer to deep hole drilling he was looking for earlier

Brian

Edited By Brian Wood on 10/10/2014 17:38:04