Thread: Tailstocks

We all seem to have missed the point I made about drilling on the lathe.

If you drill a blank for a kit that finishes with a very thin layer of material on the tube then it can be a problem withe the drill bit wandering and the risk of some part of the hole being oversized.

Sometimes, if you're only going off a pen round and you get ecc'y, check the mandrel shaft for true.

Hi Fred & All,
I have made 100's of pens on my Tough, Fred, never had a problem, but as I understand it, I think you mainly turn yours on a Metal Lathe, BIG difference.
Maybe these new pen types out now, might make it different, as I haven't turned one for ages.
Regards,
issatree.
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Originally Posted by rsser

Sometimes, if you're only going off a pen round and you get ecc'y, check the mandrel shaft for true.

Fair enough Ern. I guess that should go without saying but is something easily overlooked. However that still doesn't address the concern of the tailstock slop.

I have a Nova TL 1200, same as Corbs. Tailstock is a bit of a pig as it doesn't have a cam-lock - nor does the toolrest banjo. I'll be looking at ways to modify that when I get home.

The bed of the lathe is two pipes To fix the tailstock problem I was thinking offixing a rod or a length of angle to the outside of one of the pipes and making a matching part for the tailstock to fit over this . In theory it should be fine.

We shall see.

Originally Posted by rsser

Sometimes, if you're only going off a pen round and you get ecc'y, check the mandrel shaft for true.

I used to turn lots of pens but not for a while now.

I would always check the mandrel with a dial mic after fitting it to the lathe.

If it was out I would remove and refit it.

If that didn't work a tap with a hammer as a last resort.

When it became difficult to make it run true, then it was time to chuck it out and start again with a new mandrel. The problem seemed to get worse as the mandrel got older.

Tailstock slop can be adjusted with the careful use of a centre punch and a hammer. The idea being to swell the cast iron with lots of gentle hits. Go careful near the corners as you can break a piece off. Plenty of checking is required as you go. This method is used to adjust for wear on a well used lathe.

I hope this may be of help to someone.

Cheers

Tim

The center punch trick is sometimes used to true up carpenters' framing squares; at the inside corner to increase to 90 degrees, outside to reduce to 90 degrees. It would take a lot of punches to make much difference on a tailstock, I think.

Jointers and cross-slide vises sometimes have adjustable gibs to reduce slop, but surfaces need to be very straight. Probably adds ~$50 (?) to production cost.

Cheers,
Joe

Excuse my lack of understanding BUT-- how can the tailstock being out by 1-- 2 mm result in a pen (or anything else) being out of round or tapered? It appears to me that with the cutting tool being a free floating tool, unlike a metal lathe cutting tool, The operator determines taper and roundness and not so much re:the roundness.
What am I missing?

Fair question.

If the two centres are not aligned then it is not just a matter o the taper being determined by a free floating tool at all.

The tool may be "free Floating" and controlled by the operator BUT how does the operator move the tool in and out on a small object spinning at any where from 2 000 - 3 000 rpms so that the tool is in synch with the "high spot".?

Not only that but you get a blank that is not only not round but a bit like a cylinder that has been sliced at a slight angle on either end.

The kit, in both cases, will not match up to the turned piece.

I agree - fair question. But I think the answer is more complicated.

Theoretically, if the work is turned between centers, its axis of rotation is determined by the two centerpoints of the spur drive and the tailstock. If the offset is horizontal only, the toolrest can be set parallel to that axis, and it "should" be possible to turn a round shape. If there's also a vertical offset, you'll have a sweet old time following it. In either case, the spur drive will beat up the headstock end, and too much compression from the tailstock can produce bowing.

Pen mandrels are usually clamped at the headstock, and any offset will produce a curved, not straight, axis of rotation. No way to cut that without wobble. A steady rest could get the tailstock out of the game, but that's beside the point. (Get it? Beside the point?). Sorry, couldn't resist the temptation.

Cheers,
Joe