Some 8mm collets seem to fit tight?

[Jeff C]

I have some 8mm collets ranging from size 3 to 50 and notice that some of them seem to fit tightly when I put them in the headstock? It seems to be the smaller ones, the large ones are basically frictionless until I tighten the drawbar.

What I mean by tight would be that I have to rap on the drawbar handle with my hand to loosen them.

Is this a natural occurrence?

 

[Jerry Kenney]

Jeff, Check the slot in the collets, some have a narrow slot. All 8mm collets are not the same. Or it could be a little surface rust or burrs on them. Also check to make sure the spindle bore is clean.
It is also possible that the locating pin in the spindle bore is a little buggered. Some people remove or modify the pin to allow using wide and narrow slotted collets. The collet will tighten without the pin.

 

[Jeff C]

Thank you Jerry, I'll look at those items.

Never knew that pin could be removed either.

 

[Ansomnia]

Ron, not all 8 mm collets use the same THREAD PITCH as well as the same THREAD DIAMETER and THREAD PROFILE. Those are often the reasons for an incorrect fit.

Don't try to force the drawbar on to the collet if it feels tight. You can ruin the thread.

As usual, this information is in the books. I suggest you consult De Carle's book on Watchmaker's and Model Engineer's Lathes. The book can be bought for less than a good drawbar!

Thread diameter and profile are likely the most noticeable differences. The thread on Boley collets is the smallest diameter amongst 8 mm collets. Use an accurate Vernier caliper to check for differences in the collets you have. The thread profiles also differ. Some owners may also have also tried to retap their drawbars and/or collets, making the situation more confusing and possibly ruining their equipment.

Some of the replacement drawbars have also been threaded for a "somewhat universal" fit and will work with most collets but if you have original drawbars and collets, some of them will not work with each other even though they are all 8 mm - and I am not talking about the Mosely long 8 mm collets.

Other more knowledgeable people have discussed this on the MB and elsewhere on the Internet. Do a Google search. Here's a good one for STARTERS.

In my somewhat limited experience, while some of the other brands also seem well-made, Levin equipment seems to work the best. They seem to have been made the best and they also seem to accept more 3d party collets than any of the other brands of lathes. I guess you get what you pay for because Levin equipment can be very expensive. If I had the money I would just stick with good Levin equipment and be done with it.


Michael

 

[Jeff C]

Michael thank you and you are right books are invaluable. I ordered Ward Goodrich's just haven't received it yet. Your link was great! It made me experiment a bit. By the way my collets are Wolf-Jahn and my lathe is Peerless.

This is what I tried. I took the couple that were snug put them in another lathe I have turned them briefly (on the shaft of the collet) with a file then polished them with a Dremel. Well the fit just like the others Smooth entry into the headstock.

Thanks for the replies this helped me greatly.

 

[Ansomnia]

Ron, I'm glad you found the comments useful and fixed your own problem.

From what I've read, other people have done the same thing as you have in similar situations.

What also happens sometimes is that we will buy used equipment that have already been modified or slightly worn. So they will work in combinations that normally shouldn't.

The Wolf Jahns are somewhat bigger than average but they seem to be good collets to me. The most picky lathe is the Boley in my experience. They not only need the smallest thread diameter but they also have a shallower fit around the chuck seat of the spindle. Wolf Jahn collets will not thread properly and even when eventually threaded they will stick out. Peerless collets will thread properly without modification but will again not seat fully in the Boley spindle.

Improper seating may be of concern if you do fine turning.

Actually, I kind of like the Peerless even though most people think (justifiably) that it was a budget brand. I only have clocks to worry about so maybe watch repairers do have a point but I find the Peerless chucks to be very good value. The really bad part about Peerless lathes is their flip-over T-rests - their hinges are always sloppy and so they are pretty useless for most work.


Michael