Advice sought on pin chucks

[graduate_owner]

Hi everyone,
I've been looking at pin chucks on the web and they seem so easy to make that I thought I'd have a go. So I found a straight piece of 16mm diameter steel and milled a flat about 1" long, about 1/2" from the end of the bar. I then cut a piece of round nail of suitable diameter (about 3.5mm) and mounted it in my 3 jaw chuck. When I checked it with a dti there was about 0.3mm run out. I tried re-mounting it a few times but couldn't get the run out much less. I then checked the lathe spindle and the run out was about .02mm so I suppose the inaccuracy is with the chuck. Just to make sure I chucked some more items, drill shanks etc and the run out was still the same. I tried re-assembling the jaws but still no improvement.

Anyhow I thought I'd try it to see how it performed, so I drilled a 16mm hole in a log of about 6" diameter and mounted it on the chuck, with tailstock support. It soon started slipping under load, so I tried a larger nail diameter. This held, but after turning the log to round I was getting noticeable vibration. I removed the tailstock support just to see how well the chuck was holding, and the log started to make its way off the chuck without any tool contact. I removed the log and could see the pin chuck was now a very loose fit in the hole.

SO, what I'd like to find out from you experienced guys is:-

1. when you use a pin chuck, do you get any vibration after turning to round?
2,. do you have any idea of the run out of your set-ups, or any idea of what is acceptable?
3. does your wood become slack on the pin chuck after being turned for a while?
4. how tight is your pin chuck into the hole - do you drill the hole slightly undersized to compensate for 'wear'
5. do you have any ideas on what else may be going on with my set-up?

Any ideas / advice etc would be much appreciated.

In the meantime it's back to the drawing board, or perhaps a bigger nail in the chuck first!!

K

 

[flh801978]

I had a pin chuck many years ago on a craft supplies 6 in one chuck and I tried it a few times and the blank never stayed on it may have worked on a perfectly balanced blank but on natural edge blanks the pin just wore a large hole and the blank wobbled off

Ian

 

[jpt]

I use pin chucks quite a lot and dont have these problems.

However there are some things to remember do not use on green or soft wood as they will work loose very quickly.

Only ever use on side grain, if used on end grain it will work loose.

I always drill the same size hole as the pin chuck so if the pin chuck is 25mm I drill a 25mm hole for it to fit in. It is a bit awkward to get on but a few thumps usually works.

john

 

[graduate_owner]

Aha,
so it's the grain direction then, because I had indeed mounted the log using end grain. It might not have been the slight (?) run out that caused the blank to loosen. I shall try it again with a log mounted appropriately and see what happens before I chuck (pun) it away.

K

 

[KimG]

I have the craft supplies PC Chuck that has a 1" pin chuck, I find it is pretty good most of the time, but a tail stock support is a must as it will work loose pretty quick without it, I am virtually always using it with green wood and find it is generally stable long enough to rough out a shape and turn a tenon, I drill a 26mm hole and use a section of a 4" wire nail as the lock.
More reliable however are the pin jaws on my Sorby chuck, I use these if they are already fitted or if the piece is spalted.

 

[graduate_owner]

I've just tried the home-made pin chuck again, but this time into side grain. I used the tailstock for support and gave it a go. The chuck held quite nicely, and after a while, (just to see) I wound the tail centre back a few mm so it was no longer in contact. I was surprised to see it still held well, with no apparent movement off centre, and no sliding off the chuck either. I was taking gentle cuts, but I was still very pleased with the way it held (and it didn't cost me a penny, so I can put the cash I've saved towards a new Axminster chuck - probably the Goliath).

I've also been looking at the O'Donnell jaws, and wondering what their advantage is. I think I'll start a new thread on this and see what the regulars say.

K