Great Idea For Small Lathe Work

c-fbmi

c-fbmi

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I was looking at a tiny lathe for doing pins and small bolts etc and the guy at Modern Tool gave me a fantastic tip. My lathe is a 14 X 40 and the chuck won't tighten up on small items under about 1/2" (my 4 jaw which I tend to use all the time).

So the guy at MT said instead of spending a grand buying a small POS mini lathe, just buy a tiny 3 jaw chuck and chuck it up in my real lathe with my 4 jaw, and then have the tiny chuck for doing small work but on my bigger precision lathe. I thought this to be a great piece of advice.

Then today I'm looking through the KMS tools flyer and low and behold they have a 5" flat back 3 jaw chuck on sale for $90.......and my buddy in Calgary is going to rush right down and pick me up one. This is indeed my lucky day........I'm looking forward to playing with it and making some more trimmer pilots that I'm short at the moment.
 
You can also add the appropriate backplate to the little chuck. Chucking a chuck in a chuck can result in stacked tolerances.
 
tiriaq said:
You can also add the appropriate backplate to the little chuck. Chucking a chuck in a chuck can result in stacked tolerances.
Click to expand...

We do this all the time. Chuck the tiny part in the 3 jaw, then dial it in using the 4 jaw. No tolerance stack up at all. We rarely rely on a 3 jaw being true enough for any but the roughest work, or something you can turn in one setup.
 
Riverboy said:
We do this all the time. Chuck the tiny part in the 3 jaw, then dial it in using the 4 jaw. No tolerance stack up at all. We rarely rely on a 3 jaw being true enough for any but the roughest work, or something you can turn in one setup.
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Yep, this is exactly what my thinking was, as I rarely take off my 4 jaw............
 
You can use a three jaw or even a Jacobs to handle very small parts. When using a three jaw this way you can easily set the part up so it is truly co-axial with the machine.
 
I'm looking at a collet set for my 13x36 lathe. Not a big deal to take the chuck off. I have used a Jacobs drill chuck for small stuff that doesn't require precision diam.
 
on a 14x40 lathe the chuck is what 8 inch? putting a 5 inch in a 8 inch not sure I would spin it very fast, a 8 inch chuck should go down to 1/8 dia. do you have a milling machine? you could use the collet chuck from it in a 8 inch lathe, turn yourself a 2 inch bar to suit a 5C collet they come in all sizes upto 1 1/16 dia, make a threaded nut to tighten the collet from the back, this method turn a shoulder on the 2 inch and you can remove the holder and then it goes back in the same place every time
 
c-fbmi said:
I was looking at a tiny lathe for doing pins and small bolts etc and the guy at Modern Tool gave me a fantastic tip. My lathe is a 14 X 40 and the chuck won't tighten up on small items under about 1/2" (my 4 jaw which I tend to use all the time).

So the guy at MT said instead of spending a grand buying a small POS mini lathe, just buy a tiny 3 jaw chuck and chuck it up in my real lathe with my 4 jaw, and then have the tiny chuck for doing small work but on my bigger precision lathe. I thought this to be a great piece of advice.

Then today I'm looking through the KMS tools flyer and low and behold they have a 5" flat back 3 jaw chuck on sale for $90.......and my buddy in Calgary is going to rush right down and pick me up one. This is indeed my lucky day........I'm looking forward to playing with it and making some more trimmer pilots that I'm short at the moment.
Click to expand...

What spindle nose do you have?

I mean, I can dial in a four jaw pretty damn quick, but swapping off a D series camlock chuck takes even less time. Less than say, sticking a three jaw chuck into a four jaw, anyway.

I have seen more than one chuck stuck in another over the years, but it was mostly on machines that needed a crane to lift the chucks. And the normal work pieces.

And as long as you have a little spare material on your stock, and are doing a job that does not need to be swapped in and out of the chuck repeatedly, it really doesn't matter how bad the runout may be. A quick skim off the OD and the part is running dead nuts true.

A 5 inch chuck is pretty substantial. And at that price, I would want to see it in person before deciding it worth spending money on.

Personally, I would expect you to be happier with something along the lines of a 3 or 4 inch, decent quality chuck, mounted on a stub arbor or a 5C collet mount, that you could hold in the 4 jaw. Or better yet, a collet set and drawbar.

Cheers
Trev
 
c-fbmi said:
So the guy at MT said instead of spending a grand buying a small POS mini lathe, just buy a tiny 3 jaw chuck and chuck it up in my real lathe with my 4 jaw, and then have the tiny chuck for doing small work but on my bigger precision lathe. I thought this to be a great piece of advice.

Then today I'm looking through the KMS tools flyer and low and behold they have a 5" flat back 3 jaw chuck on sale for $90.......
Click to expand...
Thanks for that tip. I will certainly pick up a cheap 3 jaw for this same purpose.
 
trevj..........a 5" chuck is only a touch larger than my palm, my 4 jaw is about 12-14" across and my gripping jaw flats (of course they are curved) are about 1/2" across. Chucking up something 5" in dia is easy and totally within the working size on this machine with the 4 jaw. As far as precision goes, like you said first skim solves that issue and I'm sure it's still better than a drill chuck.
I'm sure, as has been mentioned, there are faster and multiple ways of going about this, but my time isn't critical and this is real simple so I can grasp how it all works. I'll just make an extended chuck key for the little guy and I'll be set for little work.
 
I've got a 4" four jaw with a stub arbor I use for doing the same thing but in reverse. I use it in my 6 inch three jaw when I want to center some small part to a higher degree of accuracy.

The issue you'll find is the speeds. Smaller parts need a higher speed to get a nicer finish. But your idea will certainly hold the chuck. And with it being in the four jaw centering the part dead on will be a breeze. The Ultimate Adjust-Tru Chuck? :D

Another option to the 5" three jaw would be an ER32 chuck with a straight shank. ER32 collets go up to about 3/4" and down to less than 1/16". Ebay has a wide variety of ER collet chucks with a crazy array of different taper, collet and parallel shanks for dirt cheap out of Asia and mailed right to your door. And I'm pretty sure you'd find the same options from Bangood. One I found in a blink has a 32mm shank diameter by 100mm long. That would sit in your chuck like a charm.

Another option would be a set of 5C collets and collet blocks. The square one would obviously fit your chuck like a dream. And if you're working with sizes in between the 5C sizes where an ER would work better you can buy an ER32 collet chuck that has a 5C shank. That would be interesting because the chuck could be moved from the block to any other 5C holders for doing follow up work on the mill.
 
I'd use a chuck arbor. Of the simple reason that lining up the jaws and the keys to miss the jaws of your 4 jaw is a real PITA.... Don't ask me how I know... I did over 1000 pieces that way, and each and every one of them was a PITA... Use the arbor, and save yourself a lot of grief.
 
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