I have a 5" 6 jaw chuck that is my go to chuck on the mini lathe. It cannot grip anything smaller than about a half inch diameter. So I end up switching it out for the original 3-jaw that came with the lathe. I bought a cast iron adapter plate from Little Machine Shop. It had a 1" x 10 tpi thread so I turned a piece of 1018 steel to .995" and single point threaded it on the lathe. Now the mini lathe chart only goes down to 12 tpi but LMS has a neat program that will compute the gear train to make any pitch from 1 to 256 tpi. It came up with 80 on A and 50 on D. Checked that with a scratch thread and it was right on. Then I simply faced the adapter on the lathe. Made up 3 screw points for the 6mm x 1 chuck thread and transfered the holes to the adapter plate.
I checked it several times and I can get it set to within .002" of runout. If I need better I will just have to change out to my 5C collet chuck.
Thanks Paul, The LMS (Littlemachineshop.com)has a lot of info on their web site. They even have plans for a wobbler engine, lathe info, mill projects, threading, tapers, drilling etc. There are 3 headings on their home page with a lot of info. They are:
Learning Center.... Support...... and Info Center
Paul Jones (11-02-2016)
Yes indeed a lot of info for the home shop guy. I initially found the threading calc under Learning Center in the How To section.
It would be worth anyone's time to check out all of the sub headings just to see what is available for free information on the LMS web site. And they have a lot of spare parts for mini mills, lathes, and tooling of all types.
Nope, I do not have any stock in the company but I have bought a lot of parts/tooling from them.
Allow me to mention that, just in case the LMS calculator should disappear, there's a change gear calculator available on my website. Look for CHANGE.
Home Shop Freeware
Thanks Marv, I do have your change gear program and almost all of the other calculators. I have DosBox on my win7 hard drive but have not had it loaded recently but it is handy and I can convert whenever I need it. One of these days I will load it on this machine.
I think anyone that needs to figure a cone, cord, miter, compound angles, threads, thread wires and the list is almost endless should take a look at your programs. The little dos programs add up to a "Machinist Calculator" so if anyone ever needs to calculate something they should give your programs a shot.
Thanks for all your work in making the programs and in making them all available at one web site.
Over the weekend I had to change-out my 6" 3-jaw chuck for my 8" 4-jaw chuck on my geared head lathe and thought it would be much easier sometimes to just use my old 5" 4-jaw from my mini lathe and add new arbor for holding in the 6" 3-jaw chuck. I looked at this posting to see how you did the arbor when I notice your 3-jaw chuck with the arbor has four adjustment screws (I think you already posted the adjustment screw modification on HMT). I like the convience of chucking a smaller 4-jaw chuck in the 3-jaw chuck.
Question: Since you have the four adjustment screws, I wondered why you couldn't adjust the 3-jaw chuck TIR to be better than 0.002" and mark the arbor with a witness mark for holding it the same way each time in the 6-jaw chuck?
Well I had such a nice fit on the register that I did not want to turn it under size at the time I made the adapter. However you are correct and It was quite easy to turn the register under size a bit and now it is better than .0005" or 5 tenths inch. I like it much better now.... Thanks for the motivation.
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