Building A Set True ER 40 Collet Chuck

I started working on the back plate for the chuck. I took a pice of 5" diameter CRS, chucked it up, faced it, single pointed the 1 1/2-8 threads, and cut the register.

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I threaded it on the spindle to finish. The OD was trued up.
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I also trued up the rear face and polished the OD.
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Next will be to cut the recess for the chuck.
 
My version of the set true ER40 collet chuck is finished.
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After making the backplate, I cut a recess for the chuck to set in.

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This is the finished chuck on my lathe. The total length is a little under 3 inches.

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There are 4 set screws around the chuck to center it. There is .020" adjustment in any direction. You can also see the hole for a .375" diameter Tommy bar.

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The 1 1/2-8 threads are a good fit. The assembly threads on smoothly but it takes both ands to do it. The threads are close enough fit to offer sone resistance and the register is cut to 1.509" . The spindle register is 1.5008".

I put the shank of a .750" end mill in the chuck and set it as close as possible with a .001" indicator. I will get it closer using a .0005" indicator, but I am very happy with this project.

I will be reworking all my 1 1/2-8 attachments to this same fit so they are all closer no matter what they are on.

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Very nicely done, I really like the short length from the spindle bearing.
 
Mark
I have one question and that is, is that the second one you made? And if so, was the first one that far out you needed to make a better one. No doubt that being able to adjust there is no reason for runout. If I had seen that before I made my ER32, I would have made it like that, that is gorgeous. Again there is nothing that can not be made. One of my set backs is hitting the numbers, if it has to be precision I will work very hard to hit them but if it is just number out there it in my territory now I can make it undersized it I want to. Making the hacksaw I'm building it holds two sets of bearings, one in plate steel and the other in rectangular steel tubing. The boring head was just what I needed and pulled the four holes to within .00001. I was very happy with that. Made a little bit more progress on it tonight and I need to get some pics so I can reminisce and share with others. It is just that easy, just get in the shop and do it!
Enjoy all you do, thank you for sharing
 
Nelson,
Yes, that is the second one I made. The first one is fine. I can take it on and off a dozen times and it always repeats within .001". This second one is so I can get to within .0002". Don't feel alone trying to hold close tolerances. It is time consuming and tedious. When I build something precision, everything has to be as close to perfect as possible. You sneak up on the dimension. You take tiny cuts to not overshoot. You make one or two "ghost" passes to make sure there is no tool push off. I had to turn a shaft today .625" diameter 9 inches long. Tolerance is +/- .0002 over the length. ( It is part of the gear assembly I am making. I cut it .010" over, check the length for taper. Adjust the tailstock tiny amounts and taking a .001" cut until no taper (this took 3 passes and very small adjustments. Then I cut it .005" over, then .001 cuts until I am .002 over. Then two "ghost" passes, then "fuzz" cuts until I am .001" over, then two more "ghost passes, and finish by polishing to size. This takes hours and many passes at fine feed rate, but the reward is a perfect part.

Anyone who wants a .0002" tolerance and turns to hit i in a few passes is lucky, not skilled.
 
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