Making a collet chuck out of a collet block

[mickri]

To get full use of my er32 collets I would like to have an er32 collet chuck to fit my 12x36 craftsman lathe so I could pass a workpiece through the headstock. I have making a collet chuck on my to do list. I could buy one at a cost of around $100.
While looking on Ebay I came across listings for er32 collet blocks. Most were sized at 40mm (1.56") across the flats. This is too small to bore out and thread to fit my lathe, 1.5" x 8 tpi on the headstock. Then I came across one listed on Ebay as being 45mm (1.755") across the flats. Price just over $30 including shipping Also saw one offered by Shars listed as being 1.75" across the flats. Price around $35 plus shipping.
!.75" across the flats would leave 1/8" wall thickness after boring and threading for 1 1/2 x 8 tpi. Is this enough wall thickness? It would be way easier for me to bore out and thread a collet block than making a collet chuck from scratch. I don't have anything in my scrap bin that would be the right size so I would have to buy the raw material and I would also need to buy an er32 collet nut. This would cost me the same if not more than buying a collet block.
I live out in the country and the nearest town is a 25 mile round trip. No source of raw materials there. I would have to either drive to Visalia, 70 mile round trip, or Fresno, 100 mile round trip, to try to find something. Easier for me to buy online. This gets expensive with the shipping. If I can convert a collet block to a collet chuck I would be ahead of the game.

What do you guys think about this?

 

[Bob Korves]

Another option is to use the collet block(s) mounted in a chuck, three jaw or four jaw depending on the collet block configuration and/or the chucks you have. If you use the four jaw, then you have a "Set Tru." No added costs, nothing to make...

 

[mickri]

I thought about doing exactly as you suggest Bob. The downside would be that I would have to dial in the collet block every time I wanted to use it. I know that my 3 jaw has some run out. I don't remember how much. I would also expect the outside of the collet block to have run out too. The purpose of having a collet chuck is to eliminate the run out and avoid having to dial indicate the work piece.
Another thought is do I even need a collet block if I am going to put the collet block in a 3 or 4 jaw chuck. Why not skip the collet block and just use the chuck.
The ideal situation is to make all of the chuck. Not convert something. This would pretty much guarantee that the chuck would not have any run out. Even if I bought an already made chuck it would probably still have some run out just due to the difference in the threads.
This is not something that I have to do right now. Just something that I am thinking about. My main priority right now is making the tool holders for my norman style qctp.

Thanks for the suggestion.

 

[Bob Korves]

Some work needs to be accurate, other work, not so much. A collet chuck mounted to the spindle will have runout, how much determined by inaccuracies built in to the machine and tooling, and luck of the draw in purchasing them. That inaccuracy can not be dialed out. Improvements can be gained by clock indexing multiple tooling, but that takes lots of time, much more time than dialing in a 4 jaw or set true. Three jaw chucks, much the same. With a set true chuck or a 4 jaw chuck, you can dial the work in to whatever your tolerances are for a given job. Using collets is not so much for accuracy as it is for quickly repeatable workholding to a "reasonable" level of accuracy for the job. Collet systems can be tweaked to be more inherently accurate, and spending plenty of money often helps, but there is no magic in collets, there are multiple inaccuracies in most collet setups. I like the idea that I can dial the collet block in easily as much as is desired for the work at hand, and still get quick change parts in and out of the collet. I also have a 5C collet closer system that is easy to install and be ready to do parts when "good" accuracy is good enough.

Speed and ease of dialing in work can be much improved by practice and understanding a few details. I wish that some of the fast 4 jaw YouTube guys like Adam Booth and Keith Fenner would not just show off while they are dialing in quickly, but also give a running spiel of the process going on in their minds, likely subconsciously after so many years of practice.

 

[mickri]

I always like your comments Bob. They are good advice for a newbie like me. I am getting better at dialing in my 4 jaw chuck.
My lathe came with an extensive set of 3c collets and the drawbar to hold them into the headstock. Haven't tried to use them yet. I also have an er32 collet chuck with a MT2 shank threaded for a drawbar. I have not used it in the headstock yet. Just in the tailstock to hold drills.

I have been reading up on how to true up the jaws on my 3 & 4 jaw chucks. Don't know if I am ready to attempt that quite yet. I have a small 3" 3 jaw chuck that I might practice on. It has a very limited range of movement because the #3 jaw is missing the first tooth (wrong terminology??) that engages with the scroll. I have not used it yet.

 

[Dave Paine]

If you want an easy solution which may only have the runout of the chuck, consider a straight shank ER32 collet chuck. You will loose through hole capability.

Martool straight shank ER32 collet chuck

Another option is an ER32 collet chuck with MT taper. These are available at Eurotrade. I have seen posts on the forum about the shipping rates from the UK being reasonable.

ER32 MT collet chucks at Eurotrade

If you need through hole then an ER32 hex collet block will work, again will have the runout of the chuck. This states 1.75in between flats. No idea if you can bore and thread the end for the spindle.

RE32 hex collet block at Little Machine shop

 

[jdedmon91]

There’s another option you can make a back plate that threads on your chuck and buy one of the bolt on adaptor for ER 32 collets. That is what I use on my lathe of course I just purchased a backplate


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[Winegrower]

If one is concerned about the budget, make another chuck key and build a mount for your dial indicator on your QCTP. Adjust stock in the four jaw chuck as needed, stick in the indicator, spin the work around 180 degrees, using one of the jaws as a horizontal reference. Note the high and low readings, then with both chuck keys at once, loosening one and tightening the other, turn them to move the dial indicator so it reads at the midpoint. Then rotate the chuck 90 degrees to the other pair of jaws, and again with two keys just move the dial indicator to whatever the midpoint reading was. Repeat if necessary to fine tune, but you'll hit it the first time with practice.
With this, no collets, no three jaw, no trying to eliminate chuck runout, etc. I really never use anything other than the 4 jaw chuck.