MT5 shank to R8 socket sleeve

[veggiedog]

I am considering purchasing an MT5 to MT3 taper sleeve, cutting off the tang, and then boring the MT3 hole to accept R8 collets. My 13x40 lathe has a spindle with an MT5 bore, and I would like to be able to use R8 collets to hold things like the straight shanks of my expanding arbor set. I plan on building a draw bar and a plate to fit into the back end of the spindle hole to that I can draw the R8 collets into the spindle bore adapter. My hope is that by machining all of this on the lathe, I will end up with a very precise holding system for standard size round shafts that fit my R8 collet set.

As a newbie to machining, am I considering a silly solution to a non-existent problem? Is there an easier option? I can dial in round objects in my 3-jaw chuck, but I typically need to use shims, and the 4-jaw is a bit cumbersome to switch out and dial in, and the R8 collet solution seems somewhat trivial to implement. I have not been able to locate an MT5 to R8 sleeve but it doesn't appear that it will be too hard to machine.

Advice will be appreciated.

Post note: I just now disassembled and lubricated my 3-jaw chuck at which time I noticed that I had #2 and #3 jaws switched. Not sure how, as I am aware that it matters. Oh well, now they are within 2 thousands which was better than before and may now approach the accuracy of a collet? Anyhow, could it still be that a collet holder for the mill is still reasonable? Would it be easier to just make an R8 collet holder to fit in my 3-jaw chuck so that I can avoid having to remove the 3-jaw to use the collet holder? I could index the collet holder to the chuck to preserve accuracy...

[veggiedog]

No cnczone advice yet, but further researching indicates that a 5C collet holder is probably more usefull in my lathe. I have located collet blocks that I can chuck up in my 3-jaw or 4-jaw chuck, but I was hoping for something that would mount directly in the 5MT spindle of my 13x40 Enco Geared Head Gap Bed Bench Lathe.

I found this home built unit that is very close to what I envisioned:
http://www.kinzers.com/don/MachineTools/collet_closer/
and I would be willing to attempt something like that.

I also found this adapter on the Grizzly web site:
http://www.grizzly.com/products/G4026
and that looks like a viable solution, although a little more complex than I envisioned, and Grizzly may not have a unit to fit my Enco lathe although I am willing to give them a call if I don't find a simpler solution.

My concerns: my solution may be overkill, there may already be off-the-shelf solutions, or I am addressing a non-issue and I should just get used to truing things up in my 4-jaw chuck.

Feedback will be appreciated.

[RICHARD ZASTROW]

Maybe Hardinge or Royal Products has something to fit your lathes spindle. I've found a few useful things there.

Dick Z

[veggiedog]

Originally Posted by RICHARD ZASTROW Maybe Hardinge or Royal Products has something to fit your lathes spindle. I've found a few useful things there. Dick Z

Thank you for the pointers: I visited both sites and was unable to find a simple solution. Harding no longer offers manual chuck closers, and Royal Products offers lever solutions similar to the Grizzly model that work in conjunction with a cam-lock collet chuck. Rather than pursuing a collet chuck, I am favoring the solution detailed at the first web site pointed to in my earlier posting (a simple spindle adapter):
http://www.kinzers.com/don/MachineTools/collet_closer/

I plan on boring out the inside of a hardened and ground MT5 to MT3 sleeve to fit a 5C collet, and threading a piece of 1.5"x1.124" piece of DOM tubing to act as a collet closer, with a handwheel on the left side of the spindle, similar to the unit in the link except without the spindle nose protector/collet extractor.

However, I am concerned that the MT5 taper may slip while holding a work piece in a 5C collet. Is this a warranted fear? Will the MT5 taper securely hold without slipping when pulling the collet and MT5 to 5C collet adapter back against the taper using the 5C collet closer? I am worried because I would like to keep the lathe's MT5 spindle taper in pristine condition.

I purchased a 5C collet set today ($135 on sale from Enco) that comes with a front acting collet fixture (along with other collet blocks), and I may look into using that approach instead of the through the spindle approach by machining a nose cone that pushes the collet into the spindle rather than pulling from the back, but I still like the simplicity of the pulling from the back approach.

I also plan on milling a QC tool holder that uses the rear-acting collet closer that also comes with the Enco kit so that I can employ 5C collets to hold boring bars in my lathe's QC tool post. I suspect I will make the QC tool holder first so that I can bore out the MT5 to MT3 sleeve using my Mecabore style boring bars with carbide inserts in the home built collet holder: the collet holder will be made of cold rolled steel like the QC ball turning adapter I made in a previous effort (http://www.flickr.com/photos/2994172...7612721013556/), and I can make the QC holder on my IHCNC mill. I have been using my Mecabore style boring bars using standard QC tool holders, but I suspect that the rigidity of a collet will provide a more stable and simpler hold on the boring bars.