MT3 Drawbar Shank Dimensions

[John Hasler]

I'm modifying an Avey MA-6 drill press[1] for milling. The quill has an MT3 taper, no drawbar. Obivously, for milling I need some way to retain a shank. The usual method of drilling the splined shaft is out: the shaft is three feet long. I've come up with several possible solutions, but they depend on knowing the exact dimensions of a drawbar-type MT3 shank. So: how far up into the quill will the top of such a shank be, and how deep is the threaded hole in it? Is this reasonably standardized? I don't have any such shanks and can't afford to buy tooling that I might never be able to use.

[1] This is not your typical Chinese drill press. It weighs about as much as your Bridgeport, is seven feet tall, and has a knee-mounted table that could seat a family of four. The column is cast iron and has about a square foot of cross-section.

 

[SEK_22Hornet]

I see both CDCO tools and LMS have MT# collets individually (I checked their websites) - they are a whopping $8 each at CDCO. I think Shars may also have some. At that price I think I'd just order one to use as a sample to play with. I know I've wasted a lot more than that on projects that didn't work out (not intentionally, of course).

 

[John Hasler]

I'd just order one to use as a sample to play with.

I'll do that eventually, I suppose. I've got quite a bit more to do on the project before I'll be ready to make chips. I'd like to know if the dimensions on those things is consistent from one manufacturer to another, though, as there seems to be no standard for drawbar Morse shanks (I know there's a standard for Morse tapers with tangs).

 

[pdentrem]

John
Do you need dimensions? I have a set similar to the CDCOs. Let me know what you're looking for.
Pierre

 

[SEK_22Hornet]

I looked through the information in the Machinery Handbook that I have and did not see any thing on Morse taper with drawbar - all their information is on the tanged version, so I'm guessing there isn't a real standard on the drawbar version. You might also contact LMS to get some dimensions from them for comparison to the ones that Pierre has. I've heard that they are usually very helpful at LMS.

 

[12bolts]

....The usual method of drilling the splined shaft is out: the shaft is three feet long. ....

John, how do you plan on using a drawbar without a thru hole?

Cheers Phil

 

[John Hasler]

Do you need dimensions?

Yes. I need to know how far up into the quill the shank is going to extend (I know that this will be at least slightly variable) so that I can figure out how far down below the bottom of the tang slot my threaded rod has to extend, and how deep the threaded hole in the end of the shank is.

 

[John Hasler]

John, how do you plan on using a drawbar without a thru hole?

There is a .375" X 1.125" slot for getting at the tang of the shank to drive it out. I plan on fabricating a T-shaped part with the vertical leg of the T threaded. I will fit that part into the slot with the threaded part hanging down. I will then screw the collet onto that threaded rod. The horizontal bars of the T will stick out the slot. I will use some sort of cam or nut (I'm considering several approaches) to drive the T up to pull the shank up tight and down to release it.

 

[SEK_22Hornet]

If you were to use a collet chuck for say ER40 collets, you could modify the shank of it, if needed, one time, lock it in one time, and still change cutters very easily using the collet chuck. Just a thought...

 

[John Hasler]

If you were to use a collet chuck for say ER40 collets, you could modify the shank of it, if needed, one time, lock it in one time, and still change cutters very easily using the collet chuck. Just a thought...

That's the easy way out, but then I wouldn't be able to use it as a drill press without buying a million collets. I'd also give up the abiltiy to use Morse taper tooling.