Convert My 3/8" Drawbar To M12

[Ralf]

OK, here goes my first post on this forum. I'm very new to machining so please excuse my ignorance. I did a search but couldn't find what I was looking for.

I bought a Mill Drill, it's a Jui Chun RF-30BPF made in Taiwan. I haven't put it on its stand yet, that's on the agenda for Thursday. I didn't receive a collet holder with it but did get a drill chuck. It's a MT3 spindle but it has, what appears from rough measurements, to be a 3/8" drawbar. I'm in Australia, think of it as a third world machining backwater. I can only seem to get M12 collet holders here. I'd happily pay the premium to ship a 3/8 version from the U.S. but that restricts any other tools in future.

So I'm thinking of having an exchange M12 drawbar for everything except my drill chuck. Is this as simple as some M12 rod to put tension on the tool or am I over simplifying the purpose of the drawbar?

Any suggestion welcome?

Many thanks

Ralf

 

[Andre]

M12 allthread or "Readyrod" with a nut and washer welded to the end, and cut to the right length should work like a charm. If your drawbar has an auto eject feature, (no tapping out the taper) some more thinking and design might be needed.

I'd take a look at the old one and make a new one but with the different thread.

OR, can you tap out your collets to 7/8-20? On some collets the threaded portion is not hardened........Hmm

 

[Ralf]

Thanks for the reply, Andre. I pulled the drawbar out and it's just a simple rod. Haven't checked the top section yet to see if it will take a M12 rod but will do shortly.

I don't quite understand the tapping out the collet holder to 7/8", I probably could but that's a huge rod. The M12 is actually larger than 3/8" if that what you were thinking.

 

[Andre]

Thanks for the reply, Andre. I pulled the drawbar out and it's just a simple rod. Haven't checked the top section yet to see if it will take a M12 rod but will do shortly.

I don't quite understand the tapping out the collet holder to 7/8", I probably could but that's a huge rod. The M12 is actually larger than 3/8" if that what you were thinking.

Oh okay, I was thinking R-8 collets. Sorry about that

So then tap out the collets to the same thread as your drill chuck, so it's all uses the same drawbar.

 

[darkzero]

I believe Andre meant 7/16"-20 which is what R8 uses. Wouldn't work anyway as 7/16" is smaller than M12.

 

[Ralf]

Yes, my issue is all the common drawbar are smaller than M12, so retapping isn't an option. I guess it may be possible to take a holder without a drawbar tapping and modify it with a 3/8 tap.

I'm inclined to just use a M12 drawbar if it will fit. The drawbar doesn't seem particularly sophisticated, just a means of fitting a MT3 without the issue of vertical dimension changes in use as is the issue with a normal MT arrangement.

Thanks all for all the help.