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View Full Version : Can I retap a 1/2" 24tpi UNF female thread -> M12?



HankMcSpank
17-07-2009, 12:09 PM
I need to mount a 13mm drill chuck onto a stepper motor shaft (don't ask!)

It seems most 13mm drill chucks come with a 1/2" female thread. Therefore I need a stepper motor shaft (M8) to 'drill chuck' thread widget/adapter ....obviously no such beast exists.

Now then, I could lay out for a 1/2" 24tpi UNF die ...but this is a one off that I'll never use again...so that not very cost effective. Therefore I was wondering ...would it be do-able to just re-tap the drill chuck's existing female 1/2" 24tpi UNF thread...to be an M12? (because I already have metric taps/dies)

Or will this be problematic?! (one issue jumps out, is that 12mm is slightly smaller than 1/2")

(btw the end result - if I get there - will be under light load)

HiltonSteve
17-07-2009, 12:16 PM
Why not buy (or borrow) a 1/2" UNF bolt, cut the head off then drill it out to suit your stepper then put in a couple of grub screws in to hold it place.

JD!

HiltonSteve
17-07-2009, 12:21 PM
Thinking about it, leave the head on then you can screw the chuck up to it and also put the grub screws through the flats on the head.

HankMcSpank
17-07-2009, 12:31 PM
Why not buy (or borrow) a 1/2" UNF bolt, cut the head off then drill it out to suit your stepper then put in a couple of grub screws in to hold it place.

JD!


Super idea.... I guess some folks know how to go about this the right way & some folks don't (I'll be in the latter camp - so thank heavens for forums like this!)

(BTW: For once, I already have some suitable 1/2" 24tpi bolts!)

John S
17-07-2009, 02:15 PM
Are you sure it's 1/2" x 24 ?

Most chucks I have seen are 1/2" x 20 UNF
BTW Steve if you 'borrow' a bolt what happens when the guy wants it back and you have gronched it up ? :question::question:

.

HiltonSteve
17-07-2009, 02:51 PM
I was basing the "borrow" coment on what people say to me when they want to "borrow" something, nine times out of ten I never see it again....!

HankMcSpank
17-07-2009, 04:27 PM
Are you sure it's 1/2" x 24 ?

Most chucks I have seen are 1/2" x 20 UNF
BTW Steve if you 'borrow' a bolt what happens when the guy wants it back and you have gronched it up ? :question::question:

.

It's great to nestle in the bosom of those that know.

I went and checked what I'd bought, transpires I bought a 10mm chuck (not a 13mm chuck)

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=370084970268&viewitem=&salenotsupported

"3/8" x 24 thread."


Fortunately, the bolts I have were specifically bought for it at the time (a failed idea that I had, that I can now re-use these bolts for)