Keyless chuck loosening in reverse

[MamTor]

I'm currently drilling and tapping holes in metal and trying to use the pillar drill to start off the threading.

So I simply drill the hole, then swap the drill bit for the tap without moving anything else, and then start tapping by hand-turning the chuck via the top pulley.

This method works really well and I can get about a 1/3 of the way through the hole (2cm thick aluminum) before it gets too hard to turn, and I then loosen the chuck, raise the spindle, and swing the table round and attach the tap wrench to continue.

But half the threaded holes I'm doing are LH thread, and obviously I have a special 'anti-clockwise' tap for that. But when I use the pillar drill to start off the threading, the chuck loosens meaning I only manage about 2 complete turns of the tap before the chuck can't grip it any more. The shaft of the tap is about 11mm diameter so plenty of material to grab onto. As far as I can tell, the tap has a parallel upper shaft (I don't have a micrometer to check though).

So my question is simply, do some keyless chucks only grip when spinning in the normal direction, e.g. clockwise? I'm sure the diameters of the clockwise/anticlockwise taps are identical, so the only difference I can think of is the direction of the chuck.

 

[MusicMan]

Yes I think so, they use "one-way" bearings that spin one way and clamp the other way. And I doubt if you can get the opposite-handed hand chucks!

 

[Rorschach]

Yes they are designed to tighten when drilling standard RH holes. Some will hold ok as long as you aren't gripping the body of the chuck but most will loosen in the circumstances you describe.

If you have a keyed chuck, swap to that, that's what I would do on my pillar drill but then I have lots of different MT2 shanked tooling. If you only have a keyless chuck, take a bit of steel rod, grind a point on it (cordless drill against the grinder so it's centred) and put this in the chuck. Use that to put in the divot in the back of the tap and hold it vertical while you turn the tap wrench.

Oh and also, do you need to tap the full 2cm? Depending on your job you may be fine with less, you only need 3-4 threads engaged for full strength of the thread.

 

[Wend]

Presumably a keyless chuck with a locking ring (like https://www.amazon.co.uk/Keyless-2-20UNF-Self-tighten-Multiple-Purposes/dp/B088X1JKKL) would work?

 

[chaoticbob]

What you need perhaps is something like this:

You mount the wrench on the tap, then put this thing in in the chuck, engage the point with the hole in the back end of the tap and bear down on the quill with one hand whilst turning the wrench with the other. It gives the tap enough support to get the thread started true. Works for me anyway!

If you don't have anything suitable drop me message - I have many, I lose them, quicker to make a new one than search, then they turn up... Happy to bung one in the post!.

Rob.

 

[Rorschach]

What you need perhaps is something like this:

View attachment 104098

You mount the wrench on the tap, then put this thing in in the chuck, engage the point with the hole in the back end of the tap and bear down on the quill with one hand whilst turning the wrench with the other. It gives the tap enough support to get the thread started true. Works for me anyway!

If you don't have anything suitable drop me message - I have many, I lose them, quicker to make a new one than search, then they turn up... Happy to bung one in the post!.

Rob.

That's what I tried to describe above, should have done a picture like you lol.

 

[J-G]

That 'Male' centre will only be good for taps about 5mm Ø + Smaller taps will need the 'Female' version.

I usually use another tap in the chuck - with the opposite 'cone'.

 

[MamTor]

Thanks for all the replies, and that's a very kind offer chaoticbob.

I probably would have taken you up on that offer, but I managed to get hold of a sprung tap holder which fits the top of my t-handle tap wrench perfectly. And it cost so little it makes me wonder why these aren't included with tap/die sets as it makes a big difference and I'll be using it every time now.

 

[chaoticbob]

That's what I tried to describe above, should have done a picture like you lol.

Apologies Rorschach, I didn't read your post attentively enough before replying with the same method myself.
Good to see that the problem has been solved!
Rob.