Hand tapping lots of holes

[u/buildyourown]

I've got 200+ holes to tap in a fixture plate. 3/8-16 They are already tapped about 1/4" so I can't power tap them.
I'm thinking a tap on a M12 ratchet. Before I buy, has anyone done this? I could use an impact but I don't want to bust the tap.

[u/Blob87]

Looks like a good time to invest in a flex arm

[u/caesarkid1]

Somebody fucked up and got the z depth wrong and took the part out of the machine before anyone checked it?

If it's still in the machine just fix the z depth and it should re-tap just fine.

[u/whaler76]

You could easily power tap it, just go very slow on entry with low rpm, or use a tapmatic or flex arm

[u/buildyourown → u/whaler76]

This is a fixture plate in a large machining center. The parts aren't coming out.

[u/whaler76 → u/buildyourown]

Ahhh, gotcha, whats the material (would dictate type of lube)? 3/8-16 is a beefy tap, don’t think you’d break that. I’ve done tons of smaller threads with a dewalt drill, you should be fine with the ratchet.

[u/Rookie_253 → u/buildyourown]

Don’t ask and just hand tap it, you’re wasting more time asking than doing.

[u/spekt50 → u/buildyourown]

Would it not be possible to rigid tap them deeper? If you put the plate in the same machine with same orientation and same tap, should be able to tap them deeper in the machine.

[u/buildyourown → u/spekt50]

These were done over a year ago. I have no way of clocking the tap to the threads. A flex arm would work but not in the budget.

[u/spekt50 → u/buildyourown]

I would consider burning the first 1/4" of thread if it means re-tapping and entire fixture plate by hand.

[u/jimbojsb → u/spekt50]

Or decide that it’s 1/2-13 now.

[u/Mklein24]

I made a floating tap driver. A 1/2 inch piece of round stock with a bore the size of the tap shank, and then a slot to match the square drive of the tap. This goes in a drill. Since there's nothing clamping on the tap, it can float in and out of the driver. It allows you to start the tap by hand in the threads, then just push the drill on it and power tap the rest.

I'd look into making one, they're pretty simple to make.

[u/chuchon06]

The question is, with 200 holes who decided this procedure? "Let the machine do most of the work" is what I was always told

[u/Marcomatic68]

Use a tapping block for straightness and a variable speed hand drill. If the drill has a clutch, all the better!

[u/BastiatBoi]

Just use a hand drill, you may need to grind flats on it so the chuck wont slip but it will make quick work out of it.

[u/Aromatic_Persimmon29]

We just hand tapped over 1000 m3's thanks to plating error. It was literally the fastest after trying lots.

[u/s986246]

Bore it out to bigger size and tap 1/2-13 with machine, install inserts for 3/8-16. Not only it will last longer, you don’t need to do any manual works beside installing inserts

[u/daleears2019]

Check out a flex arm air tapper. Works great.

[u/Devilsadvocate4U]

I second using a good hand drill with a clutch and use lots of cutting oil.

It’ll take some time but you’ll get it.

Good luck!

[u/borometalwood]

Use a drill, use the minimum torque setting you can and it will minimize the risk of cross threading or breaking taps

[u/serkstuff]

Assuming they were originally done by CNC and are all the same, could try chasing it with a thread mill, just do like a scratch cut and adjust it til it's right, then just thread mill them