Educate me about taps

[henpecked]

The tighter the tolerance the more torque it will take to tap the hole. Increasing your chance of breaking the tap.

[DLI Chip Maker]

I generally run H2 or H3. H1 will get real tight with a lot of fastners. H4 & bigger produce "looser" threads, which ain't a big deal if the fasteners are just holding parts together, but if the thread or fastener itself serves any function in alignment, you don't want a sloppy fit.

As for the taps themselves, I recommend OSG spiral flute bottoming taps for most purposes. Expensive, but about the best there is. I've tapped hundreds of holes in all kinds of materials with OSG #10-32 taps and not broken them, and I rigid power tap in a 3 HP knee mill. Spiral flute taps will push chips out the back, allowing you to thread without interruption.

Also, remember, the foremost cause of broken taps (especially small ones) is lateral pressure, followed by lots of back & forth or interrupted cutting. If you can keep them straight, keep them turning and not back up, you'll have great success.

The tighter the tolerance the more torque it will take to tap the hole. Increasing your chance of breaking the tap.

The tap tolerance has nothing to do with that. The "tolerance" you're referring to is a function of hole diameter; 100% thread will have more resistance than 75%, no matter the tap. And a hole under the minor diameter size means the tap is also drilling, which is a problem. That said, see above; rotational torque is not the cause of most broken taps.

[PSS]

I generally run H2 or H3. H1 will get real tight with a lot of fastners. H4 & bigger produce "looser" threads, which ain't a big deal if the fasteners are just holding parts together, but if the thread or fastener itself serves any function in alignment, you don't want a sloppy fit.

As for the taps themselves, I recommend OSG spiral flute bottoming taps for most purposes. Expensive, but about the best there is. I've tapped hundreds of holes in all kinds of materials with OSG #10-32 taps and not broken them, and I rigid power tap in a 3 HP knee mill. Spiral flute taps will push chips out the back, allowing you to thread without interruption.

Also, remember, the foremost cause of broken taps (especially small ones) is lateral pressure, followed by lots of back & forth or interrupted cutting. If you can keep them straight, keep them turning and not back up, you'll have great success.



The tap tolerance has nothing to do with that. The "tolerance" you're referring to is a function of hole diameter; 100% thread will have more resistance than 75%, no matter the tap. And a hole under the minor diameter size means the tap is also drilling, which is a problem. That said, see above; rotational torque is not the cause of most broken taps.

The info I wanted! Thanks