Tapping for 10-32

[oskar]

I do a fair amount of 10-32 tapping on aluminum and it’s a hard going. I use a 5/32” drill which came as a set with the tap but I wonder if another drill size may do the job faster

As an example I also tap a lot of M5 and I was using #19 drill which was also a hard going but I discover from a thread in another forum that an 11/64’ drill is much better and in it is.

Is the 5/32” drill the best for 10-32 tap?

 

[WarrenP]

You can always try one size larger , 3/16, and see what you think. Seems aluminum shouldnt be to hard to tap though.. but the extra room would probably make it easier, should still get good threads... only 1/32 inch differece. Have you tried a little wd40 while tapping?

 

[pacifica]

It will depend on how much distance you need between the root and crest. How much pulling force will be on the threads?

Definitely with 6061 aluminum there is a point where too shallow of threads is a failure issue.

Try a #20 drill?

 

[T Bredehoft]

Starrett's tap and drill card (which every one of us should carry in his shirt pocket,) says the tap drill for a 10-32 screw is a No. 21, .159 diameter. 5/32, .156, is just a bit tighter, Always use a lubricant when tapping, even if it's beeswax. (No 20 is .002 larger yet).

 

[Dan_S]

A #21 drill is what is recommended for 10-32 and that only 0.0027" bigger than 5/32". I'd recommenced a good spiral point H3 class tap before a new drill.

 

[markba633csi]

#21 drill (0.159") is spec for 10-32
5/32 is 0.156" which also works fine for aluminum.
For steel I would stick with #21 or even #20

 

[benmychree]

A #21 drill is what is recommended for 10-32 and that only 0.0027" bigger than 5/32". I'd recommenced a good spiral point H3 class tap before a new drill.

Use a spiral point tap only if it is a through hole, as the tap forces the chip forwards in the hole, and would likely jam up if used in a blind hole; if it is a blind hole, use a spiral fluted tap, which ejects the chip out through the flutes.

 

[T Bredehoft]

Note that a SPIRAL POINT tap drives the chip ahead of it, while a SPIRAL FLUTE tap pushes the chip behind it. SPIRAL is not the key word. POINT points the chip ahead, FLUTE flutes the chip behind.

 

[Dan_S]

Use a spiral point tap only if it is a through hole, as the tap forces the chip forwards in the hole, and would likely jam up if used in a blind hole; if it is a blind hole, use a spiral fluted tap, which ejects the chip out through the flutes.

That's not completely true, people have used spiral point taps for everything for longer than I've been alive, specially in home and small job shops. I have both types in my shop, but that's not a luxury everyone can afford. My personal preference is YG spiral flute bottoming taps, but those aren't cheap.


However, I recommended a spiral point tap, because he doesn't mention how he is tapping the hole. If he is power tapping or using a tapping guide then either type is fine, but if he is tapping by hand with no guide I would not recommend a spiral flute tap, its to easy to break.

 

[benmychree]

Note that a SPIRAL POINT tap drives the chip ahead of it, while a SPIRAL FLUTE tap pushes the chip behind it. SPIRAL is not the key word. POINT points the chip ahead, FLUTE flutes the chip behind.

I believe that is what I said in my post -----