Crazy number of different thread systems

[markba633csi]

6-32 has a comparatively thin shank vs. thread unlike 8-32 and 10-32. 6-32 tends to fracture and/or cross thread more easily than either of the larger sizes, I've found.
4-40 has a favorable shank vs. thread ratio as do 3-48 and 2-56. 6-32 seems the outlier

 

[WobblyHand]

6-32 has a comparatively thin shank vs. thread unlike 8-32 and 10-32. 6-32 tends to fracture and/or cross thread more easily than either of the larger sizes, I've found.
4-40 has a favorable shank vs. thread ratio as do 3-48 and 2-56. 6-32 seems the outlier

Max minor diameter 6-32: 0.0989". Nominal 6-32 diameter: 0.1380" Ratio: 0.7166, one of the weaker threads as @markba633csi said.

I haven't busted a 2-56, or 4-40, but have broken a 6-32 tap. Actually, the only tap I've ever broken was the 6-32. Never was able to extract the broken tap.

 

[markba633csi]

Yep, same here- only tap I can remember breaking is 6-32 and that goes back a few years

 

[RaisedByWolves]

View attachment 497810

Let’s not get all “Broke back mountain” here.

 

[David2011]

I remember reading an article, many years ago, in late "60's" vintage Readers Digest where the Japanese had taken a wire the size of ha hair (their description not mine) and they had drilled a hole through it. Being proud of their achievement they decided they would send it to the only other group they thought could/would appreciate it, the Swiss, thinking they might want to buy the technology to drill such small accurate holes. They shipped it off then awaited to hear from the Swiss, 5 or 6 weeks later they get a package from the Swiss and open it to find their wire so they place it under a microscope to see if the hole is there; and it is truly the same wire and upon inspection discovered that the Swiss had threaded the hole for them.

I remember that as well.

 

[GeneT45]

I don’t get the 6-32 hate?

I’ve done 4-40 and smaller in tool steel by hand to about 3/8” deep without too many issues.

I do have some tap guides for small stuff like this, but they don’t always fit the application.

It’s all in the wrist.

Until last year I had gone perhaps 20 years without breaking a tap. Then I tried to tap 5 #2-56 holes to 3/8" depth in 17-4PH. I've been assured it's been done. After three taps I remade the part in 4140 with much better results. It's not *all* in the wrist...

GsT