3/8 and 1/2 UNC tap shank sizes--- What's going on here??

ChipSplitter

Titanium

Joined

May 23, 2019

Location

Maybe

• May 29, 2020

• #1

I knew this for a while but was just freshly reminded of it again.
Why on earth is a 3/8" tap shank bigger than a 1/2"..???
Why couldn't they have been made the same size for standardization?

 

kustomizer

Diamond

Joined

Aug 17, 2007

Location

North Fork Idaho

• May 29, 2020

• #2

If you think our tools are strange look at the ones the plumbers have

 

M

MattiJ

Titanium

Joined

May 31, 2017

• May 29, 2020

• #3

I know it's from M.C.T.I. standard but have no idea what that standard actually is. Sounds like ACME from Road Runner cartoons

Square shanks even on most Metric taps from European manufacturers seem to match the "MCTI" standard

 

M

MattiJ

Titanium

Joined

May 31, 2017

• May 29, 2020

• #4

Nevermind: USCTI - United States Cutting Tool Institute (formerly MCTI).

 

M

MattiJ

Titanium

Joined

May 31, 2017

• May 29, 2020

• #5

http://balax.com/sites/default/files/Tap-Blank-Dimensions.pdf

 

pavt

Stainless

Joined

Jun 30, 2013

Location

20 miles north of Buffalo NY

• May 29, 2020

• #6

kustomizer said:

If you think our tools are strange look at the ones the plumbers have

Click to expand...

No thanks, I just don't swing that way.

 

kustomizer

Diamond

Joined

Aug 17, 2007

Location

North Fork Idaho

• May 29, 2020

• #7

pavt said:

No thanks, I just don't swing that way.

Click to expand...

I see

 

ChipSplitter

Titanium

Joined

May 23, 2019

Location

Maybe

• May 29, 2020

• #8

kustomizer said:

If you think our tools are strange look at the ones the plumbers have

Click to expand...

You perverted @#$%@.......

 

ChipSplitter

Titanium

Joined

May 23, 2019

Location

Maybe

• May 30, 2020

• #9

MattiJ said:

Nevermind: USCTI - United States Cutting Tool Institute (formerly MCTI).

Click to expand...

That still doesn't explain the logic for having a larger shank on a smaller tap

Probably a conspiracy to break 1/2" tap shanks.......

 

M

MattiJ

Titanium

Joined

May 31, 2017

• May 30, 2020

• #10

ChipSplitter said:

That still doesn't explain the logic for having a larger shank on a smaller tap

Probably a conspiracy to break 1/2" tap shanks.......

Click to expand...

1/2" tap shank passes the threaded hole completely and that is handy sometimes. Still doesnt explain why the smaller MCTI taps like 3/8" are not dimensioned same way.

 

M

Milland

Diamond

Joined

Jul 6, 2006

Location

Hillsboro, New Hampshire

• May 30, 2020

• #11

MattiJ said:

1/2" tap shank passes the threaded hole completely and that is handy sometimes. Still doesnt explain why the smaller MCTI taps like 3/8" are not dimensioned same way.

Click to expand...

Probably because when you get down to 0-80/M1.6 the shank just snaps?

 

M

MattiJ

Titanium

Joined

May 31, 2017

• May 30, 2020

• #12

Milland said:

Probably because when you get down to 0-80/M1.6 the shank just snaps?

Click to expand...

Much true for the smaller sizes but still doesn't explain why the 3/8" tap has larger shank than 1/2"

I have DC Swiss N421 "thin shank" taps down to M4 and they work fine in that size, no idea if thin shank commonly exist even in smaller sizes.

 

pavt

Stainless

Joined

Jun 30, 2013

Location

20 miles north of Buffalo NY

• May 30, 2020

• #13

Huh, that's weird. And to be honest, I never noticed or cared about it. As long as the square end fits my tap wrench. I just measured a pair of Widia/GTD taps, the 3/8-16 tap shank was .375 and the 1/2-13 shank was .365

Frankly, I've got more important things to worry about.