Where to find Imperial taps with metric shanks at a reasonable price?

[F35Machinist]

As the title says, I am looking for a good source for imperial size taps with metric shanks. Also, I wanted to rant about how absurd ANSI shank sizes are. Most of the ANSI shanks are just above what would be a .5mm increment for a collet. For example, a 4-40 tap has an ANSI shank of .141" which comes out to 3.58mm and must be held in a 4mm collet. I know that there are Japanese and European brands that have what I am looking for, but they are all double the price of the ANSI shank taps! Why does grinding the shank to 4mm instead of 3.58 change the price from 10-15$ to 25-30$? Also, the lead times tend to double as well. Any feedback from tool makers would be much appreciated. I wish I could meet the engineer that came up with the ANSI shank sizes and wring his throat.

 

[mhajicek]

It costs more because of quantity. Just get on-sized tap collets and be done with it.

 

[Mike1974]

Per your example - #440- having a .141" shank which is 3.58mm... what's wrong with using a 4mm or 5/32" if you are worried about slipping (seems awful small for that), get a tap collet with the square drive...

 

[Scottl]

Per your example - #440- having a .141" shank which is 3.58mm... what's wrong with using a 4mm or 5/32" if you are worried about slipping (seems awful small for that), get a tap collet with the square drive...

Or, you could machine a set of sleeves, split on one side, and use larger collets for them. If you are worried about slippage put setscrews that bear against the flats.

 

[Orange Vise]

Also, I wanted to rant about how absurd ANSI shank sizes are.

I agree. Someone may have screwed up a long time ago, although I suspect there's more to the story.

ANSI Inch and ANSI Metric taps of similar size share common shank sizes, e.g. 1/2" and M12. Helps reduce the number of different tap collets you need to buy.

What makes no sense is the damn ANSI 3/8"/M10 tap. The shank is just over 9.6mm diameter, which is larger than the minor of any 3/8" or M10 thread, so extended length taps can't be used for deep tapping without modification. The next size up, 1/2"/M12, uses a ~9.3mm shank diameter, which clears the thread minor.

I believe this issue is limited to ANSI taps. ISO/DIN M10 taps don't seem to have this issue.

Anyone know the backstory behind the ANSI 3/8"/M10 tap shank? Why is it larger than that of the 1/2"/M12? Did some major aerospace or automotive company force it many decades ago?

 

[Scottl]

Not that discussion of how those shank sizes originated isn't interesting but as I see it the problem is that the OP does not want to pay the higher prices for the ones with even metric size shanks. Therefore it seems the only practical choice is to adapt the tooling to fit the existing sizes.

Also, when those taps were originally designed the intent was always to drive them from the square section so only a modest friction fit was required for the shank to keep it from falling or pulling out. I believe gripping them tightly by the shank such as in a collet is a fairly modern practice.

 

[gustafson]

It costs more because of quantity. Just get on-sized tap collets and be done with it.

less than the cost of an odd tap, depending on your collet series

 

[Orange Vise]

Not that discussion of how those shank sizes originated isn't interesting but as I see it the problem is that the OP does not want to pay the higher prices for the ones with even metric size shanks.

@mhajicek addressed that in Post #2.

The higher prices aren't for custom ground shanks. The on-size metric shanks are standard taps that conform to JIS, DIN374, etc that aren't popular in North America.

It might all be a moot point anyway. Even a standard (non-tapping) ER collet will typically work fine as it has a 1mm collapsible range. Although runout isn't optimal at the bottom half of the range, we're talking a few tenths of runout. The drilled hole preceding the tap isn't even round. It's lobed. And the tap is following the drilled hole.

 

[gustafson]

I agree. Someone may have screwed up a long time ago, although I suspect there's more to the story.

ANSI Inch and ANSI Metric taps of similar size share common shank sizes, e.g. 1/2" and M12. Helps reduce the number of different tap collets you need to buy.

What makes no sense is the damn ANSI 3/8"/M10 tap. The shank is just over 9.6mm diameter, which is larger than the minor of any 3/8" or M10 thread, so extended length taps can't be used for deep tapping without modification. The next size up, 1/2"/M12, uses a ~9.3mm shank diameter, which clears the thread minor.

I believe this issue is limited to ANSI taps. ISO/DIN M10 taps don't seem to have this issue.

Anyone know the backstory behind the ANSI 3/8"/M10 tap shank? Why is it larger than that of the 1/2"/M12? Did some major aerospace or automotive company force it many decades ago?

I have two different size tap shanks in my tool box for larger taps. Some smaller, never bothered to figure out why

 

[MachineAmateur]

Well i bought a nice set of square key collets, M4 - M14 and that was the day i learned something new about taps and that is the variation in shank sizes. I have yet used a single one of them as none of taps i buy is correctly sized. Typically the mismatch is about 0.1mm (shank oversized, for example today the key was correct but M6 shank was 6.3mm and hole 6.2mm.). It is possibly manufactured to JIS standard or something silly. Information is not available.

 

[FamilyTradition]

I recall reading another thread here on PM about inch tap sizes being the bastard child of a few different standards early in the 20th century. Hence the number sizes for smaller taps (#4, #8, etc) and fractional the bigger you go.

The same issue is probably occurring with shank sizes, different early standards that got lumped together to form the current one. The standards don't have to make sense, they just are there to get everyone on the same page.

Per your example - #440- having a .141" shank which is 3.58mm... what's wrong with using a 4mm or 5/32" if you are worried about slipping (seems awful small for that), get a tap collet with the square drive...

Might even be able to squeeze it in a 9/64 (.1406, would be a tight fit).

Well i bought a nice set of square key collets, M4 - M14 and that was the day i learned something new about taps and that is the variation in shank sizes. I have yet used a single one of them as none of taps i buy is correctly sized. Typically the mismatch is about 0.1mm (shank oversized, for example today the key was correct but M6 shank was 6.3mm and hole 6.2mm.). It is possibly manufactured to JIS standard or something silly. Information is not available.

Could also be poor workmanship, or gaging issue during manufacture.

@Scottl has a good point about driving squares. Hence the nomenclature - the taps were meant to be driven using the square.

If you look at a lot of taps made 50+ years ago, manufacturer labels were stamped into the shanks, I doubt they intended this to be a precision surface for tight clamping.

 

[Scottl]

And on the subject of taps not being meant to be tightly gripped by the shanks, my Lisle tap socket set uses O-rings to retain the shanks in oversize bores. All driving force is transmitted by the square recesses at the back.

And I still have a few older taps with the numbers stamped into the shanks, often with raised metal around the edges.

 

[BT Fabrication]

As the title says, I am looking for a good source for imperial size taps with metric shanks. Also, I wanted to rant about how absurd ANSI shank sizes are. Most of the ANSI shanks are just above what would be a .5mm increment for a collet. For example, a 4-40 tap has an ANSI shank of .141" which comes out to 3.58mm and must be held in a 4mm collet. I know that there are Japanese and European brands that have what I am looking for, but they are all double the price of the ANSI shank taps! Why does grinding the shank to 4mm instead of 3.58 change the price from 10-15$ to 25-30$? Also, the lead times tend to double as well. Any feedback from tool makers would be much appreciated. I wish I could meet the engineer that came up with the ANSI shank sizes and wring his throat.

why bother with metric shanks. just buy the correct imperial holder....... who cares about the price. when you need it, you need it and you pay for it.