Tap number designation clarification

[mjk]

May sound like a newbie question but I've not had to look for this before
When I purchase a tap, I'll look for eg 10-32 2,3,or flute, coated etc.....based on catalog recommendations, I'm not machining space station parts
I was at my local flea market Saturday and found a box containing cards of taps, all in the sizes that I normally use(break)
Price was right, 2 of the cards 12ea are HY-PRO with label 194-32 GS.
a version of 10-32?

 

[Doozer]

May sound like a newbie question but I've not had to look for this before
When I purchase a tap, I'll look for eg 10-32 2,3,or flute, coated etc.....based on catalog recommendations, I'm not machining space station parts
I was at my local flea market Saturday and found a box containing cards of taps, all in the sizes that I normally use(break)
Price was right, 2 of the cards 12ea are HY-PRO with label 194-32 GS.
a version of 10-32?

The 194 could be the major diameter, not sure.
The nominal diameter should be (#10 x .013")+.060"
which is .190". That being said, the major is smaller than the nominal. So either this tap is oversize or it is just part of the part number. Tap a hole with it and gauge the hole it produces.

-D

 

[dandrummerman21]

You normally break 10-32 taps? I can see 10-24 but 10-32 being a fine thread, should be easy.

That said, what does the tap measure, diameter wise?

.194 should be the max tap diameter, about .192 should be the minimum, for a #10-32, as given from a chart in the machinery's handbook.

I would imagine its probably a special thread.

 

[mjk]

actually since I "found" form taps, breakage is almost non existent on new work
But in doing repair/refurbish sometimes I find something in a thread that wasn't supposed to be there
These 2 cards were part of a 300 pc+/- assortment of new taps and a box of 100+ number drills (all new)
Yes probably a special I'll check the diameter, and tap a hole with a "std" 10-32 tap and compare
Thanks for the replies

 

[EPAIII]

If you are not doing production work then tap breakage should be a rare event. I have 4-40 and 6-32 taps that are close to 60 years old and they are just fine. You may need to work on your technique.

Some device for guiding them may be in order. If you have a drill press there are tap wrenches with guiding sleeves that fit in the chucks. I am not talking about power tapping, just guided manual tapping.

And TapMagic is a good fluid to use but there are other good ones. I usually just dip the tap into a small pool of it. But while not being the best, any oil will help. And back out a half or full turn to break the chips when you feel resistance. If the flutes become loaded with chips, take the tap completely out and clean them off. Keep a small brush (toothbrush) handy.

 

[rons]

Those are made by OSG.
Tap a 10-32 hole with normal tap.
Tap a second hole with the new tap.
Compare the fit. If it's a looser fit then you lost. Otherwise you won.

 

[morsetaper2]

Oversize tap for situation where holed is tapped, the part gets plated or anodized afterward? #10 thread is tapped oversize such that after plating build up, the #10-32 thread is "in-spec"?

 

[kenton]

 

[mjk]

Well although the labels on the 2 trays of 194-32 were what appeared to be sealed, the taps were actually marked 10-190
with a #21 in 1/2" aluminum threaded hole accepted the go, refused the no-go