Taps.

[RogerP]

I have acquired some SKF taps 10 x 32 UNF which are different from any type I seen before.

The cutting thread is continuous, there are no flutes, and in cross section the tap is a Reuleaux triangle (sort of triangular with rounded corners).

Anyone come across this type or have any information?

 

[Johnboy]

Sounds like a roll tap. These form the thread rather than cutting it. Will be a different size hole to that for a normal tap. Use these at work for threads in aluminium, gives s strong thread.

John

 

[RogerP]

Thanks John.

I now see (having put on my strongest specs) that they are also marked with the drill size needed - 4.4mm.

 

[woodpig]

Yes, it's a thread forming tap rather than thread cutting tap.

http://balax.com/sites/default/files/Th ... utting.pdf

Not tried them myself as they don't seem as popular as the normal type.

 

[Go slow]

Those taps ar fluteless for a reason they are used on thin steels that have a pierced. Hole with like a rough exit to give a few extra threads.
These are used on car bodies, sheet metal boxes etc

The new type are are still fluteless but run very fast on cnc

 

[metaler]

As has been said, these fluteless taps are particularly good for tapping holes in thin material. I do though use them for deeper holes where the benefit is that due to no swarf being produced the screws used in them just float in.

An important point to take note of is that due to the hole being formed, rather than cut, a larger drill size has to be used. In this case the forming process takes care of the larger drill with an adequate thread depth still being produced. Also, the forming process can harden the material resulting in a stronger thread.

The following shows some drill sizes for metric threads M3 2.8mm M4 3.7mm M5 4.6mm M6 5.6mm M8 7.4

Harold Hall