Tapping KOVAR

[blackc1]

I need to hand tap 1-64 unc 3b threads in kovar. Sources for kovar info mention that the material has a tendency to flow back into the hole when tap drilling so i am using a #52 size tap drill which is .001 in dia. larger than the standard tap drill for a 1-64 thread. Can any one tell me if my plan is correct or have any other tips please let me know.

[WayneHill]

I do not have experience with Kovar.

Have you tried using a form tap and bees wax?

The tenancy of the material to flow back in the hole is similar characteristic to stainless steel.

[fizzissist]

Yuck.

Assuming this is where you got the back-flow info??

High Temp Metals 800-500-2141 - Kovar Technical Data

They recommend a coolant with "fatty esters"....which reminds me of how well 1/2 & 1/2 works when tapping copper...

I'd go with the largest tap drill you can get away with for the min. % thread, and the smallest H# available in that tap size.

I've found that OSG or Emuge taps have performed the best for me in very small sizes.

[taylors]

I just ran a bunch of kovar parts with 0-80 threads. One thing I do with form tapping is run my coolant really rich up around 12-15%. And yes it shrinks back just like titanium. But i ended up injecting Moly-dee into the holes with a syringe before tapping. It worked great.

[fizzissist]

I just ran a bunch of kovar parts with 0-80 threads. One thing I do with form tapping is run my coolant really rich up around 12-15%. And yes it shrinks back just like titanium. But i ended up injecting Moly-dee into the holes with a syringe before tapping. It worked great.

Not in kovar, but in 304L, did essentially the same thing. Turned off the coolant, blew all the holes out, then just before the tap went in I brushed on the Moly-dee with an acid brush. (gently, so you don't get hair in it.. )

One thing I found was that using a good quality metric drill (I think it was a .055", or 1.40mm) gave me a lot of comfort, as well as lots of holes, and they gaged in spec. Have done hundreds of blind 0-80's that way. Love them formers!!