Cutting an oversize thread

[yukon_rose]

I'm repairing an old die head. A part is missing. It looks like a 1/4-24 cap screw but that size just wobbles in the hole. I measured the minor diameter at .209". That computes to a major diameter of .271".

Will a 1/4-24 split die expand to .271" or is this a job for the lathe?

Gary

 

[macardoso]

I'd do it on the lathe personally. Get a set of thread wires and cut it to the exact size you need. Not sure how easily you can get a die to expand that far. Usually you're changing it by a few thou.

 

[MrWhoopee]

9/32-24 is a thing, not common (or cheap) https://www.newmantools.com/price/taps_ns_pr.html
but still a thing. A die will break before it expands that far. Single-pointing is definitely the way to go here.

 

[rgray]

I have also run into an item with a 9/32 thread. Mine is 32 tpi though.
I did manage to buy a tap and die, but they are hard to find. My only reason to have them is for thread chasing.
No don't try to get your 1/4 die up to that size. It will surely break I think.

One spec I find (mitsubishi carbide web site) shows thread depth at .026 for 24 tpi (.052) My little fish gauge says .054 for 24 tpi.
That's .261 & .263 a little different from your number.

 

[macardoso]

This is my go-to for cutting threads. You give it the size and tolerance fit, and it calculates everything, including your over-wires tolerances.

UN imperial screw thread calculator

theoreticalmachinist.com

 

[BtoVin83]

helicoil

 

[benmychree]

Yes, chase the thread and have done with it. What sort of die head is it?

 

[cbellanca]

Are you sure this is a metric M6x1 thread

 

[tcarrington]

or what if it were an M7? I have a set of chinesium clamps that use what looks like M9. Go figure.

 

[Flyinfool]

Those dimensions are real close to being an M7 x 1.0 thread.