Rubber Molding for Checking Thread Profiles

[jvisosky]

In order to check thread profiles on our parts, we use a product called ReproRubber. Its a two part mixture that when mixed and placed over the threads, it hardens and allows us to verify the profile. This stuff is rather expensive and we are looking for alternative solutions.

I've found a few possible alternatives but I wanted to put this out there to see if anyone had some suggestions.

 

[griffengm]

Not sure from your description how much heat is allowable but there are several low temp (120-200 DegreeF)compounds available through McMaster Carr. They are listed under Cerro alloys. They give good detail and are not too difficult to work with.
Another material that gunsmiths and mold makers used is sulfur. They melted it, poured it in a gun barrel or mold. It gave good detail with minimal shrink. Worked well for internal threads with the addition of a tab for handling.

Griffy

 

[aspearin1]

It sounds to me like paraffin wax may also work. Self-lubricating, low melting, reuseable. It may not have the rigidity necessary, but may be worth a shot.

aspearin1

 

[PMS132]

Try a silicone or urethane rubber mold making material. Be sure to use a mold release with the urethane or it might stick.

 

[jvisosky]

griffengm, the application is room temperature. Its a room temperature cure, sets up in around 8 minutes and hardens to a rubber like consistency. But I'll still look in Carr just to see.

 

[griffengm]

jvisosky,
I used a similar material from Devcon for a time to make holding fixtures. To reduce the amount actually needed, we used a rough core made of steel and cast the rubber around it. This let us reduce the castable by 4-6 X.

Griffy