Correct "rubber" or urethane pad and durometer for flowforming ribs question

[lakeracer69]

Hi All, I've poked around and haven't been able to find what type of rubber pad and the durometer to use for forming with a 20 ton press. I tried tonight and was reasonably successful with a piece of 1 " thick horse stall mat of unknown composition and durometer. What is everyone using and can it be found cheaply. : )

[jaredyates]

I hear that some folks have used mats intended for cows. Not sure how that compares to mats intended for horses.

[Chris In Milwaukee]

I used "cow mat", myself, from a friend's dairy barn. I'm not sure if it's any thinner/thicker than what you have there. Take a look at this thread, starting around Post #29 to see what I used:

https://bearhawkforums.com/forum/bearhawk-patrol-plans-build/19435-having-a-rib-party?p=21467#post21467

Also, N3UW has some good info on his YouTube channel for this where he describes the material density he used.

~Chris

[BTAZ]

I used a stack of pieces cut from some scrap ESD matting. The mat was about 3/16" thick and I stacked four or five layers on top of the part.

[N3UW]

The thing you want to make sure about is that the rubber you use is hard enough. If it is not hard enough it will deform without putting the necessary pressure on the bends and sides. You will not get crisp edges. The material i used if you pushed on it hard with your finger, it would not deform. About the hardness of the outer tread of a car tire.

[N3UW]

The rubber I used was a piece of Abrasion-Resistant Polyurethane Rubber Sheet, Semi-Clear, 12" x 12", 1" Thick. It had a hardness of 60A (durometer). I sourced it from McMaster Carr. The item number is 8789K81. You can check out their catalog and look for the relative hardness of different rubber they sell. I tried some sheets of inner tube rubber and some matt rubber and they were all not hard enough to do a good job. If you go too hard, your press will not have enough strength deform the rubber. I found than some commercial rubber mat presses used 60a hardness material in their presses.