Are these oldhams too small?

[mrcodewiz]

I came across some oldham couplers on the web advertised at $5 with a very lousy description. They were just called clamp oldham 1/4 X 5/16 .75 OD which I assumed meant a single hub with 1/4" bore diameter and 5/16 bore depth. At $5 a piece, I decided to order 4 of them along with some acetal discs. I wasn't sure that the .75 diameter would be strong enough but I looked at this product detail chart from McMaster thinking they might be similar:



My thought process was the .75 diameter 1/4" bore oldhams at mcmaster had a peak torque of 93 in pounds which equates to 1488 ounce inches - way more than the 425 oz inch stepper I planned to use on the X and Y of my G0704. I will admit - this was a complete guess on my part and I may not even be comparing apples to apples.

As it turns out, I received 4 full assemblies with 1/4 bore on one side and 5/16 on the other:




Turns out these are Huco couplers. I looked up the part number off the coupler and came up with these 2 charts:





So it looks like this is a 24 bore code and a size 19. According to the Huco chart, the torque capacity is 15 lb-in which is only like 240 ounce inches - a big difference from the mcmaster couplers (which I found out are Ruland as I ordered one for the Z).

So will these things snap if I try to hook them up to some 425 oz-in steppers?

[mrcodewiz]

Looking at Ruland's site, it appears McMaster lists the static break torque value and not the rated torque. The Ruland .75 diameter couplers are actually rated at 20 inch pounds.

[mrcodewiz]

I'm just thinking (typing) out loud now - what if I were to make new 'discs' out of aluminum? I would lose the ability to break if it encountered too much torque but I would retain the quick-disconnect and ability to deal with some slight misalignment which is what I mostly like about these.

[mrcodewiz]

Well, I decided to go with the 1" OD oldhams for the G0704 and I will attempt to use the .75" ones on the X2. If they snap, I will replace the discs with aluminum.