Torx T20 specification?

[HughesTooling]

Anyone know where I can get full specs for Torx drive sockets? I found details for Go\No Go gauges here, but not sure that's helpful. I also downloaded a screw from McMaster Carr but it doesn't look right if I make sketches using the Go\NoGo info.

You can see the Go sketch creates overlaps and wouldn't fit into the socket

I have created a sketch that fits between the Go and No Go sketches but not sure it's correct or good enough. See attached design. I've just extruded the socket form to use in a Combine Cut later in the design. I've just played around with the small fillet rad to make something that fits. I only have Od of 3.95mm and Id of 2.85 that's fixed from the specs.

Thanks Mark

[MRWakefield · Accepted solution]

Here's a link to ISO-10664 Hexalobular internal driving feature for bolts and screws that I've just found by Googling. I'm sure this shouldn't be available for free but there it is! At the end of the document you'll find a drawing of a "Representation of hexalobular internal driving feature contour". I've not checked but I expect this falls between the Go and Not Go gauge profiles you already have.

[HughesTooling]

@MRWakefield  Thanks for finding that. I did find the same doc in Russian but wasn't sure it was what I needed. Still not sure, when I put those numbers in, see below with just the No Go sketch activated.

The info in the document I linked and the one you linked match for manufacture of the gauges and there is a small overlap but 0.008mm at the points seems a bit optimistic!

Thanks Mark

[MRWakefield]

Hmmm... yes, 8 microns is a bit tight! I wasn't sure whether that drawing was nominal or just a guide. If I manage to find anything else I'll let you know.

[chrisplyler]

I'm only guessing here, but I suspect that the only source for the actual dimensions of the patented tool is the patent holder and whomever else that patent holder has licensed to.

Other, very SIMILAR hexeglobular drive/socket pairs may have been developed by others via reverse engineering (measuring), but they wouldn't know the actual, original spec.

My suggestion is, since you're basically doing the same thing, to just make it slightly smaller so you have the greatest likelihood of your drive fitting most any socket head you come across. Sure, you might experience slightly accelerated wear and slightly lower max torque delivery, but my guess is that you'll get through life just fine with it.

Like I said, this is just a guess. I could be way off base.

[HughesTooling]

Looks like the patent ran out in 1998 so I should be OK copying. I think I'll go for the sizes from the last page of the PDF @MRWakefield  posted. There's only 0.04mm perside between the go, no go gauges so not much to play with.

I'd made a mistake in my last post as I'd forgot to change the small radius to 0.1 of the outside diameter, looks better now.

This shows the size at the points for go, no go.

Thanks Mark

[MRWakefield]

Ah yes, that looks better.

What I discovered was that it appears to have been invented by Camcar Textron back in the late 60's and that the patent ran out some time in the 90's. As far as I can tell the ISO published it as a standard in the late 90's, around the time of the expiration of the patent. Anyway, I'm glad it helped.