SRX Encoder Mount Question

Does anyone know the length of the screw that comes with the SRX magnetic encoder mounting kit?

More detail is needed.

The factory CTRE housing uses a 2-28 x 7/16" screw to hold the two sides together, then a 3-48 screw of indeterminate length for mounting to a gearbox. (Source PDF)

AndyMark sells their own mounting kit made for the Toughbox Mini/Micro, which also doesn’t call out a length–but the length is also designed to be adjusted until the magnet is properly spaced.

If you’re trying to source replacement screws, I’d figure out which one you’re using and reach out to them for more information. (I’d agree both should add a length to their screw sizes.)

3-48 Fasteners are readily available if you have a length issue.

Hillman Fasteners that supplies most ACE Hardware stores (and other big box stores) has 3-48 in Cap Head Hex in lengths of 3/16, 3/8, & 1/2. So those should be available locally.

McMaster Carr has Cap Heads 3-48s from 1/8 to 1 inch.

We 3D print a mount for the encoder, and use larger size 8 or 10 mounting bolts to match the COTS gearbox. The supplied 3-48 bolts thread into the mount plastic just fine.

I use a depth micrometer to measure the actual height of the mounting bracket, so that I can adjust the magnet height (drill depth) to achieve a nominal 0.040" gap below top of the mount.

If interested in the AM version, the picture shows 21 threads on the screw, plus a bit of shank, so it’s basically a 1/2" screw. I did the same math on this back around the end of January and bought 1/2" at the local hardware store, and our controls guys got them mounted OK.

I recently looked at the model and I think there is only room for pan or button head 3-48 screws.

-Andrew

I am referring to the kit sold on AndyMark. Thank you for the information. I never thought about counting the threads in the photo.

You’re welcome. Sometimes I’m not sure if my crosswise thinking is a blessing or a curse. :] Given that my temptation a few years ago to buy a bunch of 5/16-16 threaded rod and throw away all the rulers only lasted about two tenths of a second, I’m tentatively going with blessing. :rolleyes:

Now that we have the screw issue settled, does anyone know if the 7/8" grommet is an ID measurement or an OD measurement?

Do you have the file for the 3D printed mount?

I believe that to be the ID. We have used some of the AM kits with the grommets for some off season work, but the grommet is not quite thick enough and by the time there is any compression in the grommet the plastic of the encoder enclosure is touching the end of the shaft. This works, but we can never get a green light for spacing (the shaft and enclosure are too close). I think we are going to try to 3d print some spacers to go between the gearbox and the encoder enclosure.

We bought some at Ace. We used grommets for a 7/8" hole. These had about a 5/8" inside diameter which is what you need. The screws pass through this hole and go into the mount holes on the encoder pad or equivalent holes on a TB mini or micro, which are about 5/8" apart (0.586" shown there and on the mechanical drawing of the encoder manual). The grommet gets opened a bit, but apparently serves to stabilize the encoder over the use of just the two screws.