size of set screw to hold gear to shaft?

I'd forget the key and use 2, 5/16 set screws that would go into the shaft about 1/4 inch. This would stop movement in both directions.

Fit a key by all means but not set screws. Shapers have intermittent load due to their cycle, that will only want to shift the gear along the shaft, I've yet to see a set screw that will prevent that. Fit a roll pin, preferably with another smaller one inside that one, too.

Tom

Or use one these...

No key, stress raisers, or setscrews, and resists both torque and axial loads. You do need to pay attention to the minimum required hub diameter.

Ned Simmons

The pin in the gear may be acting as a torque limiting device as well as holding the gear in place. I would recommend that you use a tapered or straight pin rather than the setscrews because the setscrews are only good enough to hold the key in place but won't keep the gear from moving. If you bore the shaft to lock the setscrews in place the threade will get buggered on the bottom unless you use a setscrew turned down on the end to match your bored hole.

John

Although I'm a follower of these type fasteners, in this application with that diameter shaft and gear size, I'd have reservations. In matters like this, why not replicate the original? It hasn't failed in service, just that the shaft has been bent. Isn't it called KISS?

Tom

Will there be flats on the shaft? If so..a 1/4 is what Id use, unless serious side loading...then go to 5/16. Flats..no matter how small..are a Good Thing for setscrews to bear on. Drop a tiny bit of brass brazing rod down the hole before screwing in the set screw. It saves on galling the shaft...though a flat mitigates some of this.

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

Good question. I think the pin is about 3/8" diameter. The area around the ends of the pins on the hubs has considerable scarring from me trying to remove the pins. I could *maybe* drill the shaft slightly undersize, line up the gear on the shaft, and ream it inline and then press in a new pin and file its ends flush. But I'd figured pinning was just "the old way" to attach a gear to a shaft. While there is side thrust, there isn't that much - this machine is run by a 3/4 hp motor. I also considered drilling/reaming a new hole and pinning it but there is a real hard limit on how many times you can drill a hub 3/8" without really weakening it.

I would love to avoid having to stroke a long internal keyway in a steel gear. Maybe I'll consider using a tapered pin. I hate using tapered pins because they are essentially a permanent installation. But I've used them before and they do work well, plus I have several taper pin reamers.

Grant

No flat, no. I was thinking cone point, running a hand drill through the set screw holes to form the cone, and only then tapping the hub set screw holes.

I'm having a hard time believing that with two beefy set screws torqued in, that the gear is going to slide sideways. The helical angle is maybe 30 degrees.

GWE

I agree, but Grant seems to have rejected the original setup. The locking hubs address all the concerns about combined torque and axial loads and ease of disassembly. I think a key and setscrews are likely to be disappointing on both counts. A rollpin and key would take the loads, but would not be as convenient as the b-loc hubs.

I'd have no reservations about the locking hubs as long as the recommendations regarding minimum hub dimensions are observed.

Ned Simmons

Using a hard pin may be the old way. Wouldn't a roll pin, especially a roll pin filled with the next size(s), be plenty strong and self holding? If the manufacturer thought it needed a

3/8 pin, I guess I would start there; or I would go with a quarter and increase if there were problems as our forefathers often erred on the side of overbuilding. A roll pin should come and go fairly easy compared to an interference fit pin. Here happens to be a chart of shear capacities: the whole world singing. . . . DanG

Get thee hence to MSC or whoever and get some taper pins and a taper pin reamer. They work better than roll pins and set screws and are easy to install and remove.

Mark Rand RTFM

I'm sure he'll thank you for that advice, Mark. :-)

US$51.70 plus shipping:

BTW. When was the last time you actually saw taper pins used on new equipment?

Tom

Take the 3 minutes it takes to file a couple flats on the shaft. Cone points are good..but they displace a surprising amount of metal. And someday you may want to get the shaft out again.

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

You know, given that I couldn't get the pins out this time and had to cut the gear off the shaft, then bore it out until the shaft remnant collapsed, I'm wondering about whether to just weld the damn gear onto the shaft. Oh, well, I suppose all that heat would probably distort things.

I do have taper pin reamers, due to my having offered my services to help refurbish equipment at the Boeing Museum of Flight. Taper pins effect solid repairs. Maybe I'll just pick up a couple. I'm not going to use No. 7, though.

Ya know, a roll pin would be pretty slick too. Hmmm ..

Grant

Do the taper pin just because it takes a wee bit of skill to do it perfectly.

Taper pins are a lot easier to get out if you shear one. The other good thing about them is you don't have to go to the next size if you re-ream the hole. I have a full set of tapered reamers and a bunch cut off the end for half sizes when there is no clearance for the reamer.

By the way, where is the Boeing Museum?

John

Roll pins are indeed good. And they are not bad shear safeties either.

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

If it can move axially, it will! I would use a taper pin; just make sure you don't peen over the small end! Bob