Threaded Woodruff key

[682bear]

Nothing a central threaded hole in the middle of the axle over come. I've never used a threaded key, but I'd imagine trying to line up the axle thread with the wheel thread would be pain.

Unless it's a situation where you don't want or can't have a threaded hole in the middle of the axle...

Lining it up isn't a big deal if it is a slip fit or very light press fit. When I did this on my lathe gear it was a fairly tight press fit... so it was somewhat difficult getting it lined up. I managed, though...

-Bear

 

[RaisedByWolves]

Just start at a new location and drill & tap both parts at once. Fill the old threaded hole with liquid steel - epoxy. Way easier. Or if you really think it needs to be filled with steel, drill it out and stick a dowel of steel in with Loctite.

This.

There’s no reason functionality to worry about the old half hole.

 

[pbiYoung]

The drill and tap keyway is something you do in field repair.

Dave

Right
Except these are all factory. No nuts on the end. Wheels all butt up to a shoulder and the tapped half holes in the wheels are blind holes. (do not protrude through back of the wheels)
I'm down to offset and drill/tap new holes in both parts, or disposable collars; unless someone comes up with a better idea?

Thought about starting with large enough stock to drill/tap the end and still be a full hole, and then chuck up the grossly oversized axle and turning down the whole thing to all the different sections/specs leaving the end with a now half hole and hope it all lines up but that would seem to be a lot of unnecessary chip making.

 

[pbiYoung]

I have done this... I had to machine a new gear for a Hendey lathe...

View attachment 484398

The gear on the left has a square key and a threaded key. I machined the gear, then had to re-establish both keys. It isn't too difficult IF the existing threaded hole is centered directly on the joint. (Mine wasn't).

I would machine a 'collar' to fit around your axle... just a sacrificial piece that presses on the axle, flush with the end. Locate the joint line and drill and tap the axle and collar together, then remove the collar and discard it. Line up the half hole in the wheel with the half hole in the axle and install the wheel.

The trick is to have enough tolerance on the axial positioning of the wheel to be able to carefully line up the threads on the two half-holes...

I hope that makes sense...

-Bear

Thanks....I thought about this,
My main concern was unintended gap between back of wheel and shoulder due to misaligned thread pitch but figured I could put what ever shim i needed to make up the small space. Ill have to do it twice unless i cut the axle and weld on a piece for the broken end.

 

[Chipper5783]

I have see a similar set up used in two other applications: steam turbine rotor seal housings and Dodge taper lock hubs. The difference is that only one side is threaded (you have to think about which side ought to be threaded so that you get the second function so that the part cannot walk off the shaft).

Other comments are valid, that drill and tap a shaft to hub split line as a repair is totally a legitimate thing. Example: the apron driving shaft on my little Smart and Brown lathe is integral with the pinion that engages with the rack under the lip of the bed. The gear was fine, but the shaft bushing locations was really worn. I cut the gear off and bored out where the ”shaft” would be, made a new shaft with a shrink fit into the gear, then drilled and tapped a small set screw axially into the joint, then ground off the protruding set screw. The repair is nearly invisible, working great for 8 years.

 

[Ironman2]

It's known as a Dutch key. It is very effective and prevents a gear or pulley from walking off. The downside is the fiddling around needed if the sheave or gear has to be replaced.

 

[woodchucker]

well, I have a possible way, but like others I would just drill a new hole. and tap.

Remove the existing screw while leaving the shaft in place. Get a longer bolt, and nut. put the nut on the bolt, and screw it in, tack weld or braze it in place , the threads now line up on the wheel. remove the bolt, the shaft.. make your new shaft, drill using the nut as a guide, use the nut to start the tap... the threads should be lined up. cut the nut off and surface off the weld or braze. easy peezy.

 

[pbiYoung]

Why does it have to be threaded. Is there a particular reason you can't just use a round pin?

well, I have a possible way, but like others I would just drill a new hole. and tap.

Remove the existing screw while leaving the shaft in place. Get a longer bolt, and nut. put the nut on the bolt, and screw it in, tack weld or braze it in place , the threads now line up on the wheel. remove the bolt, the shaft.. make your new shaft, drill using the nut as a guide, use the nut to start the tap... the threads should be lined up. cut the nut off and surface off the weld or braze. easy peezy.

I think that is a good idea to assure the alignment with the existing hole in the wheel, but not sure the nut (as a guide) will do much to help keep the bit from walking off the side of the shaft since only half of the hole is filled with shaft.

 

[woodchucker]

well, you don't have to use a drill bit. You can mount the shaft to a 90* fixture and the wheel on top. The 90* can be hung off the front or back of the table, swing the head, then use the mill, and and end mill. The end mill shouldn't wander if you take it slow and clear the chips. Then finish with the tap.

 

[epanzella]

Abandon the half hole that's there. Rotate the wheel to a new location and drill/tap a new hole.