Need Help: Shaft & Keyway machining

[4caseih]

I need some ideas on this project. I haven't machined much in my life but I'm trying to do this project myself if at all possible. I have a shaft and pulley setup out of my p.o.s. vertical mill that is at the end of its life. I've attached a few pictures but they may not do this justice.

The keyway is slopped out on both pieces. The shaft on the gear that mates with the pulley setup is worn down and the fit is very sloppy without having the key installed. I need to build up the shaft on the gear and I will have to bore the center of the pulley.

Major obstacle that I'm not skilled on (mainly the whole project) is making the keyway in the pulley setup. It is not a through hole to use an arbor press and a broach.

I wanted to make a new shaft for the gear but it looks like that was machined all in one piece so will probably have to build up. It was a quick inspection so will have to look further at that to make sure the gear won't press off.

 

[Don B]

The keyway in the pulley could be cut on the lathe using a boring bar with a tool ground like a shaper tool, I think I'd bore the gear out and make a new shaft a little over sized (enough to rebore the pulley a little if that is necessary) then a custom size key could be made big enough to clean up the keyway in the pulley, if you try to build that shaft up with weld it will distort quit a bit.

 

[4caseih]

The keyway in the pulley could be cut on the lathe using a boring bar with a tool ground like a shaper tool, I think I'd bore the gear out and make a new shaft a little over sized (enough to rebore the pulley a little if that is necessary) then a custom size key could be made big enough to clean up the keyway in the pulley, if you try to build that shaft up with weld it will distort quit a bit.

Can you elaborate on how I would use a boaring bar and what a shaper tool is? Again, completely new at this so if possible please dumb it down for me.

 

[Don B]

Can you elaborate on how I would use a boaring bar and what a shaper tool is? Again, completely new at this so if possible please dumb it down for me.

I mean make a tool for the boring bar that would look like a single tooth of a broach, then the pulley would be mounted in the chuck of the lathe, the spindle would be locked in one position, the tool would be aligned properly so when the cross slide is moved it would control the cut, then the saddle of the lathe would be moved back and forth the length of the keyway, and cross slide is used to control the depth of the cut, each pass taking a small cut until the required depth is obtained, slow and tedious but it works.

 

[12bolts]

Dons idea is sound, (and workable), but blind hole broaching can be difficult to get the depth cleanly and clearing the chips.
I would broach a suitable sized bush, open at both ends, (either on the lathe as Don suggests, or with a broach and press) and then bore out the old hole in the pulley and press in the new bush. This would leave you with a clean keyway and keep the blind hole in the pulley.

Cheers Phil

 

[Don B]

Dons idea is sound, (and workable), but blind hole broaching can be difficult to get the depth cleanly and clearing the chips.
I would broach a suitable sized bush, open at both ends, (either on the lathe as Don suggests, or with a broach and press) and then bore out the old hole in the pulley and press in the new bush. This would leave you with a clean keyway and keep the blind hole in the pulley.

Cheers Phil

My apologies, Phil is absolutely right about broaching blind holes, I failed to take note of that in your description, unless their is relief at the end of that internal keyway or a way to provide it, each pass will need to stepped back somewhat and might be a real challenge as a first attempt at keyways, Phil's bushing Idea might be more suited to a blind hole situation.

 

[chuckorlando]

You sure that gear and shaft are one piece? They would be using a whole lotta steel for trash can filler if so

 

[stevecmo]

I assume there is a reason it needs to be a blind hole. If not, drill / bore it out and broach.

If that's not possible I would probably enlarge the keyways in both parts and make a special key.

Steve

 

[kd4gij]

Can you pull the bearing off and snap pic of bouth sides of the gear? The shaft looks like miled steel but gear looks hard. What mill is this out of?

 

[4caseih]

My apologies, Phil is absolutely right about broaching blind holes, I failed to take note of that in your description, unless their is relief at the end of that internal keyway or a way to provide it, each pass will need to stepped back somewhat and might be a real challenge as a first attempt at keyways, Phil's bushing Idea might be more suited to a blind hole situation.

Ok, I like the sounds of the bushing for the pulley assembly.

How thick do i need the bushing material to be when i press it in to not distort where i make my keyway? Im assuming if i dont have some meat there will just shrink the width of keyway.

Here are some better pics of the shaft/gear assembly.

Im not exactly sure how to bore that out to make shaft and press it back together. It just doesnt look to me like the gear is separate.

The shaft isnt very hard. I chucked it up and ran my file on it to clean up where the large bearing slides off. It would appear it cuts pretty easy. Looks like the teeth of the gear itself are all thats hardened.

Ill get a complete pic of the pulley setup so you can see but the pulleys get smaller at the top than the blind hole. So thats why i cant punch it straight through.


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