Bore This Pulley On Lathe Or Mill? Rule Of Thumb?

[joshua43214]

haha!
It looks a bit big for your chuck.
Just stand to one side when you start it, keep the RPM's low and keep the cuts to under 0.010" deep and you should survive.
Don't expect a good finish, a hole that small needs RPM's in the 400 or greater range, but I wouldn't run it faster than 200ish (even that might be scary).
The good thing about boring is that you can stand to the right of the carriage and out of harms way. Those jaws will eat body parts sticking out like that, walk a wide path around them.
Also, do not over tighten the jaws. It is easy to warp the jaw-ways or damage the threads when not enough jaw is engaged. Get them snug plus a bit, not cranked down. You can add some paper between the jaw and the work to increase friction. Boring pushes into the chuck, so it only needs to be tight enough to keep it from slipping.

Projects like this push the limits of both machine and operator will make you more skilled in the end and give you a much better idea of limits. Just keep your heap, use common sense, and don't get greedy.

 

[T Bredehoft]

I think I'd be more comfortable if that were clamped to a face plate instead of the chuck. Yeah, you gotta indicate it, but you should become comfortable indicating things.

 

[MozamPete]

Could you not turn the jaws around so you were jamming on the inside of the pulley instead of chucking on the outside - would allow more of the jaw threads to be engaged and less 'stickly-out' bits.

Now I'm questioning myself of 'jamming' is the correct term - but using them as inside jaws and pushing out on the inside diameter of the pulley.

 

[TOOLMASTER]

If it fits, it chips.

 

[f350ca]

I've never noticed lines scribed on the jaws like that Banjo, do the jaws still clear the saddle when they'r past them? Your only boring the centre so you won't need a lot of clamping force, you'd probably be OK, I do it often on my small lathe, it only has a 4 inch 4 jaw. As was mentioned above can you reverse the jaws and grab the inside if the pulley? Don't over tighten or you could crack the cast iron in tension. You'd be fine here but if your grabbing an inside surface and taking heavy cuts make sure the chuck stays tight as the part warms and expands. Clamping it to the mill table and boring it is a good option too. I often have to do it on pulleys and gears too large for the lathe.
If you have a boring bar that takes HSS tooling you can use it to cut the keyway as well. I cut keyways on the shaper, would be the same only slower. A little front rake and side clearance and your good to go.


Locktite would probably work for this application, I just prefer welding the sleeve in or heat shrinking it.

Greg

 

[Banjo5]

Thanks for the responses.

Peter & Greg
I started out thinking about clamping on the inside of the pulley, but it is sloped and my chuck jaws only came about 1/2 way up the slope, so nothing there.

Tom - I have a faceplate, but have never used it. I have had to indicate the pulley in the 4-jaw too, so there wasn't a lot of gain using the chuck, except I didn't have to design the clamping on the faceplate. I may yet try the faceplate to get around my problem below.

I am having trouble indicating the wobble of the pulley as it lines up with the bore. I got the circumference within a thou at the 4 jaws easily enough, but it sort of wobbles slightly when I run the pulley and look edgeways at the pulley v-groove. I seated it with a plastic mallet before and after indicating, then re-checked, so I believe it's tight against the jaws. I can't quite get my Federal indicator onto the one side of the v-groove, because the jaws are in the way.(see my last photo) If I try to move the indicator toward the headstock and angle it onto the side of the v-groove, the jaws are in the way. I don't have a sideways-operating indicator, so for now I'm stuck. Any suggestions? I could chalk it?!! I thought of making a slip-over sleeve for my existing indicator point to make it longer. That would get me up over the jaws. It doesn't have to be real accurate, just show me the wobble so I can shim out from the chuck. Has anyone done that? Is there a longer point available for my indicator - it's an old Federal? I could buy an indicator with a longer point, but that takes awhile, not to mention $.

Banjo5

 

[joshua43214]

Your best bet will be to try and indicate where I marked the black ring. You will have to pull the ram up on the indicator as it passes the spokes, and hope for the best where the number is. It is OK if the indicator is at an angle, you are not concerned with absolute measurement, only relative measurement - so sine error is not a concern.

 

[Banjo5]

Thanks guys-

Problem solved - I was looking for a longer tip for my Federal gauge in my tools, and I found a new Grizzly indicator with a loooong tip I forgot I had, so I will get that set up and the pulley trued up soon.
Banjo5

 

[uncle harry]

I think the rule of thumb for many of us would be to use whatever machine will get the job done with the least amount of fuss given the tooling we have on hand. I would use the lathe personally.

Does this pulley mount on the drive shaft? If it will get hot from the engine, probably not wise to rely on Loctite.

I would bore it out bigger than the keyway as well, and make the sleeve ~0.001" over sized. If you make the sleeve too tight, it could crack the pulley. Use something softer than the shaft for the sleeve, 1018 is probably a good choice.
Looking at the pic, I think I would make the sleeve about half again as thick as the depth of the keyway. This should give a good balance for strength of the pulley vs sturdiness of the sleeve. I would also pin it after it is pressed in like Chipper5783 recommended over brazing. If you do braze, the sleeve should be undersized enough to allow the braze to flow between the parts.
Either way, you should do the final boring of the sleeve after it is installed.

Cutting a new keyway is a pretty simple procedure on the lathe. There are some videos kicking around of it being done. If you are lucky, you have a parting blade the right thickness to make the keyway. Otherwise you can grind a piece of HSS or drill rod (harden it) fairly easy. Just make sure the tool has very little rake, it will flex a bunch and too much rake will cause it to dig in. I do prefer the lathe for this operation because I can use a square tool blank, and I can angle the tool going into the bore. Angling the tool simplifies grinding a great deal because you don't have to grind a long thin tool to reach the end of the bore. When you are done, the tool can be easily reground into something else later on.
If you are not familiar with the technique, and can't find a video let us know. I have some suitable scrap and a tool I made for keyways and I can post some pics for you.

All excellent approaches. I think that red locktite being compromised by engine heat might imply the the engine had a melt down.

 

[Silverbullet]

If I read your description right this pulley is on the transmission , I would think red lock tite will hold. That said I would bore it to .125 over the bore of the key way . Then I would turn my bushing to .003 under sized, then I would put the bushing in my freezer overnite or longer then I'd set the pulley up in a press and heat the center up about five minutes with a propane torch . I'd have my wife or some one carry the frozen bushing in a foam cup as quickly as she can then quickly press it in as soon as you can set the torch down . most times it slides right in hardly any tite ness . when they warm up and cool down they lock pretty dern tite. Then you can cut the key way in the lathe as explained.