B Mann wrote: ↑
Sat Dec 28, 2019 11:38 pm
I guess I was leaning toward a weld up and machine down because I have been welding for decades and it is what I am familiar with. The mill and lathe are new tools to me.
Chuckle. Yeah, when the only tool you have is a hammer, everything looks like a nail.
OK, the oversized bushing sounds good. I am thinking I would want to clean up the pulley and press the bushing in that. Hard to see in the pictures, but the center of the pulley is worn so thin it is beginning to crack.
You actually have a respectable idea, at least in my opinion. But what I'd do is bore to clean up, then silver solder a sleeve inside. That should restore integrity. Pressing in a bore that is already compromised isn't likely to yield success (the crack you spoke of). Make sure the crack is clean, so solder will penetrate, assuming you flux well.
The sleeve bore would be well undersized, so you could then mount the pulley and bore to size, ensuring concentricity and perpendicularity. It stands to reason that getting the entire bore free of oil and dirt would be important, but I suspect that, as a weldor, you know that already.
In your succeeding post you said that the housing is tapered, so there's no way to grip it. I agree, and it's obvious from looking at the picture, although that fact had escaped me.
That said, I highly endorse the idea of using a boring head (suggested by carlquib), mounting the part in a mill. it can be clamped to the table, although that may take a little creativity, as your clamps will get in the way of the boring head. If the flange is parallel to the mounting surface, it's a perfectly acceptable way to make the setup. Once setup, you can find center of the shaft with a DTI, then turn the shaft to the desired diameter. In this case, you'll have to be happy with the material from which the shaft is made, as you now won't be able to use a hardened sleeve. Considering the condition of the pulley bore, this is likely the better choice, however.
I am familiar with oilite bearings. It sounds like a good idea. Like you said it is a metal on metal situation. I am not sure how thin you can go. if I clean up the shaft and pulley I am looking at about .170 room. By the time I put a bushing in the pulley, how thin of a oilite bearing can I use before I destroy it just trying to machine it???
All depends on how you hold the bushing. It is highly recommended that you have material longer than the bushing length, so you can grip the material without introducing any stress. You'd grip the piece, then drill (undersized) then rough turn. You would then bore to size, and turn to size. I'd recommend a couple of thou press fit in the pulley, keeping in mind that the thin wall of the bushing is going contract when it is pressed in to the pulley. You'd want to start out with a bore size that is about .003" larger than the shaft size (which has been polished smooth). The bushing will collapse at least 1½ thou, leaving you with at least a thou clearance. I suspect it is important that the assembly be free wheeling at speed, so don't shoot for a tight fit with the pulley on the shaft.
Don't try to work on the bushing once it has been parted. Thin walls such as this don't respond well to being gripped unless you can grip them uniformly (like with the proper sized collet, or pie soft jaws). That's why you make it in one operation, then part it off.
You should be able to make a bushing with a wall thickness of .03" and expect acceptable results. If you find it can be thicker, all the better.