Thrust Bearings

[rblusthaus]

Hi all

The kind of thrust bearing on my band saw, ya know, the kind that is solid with no hole in the middle, that the back of the blade rubs against during a cut, is not the kind of thrust bearing I am asking about.

The other kind, which has a hole in the middle and is sold by internal dimension, is where my Q pertains. With this kind of thrust bearing, in use, does the shaft extend thru the entire bearing or does it just butt up against it? In other words, can the thrust bearing be positioned anywhere along the length of the shaft or must it be at an end of the shaft? If it can go anywhere along the length of the shaft, how does it connect to the shaft, by set screw?

Russ

[dcarter636]

I'm having a hard tiime visualizing your question; got a pic?

My delta BS uses the outer race of a ball bearing held on the end of a stepped shaft by a screw, all of which is moved fore and aft via another screw.

[TDHofstetter]

Russ, I think I've got in my mind what you're talking about - unless I'm mistaken, what you're asking about is a "shoulder bushing", sintered bronze, shaped like two cylinders butted end-to-end, with one common bore. Typically, the shaft will slide entirely through such an animal, and someplace along the shaft will be an enlarged spot with a machined thrust surface that'll meet the shoulder on the shoulder bushing. The bushing will have a fixed mount on the machine, and won't turn with the shaft.

Optionally, it'll be a fixed mount on the SHAFT, but that's far less common; it's tough to get one to stay in one spot on the shaft - they tend to "walk", especially when they're subjected to a thrust load.

EDIT: What'cha got going? Ya got my curiosity piqued.

[rblusthaus]

A pic of what I am taking about is here

www.mcmaster.com/#thrust-bearings/=7l6uy3


Tim

I am in the final stages of my design for a treadle lathe. I have been working from a variety of other plans that I have found, and they all used a thrust bearing like the one above. These plans mount the bearing in a non thru hole in one of the vertical supports and at the end of the shaft. It appears to me that the shaft just butts up against the bearing and does not go thru - although, if this is the case, I cant understand why the bearing has a thru hole to begin with.


I would like to have my shaft go thru the bearing so that I can mount a grinding wheel outboard.

I understand what you said about the shaft having a raised portion to bear on the thrust bearing. Do you think I could use a stop collar, as the shaft material I had planned on using was one diameter the whole way, in a D profile for set screws.

What do you think? Any other methods that you can think of?

[TDHofstetter]

Ah - Ok, that'd be a radial thrust bearing with balls or needles. These'd keep the tailstock from pushing the spindle through the headstock. A bronze shoulder bushing would work just as well, provided you kept oil in it.

One very good reason to be sure the shaft goes through the bearing is ensurance that the bearing's centered. If it's not, it'll wear somethin' terrible on the end of the shaft.

A stop collar would work fine, provided it's really secure. A single-setscrew collar wouldn't be rigid enough; but a two-setscrew collar would be a lot more robust. The clamp type with one or two machine screws that cross the shaft would work even better. The single toughest style would be a large steel sleeve with a "split cotter" to hold it in place.

Of course... the shaft COULD be modified, either by turning a tenon on the end to fit through a smaller thrust bearing (which would leave a much narrower shaft to mount the wheel) or by building up a collar around the shaft with weld bead, then machining that bead down to a smooth & true surface for the thrust bearing to ride against. Either would be a lot more complicated, though.

Do be advised that any foot-powered grinder is DIFFICULT to use at best; I used to have a treadle grinder with a 24" wheel. Pumping the thing took everything I could do, then I wasn't nearly steady enough to actually sharpen anything - it takes a helper to do one or the other (preferably the treadle pumping).

[rblusthaus]

bronze shoulder bushing

I looked them up - it would fit around the shaft and has a lip to bear on the edge of the hole it is set in.

When using this setup - I still need the stop collar as well, right? That is where the thrust resistance comes from, right? Seems easier to use bearing as they are permanently lubricated or the equivalent. Although, probably does not matter, at the speeds I am likely to hit.

machining a larger shaft to size would obviously be the best way, but I do not have the ability. Gonna look around for a machine shop, must be one nearby.