View Full Version : Indicating a v-belt pulley

06-27-2005, 11:05 AM
I need to bore and sleeve the hub on the two step pulley from the countershaft of my Craftsman 12x36 lathe. I can get it in the four-jaw, but I am not sure what surface to indicate from to make sure the bore will be be concentric to the pulley grooves. I guess ideally I would indicate off the inside v surface, but how?

Second question: what is the angle formed by the V? I may be able to get set up to recut the V to make sure it is true to the bore, but it is going to be awful close whether or not the cross-slide will come out that far.


[This message has been edited by gzig5 (edited 06-27-2005).]

06-27-2005, 12:01 PM
What is the purpose of bore and sleeve? Is the pulley not commercially availiable?

Pulleys are made various ways. There are "mystery metal" cast ones where the only "machining" done is the bore finished and a tapped hole for a setscrew. There are cast iron/steel ones where bore and groove(s) are machined. How concentrically accurate one is to the other, don't know. I would suspect the machined ones are more concentrically accurate.

Without seeing the pulley, "how to hold/indicate" is difficult to answer. You would most likely need a long travel indicator.

Is the lathe/four jaw your only option? Do you have a mill, there may be other options there.

The angle of the "V" groove is dependant upon the type/style of "V" belt and the diameter of the pulley.

06-27-2005, 12:11 PM
It is an original part. Two diameter step pulley. I already bought it, so fixing it is the cheapest method. Holding in the fourjaw is no problem. I have a bench top mill as well. What would you suggest there?

There is one on ebay. #7526344861


[This message has been edited by gzig5 (edited 06-27-2005).]

06-27-2005, 12:22 PM

When I bought my Grizzly MD, I needed to replace the motor, and I went through a similar situation. I held the pulley in the four jaw chuck clamped on the smallest pulley flange at the end of the steps. I used a 1" travel dial indicator on a magnetic base to indicate one of the v-grooves. The v-grooves must be concentric to the bore for the pulley run true. I bored the pulley oversize, and then silver brazed a keyed sleeve in the oversize bore. The whole reason behind this is that the origional motor had some sort of bustard size shaft, and the new motor was a .625" shaft. My pulley was cast iron, so the brazing seemed to work well with a steel sleeve. The keyway was broached in the sleeve before it was brazed in. Reason being, that the bore was a blind hole in this pulley. I then drilled and tapped for a setscrew to engage the new keyway. And no, there was not a commercially available replacement pulley. It should also be noted that all turning and boring was done on an Atlas six inch lathe. Don't underestimate those small machines. As far as the angles, Ill let someone else chime in on that one.

06-27-2005, 12:47 PM
How did you indicate the v groove? From the side or straight in? From the side will tell me it is flat, but going straight in for concentricity looks iffy with the angled groove.
A suggestion has been made somewhere else, to indicate off a piece of round stock in the groove. That may work, but it will be clumsy. I found someplace on the web that says the angle of the groove is 40 degrees. I'll double check that.

06-27-2005, 01:04 PM
After seeing the picture, I would try to hold the boss with the setscrew in it in the chuck, then indicate the base of one of the "V" grooves. Since there is two steps I would indicate on one step then check the other, just to see if there is any runout.

If you cannot hold onto the boss, I would change the jaws to ID holding, and try to use the ID of the pulley.

After boring/sleeveing, I would true up the angles by mounting the pulley on a stub arbor.

06-27-2005, 01:10 PM
I read those posts about using the round stock. I suppose it would work, but you are right. It would be clumsy, and I don't think it is necessary. When I indicate a part like this, I mount my mag base on the cross slide, and then manipulate the dial indicator to sit vertically on top of the part. In this case, it sits vertically with the plunger sitting in the bottom of one of the v-grooves. It is also possible to indicate off the origional bore, but I assume that maybe it is buggered up, and that is the reason you want to bore and sleve in the first place. Indicating such a bore can also be tricky because of the internal keyway. If this is clear as muddy river water, let me know again. Maybe I can post some pics of a set-up.

06-27-2005, 02:28 PM
I tried to hold onto the center boss, but it didn't grip well, so I am on the ID. I can indicate off the bottom of the groove, but I wonder if it is true to where the belt actually runs? I guess it just about has to be. I guess I will try the bottom of the groove for concentricity and the side of the groove to make sure there is no wobble. I can then try the round stock in the groove thing. Anything will be a lot better than where I am now, the thing wobbles an eigth inch out at the rim. The outer diameter of this thing is 9+ inches and unless I get creative with the lantern toolpost, I don't think I can reach the outside diameter to true the groove.

The reason I am sweating this so much, is the lathe is pretty light and any imbalance in the drive causes it to vibrate horribly. It came with a stamped steel lawnmower pulley on the counter shaft and it is basically unusable for accurate work that way. Thank you all for your help.

Paul Alciatore
06-27-2005, 04:05 PM
If it has an existing bore that is in good or even fair condition, I would use that.

A quick and dirty way would be to put a piece of shaft with center drilled ends between centers on the lathe with the pulley on it and then tighten the jaws of the four jaw around it. Most chucks will allow a center to be installed inside the central bore. Remove the shaft and centers and bore away.

As for re turning the Vee, I would not unless it is really in bad shape. A slight miscentering of the pulley will not have any great effect on the performance. I doubt that it will be off enough to be out of balance any more than a cast pulley would be anyway and any slight variation in speed will likely be completely unnoticed. On the other hand, many pulleys have just barely enough metal on the sides to hold up. Any reduction may be the last straw and bring on premature failure.

If it is off balance, drill a hole or two in a place where it will not effect the srtength to bring it back.

Paul A.

J Tiers
06-27-2005, 04:18 PM
This is a job for the faceplate, with the pulley held up on blocks.

Even if it ddn't have spokes, I'd be tempted to drill holes and hold it onto the faceplate anyhow.

That way, you can shim etc to get the belt groove running perfectly true. Then you still have access to both the bore and the groove, so you can true both in one setting, and no "lever arm errors".

I made a set of blocks for the faceplate just to do pulleys etc. Holds them off the surface to get working room.

You can get the pulley as true as you need that way. No wobble unless your shaft is screwy.

[This message has been edited by J Tiers (edited 06-27-2005).]

Fred White
06-27-2005, 04:37 PM
The way that will give you most final satisfaction is to mount the pulley as best as possible to a four jaw or a face plate - indicating the bore in a close as possible.

Re-bore the pulley to size.

Make an arbor for the new diameter and mount the pulley on the arbor. Mount the pulley/arbor in a four jaw and tailstock centers - indicated in.

Now take your cutter and true up the v-ways of the pulley.

More work, but it guarantees the pulley is true.

J Tiers
06-27-2005, 11:19 PM
Why not both V and bore while on teh faceplate?

Seems like then there are fewer variables, plus, its easier to drive the pulley for cutting the V if its a bigger one. I've done it a number of times in one setup, and been very happy with results.

Moving to a mandrel has given mixed results, although mostly OK. If too big, the mandrel doesn't want to hold it, you have to drive it from a spoke anyhow, with the chance of forcing it off line.

06-27-2005, 11:58 PM
I rebore junkyard pulleys all the time. In most cases, the v-groves are cut right so don't mess with 'em. They are usually faced on the outer and face edges too.

Chuck the pully up, in a 3-jaw, on the OD and bore the new diameter. Simple as that. Any belt you use will be out more than any tweeking you'll do on a 4-jaw anyway.

Unless you're running the thing at 10,000 rpm, you should have had it done by now! http://bbs.homeshopmachinist.net//biggrin.gif

Paul Gauthier
06-28-2005, 05:56 AM
If it wobbles as much as you say cutting the angles will be a mistake, by the time you get them true your v belt will be riding on the bottom of the groove, you will probably run out of material long before you get it true anyway. If you can get it true you could use a wider belt but that may end up being too big and your belt could come off during operation.

Paul G.

06-28-2005, 10:06 AM

Thanks for the suggestions!
I got it set up. I had to grip the ID of the pulley with the four jaw to get a good hold. I indicated off the bottom and the outside rim of the V-groove, they seem to be concentric with each other and the surfaces of the v-groove. That was what I was worried about, this being a 50 year old cast part. I also indicated off the face of a groove to get rid of the wobble. Everything is less than 0.005" runout. A lot better than the 3/16" wobble I had. I shouldn't need to touch the grooves and don't think I could on this lathe anyway. The center hub is fairly thin, so rather than bore it out for a sleeve, I filled the damage with JB Weld epoxy last night and will bore it out tonight. The burr (big burr!) that damaged the bore formed a spiral groove like a thread as well as opening the bore up. This groove will hold the epoxy well. The JB is at least as hard if not harder than the material the pulley is made of. If for some reason that doesn't work, I plan on making a thin sleeve and can re-bore it later.
I'll try to post a pic of the setup and result.

06-28-2005, 10:20 AM
Just one question...If you are gripping the ID, how will you bore the ID?

06-28-2005, 10:52 AM
Look at the picture in Greg's second post. He is gripping on the ID the step of the pulley. (I hope).

06-28-2005, 02:27 PM
ER you are correct. ID of the steps, OD of the spokes. The jaws on the chuck were a bit big to fit in the 3/4 inch bore on the hub. http://bbs.homeshopmachinist.net//wink.gif We shall see how it turn out tonight.

06-29-2005, 05:23 PM
Well, it worked. It is not perfect but I got rid of 95% of the wobble. Hopefully once I install some of the Fenner link belts, the vibration will all be gone. Right now it runs smooth at low speed but vibration picks up at higher RPM. Thanks again.