Grinding wheels and HSS

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Harold_V
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Re: Grinding wheels and HSS

Post by Harold_V » Mon May 10, 2010 5:00 am

knudsen wrote:Is there any special technique to bring an out of round wheel back to life? I inherited an old Craftsman grinder from the early 70's and I have the original wheels with it. Wheels were pretty rough, clogged, rounded corners and the course had a "V" in the center. Probably my father's son messed them up when he was a kid :oops: Bought a couple of Weiler wheels locally for it, but don't like those at all. They are going back to the store to kill someone else. Dang things have a stack of plastic arbor size adapters and have to use them all to get down to 1/2" and it's sloppy. So I remounted the old Craftsman wheels and hit them with a dressing stick, the type described at the beginning of this thread. They are in a lot better shape now, but the coarse one is still out of round. Do I need to just keep grinding more off? They say type "N", if that matters to the fix. I've got a star type dresser somewhere if I can find it, maybe I need to use that? Or a diamond?
Before you make that decision, consider the size of the wheel as it now exists, and how large it was when it was new. As a wheel reduces in size, it acts softer and softer, so it may not serve you well. From the description, I can't help but think yours have seen better times.

If you find the wheels are worth restoring to usefulness, a diamond is the best approach. If you apply it with a rest, you can bring the wheel round easily. You can do the same thing with a dressing stick, although it will not move wheel as quickly as a diamond. Again, use a rest (I rarely advise a rest be used) to keep the stick from bouncing, and to keep a constant depth. Remove small increments, so the wheel makes contact only at the high points. If you try to dress the entire wheel, while you may have success to some degree, it will come at the expense of wasting far more of the wheel. Remember, your sole purpose at this point is to get the wheel back to being round. Once it is, you can then dress it smaller, until you are satisfied with the surface.

A star type dresser is generally the best choice for preparing a wheel for grinding, because it leaves the wheel sharper than other methods, That's due to the method by which it dresses the wheel. They are an impact type dressing apparatus, which removes abrasive bits by hammering. The negative aspect is that unless it is in very nice condition, it will most likely perform poorly, making the process of rounding the wheel very difficult.

Assuming yours is in good condition, with tight rollers, it can be applied with a rest, but it will be the most tricky to use of the three options at your disposal. I'd recommend a diamond, either single point, or a cluster, then a dressing stick to prepare the surface for grinding.

Regards the adapters for the new wheel(s) you spoke of, that they're sloppy isn't really much of a concern. Their sole purpose is to get the wheel near center. Wheels should NEVER be a tight fit on the spindle, for if there's any issues with perpendicularity, the risk of cracking the wheel when the flanges are tightened is very real. However, unless the wheels are well suited to your intended purpose, I'd advise returning them. You will be very best served by making the proper choice for your intended usage. These may, or may not, be suited.

I'm sorry, but the type N you spoke of doesn't tell me anything. If there's a string of information on the blotters of the wheel, letters and numbers mixed, that may.

Harold

knudsen
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Re: Grinding wheels and HSS

Post by knudsen » Mon May 10, 2010 7:57 am

Thanks, Harold!

I will try to revive them, as there's really not much gone. They were never dressed before now. 6" wheels and I guess less than 1/8" gone before I hit it with the stick. I didn't measure after dressing. I took it down just until the "V" groove was gone and the stone was clean all the way around. I was guessing the "N" was a hardness rating, but I don't know. I'll have to see what other markings are on it. I'll go after it lightly with the stick white knuckle gripped to the rest, since that's what I have on hand.

This one has decent adjustable rests on it, and runs smooth as a pickle. I was going to set it up as a general purpose grinder and use my 8" for free hand grinding. Have to ween off the rests. So, either the original wheels restored or the general purpose type I bought should be fine for this grinder. Those weilers are also awfully wobbly, like they're warped. The grinder was shaking so much I pulled the power plug long before it hit full RPM. So, if I keep those or maybe get some with less warp, is it best to center the wheel roughly by hand, then dress it to eliminate the runout?

Harold_V
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Re: Grinding wheels and HSS

Post by Harold_V » Mon May 10, 2010 2:10 pm

knudsen wrote:This one has decent adjustable rests on it, and runs smooth as a pickle. I was going to set it up as a general purpose grinder and use my 8" for free hand grinding. Have to ween off the rests. So, either the original wheels restored or the general purpose type I bought should be fine for this grinder.
For general purpose grinding, I would NOT recommend you eliminate rests. Only for grinding HSS tool bits do I recommend that.
I do recommend regular dressing of the wheels, however. If you have to bear down hard to get a wheel to cut, it's either loaded, or too hard. A wheel well suited to the application should slough off fast enough to remain sharp. Too soft and it goes away rapidly, however. If you keep it dressed, it runs smooth at all times, and should perform far better than a wheel that is allowed to get dull. A little experience using the wheel that way will provide the evidence you need to gain a full understanding of the importance of dressing.
Those weilers are also awfully wobbly, like they're warped. The grinder was shaking so much I pulled the power plug long before it hit full RPM.
Without seeing the wheels, and how they run, it's hard to second guess what is really happening, but don't discount the flanges on the grinder as being part of the problem. If they are stamped steel, they aren't the best choice. If, however, the problem exists in the wheel, that is a good decision.
So, if I keep those or maybe get some with less warp, is it best to center the wheel roughly by hand, then dress it to eliminate the runout?
While the adapter bushings aren't really intended to permanently locate the wheel, I don't think I'd go far enough to suggest you locate the wheel without them. My reasoning is that if you did something stupid,which might give the wheel cause to shift, they would prevent abrupt movement.

Grinding wheels are a delicate balance of tightening just enough, and compensation that is provided by the blotters. A wheel should stay in place by clamping pressure alone, but it should not be tightened such that the load on the flanges is too great. That would be especially true in the case of wheels that may not be dead parallel. When I tighten wheels on my grinder, the only effort is that which my holding the wheel by hand will resist when tightening the nut with a wrench. Wheels never shift, but they are tight enough for secure operation.

Regardless of the direction you choose to pursue, be certain to ring test any wheel that is mounted. That simple function can save your life.

Harold

knudsen
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Re: Grinding wheels and HSS

Post by knudsen » Mon May 10, 2010 4:19 pm

Thank you for answering my questions, Harold. Sorry, I'm not communicating well. I'm leaving the adjustable rests for the Craftsman grinder on it, and once I get it running well, I'll take the rests off my 8" grinder for HSS grinding. All the wheels did pass ring test. I read through all of you grinding threads several times, and learned to do the ring test. I was already in habit of letting them spin up good before getting in front of them. I've seen the result of an exploded grinding wheel up close and personal, and I believe the safety is very important on these machines.

I'll take a closer look at the flanges and the Weiler wheels themselves. I haven't looked at them since they ran wobbly and I pulled them off. Flanges are probably OK, since the Craftsman wheels don't wobble, but you never know. I think they are stamped, but they are pretty thick, at least 1/8" I'd say. They are zinc plated.

I didn't mean say I wanted to remove the stack of plastic bushings and mount the wheel; with the stack of adapter bushings in place, I can move the wheel perpendicular to the arbor a good 1/8" before tightening firmly. It's that sloppy. Of course, once the flanges are tightened up against it, it doesn't move. I have been tightening the wheels as you described. I did think about making a single replacement adapter bushing to replace the stack.

I'll get a closer look and try to figure out what is going on later this week when I can get back out to the shop. I just figured junky wheels and didn't investigate further. Thanks again, Harold, for all your write ups and Q&A!!!

Harold_V
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Re: Grinding wheels and HSS

Post by Harold_V » Mon May 10, 2010 11:38 pm

knudsen wrote:I can move the wheel perpendicular to the arbor a good 1/8" before tightening firmly. It's that sloppy. Of course, once the flanges are tightened up against it, it doesn't move. I have been tightening the wheels as you described. I did think about making a single replacement adapter bushing to replace the stack.
That's exactly what I'd advise, considering the huge amount of run-out the adapters permit. I was thinking much less. What you have is clearly not acceptable. I'd recommend a simple bushing, slightly thinner than wheel width, so it can't influence the flanges, and an easy fit in the wheel, and on the shaft of the motor. It should permit slight tilting of the wheel, in case the bore of the wheel isn't at a right angle to the sides of the wheel. A little clearance (ten thou, max) should provide that very feature.
I'll get a closer look and try to figure out what is going on later this week when I can get back out to the shop. I just figured junky wheels and didn't investigate further. Thanks again, Harold, for all your write ups and Q&A!!!
Happy to be of service. I just hope I have been! :wink:

Harold

knudsen
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Re: Grinding wheels and HSS

Post by knudsen » Tue May 11, 2010 10:02 am

Harold_V wrote: That's exactly what I'd advise, considering the huge amount of run-out the adapters permit. I was thinking much less. What you have is clearly not acceptable. I'd recommend a simple bushing, slightly thinner than wheel width, so it can't influence the flanges, and an easy fit in the wheel, and on the shaft of the motor. It should permit slight tilting of the wheel, in case the bore of the wheel isn't at a right angle to the sides of the wheel. A little clearance (ten thou, max) should provide that very feature.
I took a brief look at the Weiler stones last night, they did not seem to have obvious warp to them. I'll inspect that closer before mounting. I'm guessing it's all the fault of those adapters. Everyone knows you can't make everyone happy, and they are trying to make everyone happy with 4 different arbor sizes. Might be OK if they had one adapter per arbor size, but they stack. I almost didn't even mount them after looking at that. I mounted them, turned it on, then plugged it into AC from afar!

OK, when I make my adapter, I am thinking a harder material would be best. The reason being, in the center of the wheel, there is a 3/4" ID plastic bushing that is more than slip fit. So that one would remain, and I would make a single aluminum or steel 3/4" to 1/2" adapter that is an easy slip fit and a little narrower than the wheel itself, so the flanges grab the wheel. Am I thinking along the right lines? Or should I use plastic? I have steel, aluminum, brass and delrin.
Harold_V wrote: Happy to be of service. I just hope I have been! :wink:

Harold
Most certainly! And thank you again.

Harold_V
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Re: Grinding wheels and HSS

Post by Harold_V » Tue May 11, 2010 1:41 pm

The bushing isn't critical----even a dry piece of wood will serve the purpose (assuming you keep it dry). Were it my project, I'd use anything I had on hand that was near the needed size, including a rem of any kind of plastic.

Most likely won't remember, or haven't been around grinding long enough to know, but wheel centers used to be made of lead. It was perfectly adequate for the purpose, and would likely still be in use today were it not for the trend away from its use for health reasons.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

knudsen
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Re: Grinding wheels and HSS

Post by knudsen » Sat May 15, 2010 6:31 pm

Not happy with the blotters that came with the Weiler grinding wheels. Look like regular paper. So, last night I made new ones from cracker boxes. The blotters on the old Sears wheels looked awful, so while I was making 4, I made 8, so if I go back to the sears wheels, I wouldn't be tempted to use the crusty old blotters. As a model railroader, one thing I can do right is cut cardboard :D

So, tonight I made the bushings of plastic, and the weilers run nice now. I can see a slight wobble side to side, no worst than the sears wheels were, and no runout detected visually. No vibration.

Now I can get back to what I do best, making a mess.

Thanks for your help, Sir Harold!

Harold_V
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Re: Grinding wheels and HSS

Post by Harold_V » Sat May 15, 2010 10:51 pm

knudsen wrote:Thanks for your help, Sir Harold!
My pleasure. :)

Don't hesitate to dress the sides of the wheels if they have run-out that is annoying. That's common practice. It can be quite useful to do so when you're grinding a tool that has a recessed relief behind the cutting edge (like the internal grooving tool pictured). With the sides running true, you eliminate any tendency for the wheel to pick up the tool, keeping it bouncing as it's being ground.
Internal grooving tool 2.JPG
Assuming you make that decision, use a mounted diamond, so you don't load the wheel heavily. Remove only that which is troublesome, and dress both sides. That will insure the wheel runs as free from vibration as you can expect, short of balancing.

Good move on the new blotters. They should have adequate thickness to permit minor crushing, which is their purpose. I've made my share of soap box blotters in my day. :wink:

edit: The issue with wobble is often caused by the flanges. It is for that reason I recommend they be made relatively heavy, and machined, not stamped. The fixed flange should bear on a machined surface (which runs true) and be large enough to perform as a proper register. That way, once you have cleaned up a wheel that doesn't run true (on the sides), it should remount and run properly when removed and replaced.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

knudsen
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Re: Grinding wheels and HSS

Post by knudsen » Sun May 16, 2010 1:03 am

I think I will make new flanges for my 8" grinder. They are not only stamped, but are hopelessly thin. The 6" grinder I'm working on are also stamped, but are really thick, and 2 1/2" diameter. I forgot to check their flatness. I laid the new 6" wheels on a 1/4" glass pane and they appear very flat.

EdK
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Re: Grinding wheels and HSS

Post by EdK » Tue Jul 13, 2010 12:55 pm

I have a 8" grinder that I am going to use for grinding HSS lathe bits. It's a so called slow speed grinder meaning it runs at 1750RPM so it's probably not ideal but it's what I have available. I used it mainly for sharpening woodworking chisels and hand plane irons. Since I don't do nearly as much woodworking as I used to, I'm going to convert the grinder to be used for grinding my HSS lathe tool bits.

I bought the following Norton 8" x 1/2" surface grinding wheels:

38A46-KVBE
38A80-KVBE

I went with the harder wheel since the SFPM is not ideal per this excellent thread started by Harold. I'm wondering if these wheels are going to be usable or did I make a mistake in ordering those wheels?

Thanks,
Ed
Vectrax 14x40 lathe, Enco RF-45 clone mill, MillerMatic 180 MIG.

Harold_V
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Re: Grinding wheels and HSS

Post by Harold_V » Tue Jul 13, 2010 1:53 pm

Ed,
Your logic in choosing the harder wheel is spot on, but it would border on the impossible for me to suggest that they are hard enough to perform to satisfaction without giving them a go. It might very well be that you would have to step up several grades harder to compensate for the slower motor.

If, when you put the wheels to use, you find they slough off rapidly, they are not hard enough. Otherwise there's no harm in using the slower grinder. Where you'll really start noticing the slower speed is when the wheels get smaller. You'll find they won't hold their form, even for light application. Again, no harm, it's just a little bit wasteful. On the positive side, it's a lot harder to burn the tool----which is the reason for slow speed grinding.

Might be a good idea to post your results, so others can benefit.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

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