HELP

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Mr Ron
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HELP

Post by Mr Ron »

I made 2 of the grinding wheel adapters shown in the sketch. My problem is getting them concentric with the shaft on the grinder. The closest I have been able to get them was with a .005 TIR. I made the bores in the adapters about .033 larger than the shaft, to be able to use the set screws to get them concentric. I measured the shafts on both ends and they are not identical. Is there a procedure to center the adapter to the shaft? I am using a dial indicator on a magnetic base.
GRINDER WHEEL ADAPTER.jpg
Mr.Ron from South Mississippi
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BadDog
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Re: HELP

Post by BadDog »

I think you're working past the point of diminishing returns. The motor shafts aren't perfect, and you need some clearance to fit. But the main answer is that you need to dress the wheel once installed, at which point 0.005 TIR becomes meaningless. I never even measured TIR on my adapters when installed. Just installed them and dressed the wheel... about 5 or 6 years ago...
Russ
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Harold_V
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Re: HELP

Post by Harold_V »

It's hard to understand why you can't get closer than .005", but I'd certainly explore the reason why before settling. If you have any intentions of mounting a diamond wheel, you wouldn't want to live with that amount of error.

A tip that should help.

Don't loosen the screws such that they are free. Back off (just relax the pressure) the low set and snug the opposite sets, which will make minor changes in the reading. Just keep repeating that until you are happy with the results. Keep in mind, because your support is @ 120° intervals, you have to adjust two sets of screws in order for the part to move the proper amount in the given direction. One set will require more or less than the other, depending on where the low/high spot is located.

I assume that the motor shafts don't run out? If not, with the amount of clearance you've provided, there shouldn't be any reason why you can't bring the adapter true. If, however, the shaft is bent, that may not be true.

Depending on your patience, and the quality of the bearings in the motor, with the three sets of screws, you have the capability to adjust the adapters such that they won't register runout with a common DTI. Settle for the level of precision that makes you comfortable, assuming you have no intentions of mounting a diamond wheel. I also recommend you get the face true, as a wobbling wheel is not very useful, and will require dressing of the wheel sides each time it is removed and replaced. Get the flange true and there shouldn't be much change, in any. That's assuming you mount the wheel with the same side towards the fixed flange.

Harold
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Sunset Machine
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Re: HELP

Post by Sunset Machine »

I'd be afraid the setscrews would rattle loose. The .005" is bothersome, are you turning this on a mandrel? Do the bore in the 3-jaw first, then pop it onto a carefully made arbor (tight fit) for turning the ODs between centers.
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BadDog
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Re: HELP

Post by BadDog »

The original post indicates that it is a HF 8" grinder. So my expectation was that it would be used much like my 7" Baldor with the adapters. That is, just to mount a cheap/common surface grinder wheel with a wide range of options. My adapters were turned concentric/square (one setup) for the wheel bore, flipped and finished in the 3 jaw. So the presentation to the wheel was as close as my lathe can produce with some clearance for the bore to prevent binding. That bore clearance alone guarantees run out on the wheel until dressed. And there is clearance on the shaft itself. And I didn't take any undue pains making the backside work perfect to the wheel side once flipped, I just used the jaw faces to locate. I don't recall having any concern about run out of the on the shaft, and after dressing mine runs as smooth as any grinder I've ever seen.

All that said, what am I missing? For a set of common grinder hubs, why would there be any interest at all in reducing run out below 0.005 given that the wheel needs hub clearance, is not itself a high precision dimensional item and must always be dressed after install? And unlike a surface grinder (etc), such a hub won't remove and remount intact and relatively accurate to the wheel dressing if swapping wheels. If it's just an exercise in what he can achieve using a HF bench grinder, then full speed ahead. But this seems excessively fiddly for typical application.
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BadDog
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Re: HELP

Post by BadDog »

Put another way, most folks seem to say that for a non-adjust-true 3 jaw chuck a few thou run out on hard jaws is to be expected just due to required clearances for operation and realities of a cumulative tooling stack. So why would 0.005 be of concern on a bench grinder adapter hub? An A6 (IIRC?) hub used for a diamond wheel on a "carbide grinder" or a surface/tool grinder hub would be a very different matter. And perhaps if someone did want to mount a diamond or CBN wheel on a bench grinder, then again, it would be a reasonable concern, but all tolerances including the hub/hole interface would be tightened up as well. But that was not where my thoughts went relative to the OP.
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GlennW
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Re: HELP

Post by GlennW »

BadDog wrote:All that said, what am I missing?
Explained on this page.
http://www.chaski.org/homemachinist/vie ... 74#p345274
Glenn

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Mr Ron
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Re: HELP

Post by Mr Ron »

The HF grinder is brand new. I never used it with the wheels supplied. The shafts run true with no discernible run-out. I don't intend to use diamond or CBN wheels, just common surface grinder wheels. I used the original HF flange washers to hold the wheels on my garden tractor cart; a perfect fit. That's all they were good for. The HF grinder runs smooth with no vibration. I don't want off- center adapters to introduce any vibration. I machined the adapters using a 4-jaw chuck dialed in with almost zero run-out, so I know the adapters are run-out free. It's just a matter of getting them to run concentric with the shafts. I spent an hour trying to get the concentricity, but couldn't get it better than .005 TIR. I guess I will have to give it another try. The set screws I'm using are 10-32 cup point. I'm trying to get the adapters not only as TIR free as possible but also eliminate any "wobble" of the flange. Adjusting 6 screws seems a daunting task. Thanks for all your assistance.
P.S. I made the adapters as shown on this post, not the original ones shown in an earlier post.
Mr.Ron from South Mississippi
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BadDog
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Re: HELP

Post by BadDog »

Headed out shortly, so I just skimmed over that and remember it (I think) in general. Mostly what I got is what I said. For most bench grinder wheels, the clearances required make limited run out not a huge issue. I did acknowledge that diamond or CBN wheels would certainly be an exception, and noted in the thread that an additional consideration would be for damaged shafts. But I didn't see anything supporting sub 5 thou run out other than in limited application, and I saw nothing to indicate that this was an exceptional application. In any case, I don't recall paying any particular attention to installed run out or tight tolerances on my adapters, and I would be surprised if they were any closer than the OP's 0.005 TIR. I've been very happy with mine, and if he's not mounting diamond/cbn/etc special wheels (or other exception), and not interested in this simply as a learning exercise, I suspect the OP would be as well served by simply mounting the wheels, dressing, and getting on with things. I lack by huge margins the experience you and Harold bring, so I'll take another look later when I have more focus to see what may be eluding me on the linked thread. Maybe I just got lucky, one success certainly doesn't validate my process.
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earlgo
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Re: HELP

Post by earlgo »

It is a screaming PITA to try to center things with 3 set screws. Worse in sets of 2. This is why I have not seen an independent jaw 3 jaw chuck. All that I have seen have 4 jaws. With 4 contact points you get to move things 1 pair of points at a time. i.e. right to left, then top to bottom, then repeat.
Were I you, I'd plug 2 sets of holes and drill 3 more sets at right angles to the set you saved.
Even so you will have difficulty centering the adapter and then making sure the shaft axis is parallel with the wheel axis. i.e. no wobble in addition to no eccentricity.

I think that a better solution would be a wheel adapter similar to the Q-D Bushing hubs made by Browning.
http://www.regalpts.com/products/drive- ... fault.aspx
If these are made carefully and snug, then the tightening of the tapered bushing into the hub squeezes the shaft into a no slip condition. The difficulty might be in making one small enough for your application. It would be entirely custom in your case.
My dad made one of these years ago and it really worked and ran true, but not for a wheel adapter.

--earlgo
Before you do anything, you must do something else first. - Washington's principle.
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Harold_V
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Re: HELP

Post by Harold_V »

Sunset Machine wrote:I'd be afraid the setscrews would rattle loose.
You can put that fear to rest. I've used that very design since 1967 and have yet to experience any problems. I used 10-32 cup point socket head sets.

In regards to the effort required in setting three point suspension, it's something a machinist simply must be able to do. You learn to make miniscule adjustments. Once you understand the concept, it's not hard.

Harold
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GlennW
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Re: HELP

Post by GlennW »

BadDog wrote: I lack by huge margins the experience you and Harold bring, so I'll take another look later when I have more focus to see what may be eluding me on the linked thread. Maybe I just got lucky, one success certainly doesn't validate my process.
It's clear what I used and suggested for mounting vitrified surface grinder wheels on my 8" bench grinder.

I have no intention of ever running a diamond wheel on my bench grinder.

I view this thread as a waste of time and effort for vitrified wheels on a bench grinder.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
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