Surface Grinding

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ctwo
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Re: Surface Grinding

Post by ctwo »

ctwo wrote: Tue May 16, 2017 12:07 pmI've been thinking of a surface grinder...
Rockwell Delta 5x10 - the price was right. The table pad measures 6 x 13.5 and I was tempted to order a 6x12 mag chuck, but went with a 5x10 anyway.

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ctwo
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Re: Surface Grinding

Post by ctwo »

If you look close at the vise jaws, you can see little ripples. Where should I be looking? If they traverse several passes, that would seem to indicate the table is bouncing rather than something with the spindle.
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GlennW
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Re: Surface Grinding

Post by GlennW »

I'd be looking at wheel truing/dressing or grinding technique.

Grinding is as much an art as it is a science.
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ctwo
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Re: Surface Grinding

Post by ctwo »

Well that is promising. Of course I accept ignorance. It came with a diamond wheel dresser mounted to a block, with a (reverse?) slot that makes it stick out horizontally. ?? And I did not bother using it for my test grind. Can't wait for the mag chuck... UPS tracking says Wed will be a late evening...

Oh, and the tenths knob has some stiction issue. It's just a screw that pushes the spindle side down, and it looks like the motor/spindle frame pivots against the weight of the motor. Basically I want to dial in a tenth and it breaks loose and moves 4...
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Bill Shields
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Re: Surface Grinding

Post by Bill Shields »

if someone has not already advised...put it over in a corner where it is very removed from your other machines.and have the 'exit path of the wheel' pointed toward a wall or catch box with a vacuum of some sort.

there is nothing that comes off a SG that is of any interest to your other machine's life...
Too many things going on to bother listing them.
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ctwo
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Re: Surface Grinding

Post by ctwo »

I have a 6x25 foot space between the garage and house that now has the eves brought together. It is enclosed except for the gate. It is the beginning of my grinding/welding/fab area.
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Harold_V
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Re: Surface Grinding

Post by Harold_V »

I suspect that you will have issues with surface finish with that grinder, and that's due to several factors. It isn't very rigid, and it is most likely not three phase. To hope for exceptional results from those two conditions is a rather ambitious expectation.

Check the wheel on the hub for tightness. It should be snug enough to restrain the wheel so starting torque can't cause movement. Do NOT over tighten, and don't install a wheel without ringing first, nor one what has no blotters. They aren't there just for providing data about the wheel---they perform a function of spreading forces on the wheel to eliminate point loading, often resulting in cracking the wheel.

I feel an obligation to say that a wheel that doesn't ring should be destroyed so there is no future risk of you, or anyone, installing the wheel and spooling it up. ANY wheel that doesn't ring should be destroyed immediately, and that includes a new one right out of the package.

If your machine was transported and then operated without dressing the wheel, that may be part of the reason for the irregular surface. It takes far less than .0001 irregularity in a wheel to create the surface you see (.00001" eccentricity will generally translate in to a wavy surface). It can also be caused by a loaded wheel, or one that is in need of dressing due to wear (a dull wheel). Diamond dressing the wheel is all important to the results you achieve. Do not expect a great surface finish from that machine. It's highly unlikely, especially when grinding soft materials.

There are two schools of thought in how one grinds. I subscribe to the one whereby a respectable depth of cut is taken (a few thou when roughing) but a minor stepover is taken for the cut (somewhere between .020"/.050") per pass. This results in a shoulder of the wheel doing the stock removal, while the balance of the wheel does the sparking, most generally resulting in a better finish. The other school of thought requires that a shallow depth of cut be taken (a thou or less) but rapid advances of the wheel per pass (less than the wheel width). This system of grinding usually results in an inferior surface finish. Its only redeeming feature that I can see is that less of the wheel is removed when it's time to dress. Both systems appear to be similar in stock removal rate.

Rapid table movement helps avoid surface burning. I do not endorse dry grinding. The addition of coolant (assuming the machine is built accordingly) makes an immeasurable difference in the outcome.

H
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ctwo
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Re: Surface Grinding

Post by ctwo »

With all that in mind, perhaps I should be happy with what I'm seeing.

The guy said, "it's not a two tenths machine, but it could be a two tenths machine..."

And I said, "That's OK, three tenths will be just fine..."
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Harold_V
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Re: Surface Grinding

Post by Harold_V »

ctwo wrote: Mon May 16, 2022 4:31 pm With all that in mind, perhaps I should be happy with what I'm seeing.
There's room for improvement, and that will be easy if any of the conditions mentioned are the problem in regards to the wheel and how it is addressed. As for the condition of the machine, you may not have any options, but don't assume you can't improve on what you see. There's nothing quite as satisfying as a well ground surface that is flat and parallel.

I really like what Glenn said. Grinding is as much art as it is science. I used to work with a guy who could create surface finishes I couldn't match, yet we both operated the same machine on opposite shifts. Technique can be everything.

Love to hear more from you after you've done a little with the machine. I can only assume that you understand that the installed magnetic chuck will require a cleanup pass. To hope for it to be parallel is a tall order. That condition is typically accomplished by grinding in place after being carefully installed.

H
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ctwo
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Re: Surface Grinding

Post by ctwo »

Hopefully I don't gouge up the chuck.

I saw a (popular) video where the guy put the diamond dresser pointing toward the stone, slightly to the left side. Looked like if it caught it would rotate the dresser into the wheel.
Anyway, I've seen the diagram of where to place the dresser. I think the Suburban Tool channel has some decent and basic videos I can rewatch.

And I'm reading more http://conradhoffman.com/grindbalance.htm
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GlennW
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Re: Surface Grinding

Post by GlennW »

Sweep the mag chuck with a DTI to determine where it is low and by how much. That way you won't have to take 13 passes or end up too deep.

Grinding chucks is a PITA because of the large fairly soft surface, and tends to load the wheel up a bit by the time you get all the way across making more heat.

Pretty sure I used a 46H or I wheel.

I switched to wet grinding and never looked back...then you just get tired grinding chucks rather than frustrated with it!
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
jwmelvin
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Re: Surface Grinding

Post by jwmelvin »

ctwo wrote: Mon May 16, 2022 6:43 amRockwell Delta 5x10
That looks like the later "TG-3" grinder, aka No. 24-150, -151, -152 (the one I have is from 1972), for which Rockwell specifies a 6x13" capacity. (7" transverse travel and 13.5" longitudinal travel).
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