Surface Grinding

[ctwo]

I would suggest that the bottom would be ground only once, and that would be BEFORE the top is ground. That way you grind the top parallel to the installation when built. I would use the magnet to hold the chuck to the machine table. That duplicates how it is applied when being used.

It is unusual for the magnetic chuck of a surface grinder to be removed once installed. If, by chance, you remove yours regularly, it may become necessary to regrind the base, but careful handling should limit that need. Draw filing the base when re-installing should be more than adequate.

I think my magnet has an aluminum bottom. My experience with grinding aluminum is that it fouls the stone.

That might be your problem. Most folks don't use stones to grind, they use wheels. Stones don't make very good wheels.

Recommended abrasive for grinding aluminum is not aluminum oxide, which I suspect is what you're using. For aluminum, a hard silicon carbide wheel would be the choice. Please note that the green aluminum oxide wheels are NOT that choice. The wheel you'd benefit by using would most likely be shiny black in color. The green wheels are usually very soft, which is exactly wrong for aluminum.

H

I think the idea in not turning on the magnet when grinding the bottom is so the chuck is not distorted due to surface anomaly on the chuck top.

I have not ground any of the table or chuck. I did the 5 block test just to see where we are as-is.

I need to make/buy a wheel puller, and I'd like to make/buy a couple more spindles, and then set up for balancing a small set of wheels.

[TimTheGrim]

If you’re looking for wheel adapters I’ve bought 3 of these and think they’re great.

https://www.ebay.com/itm/234575867145?e ... SwsqNil~Kd

[Harold_V]

I think the idea in not turning on the magnet when grinding the bottom is so the chuck is not distorted due to surface anomaly on the chuck top.

An interesting concept. I suspect that that doesn't happen, as the force of the chuck isn't great enough to distort the body, due in part to its thickness. Could be wrong, however. I don't know that you'd want to just let it sit and be ground by its own weight, as the table travel would give it cause to move, even if the wheel didn't. Clamping pressure, adequate to restrain the chuck, would be a source of distortion, so I'm not convinced that not using the chuck itself wouldn't be a good idea. This is not a topic that I've ever had to address. When one works in industry, those matters are generally not in one's control. We operate the machines, we don't maintain them. Never in my years in the shop did I ever remove a chuck, but I sure did surface many.

I have not ground any of the table or chuck. I did the 5 block test just to see where we are as-is.

From my perspective (not suggesting I'm right) I would not worry too much about the 5 block test and just resurface the chuck on occasion. They get worn from endless stoning and use, although in a home shop environment that isn't likely to be much of a problem. Even in industry, the chuck may not be resurfaced but once/year, more or less. You know when it's time if you operate the machine regularly. My expeience is that a half thou was usually more than enough to restore the chuck to complete flatness (or, maybe better stated, a common plane).

I need to make/buy a wheel puller, and I'd like to make/buy a couple more spindles, and then set up for balancing a small set of wheels.

I suspect you mean wheel hubs, not spindles. On that subject, it isn't exactly common for the small sizes to offer the ability to balance the wheel. Larger hubs have weights that can be moved about in a captive groove, for balancing. Cylindrical grinders are generally so equipped, but I've not seen that for cutter grinders, nor small surface grinders. All depends on the size of the hub. I trust your machine uses the 1¼" bore wheels?

H

[ctwo]

The wheel hub adapter is Cat. No. 24-820. Not sure if that's the same as F320.

Large OD is 2-15/32, not sure of taper. Probably need to start with a wheel puller.

http://vintagemachinery.org/pubs/1141/27043.pdf

[Harold_V]

The wheel hub adapter is Cat. No. 24-820. Not sure if that's the same as F320.

There are differences from manufacturer to manufacturer in spindle design, so make sure that what you buy will fit your specific spindle. The hubs for my Cincinnati #2 cutter grinder do not fit my B&S surface grinder. Both can mount the same wheels.

Probably need to start with a wheel puller.

They are generally steep enough that they readily release by just tapping lightly. Needless to say, don't tap the wheel---tap the steel portion of the hub. A piece of aluminum will avoid any denting. Keep a hand on it if the restraining screw/nut is removed as they tend to pop right off. If yours hasn't been removed in a long time, it may be rusted/glued in place. Hard to say. A puller may be necessary if so.

H

[earlgo]

When I was tooling up the Delta Toolmaker, Sopko in Cleveland was the place to buy adapters and pullers. Their adapters have an internal thread and the puller screws into it and pushes on the end of the spindle. The puller bolt head is the same as the spindle nut, so the wrench supplied with the puller fits both, and the other end of the wrench fits the spanner holes in the adapter. Works every time.
www.wmsopko.com

Regarding grinding the mag chuck: you fellows sure do like to sort the fly dung from the pepper. What hobbyist needs flat within millionths? I shimmed ( GASP!) my mag chuck to the base plate and only got within .0007 corner to corner. It will have to do for the junk I make.
--earlgo

[GlennW]

If you decide to make a puller, the proper thread is .984"-16 right hand.

[Harold_V]

Regarding grinding the mag chuck: you fellows sure do like to sort the fly dung from the pepper. What hobbyist needs flat within millionths?

It's a reflection on past experiences and demands. It's difficult to do work to tenths when there's more error in the machine/equipment than the tolerance allowed.

When I operated my commercial shop, it was not uncommon for me to bid on and produce parts/tooling with .0002" tolerance. There were a few occasions where I no-bid a job with only .000050" tolerance. That was way beyond my ability due to the restrictions of my facility. At Sperry, where a secondary standards lab was at my disposal, one job I handled had only .000020" tolerance. That's the real world, folks. Like it or not, there are such restrictions.

I agree that the home shop rarely has need for exceedingly tight tolerance work, but it sure is nice to understand how one would go about performing at such a level. When you have a clear understanding you can accomplish the task by choice, rather than by chance.

H

[NP317]

I am interested to learn what kind of tolerances the James Webb Space Telescope was built to!
With temperature extremes spanning >450F, the challenges were/are extraordinary.
RussN

[ctwo]

Thanks for the info, Folks! I had found sopko. They list an adapter for the older grinder, and they list both LH and RH thread. So I think mine is LH and even though the adapter is a little smaller OD, it might work.

Sorta like Harold said, it's work enough to get it right without having the machine defeat you before even starting. Besides, who doesn't like to flex their abilities?

I saw an old video where, after sparking out, red rouge is applied to the wheel followed by bees wax (alternating 2x), then regrind without moving Z - for a very nice surface finish. May take a couple few passes, starting on opposite sides. I have the materials to see how that works. Following my grinds with lapping is a bit of work to get what's desired.

[Harold_V]

There's two theories of surface grinding. As I have pretty much always been interested in surface finish quality, I don't subscribe to the one whereby one takes a shallow depth of cut but uses a large stepover of the wheel for each pass. Instead, my preferred method is to take a reasonable depth of cut and a narrow stepover, something like .03/.05" per pass. By this method, a superior surface finish is generally produced. The corner of the wheel removes the bulk of the metal while the balance of the wheel does the sparking.

If you choose to use this method, you'll discover that as the wheel breaks down, the cutting edge move along the wheel face, but it gradually builds a taper. When the taper becomes extreme, surface finish degrades, so it's time to dress the wheel, which restores the quality of the grind.

Even using this approach to grinding, I still take what would be called a finish pass. I may or may not dress the wheel for that pass, depending on the quality of the grind being achieved. The final pass is generally only a few tenths in depth, which goes a long way towards improving surface finish. If the cutting edge has degraded somewhat, I often take the finish pass in the opposite direction, taking advantage of the sharp corner of the wheel on the opposite side.

Note that the grade of wheel plays a minor role in surface finish. A finely dressed 46 grit wheel is very capable of yielding a respectable finish, while an 80 grit wheel has a tendency to cut much hotter.

Be certain to match the abrasive type and hardness with the material being ground. That makes a huge difference in performance.

H

[ctwo]

There's two theories of surface grinding. As I have pretty much always been interested in surface finish quality, I don't subscribe to the one whereby one takes a shallow depth of cut but uses a large stepover of the wheel for each pass. Instead, my preferred method is to take a reasonable depth of cut and a narrow stepover, something like .03/.05" per pass. By this method, a superior surface finish is generally produced. The corner of the wheel removes the bulk of the metal while the balance of the wheel does the sparking.

If you choose to use this method, you'll discover that as the wheel breaks down, the cutting edge move along the wheel face, but it gradually builds a taper. When the taper becomes extreme, surface finish degrades, so it's time to dress the wheel, which restores the quality of the grind.

Even using this approach to grinding, I still take what would be called a finish pass. I may or may not dress the wheel for that pass, depending on the quality of the grind being achieved. The final pass is generally only a few tenths in depth, which goes a long way towards improving surface finish. If the cutting edge has degraded somewhat, I often take the finish pass in the opposite direction, taking advantage of the sharp corner of the wheel on the opposite side.

Note that the grade of wheel plays a minor role in surface finish. A finely dressed 46 grit wheel is very capable of yielding a respectable finish, while an 80 grit wheel has a tendency to cut much hotter.

Be certain to match the abrasive type and hardness with the material being ground. That makes a huge difference in performance.

H

My machine is light, so depth of cut is limited. I do roughing at a bit less than half wheel thickness. I have not seen large final-pass stepovers promoted. 0.100" is visible on my machine (and I do note where the wheel sparks). I read wheel options are more varied than carbide inserts. Lots to sink into.

Below is a sine bar I acquired from this forum, many years ago. I roughed the top and sides. I'm quite pleased, and who doesn't like photos?



Any guesses on how long before I'm setting up to grind the cylinders?

Not soon...