Carbide tool grinders.
#1
There is a set of videos (5 parts) on YouTube that someone made showing how he made some improvements on his "carbide tool grinder" that a lot of home/hobby metalworkers have. It is a clone of a Baldor "500" grinder.

http://www.youtube.com/watch?v=lSi3lucyR...B4341A8C46

I viewed those videos right after I purchased my grinder some time ago and set about doing the same operations on it. While it did improve the performance somewhat, I still had a pretty good vibration in my grinder at times as the spindle was speeding up or slowing down when turned on or off. At certain RPM’S the grinder would shudder as it passed through its "natural frequency". It was bad enough that it would cause a brand new incandescent bulb in the light fixture to burn out the filament every time I turned off the grinder. I quickly learned to use a CFL bulb. (lol)

At that time I basically skimmed the surfaces on the hubs to true them up, and touched up the trunnions with some sandpaper on a flat surface and called it good enough. Well, it wasn’t “good enough” after all. So recently I tore the grinder completely apart to give it a more serious effort. These are just a few of the things I noticed and tried to improve on…

I’ve been told that the reason for many failures of these Asian electric motors is because the factories often to not properly insulate the stator windings (if at all) as a cost saving measure. So I opened mine up to have a look. While it did have a very light coating of varnish on the coils, they certainly were not bonded together in a solid mass like higher end electric motors. I called a few local electric motor service companies in town and found ONE that was willing to clean up the stator assembly, dip it in a heated varnish tank, and oven bake it afterward to cure and harden the insulation. That is… IF I removed the stator from the motor housing myself. (Press fit.) Estimated cost $30 - $40.

To try to save a few bucks, I thought I would give it a try myself and bought an aerosol can of clear insulating varnish (about $6) and started spraying. It was thin. Like water. Let it dry, and spray another coat. And another. And another….

[Image: th_P4110133.jpg]

Growing tired of this, I did a little more research and found out that there were a couple of different formulas for this insulation and moved up to the next higher viscosity, (Red) A few more coats of that and I was finally satisfied that the coils were sufficiently saturated and held tightly together. Time will tell how it holds up. I did have pictures of all of this, but seem to have lost them. Smiley-signs081

The next issue was the spacers used for locating the hubs on the motor shaft. Roughly machined and WAY oversized on the ID. They certainly didn’t help in keeping anything balanced by sitting off-center on the shaft. (0.747” OD.)

[Image: th_P4080127.jpg] [Image: th_P4080129.jpg]

I turned some new spacers that are a snug slip fit on the shaft. No more flopping around and wobbling.

[Image: th_P4080128.jpg]

Even after truing up the original hubs previously, I wasn’t happy with them because I could still see voids in the castings. The mounting holes weren’t drilled very accurately either and the bolt circle pattern was off kilter, making it hard to bolt on a grinding wheel. I had purchased a diamond wheel a long time ago to put on the grinder for touching up carbide bits, but I never did install it. The diamond wheel is 3X heavier than an aluminum oxide wheel, which is a lot of mass to spinning at 3400 RPM. So I set about making some new hubs from some solid 6061 round stock.

[Image: th_P4030119.jpg]

You can see the voids in the lower two original hubs. [Image: th_P4010119.jpg]

I went back and squared up the table parts and the wheel housings on the mill this time, making sure all the surfaces were flat / square / parallel to each other. The housing surfaces were going off at different angles causing most of the problem tilting the tables up and down. I also partially counter-bored the wheel housings around the mounting bolt holes because they are so close to the edges, the bolt heads rubbed on the sides making it nearly impossible to get a socket wrench on them.

[Image: th_P4070120.jpg] [Image: th_P4070121.jpg]

So here it is, all back together, and greatly improved. The first thing I notice when turning the grinder on now is that it takes a lot longer to spin up to speed now due to the extra weight of the diamond wheel. The motor is working extra hard to get that mass moving now, so I’m sure the magnetic fields pulling on those windings are extra strong now. Hopefully my DIY insulation job is up to the task. I do know I’ll feel safer with the solid hubs hanging onto those wheels though.

[Image: th_P4080132.jpg] [Image: th_P4080131.jpg]

For what it’s worth…
Willie
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#2
Willie,
I thought the video's were very informative, and I have to say he has a very smooth running machine.

You did a real good job with yours and now it seems you have a first class grinder Smiley-signs107
Smiley-eatdrink004
DaveH
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#3
I will have to get one of those for my shop, I have not seen one up here but try to stay away from places like busy bee etc I drop too much money there. tom
Logan 10x26" lathe
SIEG 12x40" lathe
RongFU 45 clone mill
6" import band saw
Baldor Grinder
thousand of tools+tooling pieces 40 yrs of collecting
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#4
One thing to keep in mind (and this is mentioned in the video) is that these grinders "need work, right out of the box". The tables are difficult to adjust because of the way they bind up, and the supplied "Carbide Grinding Wheels" are basically made of concrete and painted green. Bleh

Of course it can't compete with a Baldor machine, but not everyone can afford a $1000 grinder either. With a little bit of work and a set of decent grinding wheels, they can be a useful tool in a small shop. An aluminum oxide wheel handles HSS tool bits, and the diamond wheel handles touching up brazed carbide tools. The adjustable tables handle the angles. The best of both worlds for someone like me who can't seem to hold a proper angle on anything when trying to grind a tool by hand. It's just not in my DNA I guess.... Sadno

Something else I forget to mention was that I replaced all the small, narrow flat washers that help hold the tables together. The factory washers barely reach past the slots on the trunnions. A few "fender" washers completely cover the clamping surfaces and give better support & holding power. A cheap "fix" that is worthwhile.
Willie
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#5
Willie,

Where did you get the insulating varnish from?

Ed
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#6
Ed, I got it from McMaster-Carr.

I checked out the specs on the manufacturers site. I believe the "green" varnish is the extra heavy-duty formulation and has the highest viscosity. That would be better for building up a nice thick coating I suppose, but it might not be thin enough to penetrate down into the inner layers of the windings. That's just a guess on my part.

I found this video on YouTube. It was an eye opener for me, I know that!
After seeing those wires rubbing back and forth against each other and the stator core, now I know why motors short out.Smiley-signs131



Willie
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#7
This is an in-store only item. I called the St. Paul store and the were out of stock and nothing available in the warehouse. I called the Minneapolis store and they had three on hand. Interesting item ... when I got there was they did not have one on display. When I asked they went in the back and the one the gave me had "display me" hand written on the box. Probably explains why they had them in stock ... no one knew they had them.

Anyway, there was a 25% off coupon for Easter Sunday only so that is when I picked it up. It will be a great project after I get the mill.
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#8
Ok, to bring up a really old thread ...

Assuming that 100, 150 and 220 grit diamond wheels are available from Enco. For tool grinding, which one would be the best one to get?

If I got two, which two?

Arvid
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#9
Arvid, stick with the 220 grit wheel and go at it gently. It will chew up a carbide bit in a heartbeat if you aren't careful. It does give a decent edge, but it also leaves some grinding marks in the surface.

I recently made myself a lapping machine which consists of a 1/4 hp motor and a cast iron disk/wheel that I charge with some 10 micron diamond paste. It polishes the surface to a mirror finish with a razor sharp edge after the cutter comes off of the carbide grinder. That works well for very fine light cuts, but will chip or break on any substantial depth of cut. At least that's been my experience so far. Blink

p.s.
Carbide ONLY on the diamond wheel. If you want to grind HSS as well, get a white wheel for the other side.
Willie
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#10
Arvid or Willie, could you give me the Enco Part or SKU numbers for those diamond wheels?
BTW I found the multi part video too painful to sit through, but then, I am blessed with the Baldor version (Thanks again Claude).
Busy Bee 12-36 lathe, Busy Bee Mill drill, Busy Bee 4x6 bandsaw, Homemade 9x17 bandsaw, Ad infinitum.
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