CM Block Grinder - 1/3 HP 397.19410 with Brake! My White Whale

I have been in search for a quietly rumored "classic Craftsman bench grinder that was manufactured for Sears by Paramount/Allegretti & Co. from the early 1960's to early 1980's. Affectionately known as "Block Motor" grinders because of their unique shape, these power tools have developed a large following among shop enthusiasts because of their legendary reliability, accuracy, and power."

I saw a picture of one in the "let's see your craftsman block grinders" thread. The owner said it worked; but dropped out of the thread before I could get any specifics, such as picture of the wiring, etc..

Anyway, some may already know Mrs. Torqueman has me searching for Block grinders in order to keep an eye on me. She knows it keeps me out of the bars.

You may ask, what makes this my White Whale.


Well, I have a fair amount of grinders [some say more than my fair share], Block grinders too.

But look as I have, I have not seen one for myself.


Why is it a White Whale, you may ask?

Because, it does not appear on OWWM or VintageMachinery, or other tool/garage forums I have scoured in vain for pictures, and details of it's workings.

A handsome reward was considered.


I thought I saw it, but it seemed to slip away.


Just as I dared not hope, I was eye to eye with the White Devil of my sleepless nights.


.

And...?

No freakin' happy ending to the story!?

C'mon, Torque!

Tourque: nice picture of the white whale jumping. Brent doesn't know you already own that little block and have it taken apart on another forum. i'm paying attention because i'm really curious why a grinder would need a brake. other than it being the hardest grinder to find on the planet what is the benefit of the "BRAKE"?

good luck and here to watch another quality rebuild.

Aaah, I see your handy-work elsewhere. Nice score, man. You don't waste time.

good score

You crack me up, congrats...I suppose?

Well, where is it? You can't leave us hangin....

Sorry for the bit of a tease.

Yes, I have it. Or maybe ...


I have traveled far from SE Michigan on my search of Block grinders. This one however, was in my own backyard - The D!


I brought it home for $35. Now I know why I bought the 1/3 HP Block grinder on the right - it will be a donar.












The tear-down went surprisingly easy and routinely. The outside rust and peeling paint, missing parts, and bad corroded cord/plug, led me to expect the worst.

I sprayed down the fasteners and union where the side castings and wheel guards meet with Kroil and started pulling it down to bits and pieces. This is the RH side.


The wheel looks good, no visible cracks, chips, or signs of moisture; time for a ring test. Note: the 'wet spot' is from the Kroil I put on the arbor threads.


Failed. So, it was purposely broken to prevent inadvertent use. A metallic center piece was used. Is it an adapter, or part of the original stone? To my eye the stone looks to have been formed around this piece. Is that what kept it from 'ringing'? I would have replaced it anyway, no telling about this consumable. Like fluids in a used car, they get replaced.


The LH wheel also passed a visual inspection, but failed the ring test. This one had an additional plastic adapter and the center metallic one. I retained the stone for reference or additional inspection/testing, if anyone is interested - drop me an IM.


The power cord and plug.
As a son of an electrician/TV repair man/electronic instrumentation manufacture's rep., I cannot understand how people can cut off the ground terminal.
Use an adapter man.


More of the same, this one wasn't even taped.


I cut off the bad section of the power cord, leaving a stub to which I connected my 'test' harness. I used a new tool, 3M crimper [TH-450] and 3M insulated female terminals. It runs fine, and the BRAKE [momentary switch to right] stops the wheels in a fraction of a second!


Thanks for looking, more to follow soon.

Weird that this would come up now, I just found one of these (light brake and all) near me earlier today. With any luck I'll get to bring it home Friday.


(Insert catchy saying here)

You know, after learning about the "ring test" I've found that about 50% of the grinders I brought home had cracked stones. Scarey. And cutting the ground prong should be a "slapable" offense.

OK, back with more pictures.

So, these are the 1st peeks at the workings of the Brake mechanisim. I am posting a number of angles, for reference. I have not found anything about this feature, except a part number in a owners manual. The Brake Board is on the left, the start-up relay is on the right.




I color dotted the lamp leads before the removal of the center band, the power switch is at the top of the photo.


Direct-on shot of the Brake Board, looking from RH side.


Another view of internal wiring, power switch is on the right of course.


Another view of internal wiring, power switch is on the left.


Wiring detail of start-up relay and it's P/N.




Brake Board, power switch, power cord, and relay removed from grinder.


The next couple of shots are why I go to the trouble, time, and effort to take these guys down to their final bits and pieces. The terminals on the switch are just a few mm from contacting one another. The other picture shows the corrosion on the relay and wire terminals. Trying the grinder to see if it runs is fine for price negotiation, but once in my garage/shop I go through them completly.




The following are details of the Brake Board.










Details of the power switch and it's wiring.




I make the imbossed printing to say:
UND LAB INSP
10A 250V AC
1/2 H.P.
250V AC


Mechanization.


More to follow soon.

Thanks for looking.

tourque - You're a braver man than I.

Continued.

The LH and RH castings seperated from the rotor and bearing assembly with light taping with a soft face hammer. No start-up switch screwed to the RH casting to be mindful of.

The LH & RH castings are very clean, just like the interior where the relay and Brake Board are mounted.


RH casting with stator/winding assembly attached.


The stator/winding removed from RH casting, showing tagged wires.


The rotor with felt washers, spring 'finger' washers, and bearings.


Detail of LH felt washer and spring 'finger' washer - notice the 'fingers' face the bearing. RH is the mirror image.


RH bearing removal, LH similar.




Bearing outer face.


Bearing inner face.


Inner face detail. ND 3205


Bearing measurements.




77503, New Departure [cross-references to: NTN Part Number 6203ZZC3/L103] Matches above measurements.
http://www.ntnamericas.com/en/products/bearing-search/bearing-search-results/datasheet?pid=4810&cid=RBSRD&ctc=B

More to follow.

Thanks for looking.

Tourque: I've always wondered how you were able to remove the bearings. did you make that tool because i don't remember seeing one like that in any of your other posts? looks like the right tool for the job and nice work. that block looks a lot cleaner on the inside than it was on the outside.

Nice thread!! Torqueman, thanks for letting me know about it. So how does the brake actually work? This should turn out VERY nice when you're finished with it.

How ironic, surfing CL today ,one of these showed up. 25$, has quench tray ,light and metal framed shields. In the Chi town area. Posted 8 hours ago.

Torque, those lizards look poisonous, must of been wild to see it jump out when you took the bottom plate off.
I glad to see I'm not the only that takes the electrical apart just to check. I was begging to think I was weird.
Look forward to seeing this one done.
The brake is interesting, wonder if we'll find out the reason for that.

drivesitfar said:

Tourque: I've always wondered how you were able to remove the bearings. did you make that tool because i don't remember seeing one like that in any of your other posts? looks like the right tool for the job and nice work. that block looks a lot cleaner on the inside than it was on the outside.

Click to expand...

I have been able to remove them without the bearing splitter/separator/puller. Whew!

But at <$30.00 with Amazon Prime, the "OTC 1122 1/8" to 2" Bearing Splitter" is reasonable and it is easier and less likely to cause unintended harm. Link --> http://www.amazon.com/OTC-1122-Bearing-Splitter/dp/B000O866WE/ref=sr_1_1?ie=UTF8&qid=1397698790&sr=8-1&keywords=OTC+1122+1%2F8%22+to+2%22+Bearing+Splitter

When I installed it in the above picture, I tried the reverse side of the puller, which worked fine. However, the stepped design allows (and the 'splitter' in the name implies) it to be used where the bearing tightly abuts a shaft/housing.

Here's a video of a motor bearing removal and installation. (I use a deep impact socket fitted to the inner race and a soft mallet to install new bearings.)

The other part of the set up, I already had. A SO 2-jaw puller. I removed the jaws and used long bolts to reach over the end of the arbor/shaft.

I was surprised and happy with how clean the inside is compared to the looks of the exterior.

Thanks. I don't know if this will get a custom paint job, original color re-paint, or a re-spray of just the rusty bits and leave the 'patina'.

I've got 4 grinders apart waiting for the blast cabinet and then painting. I sure hope spring comes back and stays this time.

G20-Budo said:

Nice thread!! Torqueman, thanks for letting me know about it. So how does the brake actually work? This should turn out VERY nice when you're finished with it.

Click to expand...

You bet.

I hurt my feeble brain trying to figure out the circuit from the drawing I made.

I suspect, since the arbor just stops and doesn't reverse direction, there's an opposing magnetic field set up when the switch is move to the BRAKE position. (it is spring loaded and returns to the OFF position when released)

I'll measure the resistance of the windings, measure which legs of the switch are HOT in each position, try to find more about the Diodes (Google came up with Zip on the numbers). Maybe then I will get somewhat of an idea how it works.

I bet someone on the forum knows. Let's hope the visit the thread.

Also, I plan to post on the sister forums of: OWWM and VintageMachinery. Maybe someone there has an idea.

Cheers and Beers.

cbacres said:

Torque, those lizards look poisonous, must of been wild to see it jump out when you took the bottom plate off.
I glad to see I'm not the only that takes the electrical apart just to check. I was begging to think I was weird.
Look forward to seeing this one done.
The brake is interesting, wonder if we'll find out the reason for that.

Click to expand...

Yea, little guy looks hungry. Don't know if I should feed him to keep him from biting ME, or hope he leaves - like a stray cat.

I have seen some scary stuff on these simple machines - for example, one grinder was switching the neutral. IIRC - that was the Go Blue rescue.

I tried the brake a few times, it stops the grinder like <1 sec. Not sure where that would be useful, but of course I had to have one.

torqueman2002 said:

...
The wheel looks good, no visible cracks, chips, or signs of moisture; time for a ring test. Note: the 'wet spot' is from the Kroil I put on the arbor threads.

Failed. So, it was purposely broken to prevent inadvertent use. A metallic center piece was used. Is it an adapter, or part of the original stone? To my eye the stone looks to have been formed around this piece. Is that what kept it from 'ringing'? I would have replaced it anyway, no telling about this consumable. Like fluids in a used car, they get replaced.

The LH wheel also passed a visual inspection, but failed the ring test. This one had an additional plastic adapter and the center metallic one. I retained the stone for reference or additional inspection/testing, if anyone is interested - drop me an IM.

....

Click to expand...

I received a comment/reply about the 'Ring Test' from an OWWM member.
"The bushing shouldn't make any difference unless it's loose, and even then it might not make any difference.
HOWEVER, the "ring test" only works on vitreous bonded wheels.
Resin bonded or rubber bonded wheels DON'T RING, ever. New, old, solid, cracked, makes no difference. They won't ring.
Not saying yours weren't bad, because vitreous bonded wheels are the usual/average type you'll find; just saying the ring test isn't foolproof."
Hmmm, ... not 'foolproof'! Great, now what?

torqueman2002 said:

Hmmm, ... not 'foolproof'! Great, now what?

Click to expand...

Grab your ankles, choose a religious pantheon, and cross your fingers.

Great stuff here torqueman, keep it coming.