CM pre-Block Grinder 115.19500 restore

[torqueman2002]

I thought it was time for a grinder rebuild post.

I was given a Craftsman 1/4-HP model 115.19500 pre-Block grinder.

A member from that other site, sent it to me to see if I could get it running. All I had to do was pay the shipping.

As some may recall, I have an affinity (my family says an obsession) for the Craftsman Block style motor grinders. The shipping was not trivial, as this model is cast iron.

I tore it apart and looked for a 'smoking gun'. The previous owner said it started and ran once. On the second try, it hummed, smoked, but ran when he gave it a push start. I believe he kept it from the scrap heap by giving it that push. I have seen more than 1 Block grinder, that has had the magic smoke escape, when it stalled at start-up.

I cleaned up the centrifugal switch (CS) assemblies and power switch. I removed the bearings to clean so I could get the mfg & p/n, temporarily put it mostly back together with a grounded test power cord, and powered it up.

It made that satisfying click/whirl sound an electric motor with a CS makes.

I'm waiting on replacement bearings and a new grounded power cord, then this stout little 'engine' that could, will once again!

Now, if I can figure out how to put pictures 'in line' with the text.

Oh, to see more pictures and read more of the story, venture back to where a lot of us 1st met. --> https://www.garagejournal.com/forum/showthread.php?t=447537

[goodfellow]

Best darn bench grinder for the money that was ever made. Certainly not cheap, but the quality and materials far exceeded the original price. Sears got that one right. The fact that so many of them are still in service speaks volumes.

Thanks for the post TM. I a few and use them regularly.

[torqueman2002]

Best darn bench grinder for the money that was ever made. Certainly not cheap, but the quality and materials far exceeded the original price. Sears got that one right. The fact that so many of them are still in service speaks volumes.

Thanks for the post TM. I a few and use them regularly.

Thank you, gf!

IIRC - it was your post, so many years ago, that sent me on the hunt for a CM Block grinder. The rest is history. Don't worry, my family has no clue you were involved.

BTW - I was surprised and impressed to find the bearings have a 5/8" ID. AFAIK - the only other Block grinder < 3/4-HP that uses that size arbor is the 1/3-HP model with electronic brake - 397.19410.

[skfarmer]

cool, looks fairly complete. repaint in store?

[torqueman2002]

cool, looks fairly complete. repaint in store?

Thanks sk.

I think all the pieces are there. It does not have side covers or spark arresters, but it doesn't have any mounting holes for them either.

I'm not sure about the paint, I may just slap on wire wheels, put it on a CM stand and use it in the basement shop for light duty cleaning of threads and such.

I just received the bearings for the Baldor 7312 2-speed, 0.3/0.5 HP grinder in the basement that is apart and will be finished soon. Truthfully, that acts more like a 0.75/1.0 HP CM Block grinder. It has my attention and respect every time I turn it on. 

[bonneyman]

I notice the nameplate says "Split Phase" yet I seem to recall alot of Block grinder rebuilds with capacitors. Did the motor style change when they went to the next series after yours?

[hickory n Steel]

Got a '58 Craftsman Block grinder I use all the time.
It fell one day busting one of the hubs, but it still runs fine.

Yours looks to be in excellent condition, mine is a rust bucket having spent it's life in a barn workshop on a farm before it was given to me.

[torqueman2002]

I notice the nameplate says "Split Phase" yet I seem to recall alot of Block grinder rebuilds with capacitors. Did the motor style change when they went to the next series after yours?

I don't really know how that breaks down. AFAIK there isn't a Sears/Craftsman listing of model numbers and features, which sure would be handy.

I have a spread sheet that shows some model numbers and features, but is incomplete when it come to the manufacture date that is sometimes ink stamped on the bottom cover.

Does anyone know how to post picture 'in-line' in the body of the message?

[torqueman2002]

Got a '58 Craftsman Block grinder I use all the time.
It fell one day busting one of the hubs, but it still runs fine.

Yours looks to be in excellent condition, mine is a rust bucket having spent it's life in a barn workshop on a farm before it was given to me.

Thank you.

These classic Block style grinders '... take a licking, and keep on ticking!'. 

[fatfillup]

I got the Block virus myself because of this forum

I have 2 at home and buy all I can at sales because they rarely disappoint anyone who buys one

I think I have had on 3/4 hp come through.

One at home is 1/2 hp and gets used quite often cleaning tools

[DeadNutz]

I have several block grinders but I am really loving the 10" 1hp 110V Baldor the wife bought last year.

[torqueman2002]

Best darn bench grinder for the money that was ever made. Certainly not cheap, but the quality and materials far exceeded the original price. Sears got that one right. The fact that so many of them are still in service speaks volumes.

Thanks for the post TM. I a few and use them regularly.

gf - IIRC you were the inspiration for my Block grinder quest.

Am I correct to attribute the following quote to you?
"... the classic Craftsman bench grinders that were 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.

The "Block Motor" grinder can be readily identified by the Sears manufacturer prefix of 397 or 257 (as in 397.XXXXX); which is stamped on the front label. Popular models include 1/4-HP, 1/3-HP, 1/2-HP, 3/4-HP, and 1-HP Industrial units."
Link to: "Vintage Craftsman "Block Motor" bench grinder info -" (source) Broken link

"People always want to know what makes these things {CM Block grinders} so special; here's the reason. Look at those field windings. That is some VERY thick copper wire. When compared to a modern Chinese winding, these look GIGANTIC. The imports use very thin field wire. This is what makes these "block motors" so darn powerful and long lasting."

The reason I am asking is a member on a well regarded forum has written:
"I thought the other places refer to the block grinder as the ones with center band and end bells that look like a cube.
The prior aluminum ones have end bells shaped like a tombstone, or mailbox as you've mentioned. These should not be confused with "block grinder".
The aluminum tombstone/mailbox shaped grinders were patterned from the earlier 6" and 7" cast iron machines."

I thought it was more about the supplier and quality, and not necessarily the shape.

I don't want to start a forum spat, so are there any sources you can direct me to, so that I can research more about the Block grinder origins?

Thanks in advance. 

[goodfellow]

Yes, TM I posted that message some years ago.

As to the "Block Grinder" nomenclature. It was a term that old-timers in my early experience used to designate the form factor differences of the machines. Since most bench grinders were round, the squared off shape was termed as a "Block". The point was made that these machines -- and specifically these Sears models, were more efficient and sturdy than any other home-owner grade units at the time. Many manufacturers built squared off designs, but the name stuck with the most popular design; which at the time was the Sears models. 

I believe the original block designs were actually made by DELCO (or maybe Packard/Delphi) -- I can't remember exactly, but I'm convinced one of the two was the originator of the design, and the name was originally associated with those designs. Hence the term "Block Motor" was in use many years before Sears started to offer that specific product line. Although it may have only been used in certain professional circles. It wasn't until the Sears versions hit the market that the name became synonymous with the design.

As to the terms "Flat-Top and Round-Top, or Mailbox" -- those terms are relatively new to my way of thinking. I never heard of them until well after the Block Motor craze started on forums like the GH (the old Garage Hangout where many of us originally met), GJ and GG (and some others) well over a decade or so ago.

[fatfillup]

Not that any of the regulars would make the mistake, but a Cman grinder that looks a little blockish but has a plastic case is not a block grinder.  They are low quality junk.  Have burnt up 2. 

[torqueman2002]

Thanks gf & ff.

Here's what I 'heard back' from the other site.
"I don't think there's any question on manufacturers or dates (below is a thumbnail):
1954: Post-WWII Craftsman 7"x1" (with built in bulbs) & Dunlap 6"x3/4" grinders replaced by Packard built cast iron tombstone/mailbox shaped 6" & 7" grinders.
1961: Transition from centrifugal switch to relay and source code to Delco.
1964: Delco aluminum body tombstone/mailbox shaped 6" & 7" grinders replace the cast iron machines.
1969: 8"x1" grinder introduced.
~1975: Block shape designs replace the tombstone/mailbox style. Vibration improved with reinforced endbells.
~1981: Paramount source code replaces Delco.
~1984: Paramount minor changes to Delco block designs. 3-phase 8"x1" model introduced.
1990: Import grinder designs replace ball bearing models."

Does this mean and do you agree that any pre ~1975 CM grinders are not officially Block, quality build, grinders??!! And there's no Santa Clause!

[goodfellow]

.......Does this mean and you agree that any pre ~1975 CM grinders are not officially Block, quality build, grinders??!! And there's no Santa Clause!

Personally, I don't agree with that. I grew up with the term "Block Motor" being used to designate any of the Craftsman squared format designs, as well as many older square designs by other manufacturers. Like I said, the term was used even before Sears adopted the design, but it finally stuck and became synonymous with the Sears designs exclusively. That also included the early model (round tops) from the 50's and 60's. The design was the same.   

[bonneyman]

I notice the nameplate says "Split Phase" yet I seem to recall alot of Block grinder rebuilds with capacitors. Did the motor style change when they went to the next series after yours?

I don't really know how that breaks down. AFAIK there isn't a Sears/Craftsman listing of model numbers and features, which sure would be handy.

I have a spread sheet that shows some model numbers and features, but is incomplete when it come to the manufacture date that is sometimes ink stamped on the bottom cover.

Does anyone know how to post picture 'in-line' in the body of the message?

Just a quick breeze thru the list reveals the dual voltage ones are PSC, the single voltage are split-phase. Kinda makes sense.

[torqueman2002]

 
   New day! And I've learned new truths.

Thank you gf and bman.

Now about the Easter Bunny, .....

[torqueman2002]

I notice the nameplate says "Split Phase" yet I seem to recall alot of Block grinder rebuilds with capacitors. Did the motor style change when they went to the next series after yours?

I don't really know how that breaks down. AFAIK there isn't a Sears/Craftsman listing of model numbers and features, which sure would be handy.

I have a spread sheet that shows some model numbers and features, but is incomplete when it come to the manufacture date that is sometimes ink stamped on the bottom cover.

Does anyone know how to post picture 'in-line' in the body of the message?

Just a quick breeze thru the list reveals the dual voltage ones are PSC, the single voltage are split-phase. Kinda makes sense.

I asked Brian Kachadurian on the OWWM forum. His reply follows.
"They (Block grinders) are all split phase.
All 7" and 8" grinders have the additional capacitor start feature."

[torqueman2002]

OK, new day! 

I'm over BK 'harshing my buzz', and I will continue to call this and other select pre ~1975 CM grinders as Block and pre-Block grinders.

I have finished this rebuild.
It's back together and running just like it should.


The bits 'n pieces have been cleaned and some de-rusted with Evapo-Rust. Waiting for reassembly.


A hole was drilled for a self-tapping ground screw - lower left.


New bearings are being heated on a coffee warmer, prior to installing on the cold arbor. The flanges are used to keep the bearings in close contact with the warmer. Temperature was about 110F.


Arbor shaft assembly fresh out of the freezer.


The 'hot' bearing dropped right onto the 'chilled' arbor, no force needed. More information about this LH bearing later.


Because of the inner-most ridge in RH bearing bore, that bearing was installed into the RH end bell from the outside.

The 2 'U' shaped power cord strain-reliefs and plastic bushing were removed from the power cord and the grinder.
The original hole was enlarged to a bit over 1/2".
The modern Heyco strain-relief is a better choice. The red handled pliers were used to install the Heyco (to the left of the pliers) and power cord.
The black bushing and ring above the pliers are alternatives that were not used, due to space limitations.


View of the power cord and strain-relief installed - outside of bell end.


The LH bearing was a 'loose' fit in the bell end bore and on the arbor shaft. A small amount of retaining compound was used in the bore and on the arbor at the bearing surfaces.


The next several pictures detail the LH bearing, shaft, end cap, bearing spring, wheel spacer, wheel guard, and screws.

Note: The wheel spacer, shown on the arbor shaft, is installed after the wheel guard, end cover, bearing spring and 3 screws are installed.


The 'fingers' of the bearing spring face towards the bearing.



From left to right: Wheel guard, end cap, bearing spring, LH end bell.


View of properly aligned bearing spring. Note even spacing of bearing spring around the bearing.

[torqueman2002]

View of RH end bell with centrifugal switch installed.
Note: The rust has been removed from the end bells, and treated with Ballistol.


Winding assembly installed in RH end bell, with wires routed through 'cut out'.


View of ground wire.


Bottom view with LH, RH-end bells, arbor assembly, center band, and power cord installed.


Bottom cover installed with original feet.


That's it, it's done. Ready for power-on test.
The multi-colored Xcelite drivers on the peg-board have hollow shafts.
They were very useful restoring this pre-Block dated 3 57.
They were bought by my dad to service radio and TV equipment after his WWII tour of Germany and Austria was up.


View of a short live test. The camera flash and shutter speed don't show how fast the arbor is spinning.
Don't try this at home! The flanges made an unhappy noise!   


Can you see the 'new' improvement?


OK, here's a better shot.
Found these (labels) hiding on the workbench, left from another Block restore.


Now, all it needs are 2 new wire wheels and a Craftsman stand.

Thanks for looking.
 

[goodfellow]

Good work as always TM -- you keep the CM Block legacy alive and well. My two units (1/3HP and 1/2HP models) are humming along just fine, and I have yet to experience any problems with these things, even though they get used a lot, and quite often overloaded and bogged down with excessive pressure on the wire wheels and stones.

[fatfillup]

Sweet rebuild on a unit well worth saving.  I give mine a workout on a regular basis.  Its funny, you wouldn't believe how many shops I go to that don't have a bench grinder at all or the have an absolute POS grinder.  Or don't have a wire wheel on one.

I have 2 at the shop and 2 at home though the second at home is a relatively new addition

[torqueman2002]

gf & ff,

Thanks.

At the same time, I'm rebuilding a 2-speed, 0.3/0.5-HP, Baldor 7312B. So comparisons between the 2 are unavoidable.
The NTN replacement bearings are:
            CM: 6202ZZ                   Baldor:  6203ZZ
Bore ID: 15 mm                           17 mm
OD:       35 mm                            40 mm
Width:   11 mm                            12 mm
The CM uses cast iron for it's major castings, the Baldor has a welded steel motor housing, cast aluminum end bells and motor base, and cast iron wheel guards and covers.
CM uses 6"x3/4" wheels/stones vs.  Baldor's 7"x1"

Now I'm not saying the CM is the equal of the Baldor, far from it. But considering the initial price difference between equal models (these are not, of course), the CM holds it's own.

Still today, they are readily available, rebuildable, and very cost effective!

I know I'm preaching to the choir. Just that I don't feel I've wasted my time, money, or effort on the little Craftsman pre-Block that could - heck, can!
 

[Heiny57]

Outstanding thread and great write up. Thanks for taking the time to share with us and the rest of the people out there that might search for help.     You might pull in some new eyes to see the Gazette.

[DeadNutz]

Great writeup and I am trying to visualize everything you said.

[skfarmer]

nice job saving a cool old grinder! 

[torqueman2002]

Thanks guys. 

I know the last post doesn't have all the back ground; however, here's a link to the full restore. ---> https://www.garagejournal.com/forum/showthread.php?t=447537

If I can clear up any questions, please let me know.

Thanks for reading and commenting.