Craftsman 115-19500 Pre-block Restore

I was fortunate enough to find this "Pre-block" Craftsman Bench Grinder on local CL for $25. Unlike the later "Block" (model prefix 397 or 257), that are primarily cast aluminum, these 115 prefix models (made for Sears by Packard Electric Co.) utilized cast iron frames and wheel guards, therefore this thing is quite heavy. Was in pretty good shape for being 60 years old, and ran strong when powered on, but definitely needs freshening up.



This particular 1/4 hp model does not have covers on the wheel guards, unlike the larger 1/3 and 1/2 hp models of the same series. After removing the arbor nuts and outer flanges, I discovered the original 1959 Craftsman grinding wheels. The wheels were in good shape, but with a 60 year old grinder, it's not worth the risk to try to save them. They were challenging to get off, as they had essentially "frozen" on the arbor after 60 years.


Close-up of switch wiring.


Left-hand frame housing MUST come off first on the pre-block grinders, as they have a centrifugal switch attached to the right-hand frame that acts to disengage the start-up windings when the grinder is up to speed. LH Bearing stayed on the arbor.


By very carefully lifting the massive winding/core assembly, I was able to get access to snip the white wire leading from the winding to the centrifugal switch (which will be replaced) and remove the winding/core assembly.


After removing the winding/core assembly, you must carefully remove the screws holding the centrifugal switch to the right-side housing, because if you attempt to remove the rotor without doing so and the right-side bearing stays on the shaft, you will damage the centrifugal switch. RH Bearing stayed in the housing for me. Close-up of the position of the centrifugal switch, which is held in by two 1/4 inch screws.


More to come!

jerryd67 said:

I was fortunate enough to find this "Pre-block" Craftsman Bench Grinder on local CL for $25. Unlike the later "Block" (model prefix 397 or 257), that are primarily cast aluminum, these 115 prefix models (made for Sears by Packard Electric Co.) utilized cast iron frames and wheel guards, therefore this thing is quite heavy. Was in pretty good shape for being 60 years old, and ran strong when powered on, but definitely needs freshening up.


This particular 1/4 HP model does not have covers on the wheel guards, unlike the larger 1/3 and 1/2 models of the same series. After removing the arbor nuts and outer flanges, I discovered the original 1959 Craftsman grinding wheels. The wheels were in good shape, but with a 60 year old grinder, it's not worth the risk to try to save them. They were challenging to get off, as they had essentially "frozen" on the arbor after 60 years.

Close-up of switch wiring.

Left-hand frame housing MUST come off first on the pre-block grinders, as they have a centrifugal switch attached to the right-hand frame that acts to disengage the start-up windings when the grinder is up to speed. LH Bearing stayed on the arbor.

By very carefully lifting the massive winding/core assembly, I was able to get access to snip the white wire leading from the winding to the centrifugal switch (which will be replaced) and remove the winding/core assembly.

After removing the winding/core assembly, you must carefully remove the screws holding the centrifugal switch to the right-side housing, because if you attempt to remove the rotor without doing so and the right-side bearing stays on the shaft, you will damage the centrifugal switch. RH Bearing stayed in the housing for me. Close-up of the position of the centrifugal switch, which is held in by two 1/4 inch screws.

More to come!

Click to expand...

Looks great. It's going to be awesome when it's finished.

Where the heck do you get a centrifugal switch for a grinder that old? I would be floored if you say Sears has it and those switches are not generic, as far as I know. BTW any CS can be replaced with an external solid state current relay. You just need the Amps rating off the name plate. They are great, no contacts to get pitted or springs and weights to break or bind.

Sent from my SM-G900V using Tapatalk

Nice pre-Block, and they are stout! Nice job!

6PTsocket said:

Where the heck do you get a centrifugal switch for a grinder that old? I would be floored if you say Sears has it and those switches are not generic, as far as I know. BTW any CS can be replaced with an external solid state current relay. You just need the Amps rating off the name plate. They are great, no contacts to get pitted or springs and weights to break or bind.

Sent from my SM-G900V using Tapatalk

Click to expand...

Luckily, the centrifugal switch on this one survived the disassembly, and is in good shape. I will place quick disconnects on the electrical portion of the switch where the previous wired were simply soldered directly to the contacts. So as long as it continues to work fine, I won't try to change it out. It does have various springs that are part of the mechanism on the shaft itself, but they seem to be in good shape for being 60 years old.

Close-up of the portion of the centrifugal switch mechanism on the shaft. As the grinder gets up to speed, the brass-looking portions rotate out, pulling the black bushing in, which disengages the electric contacts on the switch, and cuts power to the start-up windings.


After spending several days in the electrolysis tank, the cast iron pieces are clean, prepped (POR-15 metal prep) and primed.


Unlike the 1/3 and 1/2 hp versions, the 1/4 hp model does not come with a light, so I drilled a hole in the correct location to mount a light.


Center panel is done with media blasting, and painted (Rustoleum Champagne Mist Metallic).

torqueman2002 said:

Nice pre-Block, and they are stout! Nice job!

Click to expand...

Thanks Doc...there's no way I would have made it this far without your previous write-up!

Nice restore. I know how a mechanical CS works. It is supposed to open as the motor approaches full speed. The electronic ones monitor the start current that drops to what is on the motor plate as the motor comes to full speed. For example, if the motor plate says five amps, you order a 5 amp relay and it probably opens at 5.5 amps or so. Three wires. The monitor is in series with the motor but is such low resistance it has no effect. The solid state cintacts are wired where the CS was. Tiny little box you can stash in the base. Works as substitute with any CS motor. We had a brand new Leeson at work that came wired that way.


Sent from my SM-G900V using Tapatalk

6PTsocket said:

Nice restore. I know how a mechanical CS works. It is supposed to open as the motor approaches full speed. The electronic ones monitor the start current that drops to what is on the motor plate as the motor comes to full speed. For example, if the motor plate says five amps, you order a 5 amp relay and it probably opens at 5.5 amps or so. Three wires. The monitor is in series with the motor but is such low resistance it has no effect. The solid state cintacts are wired where the CS was. Tiny little box you can stash in the base. Works as substitute with any CS motor. We had a brand new Leeson at work that came wired that way.


Sent from my SM-G900V using Tapatalk

Click to expand...

Thanks 6 point. I can definitely see an advantage to using an electronic switch as you described. With the mechanical version, if the switch failed (broken spring, for example) and did not disengage, your start-up winding could potentially get fried.

Finally got around to finishing up this little (but heavy) 1/4 hp pre-block.

Since the original (and very brittle) wiring was soldered directly to the centrifugal switch and power switch, and since I didn't want to go that route, I pop-riveted male spade electrical connectors instead.




Close-up of my wiring...since I added a light, and wanted to be able to have the light operate independently of the grinder power switch, I added a double male-female adapter to the hot side of the switch to power the light, and then used a Wago lever nut to tie all my neutral wires together.



My grinder was missing the bottom plate (and feet), so I fabricated one mounted it and the feet.



Finished product once re-assembly was complete.





This was my first restore, and I've certainly learned a lot along the way, but I'm happy overall with the way it turned out.

Now, on to the next one as I've got five more grinders waiting for me!

great job and great write up

emeraldcoupe said:

great job and great write up

Click to expand...

Yes, indeed!


I like the idea of the spade terminal connections and addition of the lamp.

This restore turned out very nice!

A couple of questions, if you don't mind.

• Where did you find/source the lamp?
• What color/brand did you use for the rest of the Block? It is a nice combination with the Champagne Mist Metallic center band.
• Are the rivets 1/8" aluminum?

Thanks for posting.

torqueman2002 said:

Yes, indeed!


I like the idea of the spade terminal connections and addition of the lamp.

This restore turned out very nice!

A couple of questions, if you don't mind.

• Where did you find/source the lamp?
• What color/brand did you use for the rest of the Block? It is a nice combination with the Champagne Mist Metallic center band.
• Are the rivets 1/8" aluminum?

Thanks for posting.

Click to expand...

Thanks Doc!

I was fortunate enough to find two of these lamps in like-new condition on eBay for under $20 and was able to media blast/prime/paint it to match the center band and eye shields, which were actually sourced from another grinder as mine only had the eye shield mounts when purchased (looked like the spot welds that hold the glass frame to the mount had failed as some point).

I used the previously mentioned Champagne Mist (a very light gold color) for the band, light and eye shields and Rustoleum Forged Hammered in Chestnut for the body, followed by several layers of clear on both.



I ended up using stainless steel (1/8 x 1/8) semi-tubular rivets, and setting them with a rivet clincher. I actually slightly messed up one corner of the badge during this process (trying to use a hammer to set the rivets). I've since got an arbor press and will try this instead on my next resto.

You should add a few pics to the Pre-Block thread:

https://www.garagejournal.com/forum/showthread.php?t=339921&highlight=pre+block+love

exmaxima1 said:

You should add a few pics to the Pre-Block thread:

https://www.garagejournal.com/forum/showthread.php?t=339921&highlight=pre+block+love

Click to expand...

Good idea!

exmaxima1 said:

You should add a few pics to the Pre-Block thread:

https://www.garagejournal.com/forum/showthread.php?t=339921&highlight=pre+block+love

Click to expand...

Done!!

Very nice restoration, and great write-up!

Great looking refurb.

jerryd67 said:

I was fortunate enough to find this "Pre-block" Craftsman Bench Grinder on local CL for $25. Unlike the later "Block" (model prefix 397 or 257), that are primarily cast aluminum, these 115 prefix models (made for Sears by Packard Electric Co.) utilized cast iron frames and wheel guards, therefore this thing is quite heavy. Was in pretty good shape for being 60 years old, and ran strong when powered on, but definitely needs freshening up.

This particular 1/4 hp model does not have covers on the wheel guards, unlike the larger 1/3 and 1/2 hp models of the same series. After removing the arbor nuts and outer flanges, I discovered the original 1959 Craftsman grinding wheels. The wheels were in good shape, but with a 60 year old grinder, it's not worth the risk to try to save them. They were challenging to get off, as they had essentially "frozen" on the arbor after 60 years.

Close-up of switch wiring.

Left-hand frame housing MUST come off first on the pre-block grinders, as they have a centrifugal switch attached to the right-hand frame that acts to disengage the start-up windings when the grinder is up to speed. LH Bearing stayed on the arbor.

By very carefully lifting the massive winding/core assembly, I was able to get access to snip the white wire leading from the winding to the centrifugal switch (which will be replaced) and remove the winding/core assembly.

After removing the winding/core assembly, you must carefully remove the screws holding the centrifugal switch to the right-side housing, because if you attempt to remove the rotor without doing so and the right-side bearing stays on the shaft, you will damage the centrifugal switch. RH Bearing stayed in the housing for me. Close-up of the position of the centrifugal switch, which is held in by two 1/4 inch screws.

More to come!

Click to expand...

Hi Jerry. Can you tell me how to get the housing off? I found one at the garage sale. Thanks.

New sale price? Lol

jerryd67 said:

Luckily, the centrifugal switch on this one survived the disassembly, and is in good shape. I will place quick disconnects on the electrical portion of the switch where the previous wired were simply soldered directly to the contacts. So as long as it continues to work fine, I won't try to change it out. It does have various springs that are part of the mechanism on the shaft itself, but they seem to be in good shape for being 60 years old.

Close-up of the portion of the centrifugal switch mechanism on the shaft. As the grinder gets up to speed, the brass-looking portions rotate out, pulling the black bushing in, which disengages the electric contacts on the switch, and cuts power to the start-up windings.

After spending several days in the electrolysis tank, the cast iron pieces are clean, prepped (POR-15 metal prep) and primed.

Unlike the 1/3 and 1/2 hp versions, the 1/4 hp model does not come with a light, so I drilled a hole in the correct location to mount a light.

Center panel is done with media blasting, and painted (Rustoleum Champagne Mist Metallic).

Click to expand...

ARFLY said:

Looks great. It's going to be awesome when it's finished.

Click to expand...

Unfortunately, my centrifugal switch plate on the right side was broken during disassembly - any ideas on what to do?