Craftsman Block Grinder wont spin

[kirk69nova]

I bought a CM Block grinder model 397 19340. It worked when I plugged it in prior to buying it. I brought it home and when I hit the power switch it made an audible pop and a white flash came from underneath it. I unplugged it, checked it out and did not see anything visibly burnt (I am sure something is however). I plugged it back in and, hit the power button and the motor tried to spin but would not. I spun it by hand and it came right up to speed. I have been doing this for a few months but want to fix it now. So all you "blockheads" out there where do I start to get my grinder working properly?

 

[drivesitfar]

Kirk: post this over on the Block grinder thread for two reasons. one you will get more help there and two you will add another fix issue to that awesome thread.

my guess is it is a capacitor or relay that needs replaced or maybe a wire broke, but i'm far from the expert in fixing these.

since you are a new member i want to welcome you to the forum and also give you some advice. it's always best to post pictures when you are asking questions or able and if you learn how to fix that block over on the block thread you might want to buy a few more so you never have to change wheels when doing a project.

here's the link:

http://www.garagejournal.com/forum/showthread.php?t=157794

cheers

 

[torqueman2002]

^^^ What he said.

We'll help you figure it out.

BTW - the symptom you described is due to the start-up coil not being energized.

The purpose of which is to over come the inertia of the rotor/wheel assembly, when going from the at rest condition to ~3/4 of the run speed.

The start-up coils are electrically removed from the circuit by 1 of 2 methods.
A mechanical switch opens when a centrifugal weight on the rotor reaches a calibrated RPM.
OR
A current-differential relay opens the start-up circuit.

It is also possible the start-up cap has failed, but I'm not sure what symptom that produces.

At any rate, the good thing and the reason the Block grinders have a following, is they can be fixed.

Does yours look like this?

I would bet it has a relay and a start cap. Also, those power switches are a weak point.

Looking forward to hearing more about your Block.

 

[mrpizza]

Man, i need to dig mine out and restore it.

 

[Leadberry]

I bought a CM Block grinder model 397 19340. It worked when I plugged it in prior to buying it. I brought it home and when I hit the power switch it made an audible pop and a white flash came from underneath it. I unplugged it, checked it out and did not see anything visibly burnt (I am sure something is however). I plugged it back in and, hit the power button and the motor tried to spin but would not. I spun it by hand and it came right up to speed. I have been doing this for a few months but want to fix it now. So all you "blockheads" out there where do I start to get my grinder working properly?

Sounds like you have a blown start cap.

^^^ What he said.

We'll help you figure it out.

BTW - the symptom you described is due to the start-up coil not being energized.

The purpose of which is to over come the inertia of the rotor/wheel assembly, when going from the at rest condition to ~3/4 of the run speed.

The start-up coils are electrically removed from the circuit by 1 of 2 methods.
A mechanical switch opens when a centrifugal weight on the rotor reaches a calibrated RPM.
OR
A current-differential relay opens the start-up circuit.

It is also possible the start-up cap has failed, but I'm not sure what symptom that produces.

At any rate, the good thing and the reason the Block grinders have a following, is they can be fixed.

Does yours look like this?

I would bet it has a relay and a start cap. Also, those power switches are a weak point.

Looking forward to hearing more about your Block.

The purpose of the start circuit is to generate a rotating magnetic field. When the rotor isn't in motion, the field needs to be rotating to motivate the rotor in one direction or the other. A 3-phase machine achieves this inherently, but a single phase machine needs a method of inducing a phase shift in the start coil, hence the start cap.

 

[exmaxima1]

Sounds like you have a blown start cap.



The purpose of the start circuit is to generate a rotating magnetic field. When the rotor isn't in motion, the field needs to be rotating to motivate the rotor in one direction or the other. A 3-phase machine achieves this inherently, but a single phase machine needs a method of inducing a phase shift in the start coil, hence the start cap.

The Split Phase grinders don't have a cap. They employ a separate winding to get spinning. The problem might be a relay or loose wire. Or worse case, a shorted winding.

 

[kirk69nova]

Here are a few pics. This site is what turned me onto these block grinders. I love seeing anything old restored and all the old tools brought back to life are so cool to me. Thanks so far and hopefully Ill get this working the way it should. Looks like there is not a capacitor???

 

[exmaxima1]

Here are a few pics. This site is what turned me onto these block grinders. I love seeing anything old restored and all the old tools brought back to life are so cool to me. Thanks so far and hopefully Ill get this working the way it should. Looks like there is not a

[/URL]

One of the windings sure looks dark or burnt to me

 

[kirk69nova]

I can't see any discoloration of the larger copper colored windings. However looking a little closer there are also smaller reddish colored windings. As you can see in the pic the one coming from the white wire is not connected to anything. I cant imagine that is good. Any idea where it should go? Can it be repaired?

 

[torqueman2002]

I see a couple of abnormal things.

 

[kirk69nova]

The terminals look suspect in what way? I am not sure what you mean by over current coils, start up. Electricity is not my friend, torqueman, so you may need to dumb it down for me!!

 

[torqueman2002]

The terminals look suspect in what way? I am not sure what you mean by over current coils, start up. Electricity is not my friend, torqueman, so you may need to dumb it down for me!!

OK.

It's hard to tell from the picture, but are the switch terminals clean and tight? I looks like there may be a wire or solder or ?? lying across them.

The coils are the start-up coils. They look like they have been subjected to too much current and are discolored. This can happen if the relay sticks, or the rotor is prevented from turning with the power ON.

 

[torqueman2002]

I have pictures of a 1/2 HP CM flat top Block Grinder m-397.19340, that is now with fellow member: u118224.

There are pictures of the internal wiring on a known-good-grinder. Maybe you can see where that wire should go.

My guess is the plastic tie wrap for the windings melted and the wire should go somewhere into the start-up coil winding.

It can be rewound by an electric motor re-builder. I suspect you'll find it prohibitively expensive. Then there's the actual part that failed. It may or may not be the relay.

Slide Show
http://tinyurl.com/CM-half-HP-ft-Block-397-19430

 

[kirk69nova]

If the red colored windings are the start up windings then it would make sense that a broken connection within these windings could be the issue as to why it won't start on its own.

I did find another broken red winding that looks like it is probably where the one in the pic broke from. Is there any way to get these two pieces back together? Can copper be melted back together?

 

[Leadberry]

The Split Phase grinders don't have a cap. They employ a separate winding to get spinning. The problem might be a relay or loose wire. Or worse case, a shorted winding.

I was just explaining the purpose of a start cap. All single phase induction motors use start windings. Regular split phase just omits the start capacitor.

I can't see any discoloration of the larger copper colored windings. However looking a little closer there are also smaller reddish colored windings. As you can see in the pic the one coming from the white wire is not connected to anything. I cant imagine that is good. Any idea where it should go? Can it be repaired?

I think you found your problem. If there's a start winding lead connected to that white wire, and it's not connected to the start winding, you have an open in the start circuit. The only way to fix this is to reattach that lead to the start winding. This is easier said than done, as those wires are coated with an insulating varnish. You might be better off taking it to an electric motor repair shop and see if they can do anything.

 

[Leadberry]

OK.

It's hard to tell from the picture, but are the switch terminals clean and tight? I looks like there may be a wire or solder or ?? lying across them.

The coils are the start-up coils. They look like they have been subjected to too much current and are discolored. This can happen if the relay sticks, or the rotor is prevented from turning with the power ON.

Both of my blocks had different color varnish on the start windings. One was redder, one was yellower. The start windings on his stator don't really look bad to me.

 

[exmaxima1]

I did find another broken red winding that looks like it is probably where the one in the pic broke from. Is there any way to get these two pieces back together? Can copper be melted back together?

Copper is easily soldered. The issue will be getting access to it.

Motor windings have a high temp varnish that you must abrade off where you want to solder. I usually use a pocket knife or Xacto knife to scrape it off, but you can also use sandpaper or even a sanding drum on a Dremel tool. Then use rosin solder to make the connection.

 

[kirk69nova]

I do have access to both ends pretty easily. Ill check to see I can get a soldering iron in there without trouble. So I can sand the varnish off and solder the two ends? Do I need to reapply any varnish if I am successful at getting them back together? If so what can I use?

 

[exmaxima1]

I do have access to both ends pretty easily. Ill check to see I can get a soldering iron in there without trouble. So I can sand the varnish off and solder the two ends? Do I need to reapply any varnish if I am successful at getting them back together? If so what can I use?

If you have enough space and wire length, cleans the ends and twist them together---it's always best practice to have a mechanical joint before you solder. Then heat and add the solder.

As far as insulating after soldering, the ideal repair would be to slide a sleeve up one of the wires before you connect/solder, and then slide the sleeve over the repaired joint to insulate it. Any sleeve will do as long as it is plastic or rubber, even a decent soda straw will work in a pinch, but something that handles heat better is preferred. Maybe the sleeve off a crimp connector? And then tie wrap the wires to make sure they don't get caught on any moving parts.

 

[Fretters]

I do have access to both ends pretty easily. Ill check to see I can get a soldering iron in there without trouble. So I can sand the varnish off and solder the two ends? Do I need to reapply any varnish if I am successful at getting them back together? If so what can I use?

Just scrape a bit of varnish off with a sharp edge held at just over a right angle to the wire, so that you're pulling the edge over the wire slightly rather than pushing against the wire. Using an abrasive on copper always risks minute fragments embedding in the copper.

With regards to insulation, either heatshrink sleeving else nick some of the wifes nail varnish and use that.

 

[kirk69nova]

Looks like I got something to do tomorrow afternoon! Thanks for all the help. I'll post up how things go.

 

[kirk69nova]

I see a couple of abnormal things.

I did not see the second photo that you made comments on earlier so just to respond. The two things you pointed out are not really there. The dark spot on the relay is a shadow and the spot on the light cord is not a burn mark but it discolored. Probably from something on my workbench.

 

[torqueman2002]

I did not see the second photo that you made comments on earlier so just to respond. The two things you pointed out are not really there. The dark spot on the relay is a shadow and the spot on the light cord is not a burn mark but it discolored. Probably from something on my workbench.

Sounds like you are on the right track with the disconnected start-up winding wire.

Looking forward to reading how you make out.

 

[kirk69nova]

I know that I am not good at soldering, I need to practice. But can someone help me here. I cannot get the solder to stick to the copper wire, it just rolls off. I scraped the varnish off with a razor blade and then used sandpaper to clean it up better. Then I twisted the wires together and then tried to solder. When it did not work I unraveled the wires and cleaned them again. I watched a few YouTube vids to see if I could learn what I was doing wrong. I saw on there if I soldered each wire individually and then twisted them together I would stick better. Well I could not get the solder to stick to the individual wired either. Any suggestions?

 

[kirk69nova]

I wonder if the winding wire is aluminum not copper??

 

[torqueman2002]

Soldering wire that has been in use is not as easy as soldering new wire.

I use rosin core solder like you and also apply rosin to the wire/joint.

Use rosin flux paste on the joint and tip to thoroughly clean them before applying solder.
http://www.amazon.com/Rosin-Paste-Flux-2-oz/dp/B000PF0RBW/ref=sr_1_2?ie=UTF8&qid=1419116939&sr=8-2&keywords=rosin+flux+paste

A clean and 'tinned' tip is essential for a good solder joint.
http://www.instructables.com/id/Soldering-101%3A-Lesson-1%3A-Tin-the-Tip/

The wire and/or tip look clean, but if the solder does not stick, they need flux.

 

[Leadberry]

1. The wires need to be clean. Did you wipe them down with alcohol after sanding?

2. Make sure you're using the soldering iron to heat the wires, then apply the solder to the heated joint. Simply melting the solder onto a cold joint will not give you results. You can melt a bit of solder onto the tip of your iron and press it into the wires to assist with heat transfer.

 

[kirk69nova]

Thanks for all your help. It is up and running!! I am still not totally convinced I got a good "weld" with the wires...but it works. The reason I am not convinced of the integrity of the joint is because it did not seem like a lot of solder flowed into the joint. But I am used to soldering stranded wire not solid and I imagine they solder differently. So I recleaned and retinned the iron and used flux this time. I was not using flux before. I am not sure if getting my iron prepared or the addition of flux or both things were the issue. Here is the soldered joint.



Here is the "varnish".



And the joint after a few coats of super **** red hot red.



I tucked the wires away from moving parts and wire tied everything out of the way.






And a video of it back on the stand I made.
Craftsman 397 block grinder:
<iframe width="560" height="315" src="//www.youtube.com/embed/nTh82AEeo0g" frameborder="0" allowfullscreen></iframe>

 

[Fretters]

And the joint after a few coats of super **** red hot red.

Nice choice of colour.

Tinning copper wire can be a pain. If it looks like you have good cover on the wires, I wouldn't worry too much about it. Worst case scenario, you have to rework it again if the joint fails at some point.

If you need to do it again though, try and get hold of some proper 60/40 rosin solder instead of that lead free **** they're selling these days. Make sure your tip, (a spade tip is better than a pointed tip for this task), is hot and clean, apply a little solder to the tip and then wipe the tip up and down the exposed portion of wire whilst you steadily supply solder as needed to the wire, (best applied from the opposite side of the wire to the tip, so that you know the wire is hot enough to flow the solder rather than just the tip melting the solder and making it appear like it's flowing onto the wire). For tinning thicker wire, you literally need to do several things at once. Apply the heat from the tip to get the wire hot enough to flow the solder, apply solder as necessary and rub the solder onto the wire to get it to hold and flow. Even with flux, that slight rubbing motion can make all the difference between the solder actually taking to the wire as it should or it just tentatively sticking to the surface of the wire, which is no good.

 

[torqueman2002]

Nice job. I think you just wanted our company while you worked on it though.

I say that because you discovered the broken wire.

I was all over the place with burnt this, smoked that, ....

I like fixing things. Nothing beats that feeling when you flip the switch, turn the key, ... and it works!

 

[jakemac]

Oldie will love that color !

 

[kirk69nova]

Nice choice of colour.

Tinning copper wire can be a pain. If it looks like you have good cover on the wires, I wouldn't worry too much about it. Worst case scenario, you have to rework it again if the joint fails at some point.

If you need to do it again though, try and get hold of some proper 60/40 rosin solder instead of that lead free **** they're selling these days. Make sure your tip, (a spade tip is better than a pointed tip for this task), is hot and clean, apply a little solder to the tip and then wipe the tip up and down the exposed portion of wire whilst you steadily supply solder as needed to the wire, (best applied from the opposite side of the wire to the tip, so that you know the wire is hot enough to flow the solder rather than just the tip melting the solder and making it appear like it's flowing onto the wire). For tinning thicker wire, you literally need to do several things at once. Apply the heat from the tip to get the wire hot enough to flow the solder, apply solder as necessary and rub the solder onto the wire to get it to hold and flow. Even with flux, that slight rubbing motion can make all the difference between the solder actually taking to the wire as it should or it just tentatively sticking to the surface of the wire, which is no good.

Thanks Ill keep this in mind the next time I have to solder. Good info.

Nice job. I think you just wanted our company while you worked on it though.

I say that because you discovered the broken wire.

I was all over the place with burnt this, smoked that, ....

I like fixing things. Nothing beats that feeling when you flip the switch, turn the key, ... and it works!

Well in reality, my grinder has been like this for a while. I just happened on a thread on GJ about repairing CM block grinders and saw all the useful info on here. So that kinda have me the confidence to try to fix it. I really thought it was gonna be the relay. In fact, I had no idea there were two separate windings with one set specifically for starting the rotation of the shaft. So when I read that and then a closer look showed me the broken wire and it came together. Also, I would have probably never attempted to fix the broken wires had exmaxima1 not told me they could be repaired. So, yah, I enjoyed the company over the last 24 hours but you may not realized that I gained the confidence to do it by all of you who chimed in.

 

[McBrownie]

Kirk,

Glad, but not too surprised, that it was a straightforward fix. I couldn't help but notice in your video that your light is wired to the power switch. That drove me nuts on my split-phase, so here is what I did.

My original wiring looked liked this:
View media item 40372
And I changed it to this:
View media item 46178
Using one of these:
View media item 46179
And then installed a switched lamp socket:
View media item 41437
Problem solved and I can now turn the light on without having to turn the grinder on.

 

[kirk69nova]

I could see how this modification would benefit me if I used the light for other purposes. But where I have the grinder set up in my garage the light is only used when I have the grinder on. I would certainly consider this if the grinder ever gets moved closer to my workbench.