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How to Open up Gorton 375 Spindle and Replace Bearings?

Steve H. Graham

Aluminum
Joined
Nov 6, 2007
Location
Miami
I just bought a Gorton 375. Paid $350 to have it shipped, and now I find the bearings are gone. I am here to see if anyone can help me.

The only manual I have is pathetic, and the parts diagrams are microscopic. I'm figuring out how the spindle is put together as I go. I opened up one end, exposing the bearing. The other end has some weird fasteners, and I don't have the tools to turn them. I am hoping that once I get these things out, I'll see how to get the bearings out.

I am posting photos. Can anyone tell me what I need to get this end of the spindle apart? I'm thinking I may have to weld some kind of cheesy spanner together, but I don't know if it will work. Also, if anyone here knows what kind of bearings I need, I would appreciate the info.

02 04 20 Gorton 375 grinder end of spindle 02 small.jpg

02 04 20 Gorton 375 grinder end of spindle 01 small.jpg
 
I just bought a Gorton 375. Paid $350 to have it shipped, and now I find the bearings are gone. I am here to see if anyone can help me.

The only manual I have is pathetic, and the parts diagrams are microscopic. I'm figuring out how the spindle is put together as I go. I opened up one end, exposing the bearing. The other end has some weird fasteners, and I don't have the tools to turn them. I am hoping that once I get these things out, I'll see how to get the bearings out.

I am posting photos. Can anyone tell me what I need to get this end of the spindle apart? I'm thinking I may have to weld some kind of cheesy spanner together, but I don't know if it will work. Also, if anyone here knows what kind of bearings I need, I would appreciate the info.

View attachment 277676

View attachment 277677

Don't make a problem out of a solution.

Hook spanners and pin spanners are still sold, various sizes, including adjustable. In sets, and in sets of adjustable ones as well.

So, too bearing pullers, all types.

Save the cheese for welding Pizza's together.

:)

Rolling-element bearings are nearly always marked. And then there are precise size measurements. Type of bearing ID, OD and width, plus some detective work, and you can find a set.
 
Does the back half of the arbor come off with a puller?

I found an adjustable pin spanner that comes with square pins. Maybe there is hope.

Thanks for the help.
 
Steve: The part furthers to the right in the picture looks like the back half of the wheel mounting hub,the small thread at the end looks like it is left hand . And the wheel flange nut thread also looks left hand which would make sense with CW spindle rotation.
 
Robin Renzetti recently released a YouTube video on rebuilding a precision spindle.
I strongly encourage you watching it before you take it apart, in order not to miss important details, like noting the timing of the bearing races, etc.

YouTube

Paolo
 
Once the tool arrives, I plan to see what I can do. My best guess is that a puller will remove the back half of the arbor, and then I'll have to find out if age has welded the spindle to the threaded parts.
 
Steve;
I've got a Gorton 375 also. The bearings aren't in need of replacement yet but I'll be following this thread with interest. Good luck.
 
Oh, boy. When people at Practical Machinist start looking to me for help, it's not a good sign at all!

I'm hoping the bearings are the only issue. The grinder trips my GFCI every time I turn it on with the spindle and motor connected. With no load, the motor does not trip the GFCI. I am hoping it will not trip it once the bearings are fixed and the motor doesn't have to work so hard.

My understanding is that the previous owner, who apparently does not have a GFCI, was using the grinder as it is, with the tight bearings. I suppose the lack of a GFCI masked the grinder's problems. He probably thought that as long as the motor turned, the grinder was okay.

I am assuming the bearings should turn freely, like the bearings in every other grinder I've ever seen or heard of.

The motor is really strange. It's an old GE, and it has rubber mounts covering the ends of the shaft. I can't figure out how to get into it to look for problems. I can't see a capacitor anywhere. I was thinking a bad capacitor might cause current to flow to the casing. I have a feeling a local motor shop would have no idea how to deal with the rubber mounts. I'm afraid I'll tear them if I pull them off, and what are the odds GE makes new ones? Not good.

02 04 20 Gorton 375 grinder motor small.jpg
 
The motor shouldn't trip the GFCI, independently of the load. What could happen is that it takes longer to come up to speed and, possibly, that's enough for the starting winding to heat enough to expand or whatever and a spot without insulation to make contact with the ground. I believe that GFCI are tripped by 10-30 mA of current and have a delay of at most tens of milliseconds (I think shorter than the time taken by the motor to get up to speed and disengage the centrifugal switch even without any load ...But I could be wrong on this).
Are you sure that it is not tripping the over-current protection in the breaker (i.e. do you have the GFCI protection as a feature of the breaker, or is it a GFCI protected outlet)?

Paolo
 
I have read that many old motors are designed so there is a current imbalance even when they work correctly. If that's right, I suppose the higher current resulting from a stiff spindle could make the imbalance worse and pop the GFCI. I am going to be looking for more info on an electronics forum.

My hope is that once the bearings are fixed, I won't have to do anything with the motor.

The GFCI is a wall socket, not a breaker.

I got some info from PM member Mcritchley, who has done a bearing replacement on one of these. I will post what he sent me. Looks like it will be a huge help. I'm sure someone else will need it sooner or later.

The next step would be to remove the wheel hub, we used a puller to slide it off

The lock the shaft in place we made two thin nuts tightened against each other on the pulley end. We then clamped the double nut in a vice.

Next we loosened the wheel side nut. We made a socket with a bunch of pins. Once that is loose you can remove the bearing lock ring that retains the outer race. I have a good pin spanner that I bought from McMaster car. I had to hit the end of the spanner with a dead blow hammer to knock the lock ring loose. If I recall correctly all of the nuts were conventional right handed threads.

Next remove the nuts on the pulley side of the shaft.

You can then tap the shaft out pushing on the pulley side. The single bearing on the pulley side has a tenth or two of clearance so it pushes out easily.

I may have missed something or forgotten the order of disassembly of the hub end. It’s been a while since I had I apart.

Here are the tools I used for disassembly. Missing are the two nuts that lock into the shaft.

01 07 20 mcritchley tools for disassembly small.jpg
 
My puller and pin spanner arrived. The puller popped the arbor hub off the shaft. It was on there pretty good. When it came off, it was pretty energetic.

The pin spanner is not ideal for this item. I thought I was ordering a spanner with square pins, but it has round ones. It's not easy to hold it in place, and when I apply a lot of pressure, it comes loose.

The spanner slots are a little chewed up, and for some reason, Gorton only put two in the nut. I'm thinking I may mount the spindle on the mill and drill some holes in the nut. This should make for a better grip.

I got some Sea Foam Deep Creep and put it on the nut yesterday. I left it to soak in.

I don't know the best way to hold a slick round part so it won't slip. I have rubber jaws in my bench vise. I'm hoping they'll be enough.

After this, I can think about the nut on the shaft.
 
The pin spanner is not ideal for this item. I thought I was ordering a spanner with square pins, but it has round ones. It's not easy to hold it in place, and when I apply a lot of pressure, it comes loose.
You wanted a "hook" spanner, not "pin", but if time is of the essense just file or grind the rear edge of the round pin to a flat so if anything fails it is the easy to replace spanner, not a buggered-up hard to replace nut.
 
I am not sure that your bearing are the issue. A GFI hooked to an open frame motor mounted on a GRINDER is the reason the gfi trips. I am sitting next to my Gorton 265 the spindle turns smoothly, but no loosely. Tripping of the GFI is a useless way to diaignois Spindle bearings. Are the bearings loose on end play Y/N, Are the bearing Notchy when Turned by hand Y/N, Do the bearings feel to hot to hold after 30 minutes Y/N, Do the bearings scream when loaded, much quieter no load. Y/N.

If the answer is not yes 3of4 you are wasting money and time. Put that GFI in the bathroom were it belongs. It is Called a" Ground Fault Interrupter" Not a motor overload spindle bearing condition device.

It faults out because the open frame motor has lots of grinding dust inside, making a path to ground.
 
Thanks for the replies.

About the hook spanner, it won't fit this kind of nut. There is nothing for it to rest on.

The bearings spin smoothly but with considerable effort. It's not like a bench grinder; you know how easily they turn. They don't feel notchy. I heard a squeak the first time I turned them by hand. I have never been able to get them to turn using the motor because it dies instantly.

I don't have another grinder to compare it to. It just seemed wrong for it to be so hard to turn compared to things like the bench grinder, the drill press, my mill, and so on.

I would put the grinder on a non-GFCI circuit, but the whole shop is wired that way.
 
When I opened the grinder up and looked at the motor, I had never seen anything like it before. I assumed it would be a real pain to replace. Now I'm looking around on the web, and it looks like 1/4-HP 1725 motors with rubber mounts are very common. TEFC versions cost twice as much, though. Maybe this is what I should look into.

If grit is the problem, though, why does the motor run fine without the belt attached?
 
The story gets weirder.

I just turned the grinder on, assuming I would have to go reset the GFCI immediately. The motor ran. I turned it on more than once, and I had no problems. I took the belt off and applied pressure to the motor pulley while turning it on, to simulate bad bearings. It still started and ran.

I have no earthly idea why it's working. I blew grit out of it yesterday, but it still would not start under load after I did that. I also oiled the motor's bearings with mill spindle oil, but I don't think that was the problem.

I ran it for several minutes, and the shaft on the wheel end of the grinder got too hot to hold onto. The other end stayed cool.

Now it appears that the motor and electrics are fine but the bearings are, in fact, on the way out. My guess is that the wheel-end bearing is the problem. The other end did not get hot. I guess I'll replace both bearings unless they're expensive, in which case I'll just keep the good one. Once I've mastered disassembling this thing, it will be a very easy job to get it apart in the future.
 
When I opened the grinder up and looked at the motor, I had never seen anything like it before. I assumed it would be a real pain to replace. Now I'm looking around on the web, and it looks like 1/4-HP 1725 motors with rubber mounts are very common. TEFC versions cost twice as much, though. Maybe this is what I should look into.

If grit is the problem, though, why does the motor run fine without the belt attached?

TEFC was "standard" around a printing plant. Paper dust issue. Similar, sawdust-making bizness, paint shops and such.

I'd want the same around a grinder.

Do it right "once" and move-on to more challenging "stuff", IOW.
 
Two considerations.
1) Bearings: the aren't necessarily shot. It could well be that the grease has dried out and is now too hard and too viscous. Possibly, you can get a few extra miles out of them by flushing them and packing them with the right amount of the proper good quality grease (unless you've already done it, watch Robin's video on rebuilding spindles).
Personally, it might be lack of practical experience, but I don't see taking apart and rebuilding a precision spindle anything trivial, even after rebuilding the very same spindle ten times.

2) Generally, grinder motors are better dynamically balanced than regular motors and they're mounted on vibration-dumping mounts. Regarding the loss of current to ground, I'd bet that the leakage was caused by the grit either at the centrifugal switch or at the start winding.

Paolo
 








 
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