Thornton mechanical lab surface grinder

B

Batmanacw

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I've had this surface grinder for around 15 years or more. Starting out it didn't grind very nice but after I learned about clocking the wheel and better techniques the quality of the surface has gotten much better.

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We really didn't know what oil to run in the spindle so we started out running SAE 30 non detergent. The seals leaked pretty badly starting out. All these years later the seals barely leak at all unless I put in a lot of oil. I usually fill the oil cup and warm up the machine, then refill it again.

The machine runs really smooth. It is extremely accurate and everything glides beautifully. I really love this machine and it is surprising to say that after the initial rough finish.

I don't know what I should be running in the spindle and Google is no help. I don't know if running a thinner oil will give me an even better finish. I do know I'm not getting much heat. I don't know if using such a thick oil had caused damage but the machine really runs nicely.

I am thinking I should try some 6 wt to 10 wt oil just for kicks.... I'm not entirely sure the thin oil won't just fall out of the old seals......

What do you think?
 
Is the spindle slightly tapered, and the housing as well, on your grinder?
 
Bob Korves said:
Is the spindle slightly tapered, and the housing as well, on your grinder?
Click to expand...
If it was, 30 weight oil would cause big problems such as heating and/or seizing up, I would suspect that it has ball bearings, and think that weight oil is too heavy. Grinders usually do not use seals, just a clearance closure/ laberynth.
The spindle on Bob's grinder uses a tapered spindle in a bronze tapered box using a collar to maintain a very small clearance; it uses a very light oil for lubrication.
 
benmychree said:
If it was, 30 weight oil would cause big problems such as heating and/or seizing up, I would suspect that it has ball bearings, and think that weight oil is too heavy. Grinders usually do not use seals, just a clearance closure/ laberynth.
The spindle on Bob's grinder uses a tapered spindle in a bronze tapered box using a collar to maintain a very small clearance; it uses a very light oil for lubrication.
Click to expand...
Mine has never had heat issues but I'm asking for a reason. I'd like to keep it running well. This grinder isn't a crazy high tolerance grinder.

I've never had the spindle out.
 
Janderso said:
Why do you ask Bob?
Click to expand...
What John York said in post #5... A tapered spindle with a plain bearing needs to not have any crud in it, must be carefully adjusted for end play, and must use a high quality light weight oil with a viscosity closer to paint thinner. If there are ball or taper bearings in there, you do not have a tapered spindle.
Batmanacw said:
Mine has never had heat issues but I'm asking for a reason. I'd like to keep it running well. This grinder isn't a crazy high tolerance grinder.

I've never had the spindle out.
Click to expand...
Properly set up and taken care of, a tapered plain bearing spindle can do excellent work, with better runout at speed than many precision ball bearing setups. You must really understand the word "clean," and keep contamination out of the spindle bearing area.
 
Bob Korves said:
What John York said in post #5... A tapered spindle with a plain bearing needs to not have any crud in it, must be carefully adjusted for end play, and must use a high quality light weight oil with a viscosity closer to paint thinner. If there are ball or taper bearings in there, you do not have a tapered spindle.

Properly set up and taken care of, a tapered plain bearing spindle can do excellent work, with better runout at speed than many precision ball bearing setups. You must really understand the word "clean," and keep contamination out of the spindle bearing area.
Click to expand...
This isn't a high dollar machine. I'm pretty sure it's ball bearing. I don't want to tear the spindle apart when it runs so well. My buddies Harig uses crazy expensive thin oil. This old Thornton has run great for years on 30 wt. I think we can easily assume that it not a taper shaft set up.
 
Turns out I was right. It is definitely a ball bearing set up.

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It uses felt seals and a screw in cap to hold the oil in.


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The end play is set by the nut that holds on the pulley.

The shaft was knurled a bit before re-cutting to tighten the bearing fit. It needs lightly cleaned with some scotch brite to remove corrosion but not enough to change the fit.

20210830_100504.jpg


I gave a push/pull on the spindle before removing it and there was some end play. I will take that out before I'm done.

I sure learned a lot in the last 30 minutes.



I still don't know what oil to use. Lol!
 
Check your bearings closely for wear and damage. Surface grinders live in a world of metal grit and grinding wheel dust, which must be kept out of the bearings, or they will rapidly get damaged. Make sure you have some kind of sealing system that works properly, no missing parts or aftermarket wannabe sealing, everything in the bearing area tight and spotless when it goes back together.
 
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