No Weld Grinder - Bearing heat question??

K

KayakWilderness

Member
Just finished my NWG after ordering the plans a couple of weeks ago. Top SFPM is around 6800. While running at that speed the 2 contact wheels (2" and 3") get around 145 F. That reading is actually from the bolt holding the wheels on so actual bearing temp I assume is slightly higher. Seems to be working well but would like some assurance that this temp is not damaging the bearings. The bolt holding the wheel is not torqued too tight - wheels spin very freely. Can't wait to start grinding knives with this thing - really eats up the metal compared to my old grinder! Any advice would be appreciated - thanks.
 

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6800 SFPM? WOW!!!! That's humming. I max my grinder out at 4,800 SFPM and don't use that speed, and that's just too fast for me to be comfortable with - it will throw some sparks. I normally profile around 3500 SFPM, and that's plenty fast for me. What RPM is your motor? Diameter of the drive wheel? Looks like your pulley's are the same as I've got, 4 step, and 2", 4" ends.

I won't comment on max temperature of bearings - I'm sure there is a factory spec for your bearings.

Nice build on the grinder.

Ken H>
 
KenH said:
6800 SFPM? WOW!!!! That's humming. I max my grinder out at 4,800 SFPM and don't use that speed, and that's just too fast for me to be comfortable with - it will throw some sparks. I normally profile around 3500 SFPM, and that's plenty fast for me. What RPM is your motor? Diameter of the drive wheel? Looks like your pulley's are the same as I've got, 4 step, and 2", 4" ends.

I won't comment on max temperature of bearings - I'm sure there is a factory spec for your bearings.


Nice build on the grinder.

Ken H>
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Thanks Ken. The step pulleys are 2"3"4"5". Motor is 1750 RPM and drive wheel is 6". Using the calculations in the NWG plans, I should get speeds of 6869, 3663, 2061, 1099 SFPM using these pulleys. I did check with Ron at Beaumont Metalworks regarding the bearing heat. He stated this heat was within spec and should get better as the bearings lose some of the grease.
 
All bearings fail eventually. They are only a few bucks apiece and are easy to change out. The hotter a bearing gets, the sooner it will fail. I'd say you aren't too hot.
I have grown to prefer a faster grinder myself but I still have to be able to slow it down to really slow.
 
Well, maybe as I get more grinding experience under my belt, I'll move up in speed. Right now, I'm not in a big hurry at all.

Per my calculations your speeds are right on - and you have a GOOD selection of speeds. I looked for a pulley in your ratio, but didn't find it (or too expensive?), anyway I wound up with a 2, 2.5, 3.5, & 4" ratio.

Some folks actually grind at 7,000 SFPM? Talk about sparks flying. Maybe that's why I hear about fires from the dust?

Ken H>
 
BossDog said:
All bearings fail eventually. They are only a few bucks apiece and are easy to change out. The hotter a bearing gets, the sooner it will fail. I'd say you aren't too hot.
I have grown to prefer a faster grinder myself but I still have to be able to slow it down to really slow.
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BossDog,

Just curious - when you say "really slow", what SFPM is that? Is 1100 SFPM too fast for finishing work?
 
You should keep some spare bearings around.

That will reduce down time when they eventually fail.

They're cheap insurance.
 
KayakWilderness said:
BossDog,

Just curious - when you say "really slow", what SFPM is that? Is 1100 SFPM too fast for finishing work?
Click to expand...

Generally around 1k but even down to 500sfpm comes in handy occasionally when I have a small stubborn spot.
 
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