Slowing down a 3450 rpm grinder with pulleys for putting a radius bevel on chisels and plane irons

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Forum topic by ElChe posted 02-03-2015 01:33 PM 722 views 0 times favorited 4 replies Add to Favorites Watch
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630 posts in 756 days

02-03-2015 01:33 PM

Topic tags/keywords: bench grinder sharpening rpm slow down radius grind norton wheel pulley rheostat

I just scored a free fake 3/4 hp (5 amps) 8” grinder that runs at 3450 rpm. I want to slow it down to 1750 rpm or lower to put a radius grind on chisels and plane irons prior to sharpening. It is quiet so I am assuming it is some sort of induction motor so I don’t think I can slow it down with a rheostat. My thought is to build a platform for it where I can mount pulleys on the shaft and then run belts to a separate shaft with pulleys for a Norton friable grinding wheel on one side and a buffing wheel on the other side. Has anyone done this? If so what size pulleys?

I’m cheap and don’t want to fork out the money for a slow speed grinder as I can source a nice shaft/ pulleys/bearings from a buddy who works with HVAC.

Final question: if I’m careful with grinding and take my time so as not to overheat the tools, can I run a Norton type friable wheel at 3450 rpm for the bevel grind? I plan on using a Lee Valley tool rest as the stock tool rests on grinders even expensive ones are marginal to awful (the tool rests on my freebie grinder are awful stamped crap).

Thanks. Tom

-- Tom - Measure twice cut once. Then measure again. Curse. Fudge.

4 replies so far

View johnstoneb's profile


2104 posts in 1592 days

#1 posted 02-03-2015 01:42 PM

You need to check with manufacturer. Grinding wheels come with a maximum speed label on them.

-- Bruce, Boise, ID

View ElChe's profile


630 posts in 756 days

#2 posted 02-03-2015 01:53 PM

Good point. I don’t want the wheel to disintegrate for sure! The Lee Valley wheels are rated max 3600 rpm for 8” wheel so that looks good so far. Thx for the advice! Tom

-- Tom - Measure twice cut once. Then measure again. Curse. Fudge.

View jdh122's profile


878 posts in 2237 days

#3 posted 02-03-2015 02:04 PM

I use a 8 inch bench grinder at full speed (probably 3450) with a white LV friable wheel. As long as you make sure to dress the wheel frequently, take light quick passes and dip in water you can certainly do your sharpening without slowing down the grinder or burning the steel. Like you’re planning to do I use the Veritas tool rest – the one that came with the grinder was terrible junk.

-- Jeremy, in the Acadian forests

View brtech's profile


882 posts in 2342 days

#4 posted 02-03-2015 03:30 PM

Pulleys are simple to deal with. Check out:

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