Bench grinder rpm

[robatman]

Hi all,
I have a cheap ryobi grinder which has a belt on one side and wheel on the other. I got it primarily for the belt, (which is ok for light shaping, but bogs down alot!!) but now want to give the wheel another go at grinding a bevel.
After losing the temper of a few plane blades (no drama as i picked them up from a garage sale for next to nothing), i realise a new wheel could make the difference. My questions are:

Is the 2850 rpm too fast for grinding plane and chisel blades??

Which wheel?- i have read various discussions of white/grey etc, but which will suit the speed of the grinder?? or does that not apply.

Thanks
Robert

[Dean]

Type of wheel doesn't apply regarding speed, as long as the wheel is rated to be spun up at those RPMs. White wheel for High Speed Steel, grey is fine for carbon steel.

2850RPM is fairly standard for high speed bench grinders. And yes, if you are not careful, you can lose the temper (and lose your temper too ) if you engage the tool to the wheel for too long continuously without using a coolant. Have a tray of water or special grinding coolant nearby and make a grinding pass, them dip tool in water for a second or three, then repeat the process. As long as you are patient you can grind just fine on a high speed grinder without doing damage to your tools.

You can buy slow speed grinders and water cooled grinders which won;t casue damage to your tool, but they take longer to do their thing, so each grinding method has its catch I guess.

[derekcohen]

Robert

Grind your blades on the belt, not the wheel! This will do so so much cooler. Have a look in the "Best" section, or do a search on Belt Sander Grinder, for tips in this regard.

Regards from Perth

Derek

[routermaniac]

You can very successfully grind the bevel on planes and chisel blades using a standard 8 inch grinder. You will have to take the time to make a decent tool rest (see aprcotrippers post for ideas) but I assure you it will never be the same. Much faster than a belt grinder and unless you are careless you will not ruin any blades. It has taken 95% of the work out of my sharpening. A 6 inch grinder which is usually what you get when you buy combo grinders isn't as good as the hollow bevel is too "rounded".

regards
Marios

[derekcohen]

Much faster than a belt grinder and unless you are careless you will not ruin any blades.

Marios

There are not many greater understatements than this.

Unless you are careless..

It only takes a split second on a high speed grinder to render the edge useless. Yes, an experienced user can grind on a high speed grinder, but the relevant word here is experienced.

I have a high speed grinder, a slow speed wet grinder, a belt sander grinder, waterstone grinder, and meat grinder (ok, ignore the last one). The only one that is safe is the slow wet grinder - but it is sooo s-l-o-w that it is hard to take seriously. The belt sander is the best compromise around. Ask Tage Frid (ok, don't - he is pushing up daisies - but this was his first choice as well). Plus you can change grits.

Here is my Mk II jig. There is a link to the Mk I jig, which is a simpler construction.

http://www.woodworkforums.ubeaut.com...ad.php?t=16156

Regards from Perth

Derek

[China]

I have a 8" grinder with one of the new blue wheels best thing I've ever used, I don't have any special rests or jigs except for carbide cutters, take your time and learn how to do it right, the last time I burnt a blade was at trade school 35 years ago

[scooter]

Knew Marios' post would hook you in, Derek

With respect to your jig, which I think is excellent & plan to replicate sometime soon, I think you overstate the difficulty of grinding woodworking tools on a bench grinder.

Yes, it is possible to burn a blade. OK, now that's out of the way: if one takes it slowly, lets the abrasive do the work, keeps the wheel "sharp", & uses a decent toolrest (homemade or shop bought) in my opinion it's not too hard, even for a novice, to hollow grind a blade on the grinder.

Is it easy, in ignorance & carelessness, to burn a blade? Yes.

Is it easy to not burn a blade if one takes note of what burns a blade & bears that in mind when underway? Equally yes I reckon.

Is your belt sander rig a good way to sharpen? It certainly seems so.

My point is, I guess, that a bench grinder is a pretty common tool in the workshop, more so than a belt sander, & is more than capable, even for a novice, of achieving the same goal, ie a properly ground bevel. edit:how many bloody commas in that para...


Cheers...............Sean, ground plane

[mic-d]

I use an 8" grinder with a speed of 1475rpm and a AlOx wheel. I hold 2 fingers near the tip of the blade when grinding and use a very light touch. When I first started out sharpening I burnt my fingers a couple of times, but not the blade. Now I can grind a nick out , or the secondary bevel right off without stopping to cool the blade and it only gets warm to the touch. It's all about lightness of touch.

Cheers
Michael