Why does a bench grinder rotate downward?

[froglips]

I was contemplating my naval, when this occured to me.

Why do bench grinder wheels cut in a downward rotation?

I have found it much easier when I grind a chisel, if its held below the center point. Or, if I angle the edge to be cut near the top (say 1 or 2 oclock if you looked at the side of the wheel).

In some digging, I did learn that honing wheels should rotate away from you.

But, I couldn't find a good reason "why" the grinding wheel rotates towards you.

There are factors like the tool rest, safety and burr size.

But, in my mind, if a tool was being pulled away from me, wouldn't that be safer should it slip?

Thanks,
Jim

 

[Canuck]

I think that you are onto something, Jim. I too have often wondered about grinder direction. It seems to me (I could very well be wrong!) but when I saw a Tormek grinder demo at Woodcraft awhile ago, I thought it's wheel travel was away from the operator. (My VS Delta wheel heads right at me.:5eek

Hopefully someone who is more sharpening savvy than I will chime in to help us out with this question.

Another inquiring mind....

Wayne

 

[LeeNC]

Most bench grinder turn at high speeds. Their too rests are set so that the tool is pushed down onto the tool rest as it is ground. This also would throw most of the debris and any tool launched off of the wheel, when not using at tool rest, towards the ground instead of up into the air or you.:elvis:

Lee (CLT)

 

[CaptainCowie]

I would hate to grind something freehand with the wheel pulling up on the piece! Everything would be thrown up at your face and it would be a heck pf a job holding the piece down to the table/rest. Down is by far the safest way for them to spin.:icon_thum

 

[MikeL]

Jim, I know you're a wild man from welding class. I guess you now love metal working so much that you want to eat those sparks! :5hot:

 

[ashley_phil]

because if it didn't the world would start spinning the wrong way. in the southern hemispher they run their grinders the other direction to keep it all balanced momentum wise.:rotflm:

 

[dancam]

The Tormek manual sez you can sharpen in either direction. The caveat they offer, is that sharpening with the wheel coming towards you is more aggressive.

They also caution that honing is ALWAYS done w/the wheel going away from you (the blade could catch and seriously injure you in the other direction).

Dan C.

 

[Bas]

It's an interesting question. On the Work Sharp machine, the disc rotates counterclockwise, and you're supposed to put the tool to the disc in such a way that it rotates away from you.

Is it possible that the direction was copied from when wheels were powered by foot? It's much easier to pedal forward than backward.

 

[Canuck]

The Tormek manual sez you can sharpen in either direction. The caveat they offer, is that sharpening with the wheel coming towards you is more aggressive.

They also caution that honing is ALWAYS done w/the wheel going away from you (the blade could catch and seriously injure you in the other direction).

Dan C.

Thanks Dan,

When I saw it demonstrated, he was honing a carving knife. (Joe at the Raleigh WC.) This explains why he had the wheel going away from him.:thumbsup:

Thanks again!

Wayne

 

[Nativespec]

My Jet slow, wet grinder goes upward and I think it would be dangerous in the other direction since the tools you sharpen can be very sharp. They can become airborne, but I think flying away from you is safer.

A water stone can be used in any direction.

David

 

[JackLeg]

My Delta slow wet grinder has a "reverse" button on it. Works either way.

 

[junquecol]

Three words- HEAT BUILD UP. The heat runs ahead of the cutting action. If grinder was turning toward the edge, edge would QUICKLY overheat. The heat would be drawn toward the sharpened edge, rather than the mass of the body of the tool.

 

[jglord]

The Tormek has two positions for mounting the various holding jigs. In the lower or front position tools are ground with the stone coming towards the blade and if mounted in the rear position the stone is going away from the blade. They recommend using one or the other, based on the holding jig and tool being sharpened.



So I guess both have their purpose. Maybe the answer to the question is it depends on what and how you are sharpening. I'd never put my small pocket knife to a grinding wheel, but I sharpen most of my turning tools on a grinder. I guess my answer is folks smarter than I have said this is the way to do it and it works. So I follow along, because it works. :dontknow:

This probably doesn't answer the why question but I thought it might add some clarity or maybe some more confusion. :BangHead:

 

[Canuck]

Thanks a lot, John.

Your response clarifies the Tormek question that I added.:thumbs_up

(Sorry Jim if it looks like I highjacked your thread!:violent1

Wayne

 

[froglips]

Well, at least now I know the answer isn't as simple as I thought.

I can see where heat would be transferred to the cutting edge much faster when rotation is away from you.

Maybe its like how we have end grain fiber tear out if we don't use a backer board. Given metal is also made of some sort of "fiber", could it be the cutting edge would in effect "tear out"? If so, grinding downward would provide more support to the cutting end.

Sparks and grindoff junk would fly in your face, assuming you held the tool in the same center line position you'd use in downward rotation. In that case, you'd want to hold the tool higher than normal. I get the same effect holding the tool below the center line. Not good if you have people standing behind the grinder, ouch.

Thanks to all for a lively discussion.

I might be 37, but I don't think I'm done with my "but why" phase of maturing

Jim

 

[Joe Scharle]

Seems to me that the other way would tend to pull the work out of registration, unless the wheel was going very slow.

 

[NCPete]

Seems to me that the other way would tend to pull the work out of registration, unless the wheel was going very slow.

yeah, spinning the otherway, I would end up with some very dull tools very quickly:BangHead:

 

[ashley_phil]

because if it didn't the world would start spinning the wrong way. in the southern hemispher they run their grinders the other direction to keep it all balanced momentum wise.:rotflm:

geez ...a snide comment wasted.:5sigh:

 

[froglips]

Sorry, Snidely Whipl-ash-ley_phil

Your concerns are noted, I'd hate to destabilize the momentum of the planet!

Jim