Slow Speed Grinder Recommendation needed

[Exact Blade]

What is the best slow speed grinder that would work best with the Tormek bench grinder accessory?
Thanks
Dan

[Herman Trivilino]

I don't know about the grinder itself, but the Norton White Aluminum Aluminum Oxide Grinding Wheels come highly recommended.

Others have recommended some good grinders in the past, so I'm sure they'll chime in soon.

[Mike Fairleigh]

What is the best slow speed grinder that would work best with the Tormek bench grinder accessory?
Thanks
Dan

A variable speed KMG-10. 

Now if you mean traditional benchtop grinders, I've thought more than once about the 8" slow speed from Woodcraft.  It's a Chinese tool but people seem to like them once good wheels are installed.

Then of course there's the Baldor line...

[Ken S]

This arrived in today's email.  I don't know anything about it.

http://www.rikontools.com/facttag80-805.htm?et_mid=632082&rid=237810368

Keep in mind that an eight inch wheel has more surface speed than a six inch wheel at the same motor speed.  The larger wheel would give less hollow ground effect.

Baldor is certainly known as the best, and is priced accordingly.

A good grinder won't wear out.  I would check the old market, back when most grinders had an extra measure of quality build.

Ken

[Rhino]

Can you use a grinder for polishing too.  I want to polish the knives I scratched up while sharpening.  Can I put a cloth wheel on a grinder and polish?  Or is it better to buy a separate polisher?

[Mike Fairleigh]

They make both rag and felt wheels of various "hardnesses" for bench grinders.  You might need to do some trial and error to find just the right combination of material and hardness for your application.  Although - polishing on a slow-speed grinder (if that's what you're considering) might be frustratingly slow.

[grepper]

Mike's right about that.  They make all sorts of buffing, polishing and surface conditioning wheels.    Just search Google for those terms. 

I've had a lot of fun with the 3M Scotch-Brite stuff.   It makes a satin type of finish on steel.  That's handy if you have scratched or imperfect surfaces because it is good for blending imperfections or if you are just looking for a "satin" type of finish.  I've given steel a satin finish and then polished it for a polished satin finish.    Looks pretty cool.

There are buffing wheels that you can use with or without compound.  I've had good luck using the wonderful Tormek compound on felt.

I'll also agree that it's good to do some playing around first so that you know how the various wheels effect the steel.

[Herman Trivilino]

Can you use a grinder for polishing too.  I want to polish the knives I scratched up while sharpening.

Have you tried poliching them with the honing wheel?

[Mike Fairleigh]

Have you tried poliching them with the honing wheel?

I have.  It's not that it isn't capable, it's just intolerably slow (at least for me) being used for that purpose.

[Ken S]

I haven't tried it, however, I have seen one side of a dry grinder used with a buffing wheel.  Make very sure you use the back side , so that the wheel turns away from the tool.  Having a Tormek, I rarely use the second wheel (an 80 grit white wheel) on my dry grinder any more.  The primary wheel, a Norton X3 46 grit, gets occasional use. It cuts quickly and leaves a surprisingly smooth surface for such a coarse grit.

Ken

[grepper]

I've removed scratches and some pretty messed up surfaces from blades,  and here's what happened to me...

How effective polishing will be on scratches is going to depend on how deep the scratches are.  If it's much of a scratch at all, polishing on leather, with or without compound, will only result in shiny metal around the scratch. 

The way that I have found that works is to start with fairly course abrasive, say 240 or 320 grit or maybe even 400 grit, and work away until the scratch is gone.  The point is that you actually have to _remove_ the scratch before polishing.  If the knife has a mirror finish, try starting with  400 grit and see if that works.  From my experience many knives with a mirror finish can be made of very hard steel, and if too high a grit is used it will take forever to remove a scratch.   It won't work to just try to polish or buff it away.

Then slowly move up to finer abrasives.  400, 500, 600, 800, 1000 grit.  Somewhere around 800 – 1000 grit things will start to get pretty shiny.  Then, and only then, it's time to move to polishing compound and buffing wheels.  This takes time.

The thing that I found is that if you try to shortcut the process and start with very fine abrasives, it only takes longer because enough steel has to be removed to actually remove the scratch.  It also does not work to get impatient and jump from 320 grit to 1000 grit because you get a shiny 320 grit scratched surface.  That will give it sort of a "satin" finish.  Understand that what will happen is that you will scratch up the blade with whatever grit scratches of the abrasive you are using, so it will make a mess out of that area at first.  Then the idea is to remove those scratches with finer and finer abrasives.

You can do this by hand with sandpaper, but paper or surface reconditioning abrasives such as Scotch-Brite, etc., on a bench or belt grinder will really speed things up.  If you are using a high speed grinder, be careful not to overheat the blade, especially at finer grits.  Unlike the Tormek where heat is never an issue, dry grinding the side of a blade can get pretty hot fast!  If you get impatient and press hard and get a blue spot on the blade, the blade will never be the same. 

Practice on junk knives first.  Get an understanding of how each abrasive effects the surface.  Put a scratch on a blade than then try to remove it with a fine abrasive and see that you will grow old before the scratch is gone.  Just for grins, try it with 80 grit and see how much it scratches the surface.  Try each grit on a fresh area of a blade to understand it's scratch depth and cutting speed.   Play with different types of steel.  It can be difficult to remove surface imperfections on very hard, very shiny steel.  It can take a while.

Try to practice on a blade with similar steel. Very hard mirror steel acts much differently under abrasives than softer steel.  It's a very good idea to understand  your abrasives, the process, and how different types of steel are effected before attacking your favorite knife.

Anyway, that's exactly what I did.  I'm no expert at steel surface conditioning, but that's what is recommended, and what  worked for me.  Hope that helps. 

[Jeff Farris]

Very nice post, grepper.

One product that I use extensively for scratch and corrosion removal is Klingspor's Sandflex Abraser Blocks. All of the demonstrators at the woodworking shows when they were in their heyday used them to keep their workers looking brand new. I picked up the habit from the folks at Lie-Nielsen. Deneb's wife would pick up every plane after a customer looked at it and give it a once over with the fine Abraser. I keep my Universal Support polished up with one, and it always floats up and down.

[Mike Fairleigh]

+1 on those blocks.  I use them on the universal support and also on the motor shaft to clean off the rubber build-up.

I always wondered if that was Deneb's wife.

[grepper]

Thanks Jeff.

Huh.  That's a good idea to polish up the USB.  Mine in a little "hangy" and I always have to jiggle to make a fine adjustment.  Rather frustrating.  I've also thought about applying a dry coat teflon, or dry coat silicone.  Or maybe let a coat of teflon dry and then apply a layer of silicone for extra smoothness.

[Jeff Farris]

I always wondered if that was Deneb's wife.

Depends. When he started doing the shows, it was. The last couple years she stayed home with the kids and his sidekick was his sister.