Tuesday, February 15, 2011

Grinder Tool Rest - Free Plan

After watching me burn up a few tools on a high speed grinding wheel that looks like it was made from recycled earthquake rubble, my folks took pity and got me one of those $100, no-name 8" slow speed grinders with the soft white wheels for sharpening my chisels and plane irons. It works great, but like every other grinder in the world, the tool rests that came with it were not the best. I had the usual build vs. buy debate with myself, and (as usual) my inner tightwad prevailed and I decided to make my own. This is what I came up with:


It has three main parts. I have mine set up so the base mounts (more or less) permanently to the same table with the grinder.
If you wanted, you could also simply clamp it down for easy removal. The second part is a platform that rotates about a pivot so you can adjust the grinding angle. Once you get the angle set, you can lock it in place with a bolt that runs through the base and a curved slot in the right-hand platform support. Finally, a secondary platform slides in and out in another set of slots so that you can move it close to the grinding wheel after you have set the grinding angle.

The Details

If you want to make one of these for yourself, the following pictures link to PDF files containing detailed drawings of all three parts.  The dimensions given work with the common grinder shown in the first picture above.  If your grinder is different, you might have to adjust one thing or another to suit.

Base
Platform
Secondary Platform
I used Baltic birch plywood for all the 1/2" thick parts, and some 3/4" oak for the two vertical uprights on the base.  The bolts are all 1/4-20 flat head machine screws.  I used a piece of 1/4" threaded rod for the pivot pin.  An unthreaded shaft would work there as well.

Construction Hints

There are two or three things to watch out for if you decide to build one of these.  First, the holes for the pin between the base and the rotating platform all have to line up. For this reason, it's a good idea to wait until after you have assembled the base to drill the holes.

The second thing to be careful about is the location of the vertical pieces of the rotating platform. These need to be spaced so that the platform rotates freely on the pin, but without excessive side-to-side play.

Finally, it helps to make the bolt holes (but not the slots) just slightly undersize so that the bolt threads actually bite into the wood a little bit in order to keep the bolts from turning. If you do this, you can use wing nuts and/or star knobs for tool-free adjustments. If you find that the bolts still turn in their holes, a bit of epoxy under the heads will get them under control.

Mounting

When you're ready to mount the tool rest, temporarily remove the secondary platform and position the tool rest in front of the grinding wheel, centered from side to side. Then rotate the platform through its entire range of motion, and move the tool rest so that the platform is close to the wheel, but does not interfere with it at any position of the rotating platform.

17 comments:

Superhero!! said...

very useful!!

Ian said...

Another good idea. One improvement I think I would make would be to make the top piece a little longer so you don't end up with the step-down after it's adjusted. Thanks!

rmac said...

@Ian: I see what you mean about the step-down. The problem with a longer platform, though, is that it would sometimes get in the way. Think about sharpening a chisel, for example. That step-down gives clearance for the handle.

Somebody on one of the other forums pointed out how easy it would be to make multiple secondary platforms suited to various tasks, and to then simply swap them out as needed. So this is one place where you can have your cake and eat it too!

Dave said...

Great idea! Thank you for the detailed plans too!

Chunk said...

Ok so am I looking at this wrong? Shouldn't the pivot go between the two upright supports? As it's shown in the drawing, wouldn't the pivot go on the outside of the left upright?


Also, what's the dim on the right hand piece? The piece that you tighten your knob onto? I can seem to find a height of the piece.

This is a great idea! I'm making one but need to modify the design so that I can tip the table "into" the wheel for sharping mower blades. Awesome!

rmac said...

@Chunk: The base has two upright supports, and each one of them has a hole for the pivot pin. Then the platform has the piece on the right that you tighten the knob onto, and a little "ear" on the left. Both of those parts also have holes in them for the pivot pin. So the pivot pin goes through all four holes.

The overall height of the piece you tighten the knob onto is 3". That's 2-1/4" (the radius of the big curve on the bottom of the part) plus 3/4" (the distance from the top edge of the part to the pivot hole).

Hope that clears everything up. If not, ask again!

Chunk said...

@rmac. I see what you're doing. When I first started looking at it, I assumed the small pivot on the table went between to two uprights. Obviously I was wrong.

On mine, I've had to turn the base 180 degrees. That way I can tip the table far enough forward to get an angle of 60 degrees. This should allow me to get the 30 degree bevel on the mower blades that's needed. I also lengthened the base to 6-1/4" so that I could get clamps on it instead of bolting it down to the bench top.

I love the simplicity of it all and the best thing, mine has risen from the scrap bin!

So you on LJ!

rmac said...

@Chunk: Cool! Post your version on LumberJocks. I'd like to see how it turned out.

smj said...

Hi where is the PDF link?

rmac said...

smj: Just click on the small mechanical drawings in the article. Each one of them is a link to a PDF file that contains a full-sized version of the same drawing.

Jeanette West said...

Thanks for these very useful tips and tricks on how to make a grinder tool rest. But I think I’ll just buy one because this is not a project that is on my list for this year. I actually found a good quality tool rest that I think would last better than the previous tool rest that I bought.

TrophyJoe said...

Thanks for the fish!
Yup, pretty cool.

Stan said...

Late to the party, but just finished buildiing this. Thank you for providing the idea as well as the plans. Money saved for just a few hours in the shop! Works great.

denisb said...

Hmm, the first link (to base.pdf) points to the wrong drawing, I think.

rmac said...

@denisb: Thanks for the heads up! I fixed the link.

Justin said...

Thanks, I modified it in order to work with a wolverine style wood turning setup. Your plans pointed me in the right direction!

Ralph Hulslander said...

Thank you!! Very clean look and thanks for the PDF's!!

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