For the manner in which men live is so different from the way in which they ought to live, that he who leaves the common course for that which he ought to follow will find that it leads him to ruin rather than safety.

Please visit my new blog:

Thursday, November 26, 2015

Grinding Fixture (this could get heavy with pictures)

I don't freehand. Nope, just can't do it. I don't freehand simple plane irons, I sure as hell ain't gonna freehand a knife blade.

After some struggling with adapting my LV grinding rest to work with my Kalamazoo belt grinder, I decided for a different approach. Nothing wrong with the LV grinding rest...just not the appropriate application for it. It's meant for a grinding wheel, not a flat belt.

While watching a few knife making videos, something occurred to me. Instead of an angled guide that has to meet the belt, why not a FLAT surface that sits next to the belt? Hmmm.

You see, the problem with a guide that has to angle up to the belt is that knife blades are ground at much lower angles than say, a plane iron. It's difficult to get a more traditional style grinding rest to such a low angle (like...10 degrees or maybe less) against a flat belt. You end up with a guide that has to extend out to the point that it gets really flexy.

A quick call to the local metal supply place, and $30(ish) later, I'm off to the races. Let's just hope it works.

Here we go. I purchased some 1.5" by 1.5" aluminum angle at 3/16" thick and two pieces of 6" wide aluminum flat: one at 1/4" thick, the other at 3/8". I cut the angle into 6" long chunks, and the flats were cut to 6.5".

A quick mock up to get the idea. There will be two rests, one on each side of the grinder.

My favorite color, Dykem blue. I need to lay out 4 holes on each angle. Two of them will have 1/4-20 threads on one face and 10-24 threads on the other. The other two angles will have 1/4-20 threads on one face and 1/4" mounting holes.

Using my height gage and granite plate, I struck a line on each angle at 3/4".

A line was then crossed at 1" from the edge and center punched.

I set my caliper to 4". By placing one point in the center punch, I could swing an arc through the line. This would locate a second hole 4" away. More importantly, all of my holes would always be the same distance apart, regardless or where the first was located. Using the caliper helps cut down on measuring error.

The reason a Starrett automatic center punch has such a fine point is to allow it to work with a caliper. (or divider...if we're going to get into semantics)

Now we can center punch at that intersection. Easy peasy.

I'll admit to a boo-boo. Since I didn't draw out these parts first, and I was just winging it, I forgot that I wanted a couple 10-24 tapped holes in two of the four angle parts. No problem...just move the holes over a bit.

The 3/8" thick aluminum was for the tops. These will be the rest surfaces. These holes are not symmetric due to the way that they have to fit over the belt drive for the grinder. They are clearance holes for a #10 screw and countersunk deep enough that the head of the screw will be ever so slightly recessed.

The 1/4" plate is for the vertical pieces. Each one requires 4 holes drilled to 9/32".

Again with the dividers to set hole spacing.

Like I said above, the fine point of the center punch is intended to work with the divider.

One rest assembled. The screws through the top are 10-24. The screws through the side plate are 1/4-20. I'll be using #12 wood screw to mount the rest to the grinding bench.

Another view.

Both fixtures together. The idea is to keep them on the same plane. It's been a long day, and I'm happy that I got as far as I did on this project. I'll be mounting them to the grinding table tomorrow and finishing up.
Sometimes I can be a little scant with specific details. There are reasons for that. Mostly, I don't want to drone on for days and days. The other is that  I know that my way is not the only way. If you read this and want a few more specifics, just let me know, I'll be happy to fill in any blanks. I could even sketch up a quick drawing of the parts if you wanted to make this yourself.

Stay tuned...

1 comment:

  1. It'll be interesting to see the final look and how it is used.