Beautiful new knife guide

[grepper]

Mike and Jeff, I guess I should add...

We had in depth discussions here about very long knives such as machetes, and very small pocket knives and how to sharpen them on the Tormek.  It led to a lot of innovation such as the elegantly simple HK-50 rest Herman designed based on an earlier design by Ionut for small knives.

You can see some of it at the links below, and if you search around in the General Tormek Questions list starting 3 pages back and earlier, there is quite a bit more discussion:
http://forum.tormek.com/index.php?topic=1560.0
http://forum.tormek.com/index.php?topic=1592.0

Machetes:

I sharpened a machete once, and while I got it sharp, the results were anything but professional.  Because the thing was so long, I had to move the knife jig down the length of the blade several times to keep it on the control bar.  This resulted in different bevel angles no matter how careful I was.

Additionally, the machete blade had a narrow chord (distance from spine to edge) near the handle and grew much wider towards the tip.  A typical machete.  This caused me all sorts of problems, because not only did I have to move the jig down the blade as is it was much longer than the control bar, but every few inches I had to readjust the sharpening angle to compensate for the wider chord which pushed the knife edge further down the wheel causing the sharpening angle to be reduced.

Herman's HK-50 rest resolved all of those problems.  You simply lay the knife down and keep the bevel on the wheel.  Duh.  So simple!  Quick and easy too.  Like I said, elegantly simple. 

Maybe someone more skillful than me could freehand a machete blade, but it's beyond me so I need the assistance of a jig.

Very small knives with a narrow chord:

Get a pen knife and try to sharpen it using the knife jig.  The issues will immediately become apparent as the jaws of the jig hit the wheel before the knife does.  Again, the HK-50 solves this issue.

My trouble with mower blades:

The top side trailing edge of a mower blade sweeps up so the fan action generates lift.  Because the edge that must be sharpened is on the same side, laying the blade flat on a tool rest is problematic unless you have a very narrow tool rest.

The version of the rest that I am currently working on allows me to rest the back (smooth) side against the rest so that the front side gets sharpened.  This is how commercial lawn mower blade sharpeners work, for both belt and grinding wheel types.  This was part of the impetus of the design of the current rest I'm working on.
http://www.youtube.com/watch?v=JWI-108BvMk
But you can't get to the bottom of the T7 wheel, so I figured why not the front?  Additionally, other knife sharpeners use the same idea.  Check out the F. Dick Sharpener, SM-111.  It used the side of the wheel.  But it's strictly limited to knives and a little on the "costy" side:
http://sharpeningmadeeasy.com/dick.htm

My current rest, like Herman's design, also works with any length blade and blades which has a chord that changes down the length of the blade because the edge is resting on the stone, not hanging from a control bar.  It also should, but I have not yet tried it, work for mower blades.

So those are my reasons for playing around with fun new jig designs for the T7.

[mike40]

I'm sure not against homemade jigs Mark. I will probably wind up experimenting myself when different types of blades need sharpening that won't work with the available jigs or where the frequency of sharpening doesn't warrant a huge outlay for a new jig. I will certainly keep an eye on what you old timers have been designing for that kind of work.

[Rob]

To that end Mike...you'll discover there is a great deal of latent creative and inventive talent on this forum...some most certainly patentable jigs have come out as solutions to sharpening problems here and the DIY engineering skill is a delight to watch grow and evolve.  It's one of the aspects of this group that I have the most respect for in point of fact.

[mike40]

Good Rob. I also appreciate out of the box creative thinking. It is quite normal to buy a tool having some idea what it will do, but we usually learn pretty quickly what it can't do, and that is usually quite a lot. Luckily we woodworkers are used to making a lot of different jigs to do our work more accurately, so applying that thinking to sharpening is just second nature. All part of the fun I guess.

[Herman Trivilino]

I use the regular knife jig (SVM-45) to sharpen my mower blades.

http://forum.tormek.com/index.php?topic=930.msg2537#msg2537

[grepper]

I've about completed the jig.  I added height and lateral adjustability and got rid of the wood.

The ball joint is obviously adjustable to any angle.
The head rotates.
The head slides in/out on the top rail.
The top rail is not threaded to the post, so loosen the nut under the top rail and slide it up/down for vertical adjustment.
Loosen the big nut at the bottom of the post to slide laterally and to rotate the entire head assembly.

Because it's so adjustable, you don't need to worry much about exact positioning when you clamp the thing down.

The rest pad at the top is ¾" x 2".  Like this for the belt grinder, turn sideways for the T7 2" wheel.

I can cut any size rest out of cheap cutting board thermoplastic.  I drilled a hole in the rest and stuck in a ¼" threaded insert for mounting on the head.

I would have shown it mounted on the T7, but I still need a longer piece of threaded rod.  I will mount the rod with one of these on the bottom to clamp it to the bench or a piece of steel attached to the bottom of the Tormek, and one on top to clamp the bottom rail to as shown in the picture.  I already have two of these:
http://www.lowes.com/pd_301689-33599-AV301689_0__ I just need the longer rod.

A cool feature is that I can quickly move it between the Tormek, the bench grinder and the belt grinder.  I'm going to get a pliers type locking clamp so I don't have to unscrew and mess around with a regular C clamp.

I'll post a picture when it's completed.

Anyone remember the original beautiful knife rest? It was still in the concept stage... 
http://forum.tormek.com/index.php?topic=1679.0

[Herman Trivilino]

Nice work, Mark.

[grepper]

Thanks Herman.  An interesting project. 

I especially liked the original concept model that I hired a beaver to gnaw out for me.