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The Belt Sander Grinder MkI
The following article is a composite of posts written on the Ubeaut woodwork forum from February 2005. The design was subsequently published in Fine Woodworking Magazine.
are a few pictures of my newly-completed Bench Sander Blade Grinder.
I built this to repair or re-establish the bevels of chisel and plane
blades. It is based on an inexpensive (OK, cheap Chinese copy)
Carbatec bench sander.
The advantages of this jig are:
1. Firstly, it is cheaper than a Tormek (at 8 times the price).
2. It runs half the speed and therefore cooler than a Bench Grinder and you have to be a complete Klutz to burn a blade.
3. It is intended to grind a flat bevel and the set up for this takes a few seconds.
4. The 4” wide belt grinds the entire blade evenly (for a more even grind), unlike vertical wheels where you must move the blade across them.
If this set up looks simple, you should know that it is Mark 8! I went through several inspired failures until I pared the whole thing down to the basics above. Total cost was about $9 (for the chromed steel tool rest, which is a drawer pull). One aim was to permit a reproducible grind, another was to enable the belts to be changed easily, and a last was to set up the blade angles quickly. Most of this is self explanatory, but feel free to ask any questions.
of the tool rest:
The bar is 9" long and overlaps the belt sander by 2-1/2" each side (the belt is 4" wide). It is 3" from the beginning of the end wheel's curve.
The jig is bolted onto the steel frame. I drilled and inserted steel insert threads into Jarrah blocks. These are bolted from the inside. See pic below. There is no need to get obsessional about these being level - it is more important to drill the depth of the guide rest holes accurately, which is easily done on a drill press after the Jarrah bases are attached.
How to Grind
Simply, you are going to set the projection (length) of the blade
beyond the front edge of the blade holder. The longer the projection,
the lower the angle the bevel will be ground. Conversely, the shorter
the projection, the higher the bevel angle that will be ground.
2. Build yourself a jig to set the length of the projection of the blade in the holder. One such jig is glued to the right hand corner of the grey base upon which the belt sander is attached. (This sets the projection for a 25 degree bevel. I have several others for other bevel angles). The jig is "L-shaped" (consisting of a "stop" and a "fence") to set depth and set the blade square in the holder.
(edit: I subsequently realised that the amount of projection of the blade is affected by the thickness of the blade. It is better, therefore to use a combination square to measure the length of the projection for different thicknesses and different angles. Make a list of these for reference when needed).
3. You are now in a position to move the blade holder to the tool rest and grind the blade.
Note that the blade bevel should be facing into the direction of the belt if you do it according to my model. This is not dangerous and, in fact, probably safer as it will (to some degree) push the blade down onto the belt. The blade is held very securely by the blade holder and tool rest.
In practice it really works extremely well and produces perfectly square and accurate bevels.
Don’t forget, this is only to grind the primary bevel, which can be anything between 80 - 240, depending on the state of the edge. Honing/sharpening is completed on Japanese waterstones. Between honings, a blade edge can be renewed by stropping. Below is a motorised stopping machine, the honing plate.
The Honing Plate
consists simply of two sanding disks epoxied face-to-face, that is
with the velcro sides on the outside. I glued a velcro kit to the
belt sander's circular sander. The honing plate is pressed onto this.
Start up the motor and cover the plate with Veritas green rouge. Then
freehand the bevel against this. See the pictures below.
I tried it out on a few "tired" blades. They were rejuvenated to hair-popping sharpness! WOW!
also thought of building a rest for the blade, but this is
unnecessary. It is a very easy job to hold the bevel at the correct
angle (freehand) since honing is not about (much) metal-removal.
Place the blade down heel-first, and then rotate it until it is flat
on the plate.
Just remember to hone with the turn. It only requires a couple of seconds.
Regards from Perth