Poor mans grinder?

[Kevin]

This is a grinder I have in my workshop, and I have come to realise that its possible to grind a knife without the generic 2 x 72 belt grinder often favoured by knife makers.

Its a 1 hp motor with a reversible switch to change rotor direction (important!!)....

I stick on normal sanding/grinding paper that you can find in most diy shops....glue it on the plate with Elmers Spray on Adhesive......


Some makers attach the motor so the wheel horizontal (flat when working)...but I attached mine this way so I can look behind the wheel when grinding my plunge cuts to line them up.......Another way would be to put a clamp on the knife so it will not grind past that point.

With some practice, its possible to get a nice curved transition/plunge cut.....(picture to follow).
The reversible switch motor IS important so I can work both sides of the wheel so the sparks will be thrown down and not in my face!!!!....it also gives a bit more control...I keep the blade below the centre line and I grind edge up.

I am still experimenting, but grinding small blades work well...as the blade doesnt have to be moved back and forth like on a 2 inch wheel or platen, so there are no divit problem!!!......It makes a perfect flat profile.

I havent tried scandi grinds yet, but it may work...

The plate is aluminium, so I dont know how long it will last long term?.....




[IMG]http://216.46.248.210/pixc/coutel/disc-grinder.jpg
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This is a wood knife grind I made in half a minute just to show the grind pattern...By the way, those wooded paint pot stirrers that you find in diy places (usualy free) make great test piecs to practice grinding )





This disc grinder is also great for flattening handle materials, and flattening spacers.



I included the 4.5 inch angle grinder as this is a very useful tool. I always use it to grind the scale off my knife after forging , as scale eats belts, so I save money on belts. With the small angle grinder, the profile can be shaped...AND, the bevels can even be ground in place with some nice plunge cuts......Its suprising just how far you can shape a knife just with this small grinder......and if you have no other power tools to finish it off, it can be finished with files then hand finished. I use this tool before I go to a belt or disc grinder.

(caveat...all grinding can be dangerous, wear the appropriate protection and follow proper cautions and safety rules to prevent harm......My grinder is shown without guards....I do not suggest you follow my example...be safe!)

[MotorbikeMan]

didn't think about sparks nice one Coutel

[Kevin]

didn't think about sparks nice one Coutel

The way the sparks are flying is important...but, if the disc only spins one way, you lose a LOT of control........reversible switches are not too expensive.

Now, If I could fit a variable speed to it

I think that if I made a lot of knives this way, the alluminium plate could scour or wear?...I dont know yet..its still new to me and I am experimenting.

[MotorbikeMan]

What size motor is it? and have you any idea what sort of rpm?

[Kevin]

What size motor is it? and have you any idea what sort of rpm?

Its a 1 hp...dont think I would want to go smaller....I will get back to you on the rpm......

[Andy]

Does the effect of part of the sand paper moving faster then the center of the disk cause any problems?

[Kevin]

Does the effect of part of the sand paper moving faster then the center of the disk cause any problems?

Is the outside moving faster..or does it just have to cover more ground?

I havent noticed any problems......

[MotorbikeMan]

One thought, did you have to balance the disk at all?

[Kevin]

One thought, did you have to balance the disk at all?

I purchased the disc....its already been balanced (drilled)..

Balance would be very important though...

[Andy]

Is the outside moving faster..or does it just have to cover more ground?

I havent noticed any problems......

the outside is covering more distance in the same time so yes the blade comes into contact with lots more abrasive. Doesn't seem to be a problem though

[Stuart Ackerman]

the outside will wear faster, and please wear a respirator of some sort, even one of those naff polystyrene ones. the grit and steel particles find a way directly into your nose and mouth!

use a rest just above the midway point, and you will almost get an almost even grind, instead of that 45 ° plungeline. watercool the steel often.

Aluminium will last a lot longer than the one I made years ago from ten 12 inch records epoxied togerher! And that one would still be in use, except I loaned it to a mate to copy! He sold it in a divorce drama he went thru'. !!!