Question for pros: Thinning knife on belt sander with "edge leading"?

[mhpr262]

I have got a cheap but serviceable commercial belt sander that I have successfully used for thinning knives. The only downside of the thing is that the belt is basically only accessible from the right hand side, the left hand side is taken up by the running gear and covers of the belt and stuff. The belt runs "towards me". (Pic: https://cdn.preisvergleich.check24....heppach-bgs-700/scheppach-bgs-700_600x600.jpg)

So far I have thinned my knives always with the edge "trailing" for both sides. That worked well for the right hand side of the blade. I made do for the left hand side by holding the knife at weird angles and maneuvering the knive on parts of the belt where the handle would mostly not get in the way of the covers and the running gear, but it was a bit of a PITA and has caused some uneven spots and slightly mauled handles.

My question is: can the left hand side of knive be safely thinned with the edge "leading", without the knife cutting into the belt, catching and getting hurled right into my chest or stomach as I am sitting in front of the belt sander? I am fairly secure in my motor skills and I am sure I would be able to hold the knife consistently at such a low angle that the actual bevel of the knife would be gliding over the belt, like the raised tip of a ski lets it glide over the snow, but I am still a bit leery. The speed of the belt is not adjustable, so it is always running at full speed ...

 

[Pensacola Tiger]

The answer is quite simply "No".

 

[Butters]

It's normal to grind blades edge leading (edge up with belt traveling down) and you should do both sides that way if you can. How else can you see what's happening at the edge?
Provided you push the blade onto the belt at a low angle with loose hands and let the bevel find its level, so to speak, then you'll be fine.
It's counterintuitive but the blade won't cut in. Lose concentration for a second though and it may get sucked in between the belt and platen. That can be entertaining..

 

[comet_sharp]

I have never ground a knife with the edge down. In the past year I have ground over 50 all with edge up and belt running towards me. I grind them all to zero. That said I have had a belt break in half but due to pressure applied and a weak glue joint on the belt, the edge did not cut it. That said grinding a knife can be dangerous regardless of how you do it.

 

[Benuser]

Don't try this at home.

 

[Matus]

As was said already - edge up allows you to see what you do. But you should wear some decent face and upper body protection should the blade be thrown at you.

 

[nevrknow]

You "CAN" do alot of things....... drive with your feet, slap a cop. grab your wife's sister's butt.......... Doesn't make them good ideas.

+1 wear body armor.

 

[milkbaby]

Add me to the list of people that grind their blades edge up with the belt running down into the edge. It's the easiest way to see what I'm doing. Also, the metal is held at a shallow angle to the belt, so the belt is cutting the metal instead of vice versa. To me, the biggest danger is not paying attention and/or working tired, thus making it more likely to grind a knuckle or finger on the belt which is a no-no.

 

[mhpr262]

Thanks guys. I have an F. Dick Pro Dynamic 10'' chef's knife that is in dire (dire!!! thickest POS knife I have ever seen) need of thinning. Being able to grind edge up will make things A LOT easier. I had been wondering after the first post, because every video I could find on youtube of people grinding knives on a belt showed them holding it edge "up".

 

[comet_sharp]

Yes you grind edge up while looking down at your work i wear eye/ear protection and a respirator, the steel usually isnt the cause for concern but the airborne abrasive is. Id also suggest a denim/leather apron. I rarely wear an apron but I'm dumb

 

[Butters]

Yep, a full face powered respirator, apron and ear plugs are standard for me. I also wear leather gloves when hogging prior to heat treat, but afterwards I have skin in the game to feel the blade temperature.

 

[Dave Martell]

I grind with the belt horizontal to the bench running away from me. I prefer not to wear a respirator, chew on grit, or wear dust all day so I blow it all down a dust extraction tube. This isn't common at all though, a bit slower than belt running into the knife, and it takes some practice to get results you can live with but it sure is a lot less messy.

What's the answer for the OP and his grinder set up? I don't know...maybe try to remove all that crap from the belt sander that's in the way?

 

[jessf]

I'm with, Dave i prefer horizontal. Was fine with the cheapo belt sander using edge leading passes but when i dropped the coin on a Bee grinder i had to concede to its 2hp ability to do serious damage if you don't apply pressure in the proper way. If you want to do vertical edge leading strokes then do so without the rest. That way if you do catch an edge the belt will knock the knife away or out of your hand. A good reason to wear safety boots. With the rest in place the edge will just dig into the belt and kaboom.

 

[Matus]

Dave, could you post a photo of your setup? I would love to see how you handle the dust extraction.

 

[comet_sharp]

I feel if your edge is biting into the belts the youre grinding at the wrong angle and might want to consider a jig of some sort or more practice. Just my .02$ maybe a bubble jig until you learn to feel where the steel is being removed?
-Trey

 

[Dave Martell]

Dave, could you post a photo of your setup? I would love to see how you handle the dust extraction.

Sure Matus

So there's a 2HP dust collector doing the sucking using a 4" metal tube. *Don't use plastic or rubber or anything that can melt if you're going to shoot grinding dust down the pipe. I've had a fire from melting hoses before - heed my warning!

Over the years I've tried different set ups, some worked better than others. For my little grinder the best dust collection I get is to position the collector hole under the rear wheel. You would think that putting the hole behind the wheel where the dust would shoot straight down the pipe would work better but it's not true for my set up. The current set up creates a vortex around the platen and rear wheel and sucks all the light dust down the pipe, the remaining heavy debris hits the back wall and deflects down the pipe.

Also notice that I'm using a wash tub to catch the big debris but in how it's positioned off to the left side. It's that way not just to clear the drive belt but because the dust travels to the left on my machine, and that's especially true when the fan from the motor isn't blocked like it is now. I mention this so that you will think of how your grinder set up is working in how it blows dust and how you may need to adjust/experiment to get the dust collection correct. I'd advise to using a temporary set up that you can experiment with before mounting anything permanent.

Like I said above in this thread, this is my preference to use this set up because I hate respirators. Certainly using a bucket full of water to grind into would be a whole lot easier but we makes our choices.


PS....that's years worth of knife/handle making and sharpening dust on that bench. Not too bad, eh? :wink:

 

[Matus]

Thank you Dave for all the details. Finally we got to see a bit of your dungeon

You make a very valid point with that plastic or rubber. Already my baby 1x30" grinder produced enough heat when grinding steel to put the dust collecting bag (which was full of wood dust) of my vacuum cleaner (that was attached to the grinder) on fire, even though the hose is about 3m long

I should be using a 2hp grinder soon and I will have to consider the dust collecting options very carefully as there is little to no fresh air supply in my tiny shop.

 

[Keith Sinclair]

Cannot dispute Dave's thinning abilities, my spa Hiromoto is proof.

I thin with 1X42 belt & bucket of water. Edge up to down running belt. Can do both sides of knife this way. Have gained confidence just doing it, still careful and attentive while working. Try to get in the habit of wearing a respirator I don't mind it at least my glasses don't fog up like with paper mask. Also my tiny shop is in an open air garage nice when the trades are blowing. Since like restoring old handles & using some stabilized wood after sanding would notice scratchy throat from who knows what. That's when started wearing a respirator.

 

[Dan P.]

I grind edge down on a downward running belt. Sitting down, elbows on knees. Gives good control and not too fatigueing, I find. Different strokes for different folks.