Displacement Behavior - Calculating Belt Cost

ddavelarsen

ddavelarsen

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Dec 7, 2000
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Well here I am with a great opportunity to work in the shop this morning -- I'm off work, wife's still asleep -- but my current project is so intimidating all I can do is indulge in displacement behavior... :D You know, sweeping up, calculating what my belts cost this first year of knifemaking.

So what I came up with is the following:

Belt Cost Per Knife: $15.45
Belt Cost Per Inch of Overall Length: $1.59
Number of Belts Per Knife 4.6

I did this by adding up all my belt purchases this year, subtracting the number of belts I still have left, and dividing these costs by the number of knives ground and their total overall length. Wasn't this fun?

Okay, now I'm off to my shop! Really! :rolleyes:

Dave
 
Dave, my recent estimates were about the same. I use four to five to new belt per knife. The old ones from the last knife are used for profiling and other non-critical grinding. I like sharp belts and throw the old ones away as soon as their cut slows down. It adds to the cost but I get nicer grinds. Its amaizing how quickly it all adds up; including the time spent pondering such things! :rolleyes:
 
I guess it pays to use the best. My belt costs are nowhere near that - maybe half. The only time I get a single knife out of a belt is when I use the cheap <$2, 36 grit types for rough shaping handles. Those I use once and toss. Otherwise, I get several knives from every belt, making my belts per knife maybe 2 total (including the cheapie). I might use 3 on a sword, and sometimes if it's an important or difficult piece I will use a fresh 120 grit J-flex on the bolster/handle, but that belt always gets used again.

I can rough grind about 20 large blades in almost any steel with just one 36 grit 3M 977 or 967 belt. I get about the same mileage tapering tangs.
 
I caught myself in a calculation error and reduced the costs quite a bit. I edited my original post with the correct numbers and added number of belts per knife.

Jerry, I sure must be missing something. I use the 3M ceramic belts too, but can only rough out about 3 blades per belt. I'm pretty careful to use old belts for profiling, chamfer the edge, etc. I wonder if the fact I grind without gloves makes a big difference? I ditch the belts as soon as I can't hold the blade long enough to make any progress -- maybe I'm changing belts too soon. (But I can't imagine having enough skill to grind with gloves on...)

I do most of my grinding on the platen, which probably kills belts fast, especially the finer grits. I often use two 400 grit belts on one knife. This is toning down as I do more hand finishing though.

Another thing that affects my total is that knives aren't the only thing my grinder is used for, but the knives are "paying" for everything. I haven't made a lot of non-knife stuff, but probably a few belts worth.

So what are some more tips for extending belt life? Anybody have any ideas?

Dave
 
Wayne Goddard one said "Belts are free, the customer pays for them" or words to that effect. Wayne does have a real genius for distilling big issues to simple statements. You need to understand your abrasive costs, the cost of working with tired abrasives, and then pass the appropriate costs on to the customer.

I tend to hang on to old belts a little to long, but with time, I'm learning to throw them away sooner. Sharp belts simply make things go better. Now, I only have a 1hp grinder, so dull belts show up sooner I suppose. One of these days, I'm building a two horse with a serrated wheel. Profiling and coarse grinding will be easier on belts then (greater pressure refractures the grain and gives you fresh edges)

Norton Hoggers sure last well in the coarser grits.

I generally flat grind so I go through a lot of sheet abrasive as well. I estimate my abrasive costs to be a little over $20 US per knife. If I were only doing the 8+ inch bowies I love to do, I suppose it would be about $35US.
 
I also flat grind and it definately breaks the abrassive down more quickly. I ordered a 14" wheel last week hoping in part to address belt wear. Oh No... more time spent pondering stuff! :D
 
I use one glove, on my left hand. I find I mostly use my right hand for control, so there's no real need for me to burn both. I do hollow grind, though, but that doesn't explain my tapered tang grinding, which is mostly done on a platen. I used to chuck belts more frequently, but Geno Denning convinced me the 977's would last until the abrasive was gone and now I'm finding that's true. Certainly using 36 grit belts makes a huge difference. Also, I make only one pass before dipping the blade in the bucket then grind on the other side. I've also found my variable speed grinder is pretty frugal with belts, but until last year I ground everything on a 1hp fixed speed.
 
o.k. jerry, so you wear one glove on the left hand and make one pass and dip. then do the other side (the obverse side?) o.k. then how does the glove on the left hand keep the right hand from burning? :confused:
 
That's a very good question. :(

And that's why the callous on my right thumb is larger than the one on my left. Unless of course I've just been finish grinding, when I don't wear any gloves and have usually ground the callouses off both thumbs.

Actually, I grind the point area on the right right side of the blade with the edge down, so the point is always rough ground while being held in the gloved left hand. When I move from 36 grit to 60 grit for leveling and smoothing the grind, I take off the glove and just suffer the consequences to both thumbs.
 
I just got through grinding out 27 ATS-34 blades to send to the heat treater. I used 3 old worn out 36 grit belts to profile, one, thats right, ONE 60 grit Norton Hogger belt to grind the bevels, two 3M 36 grit belts to taper the tangs, six 220 grit Klingspor 312j flex belts, and six 400 grit Klingspor 312 j flex belts. Most of the blades were one eighth of a inch thick, but several were five thirtyseconds, and three were three sixteenths of a inch.
The Norton hogger 60 grit belt is amazing. As the grit is used up the steel gets hotter quicker, but it keeps on cutting.
I use a ten inch serated contact wheel.
Instead of gloves I use suede finger protectors on my index fingers. You can get them from True Grit for $.80 each.
I think one of the reasons why belts last longer for one knifemaker over another has to do with the speed and pressure used. 3M 36 grit belts need lots of speed and pressure.
Another has to do with the method. Bob Loveless' book HOW TO MAKE KNIVES has the best instructions I have seen for tapering tangs. It also recomends when grinding bevels to grind a short bevel with a dull belt first. That way when a fresh belt is used, you don't sheer off the abrasive starting the plunge cut. Tom Lewis
 
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