Which grinder?

DanL
I radiused the platen on another 1x42 sander I had here, though you could do it on the slack belt of the sander if you only have one.
For this to work best you need to do two things. First, grind material off of both edges of the platen until it is approx 2" wide. The platen on my sander was a bit wide to start with, so had to be narrowed. Then I just proceeded to round over the edge of the platen a little at a time using the belt sander until I get the profile I want. You can either round it over just a bit, or to the point that it it rounded right from the front edge of the platen to the back. It also helps to put a little radius on the top of the platen, and round the corners a bit. That way they won't dig in if you're slack belt sanding above the platen.

Removing the sharp edge on the platen helps the belt life since things are less likely to dig in and grab. It also helps if you are trying to cut tight radiuses with the belt.
The best thing is that you can use that radius to get a consistent 'shoulder' on the back edge of the blade bevel with some practice.

From the other posts. There are two ways to cut a tight curve with the sander. One is to use a stiff backed belt, so that the edge digs in. Most of the 36 grit belts I've used are twice as stiff as a 50 grit and work good at that, and at nipping errant fingers. The other way to cut a tight curve is to run a thinner back belt off to the side a bit with the belt adjuster, and work the belt right over that radius. You can get into some pretty tight curves, and cut with more control than trying to use th square edge of the belt to dig into the material.

Word of warning. If you use the adjuster to run the belt off the side of the platen to do work, alternate doing it on either side of the platen from time to time. I always liked to use the left side for cutting tight radiuses, and eventually I ended up wearing the left side of the drive wheel more on that side too, so the belt tended to work over that way, and became hard to adjust back the other way. After about three years of use I finally ordered a new drive wheel for mine which should be arriving any day.

Disclaimer, the Sears 2 x 42 isn't a commercial sander. If you want it to last, do some preventive maintenance, like taking an air hose or compressed air to blow out the crud from inside the motor. I didn't and finally shorted the motor, which is now why I'm running it using a scavenged 2hp tefc motor to run it now.

madpoet
 
I bought a Sears 1"x42"/8" about 6 months ago. I had to exchange it twice already! I only use it for short periods of time and even keep a cold wet rag on top of the motor. It works okay when it works but I can stall the motor without much trouble. Small knives are okay but the big 5160 convex grinds are wayyy too much for this little thing. I`m saving for a Grizzly 2"x72". Marcus
 
I heard of using some type of graphite on the platen to help extend the belt life. Do you guy's know anything about this? DanL
 
I myself got a craftsman 4x36" 2/3HP grinder some time ago, and I've made three or four knives on it. It did need quite a bit of modification for use in knifemaking, though. I had to contact cement a peice of suede onto the platen to keep the piece from bouncing too much on the flatgrind, and I did the same on the idler wheel for the hollow grind. I covered it all with a generous helping of graphite to keep it running, and that has also made my belts last a bit longer. The biggest problem is that I can only get a very small hollow grind due to the small size of the idler wheel(About 2"). I use a 4" angle grinder for much of my profiling, cutting deep notches or finger grooves, etc.
I agree with what was posted earlier on Sears target group, though. They don't expect us to work on anything harder than oak, and metal work is limited to making sheetmetal birdfeeders.
My next major project is to make myself a industrial-grade belt grinder. I have some designs from the net, and I'm going to make it so it will use bader wheels and 2"x72" belts. The motor will depend on what I can aquire, but I'm looking for a 1 1/2hp variable speed. Should be fun, but this is one of the more ambitious projects that I've undertaken. I just can't afford a $2000.00 grinder until I'm much better at this, and they aren't all that complicated in construction.
I'll still use the craftsman, though. It tears through wood like nobodys business, and gives a nice flatgrind. The disk is especially useful for all kinds of profiling.
Wish me luck on the big grinder, I think I'll need it.

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Wow, it really cuts!
 
Welcome to the group Osborne. A very large number of us have been in your position and have made up our own equipment or modified available used equipment. Sometimes it works better than the commercially available machines and is a darned sight cheaper.

A few months ago I had to decide between a real knifemaking grinder or this computer to go on the web with...........I am in the middle of building my own grinder with surplus parts now, a variable speed DC model using 3" belts either 97" or 130" long (both are common industrial configurations).

I have some definite ideas that I want to include like an easy to access slack belt section and a horizontal flat plate with removable hardwood bullnose to grind finger notches. Another design must is belt tracking adjustment from the operator position, I hate having to stop and walk around the machine to move the belt from one edge of the contact wheel to the other, I often run the belt over the edge when profiling and have to retrack often.

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george
www.tichbourneknives.com
sales@tichbourneknives.com

 
I've used the graphite platen surface and didn't care for it. I didn't much like the "give" it had when pushed against compared to the platen, and I found it wore very quickly. A platen needs to flat, as the name suggests. They wear over time as some areas see harder use than others, though you can re-flatten them by grinding on another sander. IMO, I'd rather buy a new platen once or twice a year than replace the graphite at least once a week. Also, it's not nearly as precise a flat surface to begin with. I'm curious how others feel on it, though.

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-Corduroy
(Why else would a bear want a pocket?)
 
I found a nice article on the Grindmaster style grinder, with some lovely pics of a prototype in Knives Illustrated. It appears to have all of the features that you mentioned, George. Looking at it, I don't see anything more complicated in it's construction than a bit of welding, and I have a friend that can do that.
I had a local maker reccamend a graphite platen to me a little while ago, but I don't like the idea of working on such a soft platen, either, so I compromised with a two ounce leather piece covered in graphite. It made flat grinding much easier by taking the bounce out. It was harder to do on the idler wheel, but it did the same thing. The craftsman just has a tendancy to make it bounce without something there.
Thanks for the welcome, BTW. Nice to find a place to talk about blades. There's not many folks that make them here in Jacksonville.
Oz
 
I have found a sheet material, cloth backed, at my local woodworking supply shop which is used to cover stroke sanding pads. A stroke sander is a large movable table with a slack belt running about 2" above the table surface, a cabinet door or other flat surface is placed on the table and the belt is pressed down to sand the surface. The psd used to press the belt onto the surface is covered with a canvas material with a graphite coating on one surface. I have no idea what it is called but a major industrial woodworking supplier would be able to tell you what it is. I will be covering the flat platen with it to reduce drag.

Oz the trickiest part in building your own machine is alignment of the wheels, I have had to scrap one attempt because the idler
roller was not true and I didn't build in an adjusting mechanism.

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george
www.tichbourneknives.com
sales@tichbourneknives.com

 
Would you suggest possibly making both sides of the idler adjustable for corrections? This would require calibration more often, I think, but it could reduce the oops factor a bit.
Just brainstorming.

Oz
 
I will be using adjustments on all wheels except for the contact wheel. This will allow me to true up to the most important wheel then I will lock down all except the tension wheel which will also be my belt tracking adjustment.

The main frame member is 3" square tubing to eliminate flex.
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george
www.tichbourneknives.com
sales@tichbourneknives.com



[This message has been edited by george tichbourne (edited 28 June 1999).]
 
I bought a grizzly 2x72 grinder and have made a few adjustments/improvements.

I have a small block of wood that I jamb between the smaller pulley drive and the support bar. This keeps the belt from excessive vibration and creates a much cleaner grind.

I removed the graphite crap from the platten. It wore too quickly and left pockets on the platen. I haven't seen the belts wear any faster. I am also tempted to have the platten resurfaced with a 1/4" plate of fireplace glass.

The only other issue I have had is that the contour grinding attachment is too weak for heavy grinding. I plan to have a new plate trued to a "real" 90 degree angle then surfaced with the above mentioned 1/4" fireplace glass.

I was spoiled with a friend's burr-king when I started but he moved and took it with him. I bought the grizzly as a replacement... it's a great deal and, given the above fixes, grinds a nice blade.

Steve
 
Steve..How big and what shape is the wedge of wood you used on your Grizzly grinder? I bought one of these a couple of months ago and have been bothered by the same vibration problem. I also got rid of the graphite strip, no problems with the metal platen so far. Mahalo! Tom
 
Chris don't hold your breath. The way tings are going this project could take until Christmas, just too many other fires to put out.

I am not one of those high priced engineering types that draw everything out ahead of time then go ahead with it I tend to work it out as I go along and make changes as I think them up. That sure slows me down a lot.

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george
www.tichbourneknives.com
sales@tichbourneknives.com

 
Hoss, The block is about 1" x 2" x 1/2". After pulling down on the tension lever and putting the belt on, I jamb the block between the adjustable ridge and the frame that holds the tension lever. This prevents the tension spring from bobbing up and down while grinding... something I found quite annoying and dangerous.

As the belts wear/stretch I sometimes need to adjust the block but so far it has worked great. I imagine anything for the block will work. I have used pine, oak, and micarta. Pine has worked the best because the softer wood wears a little notch at the best fit. With the pine I know if I wedge it to the notch all is well.

Steve
 
Hoss, the wedge is a simple rectangular block... forgot to mention that in my last post.

Steve
 
Thanks Steve, I'll try it out and let you know how it worked. Aloha! Thomas
 
Talking about the grizzly,I haveput a wheel above the platten and it took all the bounce out.I have made probably 150 knives with it but am ready for a bader.My grinder is 3 years old and stillgoing. Good luck with yours.
 
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