Sander Belt Speeds

F

flakjacket

Joined
Aug 27, 2007
Messages
54
I bought a sander a little over a month ago. Unfortunately, it's been very cold here lately and I haven't had a lot of time to use it lately since my garage is not heated and I take classes at night. Well, we had a warm spell a few days ago and I spent some real time in the garage working on my first few knives. I think I need a different grinder.

I bought a 4x36 belt sander with an 8 inch wheel attachment. Seemed pretty nice at first, but the belt speed is only 1100 FPM. I don't really think it's fast enough for knife making. Designed more for woodworking. I've been looking at a 2x42 belt sander setup for about the same price that has a belt speed of over 4400 FPM. Seems like the higher speed and cheaper belts would be much more suited to a knife maker's needs. Ideally, having the ability to adjust your speeds would be preferred. Is that correct?

I've seen the KMG grinders and clones. I'd love to have one, but don't have that kind of money or the time to build one right now. Have to spend all of my spare time working on the knives in order to finish the first few. Thanks.
 
The speed is all right for knife making (although faster is better for heavy stock removal), I think the problem with the 4x36 sanders is low HP and too much surface area in contact with the steel. You can really bog them down and you don't have a contact wheel to hog with.

The 2x42 is used by some folks around here, it'll be better, but you still won't have the HP or contact wheel. I say this to everyone, but I'd invest in some files and practice draw filing to shape. I'm sure it's not slower than the 4x36 and it'll probably keep pace with the 2x42.
 
I would suggest utilizing what ever you have at present time to make your knives. Start saving some money for a more sufficient grinder. I suggest purchasing a 2X72 belt grinder with a controllable speed. Higher speeds can removed metal faster and will save you time. Changing to the lower speeds for finishing work and touch up. :)

In the removal of metal I usually run about 1800-1900 FPM. But as I move to the finder grits I slow down to around 400-500 FPM. I like using good quality belts for grinding. Please note that when you grind out your pattern always have a bucket of water setting near the grinder. Make a couple of passes and then dip in the water to cool down the steel. This will help keep the knife from heating up. It can get a little hot on the fingers if you are not careful. :D

The better the belt the better your grind will be, not to mention a good belt will last longer. This also saves money. Hopefully, you will achieve better knowledge and understanding as you journey in this world of knife making. ;)

Putting a great knife shop together is something that takes a while. And most knife makers will agree on that issue. From reading some of your post I can see you our inspired and I believe you will do just fine. Hope this was of help to you and look to see some of your creations.:thumbup:
 
1100 FPM in my opinion is good. Just because you can't remove metal as fast, doesn't mean it isn't well suited for stock removal. I think i'm only removing metal around 900 or so FPM.

The faster the belt speed is moving, the faster you're going to heat up the piece of steel. After the blade is tempered, you really don't want to be heating up the steel to the point it changes colors.

What you have will work just fine. Just practice on it. A lot better than learning on something you have little to no control over in the 3000+ FPM range.

The finer the grit, the faster it will heat up the blade. Just a known fact =) Especially if you're working against a platen.
 
Slow is good... I just spent better than $700 to slow my grinder down (course I can speed it back up too :D ) The issue with woodworking tools is the lack of horsepower. A 4" belt running into wood isn't a problem for the sander, a 4" belt hitting steel is horse of a different color.
 
I agree with the bit about investing in some files. My first knife is ready for heat treat right now and I did the whole thing with a hacksaw, drill, files, and hand sanding. Getting the blade bevel on a 1/4 inch thick knife with just files took me a long time, but it's slow and steady.

I think you guys are right about the width of the belt. Probably more of an issue than the belt speed right now. Thanks for the advice.
 
Not real sure what the horsepower is on your 4" x 36", but all i know is that mine was like 3/4" horsepower and occassionaly i could stop the belt with my blade that I was sanding, but not so much that it slowed me down while doing stock removal. But then again, it ran at 3450 RPM, so maybe that will be the difference. Regardless, you should still be able to do stock removal with it. Learn how to use something that isn't meant for something really well and by the time you actually get a grinder meant for grinding blades, it will be a cinch to use it! :)
 
There is at least one good source for 2x36 belts out there -- if you can't find 'em I'd be willing to dig up a link. I used a 2/3 HP Sears 4x36 for my first knife, partly with 4x36 belts, but mostly with 2x36 belts. I made a sort of Mickey Mouse slack belt attachment that also has a small contact surface on it. I can take a photo and post it if you'd like.
 
Could also split your 4x36 belts in half if you can't find decent 2x36's - I hadn't ever thought to try that on a regular belt sander.
 
Working at higher belt speeds, there are more options. You can hog with a
50 grit or you can lighten the pressure against the belt , and change to a 120grit.
The higher belt speeds require a lot less pressure, therefore, a lot less heat is produced.
When shopping for a grinder, remember;There is no substitute for
"Horse Power".

A three horse grinder moving, 4800 feet, of sharp ceramic belt, a minute,
does not slow down, when you are grinding.

Horse Power, higher belt speeds[ 4000+] and quality belts makes for a lot of metal shavings.
Until you can afford a good machine, use the one you have and make a few knives. Buy the best belts you can for it and some hand tools.


Good luck, Fred
 
I am also still stuck using a 4x36 until I can afford better. My suggestions:

Norton makes 50, 60, and 80 grit belts for it in their Norzon (zirconia abrasive) series, and they work well for hogging. My first two are still going and they have many, many hours on them! That is about the only decent belts I have found. The rest are all Al-O and they work, but wear out fast!

I use the idler pulley on one end for a makeshift contact wheel when profiling blades. It is slow but easier than a hacksaw. Use them to start your vee grinds too, but finish with draw filing and hand rubbing with silicon carbide paper.

The Al-O belts work well for handle finishing. In fact, I expect that I will keep this unit for handle work even after I upgrade.
 
It might seem like putting lipstick on a pig, but I've glued 2 2x12 pyroceramic platen liners side by side onto the platen of my 4x36. Don't laugh too hard -- it works very well for critical flattening work since the 4x36 has such a low belt speed. (I had to do something if I was going to continue using it -- I put a dent in it a few years ago during a moment of high frustration.) I had to use my Dremmel tool with a diamond disk to cut a bevel on the leading edges to keep them from chewing up belts, and the extra belt tension afforded by the thickness of the liners sometimes makes it necessary to give the belt a little push a startup to get it going. I always leave a 4x36 leather honing belt mounted on it when it's not in use to protect the liners from breakage.
 
You must log in or register to reply here.
Back
Top