Contact wheel diameter recommendations

Eric T. Maier

Eric T. Maier

Joined
Apr 29, 2000
Messages
573
Hi,

I've decided to take the plunge and try my hand at grinding my own blades. I'm going to get a KMG grinder set up and want to know what diameter contact wheel I should start with. What is a good "all around" diameter ?

Thanks for the input,

Eric
 
A good all-around diameter really depends on the style of hollow-grind you like. I like nice shallow, barely-hollow grinds. This is good for a big wide blade like a bowie. In this instance, a 14" wheel is barely adequate, and a curved platen is recommended. If all you will be hollow-grinding is small pocket-knife blades, and 8" wheel is suitable. Many makers will probably just recommend a 10" to start.
 
I probably should have clarified what I'm going to be doing a little more. It will mostly be pocket sized knives, blades that are no bigger than 5" and as small as 1.5" or so.

Thanks,

Eric
 
I'd say 8 or 10. And don't forget that you can also ask Rob what he thinks. He's built lots of these things, and a great guy to deal with.
 
It's not so much the length of the blade, but the width. You can hollow grind up to 11/6" in 1/8-3/16" steel without rocking, with a 10" wheel.
I started with an 8", but quickly jumped to a 10" for all but the smallest blades. I now have a 14", and am trying to figure a way to run a 24" on my grinder.

Personally, I would get an 8", and a 10". When you start to taper tangs, the 8" comes in real handy. If you want bigger wheels later, they are aways there. :D
 
I bought the 8" wish I bought the 10".

BTW, I got a 2" contact wheel for the platen fixture. Great little addition. However, on that I wish I got serrated - long explaination, but it has to do with leaving flat marks.

So, my hindsight recommendation is:

10" Contact wheel
2" serrated contact wheel for the Platen

Steve
 
Steve,

Would you mind giving that long explanation? :D I've been thinking about a KMG-10 with a 2" contact wheel for the platen, but I also want to get the small wheel attachment. If I go with a smooth 2" then I might as well get the one that fits in the SWA.

I believe pendentive also chose the 2" serrated contact wheel for his platen, so you guys must be on to a good thing . . .
 
SteelDriver,

I don't have the serrated one, so I can't give you first hand. But I'll try and explain. Hopefully one of the power hitters here can.

Pretend you are sanding the spine of your knife. With a hard contact wheel you get these little flat spots where you stop sanding. It is interesting but I get them more with microfinish belts which are thin and hard, than I do with Norzac which have more give in the belt itself.

Noticed that for a long time.

I was watching a Bill Moran knife finishing DVD and he mentioned how much work he does with a 3" serrated wheel. Then mentioned how you don't get those marks because the serrated wheels are softer. (At least I thing he was talking about the same marks.)

------------------------
Btw, the 2" wheel is handy for quick removal of material. Like if you want to thin a scale, make a divit lengthwise with the 2"er and then flatten with the platen.

Steve
 
Thanks for the explanation, Steve. I reckon I'll be using that 2" wheel mostly for profiling work. And now I have to add Bill Moran's DVD on my wish list :D .
 
I use an 8 inch wheel on my grinder. It is a Burr King model 760, which comes stock with a 7 inch diameter wheel. I had the stock wheel resurfaced to 8 inches and that is as far as I can go with the 2 x 60 belt. I would love to have a bigger wheel, but I can't without doing some heavy mods to my grinder, and since I got it for free, I am willing to live with it for a while.

Here is an example of what the grinds look like an a big blade. The pictures below are on a blade that is 1.5 wide maximum.

Here are two variations on the same profile:
f4.jpg


This is the top blade in the above picture after regrinding the main bevel to bring it close to the false edge.
f7.jpg


Now, if i had a 14 inch or bigger wheel, I could have even more flexibility in how I want to grind a large knife.

For the size blades you mentioned, I think an 8 inch would work well. But if you are going to buy a grinder too, I would buy one that you can use many different sized wheels. We all start thinking that we only want to make one type of knife, but that doesn't last very long.;)
 
Eric,

The 8" wheel is by far the most popular in terms of sales volume. You'll find a million uses for the contact wheel other than just hollow grinding. The contact wheel is the most efficient way to remove material and provides the best belt life. If you are thinking in terms of 8 or 10"...I think you are on the right track for a general purpose...multi-use set-up.

As far as serrated -vs- smooth.....(yikes)

Serrated wheels grind faster with a more aggressive cutting action. The smooth wheel provide a better finish when using "j" weight belts from about 120 grit and up. My personal preference is smooth. If I need to cut faster, I use a coarser grit and more belt speed. A 36 grit at full speed is more than I'm comfortable with using...so I personally don't benifit from additional grinding speed. This topic is also one that can be debated with pros and cons...and personal preference. Just a few of my thoughts...


Sincerely,
Rob
 
I did order the 2" serrated initially, but have since switched to a 2" smooth - thanks again, Rob.

The reason I got the smooth was that the serrated was cutting too fast and leaving "dish marks" on the blade. As soon as I dropped the smooth in place, it was like night and day. No more marks.

Of course, I am using the belts and grits that Rob mentioned, and that may be why.

Think of it this way...ever notice that if you get a bad belt with too big a gap in the seam that it will "bump" as it goes past? The combination of my finer/thinner "J" belts and a serrated wheel was "bumping" every 1/2" or so along the belt. The knife blade looked "ribbed". Didn't matter how light I touched the blade to it, it still left the marks...

I have noticed that the smooth wheel doesn't cut as fast at the lower grits on my "X" and cubitron belts, but it's still well enough for me.

Sorry I didn't offer any help to your question, Eric. Just wanted to clarify...
 
Hmmm, I use a serrated wheel, but X weight belts. I have never felt that "bumping" must be that heavier cloth makes the wheel feel smoother. Or else, I am just used to it being bumpy;)
 
I bought the 10", witht the flat platen. With that fixture I can use dummy contact platens that will allow me to grind any diameter.

One minor point you might want to find out from Rob is what is the smallest belt you can grind with the 8" in place. I can use a 60" which while a distant second choice for serious knife work, is an easy to find size. Plus it's useful for woodwork. If I could go as small as 48 with an 8" (probably not) then I would consider it.
 
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