Surface Grinder Belt Conversion

Curtiss Knives

KD Founding Member #1, Knifemaker
Finally got me a surface grinder. It's a Harig Super 612. Here's my take on a belt conversion. Plates are 1/2" steel. I re-used the dust shield mount to attach the up-rite to. The tension and tracking arm pivots on it and has a gas strut for tension. I have a 6" serrated 90 duro wheel on the way. Man I'm ready for flat parts! Thanks for looking.
surface grinder 002.jpgsurface grinder 003.jpgsurface grinder 001.jpg
 

T4Texas

Active Member
Looks great! I'm getting ready to do a conversion on my Harig Super 612 as well and I was wondering where you are getting your wheel? Are you doing the machining yourself?
 

Curtiss Knives

KD Founding Member #1, Knifemaker
I ordered the wheel from Sunray. Call Keith and ask for the same wheel as he made for me. Costs $100.00.
 

T4Texas

Active Member
Thanks! I had planned to call Sunray and Bader. Now I'll just call Sunray. Did you have it made to fit the adapter with the 1 1/4" shaft?
 

Curtiss Knives

KD Founding Member #1, Knifemaker
The wheel is designed to bolt right on the 1 1/4" shaft. Slides right on then tighten you spanner nut down.
 

EdCaffreyMS

"The Montana Bladesmith"
Boatbuilder.... Here's my take on stones versus belts:

In my opinion the advantages are many for a belt conversion. Some will argue that a stone is more accurate, but my surface grinder, with the belts will hold a .0005 tolerance. I think it has a lot to do with the type of contact wheel used with a belt setup.....it MUST be a very hard wheel. I feel that anything short of 100 durometer is not hard enough....some folks even use solid aluminum or steel for their contact wheel.

Another advantage is that I do not have to buy, or keep the stone wheels in the shop....the good ones are expensive, and it's just one more thing that I have to buy/replace. With the belt setup, I can use any belt/grit that I use on my Belt grinders, and change them just as easily as I do on the KMG or Square Wheel.

I also think that using a belt is MUCH faster than a stone....when I first got my surface grinder, it was setup with stones, and the most I could remove in a pass was about .002"....and that was putting a strain on the machine....and took FOREVER to grind anything. After switching to belts, it's not uncommon for me to take .010 or more at a pass with a 50 grit belt.

Back to the contact wheel issue....I cannot stress enough just how important it is to use at least a 100 durometer contact wheel. The reason is.... there is always "down pressure" when surface grinding, if the contact wheel is soft (less than 100 durometer) the wheel will "cup" on a grinding pass, and your work piece will come out with a convex surface. (the hardest contact wheel that I have ever found commercially is a 90 durometer...and trust me, it is not hard enough)
Finally, consider carefully, the diameter of the contact wheel you use...I would recommend at least a 6" wheel, especially if your surface grinder is a manual model. (had the folks at SunRay custom make a 6", serrated, 100 durometer urethane wheel for me) A small contact wheel will cause serious "divots" in your work piece, simply because a person cannot maintain a smooth even speed throughout a grinding pass, coupled with the fact that the radius that comes into contact with the work piece surface is much tighter than on a larger contact wheel.
 
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SPAknives

Well-Known Member
That's what I have been wanting to do forever!!! I have a ried 6x18 surface grinder I really want to convert. Why don't you get on that for me?? Please!! Just kidding. I may have to pick your brain when I get around to doing it. Thanks a TON for the pics.
 
W

weld

Guest
I converted mine to a belt. The problem with belt like Ed said is Divots. I think the divots are caused by the splices in the belts. The problems with stones is that there is a limit to the grits plus having to dress the wheel after about two passes. Ed is also correct about the duro of the wheel. I believe I got mine from contact rubber company. Each has its pros and cons. I would stay away from Harbor Freight surface grinders simply because they do not have enough power.
 

Wayne Coe

Forum Owner - Moderator
Originally Posted by Boatbuilder
Whats the advantage of the belt compared to the stone?

You don't have to worry about a stone exploding and sending little (and sometimes BIG) pieces of stone flying all over the shop. They can hurt you.

:s12137:
 

EdCaffreyMS

"The Montana Bladesmith"
Weld,

I agree about the HF surface grinders being "wimpy" as they come from the factory. My surface grinder is a HF, and shortly after getting it, the motor went out. I pulled the motor, and took to my local motor shop. I got a call later that day from that shop, telling me that my motor needed to be rewound, and that the factory windings where aluminum! The shop overhauled the motor with copper windings, and when I re-installed that motor, it was a totally different machine! The cost was under $200 to have the motor rewound with copper, and I've not had any issues with the machine since.

Until Wayne mentioned it, I never even thought about the stones exploding! I never experienced that, because I converted to a belt while the motor was in the shop, and never experienced a stone letting go...but I have heard the horror stories and seen holes in other knifemakers' shops to verify that it's not something I'd want to be involved with. :)
 

Fellhoelter

Well-Known Member
Pretend it's a stone, and run a single point diamond across it.

I just built my conversion last week, but the 1st thing I discovered was that the belts needed to be dressed.

Put your diamond dresser in the middle of the table, fire up your grinder, touch off just to the left of center on your wheel and traverse the table on the Y axis off the belt.

Come down a couple of thousandths, and traverse the other direction until you are off the belt.

Rinse, repeat...

Done, high spot gone.

I wish I had made my wheel 2.25 or so, since the belt and wheel are the same width, any tracking error means the belt is not on the wheel at the edge, and isn't supported.
 

Curtiss Knives

KD Founding Member #1, Knifemaker
[/QUOTE]I wish I had made my wheel 2.25 or so, since the belt and wheel are the same width, any tracking error means the belt is not on the wheel at the edge, and isn't supported.[/QUOTE]
What about just taking a little width off the belt? Kinda like splitting it, but not so much.
 
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