Help on a couple of issues....

Bailey Boat

Well-Known Member
"Belt slap"... what is causing my belts to bump on the platen when the seam comes across??? If I put the least amount of pressure on the belt while using the platen I get a bump when the seam comes around.... Obviously not good...

Screwed up pins.... I check my pin stock with my fingers when it arrives but on the last 2 knives I have out of round pins showing on the scales when finishing. Almost like there were flat spots on the pin stock.... Obviously not good....

Any suggestions would be appreciated...
 
What kind of belts are you using? You might try taking a "diamond pad" and knocking some of the abrasive off at the splice. This will minimize the bump. Thinner belts are going to have a more noticeable bump than thicker belts (heavier grits). Some manufactures minimize the bump by using more of an "s" shaped splice, or a corrugated looking splice. You might try some of those belts and see what you think.

As for your pin stock... Are you peening the pins?
Also, understand that if you contour your handle around any of the pins, they are going to look skewed to a degree. Imagine cutting a cylinder at a 45 degree angle. The cross section of where you cut it will look like an oval, rather than a circle.

Another thing to consider is that pin stock is only MOSTLY round. While the tolerances are usually fairly consistent, it is possible to get an out of round section from time to time.
Peening your pins can help to a degree, as you are now filling any voids or gaps with the pin material, into what should be a round hole/cavity. On the other hand, if you over-peen, then you can distort the material out of round as well. It takes some practice, but if you start with a round hole and don't over peen them, you should end up with a nice round pin when you flush everything up.
 
I would suggest that virtually all belts will have some degree of 'thump' at the splice. Cheaper belts are probably worse. I have seen some makers reduce this with cork on the platen but this reduces the ability for a crisp grind.

As for the pins, they are quite malleable. Clamping in a vice to cut off a piece can easily create flat spots. Mosaic pins can be partially distorted just by aggressive grinding. More often, I've seen pin holes that were not drilled perfectly square and that can happen from a drill press out of true or from scales that are less than parallel.

We all share your pain. :)
 
If you stop the grinder and look at the splice when it starts to bump really good you'll notice that the splice loads up with steel really quickly. The splice area becomes a thick chunk of debris which is higher than the surface of the rest of the belt. It's so bad on light weight belts that I have had the splice eat gouges in the surface of my bevel on brand new belt that is only minutes old. That splice loads up very quickly. For the life of me, I don't know how guys use lightweight belts on a flat platen. Once I get to 220grit I have to switch to trizact belts when it comes to flat grinds.

I use a lot of J-weight belts for handles and creating edges, but for the flats? I can't crack that code.
 
I use Xweight and most heavier belts when grinding up to 120 grit and then use Scotchbrite or Trizac belts to finish.
J weight i use for handle contouring and sharpening while slack belt so thumps are not an issue.
 
I just got my grinder so I'm experimenting with different belts but I see what you guys mean. As for the pins, I'm guilty, been clamping in a small vise and cutting with a jewelers saw. I guess we learn along the way, sometimes the hard way!!!
Thanks for all the responses and knowledge...
 
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