Grinding belt splice bump

D

DARblades

Joined
Mar 6, 2019
Messages
17
I'm fairly new to belt grinding. I got a 2"x72" grinder hoping to minimize my hand sanding time. I am getting grinding patterns from the splice bump on the belts and was wondering if this is just a fact of life or am I using the wrong belts? Always apriciate experienced advice.
 
I've been trying several diferent brands and it's mostly and issue with finer grits when trying to finish the blade. tonight i'm using Klingspor Jflex 320.
 
You can lightly sand the tape on the splice to smooth out the edges
 
A soft platen helps. I glued a piece of leather on one and now use it all the time.
 
I like leather also, I only have one platen so I spray glue it on mostly just on the top and then acetone to remove the residue. Sometimes I'll use graphite coated canvas to me it seems a little firmer, I guess that also depends on the leather you use. I get my graphite coated canvas from K&G finishing supplies but it's not hard to find. Good idea to minimize hand sanding at the grinder it's much faster than hand sanding.
 
Splice bump is the bane of our existence. The klingspor belt is a fantastic belt but it's got really obnoxious splice bump. I take an old file and scrape the grit off the joint, that helps a lot
 
Gilbert M said:
Sometimes I'll use graphite coated canvas to me it seems a little firmer, I guess that also depends on the leather you use.
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Sounds like a good idea - just ordered a 4"X24" piece for $11 shipped. Should be here Sunday - I'll try it.
 
I stopped ordering Klingspor a long time ago. They grind fine for about a minute for me . Nathan says he likes them. We all find our own sweet spot of brand of belts, pressure & speed... I prefer Ceramic VSM , I get them from Tru-grit here in the Cauliflower State! I use them up to 120grit and then Cork & Scotchbrite to finish.. I also put Pyrocern glass on my Platens I don’t have any issues with bump from my process. Make note of what belts work for you. Take a black marker and write on the back of each one as soon as you stop the machine so you know what order in the future!
 
I used to use Klingspor almost exclusively. I did sort of what Nathan does. I would sand the splice against an old 100 grit belt to remove the grit at the splice.
 
Let me ask something please. Is the belt bump caused when the splice passes over the edge of the platen?
For example my platen is a little proud of the wheels. Would getting the platen flush with the wheels minimize the bump effect?

What really causes the bump? Does it happen only when the splice and the knife come in contact?

Thanks,
 
Heli00 said:
Let me ask something please. Is the belt bump caused when the splice passes over the edge of the platen?
For example my platen is a little proud of the wheels. Would getting the platen flush with the wheels minimize the bump effect?

What really causes the bump? Does it happen only when the splice and the knife come in contact?

Thanks,
Click to expand...


The bump is caused from the thickness of the belt at the splice. When grinding against a steel or glass platen, as the splice passes by it forces the ground material away, then it hops back when it passes, causing the "bump". It leaves a pretty uneven finish in the process. It's kinda like driving your car over rumble strips on the road.

Sanding the splice down is just trying to even out the thickness to cut down on the bump. It's usually just a problem with light weight J-flex belts. Heavier belts don't have this problem nearly as often.
 
deleted post ...............I didn't read that issue is with fine grit belts :)
 
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