bumpng at the seam

R

rupsty

Joined
Mar 14, 2013
Messages
42
Howdy,

I'm having issues when I grind on the finer grits (300 and above). The belts have a taped seam that bumps my knife every time it goes around, leaving a mark in the knife. Are there any ways to avoid this? Also, when finishing up and knife for cosmetics, how fast should the grinder be going? I know it's a relatively vague question but any guidance would be appreciated.

Thanks,
Rusty
 
I like using Norax belts, they don't bump and last a long time. Platen material can play a roll in "bump" too.
 
You might try running your standard belts on top of a scotchbright. Not for everyone but this padding reduces the bump to a manageable level. Dan Graves showed us this some years ago.

If you don't like your machine finishes please consider looking deeper at the ins/outs of hand finishing. However you do it, it's only the result that matters.
 
Ill have to get some of those norax belts too. Running on top of a scotch bright doesn't do well on my lil grinder.
 
I have a problem with my A45 Trizact belts being really bumpy but the A15s are smooth. My 60 grit ceramics are smooth too. Maybe I just got a belt that doesn't fit just right but I thought it was odd that the smallest grit belt was the least smooth running across the blade when grinding.
 
rupsty said:
Howdy,

I'm having issues when I grind on the finer grits (300 and above). The belts have a taped seam that bumps my knife every time it goes around, leaving a mark in the knife. Are there any ways to avoid this? Also, when finishing up and knife for cosmetics, how fast should the grinder be going? I know it's a relatively vague question but any guidance would be appreciated.

Thanks,
Rusty
Click to expand...

Rusty,
For a vague question I have a general answer. Generally, The finer the grit the slower you want to run the belt. I find each different from each MFGer has a SWEET spot in speed where it will give the best results. This goes for metal with the platen on and slack when I am doing handle sculpting. Experiment and you will find the sweet spot of speed for a given belt and settle in to preferring a certain brand at a certain speed.
 
Finer grits are typically thinner material and therefore less able to hide the thickness of the seam. Fine grit j-flex belts are notorious. In Nathan's thread on his platens he recommended filing the seam down which I have done but can't recall how much it reduced the effect. Maybe give it a try, though.
 
Everyone - thank you so much for the replies. Very, very helpful. Lots of things to try. Apparently I'm not the only one with this issue. My knives are slowly getting better but I couldn't get this one issue sorted.

As for hand finishing, I'd like to also give this a try at one point but I have no idea how to approach it.

Thanks again
 
Hey Lawrence,

I just saw your website - I'm in Santa Monica too. Finally someone nearby who makes knives! I'm going to drop by during your business hours.

COOL!
 
Search you tube for Nick Wheeler Hand Sanding knives 101. His efforts really helped me
 
Belt bump is a pain. The norax/trizact/gator type belts are better than the regular fine grit AO belts. The best solution I've found for the bump is to use a softer platen. I rigged up a piece of leather that hangs by a clip on my platen. Removable, fast. I usually tolerate the bump up until my finest grit, then use the leather platen.
 
I was going to recommend leather backing too, but I find that doesn't work good on the (expensive) structured belts. I went back to Klingspor, J-flex AO when using a soft back and love it.
 
Michael Rader said:
I was going to recommend leather backing too, but I find that doesn't work good on the (expensive) structured belts. I went back to Klingspor, J-flex AO when using a soft back and love it.
Click to expand...

Michael, You prefer the Klingspor over the Hermes J super flex? I know that the Hermes Ceramic belts are terrible but there A/O belts are the ones I prefer over all others I have used.
 
Hmmm... I haven't tried Hermes. Are the prices similar? I'm paying $3.58 per 2X72-400 grit if I buy more than 10 at USA-Knifemaker.
 
Michael Rader said:
Hmmm... I haven't tried Hermes. Are the prices similar? I'm paying $3.58 per 2X72-400 grit if I buy more than 10 at USA-Knifemaker.
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I am pretty sure that they are less, "Hermes' at www.trugrit.com I don't have my last invoice in front of me. They last a lot longer than Klingspor A/O belts and price per performance they are much better. Try some, I think you will agree!
 
Rhinoknives1 said:
I am pretty sure that they are less, "Hermes' at www.trugrit.com I don't have my last invoice in front of me. They last a lot longer than Klingspor A/O belts and price per performance they are much better. Try some, I think you will agree!
Click to expand...

I also like the Hermes from TruGrit.... The 400 grit runs about $2.50/10 IIRC

Smooth running belts and wonderful at cleaning up plunges
 
I don't take the blades up to a high grit on the belt any more... but the Hermes (blue abrasive, yellow backing) J flex belts are my favorite handle and guard contour belts! :)



They're $2.40 each from Pop's, or $2.50 each/10 from TruGrit. :)
 
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