2” Divot with Trizact Belts

deerrockknives

deerrockknives

Only thing I’m sure about, I know nothing for sure
Knifemaker / Craftsman / Service Provider
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Mar 2, 2020
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Hi everyone,

I’m new to knife making and am on the cusp of completing my first batch of blades. I’m using a 2x42 grinder (glass platen). I find myself coming off of my hogger 60 grit belt fairly clean (although I’m not good enough yet to do clean saber grinds, just FF). Also, I’m using a bubble jig.

The problem is when I go to clean up the 60 grit scratches with trizacts (a300, a100, a65, a45 progression) im getting a 2 inch divot. Im hyper aware of it, but it still seems to happen. Do you think it could be the belts just don’t match up with my grinder setup very good? Or is it just me? Any advice is appreciated.

Thanks
Greg
 
Its not uncommon, especially if youspend time working at the plunge line. You just need to continue to go slow, and be careful about where you spend time on the bevel, and where you put pressure on the blade
 
It’s not letting me post a pic for some reason, but when the belt digs in exactly 2” from the plunge.

 
If you are trying to feather the wall of the plunge, you are likely lifting on that edge, and digging the other edge into the bevel.
To clean the plunge, get a flexible belt to overhang the platen, and stay flat as you snug against it a couple times. Don't linger too long there, and check frequently for stray grinds
 
There is a tendency to let the blade torque as you're coming up into the plunge. The platen climbs into the plunge and you get two distinct grinding points (the plunge and 2" out). Focus on where your griding pressure is located on your platen, there's a sudden change in force as you hit that plunge that can put the weight (and cutting pressure) on the wrong side of your platen. Compounding this is the changing length of the lever arms (the handle length vs the tip) and you get the dreaded 2" grinder divot. Force yourself to use the corner of the belt as you approach the plunge. Visualize where your cutting pressure is located and angle the blade where the 2" bump has a tiny bit of air between it and your belt as you come into the plunge. This fixes your problem but causes the over ground plunge and funky lines that are also a signature of a new maker. You have to use lighter pressure and move quick as you come into that plunge to avoid this.


If you ever go to a knife show and look at people's work (mine included sometimes) you'll see this on the tables of a lot of well known makers. Everybody does it. When you get good, you don't do it so much but if you know how to look for it, it's a very common problem even on seemingly perfect pieces.
 
OK I understand. I’ve found it to be pretty easily avoided, what has already been said is great advice, keeping the blade moving back and forth as you’re working on the plunge (also for the entire blade) helps, another thing I’ve found to help is to put the blade at an angle and work you’re way up to the plunge (be carful though because you can easily mess up your plunge) to smooth it out.
With all that said and a little practice you can get it perfect, if it is still there it will be so minor that the naked eye won’t be able to see it.
Also most of my blades have a hand sanded finish so if there is any divot it will be removed with the sanding.
 
slalomnorth said:
I’m new to knife making and am on the cusp of completing my first batch of blades.. . . Or is it just me?
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Unfortunately, it's probably you. But this is also fortunate because you can change it. You just need more time. As said above, this is common when starting out.
Some say you can't get good without starting with 500 railroad spikes....:rolleyes:
 
slow down, watch your hand pressure, and watch the sparks. If you arent getting a full 2 inch spark tail you are applying uneven pressure. The second that spark tail changes from a full 2 inches pull the blade off and reset. And if you have a variable speed slow it way down and let belt and grit do the work.
 
weo said:
Unfortunately, it's probably you. But this is also fortunate because you can change it. You just need more time. As said above, this is common when starting out.
Some say you can't get good without starting with 500 railroad spikes....:rolleyes:
Click to expand...

Bunker Hill Blades said:
Well let’s get him in here... Mecha Mecha
😂
Click to expand...


There's no 2" divot with the spikes because they're supposed to be fully forged into knives before you heat them up in the coal and dunk them in the creek. All that's left to do is sharpen them and put on a handle.

PS the coal should have a hair dryer taped to a lead pipe, that blows air into the coals, so the spike knife gets hot enough to get what us experts call an "iron boner." That's what makes it hard enough to hold an edge.
 
Thanks for the advice everyone, I’m certainly not doing myself any favors by learning on the 2x42 flying at a million miles an hour. Eventually I’d like to get the 2x72.

Watching where the sparks fly really is helping me even things out. I’ll try to post a pic once one of my blades is complete
 
I'm sure this isn't your issue, but something to be aware of with Trizact green belts: they can develop grooves and or ridges depending on what you're doing. Imagine sanding the end of a 1/8" pin. It will gouge out the abrasives in that spot. Sure all belts do that but with Trizact green belts the effect it much more pronounced.

When I use them on my SGA I can easily end up with a high spot on both edges if I don't pay attention. Unless I re-flatten the belt it'll leave gouges in a blade when bevel grinding.

RE the 2" divot, you already got all the tips you need. But FWIW, I only grind on half the belt at a time (sort of). When the plunge is on the right I'm only using the right half of the belt. In other words my pressure thumb is not in the middle of the platen, but closer to the plunge side edge. Like Nathan the Machinist Nathan the Machinist mentioned you can have a "bit of air" on the opposite edge of the belt. For me there is almost always a 'bit of air' until I get to the final grits.

There's a million ways to do it, that's just mine.
 
Sando said:
I'm sure this isn't your issue, but something to be aware of with Trizact green belts: they can develop grooves and or ridges depending on what you're doing. Imagine sanding the end of a 1/8" pin. It will gouge out the abrasives in that spot. Sure all belts do that but with Trizact green belts the effect it much more pronounced.

When I use them on my SGA I can easily end up with a high spot on both edges if I don't pay attention. Unless I re-flatten the belt it'll leave gouges in a blade when bevel grinding.

RE the 2" divot, you already got all the tips you need. But FWIW, I only grind on half the belt at a time (sort of). When the plunge is on the right I'm only using the right half of the belt. In other words my pressure thumb is not in the middle of the platen, but closer to the plunge side edge. Like Nathan the Machinist Nathan the Machinist mentioned you can have a "bit of air" on the opposite edge of the belt. For me there is almost always a 'bit of air' until I get to the final grits.

There's a million ways to do it, that's just mine.
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How do you flatten the belt? I've been using my Trizacts with an SGA and never even considered the flatness issue.
 
N.W. Gean said:
How do you flatten the belt? I've been using my Trizacts with an SGA and never even considered the flatness issue.
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How to explain better? 🤔

Pretend you have a 1" wide knife and you're surface grinding right in the middle of the belt. Eventually the center of the belt will wear more and you'll have 1/2" wide high spots on each edge. I avoid this by (you probably do to) moving the belt left and right as I go along. That way the belt wears more evenly.

If I can't avoid this, I'll try to even it out with a diamond grindstone dresser. I hold the dresser lightly against the moving belt and move side to side.

 
N.W. Gean said:
How do you flatten the belt? I've been using my Trizacts with an SGA and never even considered the flatness issue.
Click to expand...
I've had decent success using an old, worn out 140 diamond flattening plate for sharpening stones. It comes in handy when structured abrasive belts glaze as well
 
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