How do you get consistent thickness behind the edge on the grinder?

meteorokra

meteorokra

New Member
hey y'all, i'm new here and new to knife making. i've been having trouble getting consistent thickness bte off the grinder.

i've got a pheer 2x72 454, running around 30% on the vfd with a fresh 60 grit blaze. i wet grind too, using a little sprayer.

i attached pics of my current issue on an gyuto style knife in aeb-l at 63hrc. any advice is appreciated and thanks for looking.
 

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It just takes practice... Subtle changes in pressure to get what you want. Also you need to make sure your platen is flat that can cause some issues sometimes, although I don't think it will cause what you pictured.
 
well. i've got about 30 knives under my belt and most of the time thickness bte isn't an issue, but every now and then i get something like what i posted. i've noticed a worn and wet belt can bulge in the center and cause varying bte. also a low grit belt that i've "dressed" to freshen up the grit can sometimes cause grooves from being unevenly dressed. but every now and then i get what i posted without either of the two aforementioned scenarios.

i don't think it's the platen but it won't hurt to flatten it. and the amount of practice varies from person to person, i imagine...is there a rough blade count where new makers start to get the hang of things like this?
 
meteorokra said:
well. i've got about 30 knives under my belt and most of the time thickness bte isn't an issue, but every now and then i get something like what i posted. i've noticed a worn and wet belt can bulge in the center and cause varying bte. also a low grit belt that i've "dressed" to freshen up the grit can sometimes cause grooves from being unevenly dressed. but every now and then i get what i posted without either of the two aforementioned scenarios.

i don't think it's the platen but it won't hurt to flatten it. and the amount of practice varies from person to person, i imagine...is there a rough blade count where new makers start to get the hang of things like this?
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Hmmm... Does it only happen with certain belts? And if so which belts (and grit level) did u you experience it on? I also wet grind and most 120 grit ceramics tend to want to cup out at the edges, causing the outer edges of the belt to gouge into the blade when you first make contact.
 
REK Knives said:
Hmmm... Does it only happen with certain belts? And if so which belts (and grit level) did u you experience it on? I also wet grind and most 120 grit ceramics tend to want to cup out at the edges, causing the outer edges of the belt to gouge into the blade when you first make contact.
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typically with higher grit belts, but as low as 60 grit. and i've never had cupping issues, but the opposite, where the center or the belt bows out so that about an inch from the heel is thinner bte than the heel. i'll keep practicing though. thanks for the info.
 
Rocking the blade on the platen. Pay more attention to spark shower. If its not even across the entire platen face you are Rocking the blade. Elbows in tight against body and a smooth side to side flow
 
Watch the good knife makers. they all keep elbows in, wrists against the body and have a stable stance that allows for smooth side to side motion.
As I said also watch your sparks. If your sparks start trending to one side or the other on the platen then you are twisting/rocking the blade creating uneven grinds. A 2 inch wide belt should have a 2 in wide line of sparks coming off it
 
vlegski said:
Elbows in tight against body
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In general, keeping your extremities as close to the body and minimizing the joints that move is proper ergonomics and good practice when using any tool (or doing most functional activities outside of athletics, says the ex-physical therapist with 12 years of occupational rehab experience). This (try to keep legs shoulder width apart, keep your trunk inside your base of support, keep elbows against your trunk, lock your tong hand into your hip, etc) is something I emphasize almost on day one when I teach blacksmithing and when orienting people to the machines and working in the metal shop because it's something that most people don't think of.
I think that some folks think that if they stand as far away as possible from sparks they are being safe, and it's tough to convince some of them that getting closer to the work (and sparks) is actually safer.
 
billyO said:
In general, keeping your extremities as close to the body and minimizing the joints that move is proper ergonomics and good practice when using any tool (or doing most functional activities outside of athletics, says the ex-physical therapist with 12 years of occupational rehab experience). This (try to keep legs shoulder width apart, keep your trunk inside your base of support, keep elbows against your trunk, lock your tong hand into your hip, etc) is something I emphasize almost on day one when I teach blacksmithing and when orienting people to the machines and working in the metal shop because it's something that most people don't think of.
I think that some folks think that if they stand as far away as possible from sparks they are being safe, and it's tough to convince some of them that getting closer to the work (and sparks) is actually safer.
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You described that pretty well. I put the advice into practice today and it helped a lot. Thanks billyo.
 
It kinda looks like 2” bump to me. It happens to me regardless of what belt I’m using. Try the above mentioned grinding tips and when you see it pop up don’t start your grind in the same spot. Like go to the middle of the blade rather than off the ricasso and go back and forth from there.
Also for me running at lower speeds with heavy grit belts has not been a good combo. Those belts like high speed and heavy pressure for the most part. Maybe try turning up the speed and decreasing pressure on the blade and just move at a constant speed.
For what it’s worth I would imagine I well over 1,000 blades and it still happens to me especially on longer thin blades.
 
Don't sweat it. I still get that. I just mark opposite side of the blade with a Sharpie the lenth of the uneven portion and work it on the belt there lightly (bare thumbs so you dont over heat blade), then flip the blade to the other bevel mark the same area on the side you've already worked do the same thing. Do this as many times as you need to correct problem. Then finish with a full pass or 2 on both sides to blend all the grind lines. This happens to me a lot near the Ricaso area as I don't go back all the way on every pass as not to mess up plunge line.
 
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