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Bevel migrating

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Kale Cope
Posts: 13
Eminent Member Apprentice Bladesmith
Topic starter
 

I just messed up the initial bevel grinding on a knife so badly I have to restart, and decided the best thing to do from here is to figure out what I did wrong.

I have a problem where, when I begin to walk the bevels up, the edge wants to continue getting thinner, this is worst at the tip and heel.

I also find that I have several angles running down the bevels that don’t want to join. How do those form, and how can I fix them?

I also cannot get the bevels tapering at the tip even.

 
Posted : 23/11/2022 8:47 pm
Matthew Parkinson
Posts: 0
Trusted Member Journeyman Bladesmith (5yr)
 

I see this all the time in my students work. 

you are re-setting the bevel to a different angle each pass. To keep the faceting from happening keep the whole bevel in contact with the belt and apply greater pressure to the side you wish to shift the bevel to. 

The method I teach is profile first, then square up and flatten the ricosso. at this point you can mark center for the edge. (or just eye ball it) next grind most of the length of the blade leaving a little area near the plunge  mostly un ground. (good light  is super important here)  With a table on the grinder set the plunges. i do this  using a push stick first pass apply pressure to the middle of the blade and walk the plunge into place. to thin an edge more the push stick to the top , to walk the bevel up to the spine place the stick lower but make sure the Whole width of the bevel is in contact with the belt. be careful to keep flat and not put to much pressure on off side of the belt or you will get the dreaded 2" mark.  I do all that with a course belt then skip straight to 220 most of the time. 

Grinding pressure is important, to little the belt glazes and stops cutting, as well as giving and uneven cut and putting more heat into the work. To much.. isn't an issue, unless sit is in the wrong place.  control of the pressure is what is important. the wider the section being ground the more pressure is required , the narrower (like the point) the less pressure is needed.

hope that helps. 

MP

 
Posted : 24/11/2022 9:57 pm
Kale Cope reacted
Kale Cope
Posts: 13
Eminent Member Apprentice Bladesmith
Topic starter
 

Thanks!

 
Posted : 25/11/2022 12:38 am
Kevin Stinson
Posts: 15
Eminent Member Apprentice Bladesmith
 

Posted by: Matthew Parkinson

Grinding pressure is important, to little the belt glazes and stops cutting, as well as giving and uneven cut and putting more heat into the work. To much.. isn't an issue, unless sit is in the wrong place

Om i felt i should chime in here because I find using too much pressure can stall/stop the belt on a Lower end/budget/cheap o grinder like my Palmagree 2x42 stopping the belt.(can't afford a better one right now.)

also, really there unless you turned the steel blue, i would go down grit and recut your bevels on it just for practice. If the knife is destined for the scrap bin, there is nothing wrong with putting some effort to get the bevels right and then throwing it in the scrap bin. if the edge is too thin, just thicken it up by recruiting it, so it's thicker. This is something I wish I did back when I was starting out. Chase it a bit, then throw it into the scrap bin after writing the type of steel it is on it, as you can perhaps break or cut it apart and throw it in a canister later. nothing wrong with making a fillet knife with perfect bevels. 

 
Posted : 28/11/2022 1:35 pm
Matthew Parkinson
Posts: 0
Trusted Member Journeyman Bladesmith (5yr)
 

A grinder running modern ceramic belts requires pressure to cut, this is regardless of the quality or ability of the machine. If the machine can not track under moderate cutting pressure or does not have the power it is not really suited to the task. Sanders (as opposed to grinders) are not grinders, I learned that years ago after running through several "cheap" machines when i started 20 odd years ago. 

I get the implulse to not spend on a grinder back when i started you had very little choice in "good" grinders.  If i remember right a  wilton square wheel ($1800 at the time) a Bader ($17-2500) or the bur-king ($2k+) was about all that was available, now you can get a good fixed speed for $1000 and a vairable for 12-1500.  back then i spent 6-700 trying to avoid spending that money, it slowed up my learning curve  and cost me far more than the 1000-1200 i "saved" in abrasive cost and time.. 

a good grinder is worth the money. 

MP

 
Posted : 28/11/2022 7:09 pm
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