I need grinding tips

A

andy kloot

Joined
Jul 1, 2019
Messages
9
I’m pretty new to knife making and recently got a steal of a deal on a 2x72 grinder. The problem is that it’s single speed which is fast as hell. I forged up two big Bowie’s and put a lot of work into them. I rough ground the bevels in fairly thin and then heat treated them. I threw on a high grit just to kind of polish/finish the bevels and even with passes as quick as I could manage I was still burning the edges. How can I prevent or fix this? We’re they too thin before I went to finish them? It’s a lot of work to put in and then keep ruining edges at the last minute. What can I do and how thin should my edge be before I sharpen it?
Thanks in advance!
 
What Bill said^^^ & have a water dunk bucket. Grind a pass or two then dunk & wipe on belt side, repeat. Use belts as if they were free for bevel grinding .. I only use 50-60% of the grit, then they go into the profiling etc pile!
 
another tip is to dunk the knife before every pass. So you are grinding the steel wet.

You may have to dunk every pass to keep it in check.
 
That’s what I feared but it sounds like I’m in the exact same boat as you. Right down to the uneven grind lines haha
 
If you haven't yet, you can also try some Trizact Gator belts for going passed 120 grit as they don't heat up quite as fast as the standard, non-structured AO belts. For your single speed set up I would go up to about 220 grit (A100) or 320 (A65) with a Gator belt and then just switch to hand sanding from there, or finish with a scotch-brite belt. As Bill mentioned, very light pressure. You want to make sure you're only removing scratches from the previous grit with the higher grit belts as opposed to trying to thin the bevel geometry, so get all the shaping done at a lower grit like 80.

Things will always heat up faster on the platen since the belt is being pressed against a stationary surface, so maybe you can try to convex the edges on the slack potion of the belt to bring the edge down to a decent geometry. I would also use coarser grits to convex the lower part of the bevel into the edge if you were to. You still want to have the edge thickness to the proper geometry before convexing it, but you don't have to take it as thin on the platen as you would if you were doing a full flat all the way to the secondary (cutting) edge/bevel without the convex.

These are just suggestions that can help reduce the chance of over-heating, but won't necessarily eliminate it. This is one of the main reasons it's so often recommended that you have some way to reduce the speed on your grinder, whether by VFD or by pulleys.


~Paul
My Youtube Channel
... (Some older vids of some of the older knives I made)
 
I have a single speed grinder and what I find helps is to not apply direct pressure to the edge, I use my index finger and thumb on my support hand to guide the blade and what I do is hold/apply pressure with my index finger along the spine and my thumb is a heat checker, it is just barely resting on the middle of the blade to feel for heat but no pressure is applied. My main hand applies indirect pressure by rotating the edge into the belt while maintaining pressure on the spine with my support hand. Then if I want my grind to go higher or thin the edge more I back off the rotational pressure from my main hand or apply more rotation forward. It’s hard the explain in words but it works very well for me and I normally do all my bevel grinding post heat treat and almost never have any issues burning the edge. Also dunking in water every pass once you get thinner. By using my thumb to check for heat if it starts to get uncomfortable to hold it’s getting too hot which means I could be applying too much pressure or moving too slowly
 
andy kloot said:
I’m pretty new to knife making and recently got a steal of a deal on a 2x72 grinder. The problem is that it’s single speed which is fast as hell. I forged up two big Bowie’s and put a lot of work into them. I rough ground the bevels in fairly thin and then heat treated them. I threw on a high grit just to kind of polish/finish the bevels and even with passes as quick as I could manage I was still burning the edges. How can I prevent or fix this? We’re they too thin before I went to finish them? It’s a lot of work to put in and then keep ruining edges at the last minute. What can I do and how thin should my edge be before I sharpen it?
Thanks in advance!
Click to expand...
With 40 grit belt and high speed I can grind thin as I like ...paper thin on ege without overheating ..............After that my friend .........if you want finer finsih ,HAND sanding is only option if you have only one speed like me :) I learn to use 40 grit so i can end up with quite fine finish ....several light pass with that 40 grit at finishing stage will make hand sanding more pleasure ....
40 grit belt finish..................
AWAfv9v.jpg

40grit high pressure
q4y11eY.jpg

40 grit finished on same belt ....light pressure
HXkgaDl.jpg

NxdM3wZ.jpg
 
I just tried a couple Trizact belts in 220 and 400. Also, Silicon Carbide (SC) belts in 220 and 320. And a 220 grit blue ceramic belt all from Supergrit.

I used them on my first knife that I tunred the edge blue. First, I ground the edge down with an angle grinder and 40 grit ceramic. I then tried all the belts with the trizacts on one side and the SC on the other.

They both didn't made the blade near as hot as a AO belts. might be worth it to get one of each or so to test for yourself.
 
if you keep your finger or thumb on the back of the blade with no glove to apply pressure, you wont be able to burn the edge without burning your finger first. maybe you can change the size of the pulley to change the speed? a used belt makes much more heat than a sharp one, and the higher in grit you go, the friction increases and it gets hotter faster. if you cannot control the speed, you must control the pressure and dip in water more often,
 
I forget the name so help me out.

There is a mastersmith who did demos at the Travis Weurtz hammer ins
Find those videos.

His name ?
He died recently, this year or last year
He had MS
He had a book about being the Cowboy bladesmith
He was a relatively short tiny little fellow.
 
You must log in or register to reply here.
Back
Top