2nd Knife. Need help finishing

G

Geronimo509

Joined
Jan 17, 2009
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Short story - I just bought a 2x42 grinder (Palmgren and did the mods that every youtube video said to do.)

3/16" 1084. I used the Grinder to do the bevels and got the edge to about a dime in thickness. Heat treated it in a 2 brick forge. It's currently tempering now. I don't know how to get the edge down and they sharpen it. I ruined my first knife trying to grind it down after tempering.

Long story - I made my first knife (stock removal method) with an angle grinder. It wasn't pretty. However, it started to clean up nice when I got the belt sander and I took it to some 40 grit ceramic belt. I took it to 80 and 120 grit using ceramic belts. Then I got the bright idea to to use the marketed X weight 220 grit for profiling and sharpening. I bought 220, 320, and 400 grit x weight alumina oxide belts that say they're for profiling and sharpening. First two passes on the 220 and I turned the edge blue and ruined the temper. They were pretty quick passes but it heated up so fast.

How do I use the high grit belts to get something close to an edge on it or what else can I use besides the grinder? I know the 2x42 is going really fast and heats up fast.

I ordered some Trizact belts in 220 grit and higher. Will they help me finish the blade without heating up so fast like the oxide belts? I don't want to ruin this one as it's not terrible. Again, the edge is about the width of a dime right now.

Also, I'm still terrible at grinding and have been practicing on mild steel. I even made Walter Sorrells grinding jig and still can't get even lines. I've watched the videos and read all the forum tips to get better. I'll keep practicing. And keep practicing free handed.

I'll post pictures of the second knife.
 
Dunking the blade in a bucket of water after each pass will keep the blade cool.
 
weo said:
Dunking the blade in a bucket of water after each pass will keep the blade cool.
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The first pass turned the edge blue on 220 oxide belt. I pressed it in at the plunge line and before I made it across to blade, it was blue. I read the 2x42 heats up too fast so I went twice as fast as I did while removing the stock with the ceramic belts.

I dont want to ruin this one like the 1st.
 
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This is the second knife. It's not even on both sides which is annoying but it's 100 times better than the first one. My apologies for the ridiculous size of the photos.[/IMG]
https://i.imgur.com/RzombwT.jpg[/img]']https://i.imgur.com/RzombwT.jpg[/img]']https://i.imgur.com/RzombwT.jpg[/img]']https://i.imgur.com/UMwKNH8.jpg[/img]']
 
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I've found that some belts do better when they are wet before you press a blade to them. But you're right, a 42" belt will heat up faster than a 72" one.
 
Mr.Wizard said:
You may need a direct coolant flow. Can your grinder handle that? What is the SFPM?
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Looks like it’s 4480 sfpm. 1/3 horsepower direct drive motor.
I don’t know about the direct coolant flow. I doubt it though. Also, it doesn’t have a variable speed motor.
 
The finer the belt, the slower the drive speed. It's the fine grit belts & too much speed that's heating the blade too much. A dime is pretty thick, 0.053"...
 
Why not stick with a coarser grit and take the edge down more? There is a lot of material you can remove with a coarse belt if you are at a dime's thickness.
 
Hubert S. said:
Why not stick with a coarser grit and take the edge down more? There is a lot of material you can remove with a coarse belt if you are at a dime's thickness.
Click to expand...

This may be your only option with a high belt speed if you cannot run wet. 1/3 HP isn't much for a 2" wide belt either. You may want to consider a new motor.
 
I am in the same boat with you, one speed 2x42. I figured a 120 VSM ceramic belt after HT and then trizact gator A100 (ca 200 grit). After that hand sanding from 220 with wet sanding paper (black), I realized normal red paper doesn't do much on hardened steel in finer grits. Wet sanding paper cuts fine.
I also started experimenting with scotchbrite belts.
 
Also, don't push hard on the finer grits, work without gloves to feel for the temp (tape the fingers that hold the knife if needed), dunk the blade every pass and don't put the pressure towards the edge bevel.
 
FredyCro said:
I am in the same boat with you, one speed 2x42. I figured a 120 VSM ceramic belt after HT and then trizact gator A100 (ca 200 grit). After that hand sanding from 220 with wet sanding paper (black), I realized normal red paper doesn't do much on hardened steel in finer grits. Wet sanding paper cuts fine.
I also started experimenting with scotchbrite belts.
Click to expand...
Will the trizact gator belts in 220 and above heat up like the oxide belts? I just ordered a couple to test but how is it for you?
 
my 2 cents. never shape with 220. 220 is only to remove 120 grit scratches. 220 will heat up 4x faster than 120 grit. go to 120 pre heat treat, with the edge the thickness of a dime. after heat treat, use 120 to get the edge thickness down to 020". that way after you go thru your grits you will end up with a behind the secondary edge thickness of about .010-.012 , which is very thin for a beginner. another tip, use bare hands while grinding, you finger will get too hot to hold the knife before it turns blue. i use gloves and have to be very careful not to forget to dip the blade in water. yes, the gator in 220 will heat up just as fast. do all shaping with 120 and lower.
 
you can try dunking a shop towel in water and hold it behind the blade to act as a heat sink. As noted, variable speed and coarser belts help a lot.

You can also convex the edge on the slack portion to get it thinner. The slack belt runs a lot smoother.

I typically us 36 grit to about 0.01" before 120 on slack to get down to zero to 0.003 on kitchen knives.
 
john april said:
my 2 cents. never shape with 220. 220 is only to remove 120 grit scratches. 220 will heat up 4x faster than 120 grit. go to 120 pre heat treat, with the edge the thickness of a dime. after heat treat, use 120 to get the edge thickness down to 020". that way after you go thru your grits you will end up with a behind the secondary edge thickness of about .010-.012 , which is very thin for a beginner. another tip, use bare hands while grinding, you finger will get too hot to hold the knife before it turns blue. i use gloves and have to be very careful not to forget to dip the blade in water. yes, the gator in 220 will heat up just as fast. do all shaping with 120 and lower.
Click to expand...

scott kozub said:
you can try dunking a shop towel in water and hold it behind the blade to act as a heat sink. As noted, variable speed and coarser belts help a lot.

You can also convex the edge on the slack portion to get it thinner. The slack belt runs a lot smoother.

I typically us 36 grit to about 0.01" before 120 on slack to get down to zero to 0.003 on kitchen knives.
Click to expand...
I used 40, 80, then 120 grit ceramic belt to get to a dime in thickness prior to heat treat. Now I'm ready to take it down to an actual edge. Are you saying to stay at 120 grit to get it almost all the way down to an edge? And then finish with hand sanding and sharpening stones?

Also, I used bare hands. I barely touched the blade to the belt and before I could finish running it across the belt, it was blue. It got hot in an instant, I saw blue before it burned my fingers.
I ordered silcon carbide from 220, 320, and 400 grit as well as the gator belts up to 400. They both with heat up as fast as the oxide belts? If so, I just wasted more money on unusable stuff.
 
Geronimo509 said:
Will the trizact gator belts in 220 and above heat up like the oxide belts? I just ordered a couple to test but how is it for you?
Click to expand...

My experience was no, but I guess it depends on how you grind. Keep the knife out of the jig for finishing and use fresh belts. Resurface your gator belts when it feels like they don't cut but just glide over the knife. If you keep your fingers on the knife you will develop a feeling of how the heat builds up and will be able to adjust accordingly. You might wash your clean grind line away before you develop the feeling (happens to me as well). You can then either convex to blend in or do a full flat grind. I chase the clean line for practice or grind without jig for practice. When I do a mistake I resort back to the jig to grind it out. Helps me practice before ruining a knife all together.
 
I think you will need to run a new coarse belt first, gently for the initial shaping, then drop to a smoother new belt only when you're done & don't go past a new 120 on the final belt work. Once the initial coarse work is done, the finer grits should be very light clean-up passes to just slightly reduce the scratching for final hand sand.

I've chased this stuff around as a relative newbie also & can sympathize about the work you have to do now. Next time, the thickness should be reduced a bit prior to HT. This varies with the steel type, your methods & experience, but .05" is pretty hefty to start out on grinding hardened steel. This is the problem, so the new coarse belt is the best option for removing metal without adding too much heat. Water will help, as will gentle passes, but you will have a fair amount of time ahead of you on the grinder, to get that edge down to a good slicer. The finer grits are only to finish the steel, no shaping will work with them due to excess heat with a single speed grinder. Best of luck!
 
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