Grinding hardened 3V

jdm61

jdm61

itinerant metal pounder
Joined
Aug 12, 2005
Messages
47,357
Timing has put me in a situation where I will probably have to grind maybe 10 4 inch blades from hardened CPM 3V. The only good news is that I can probably get away with a belt/Scotchguard finish. Anyone have an experience doing that? any suggestion for belts?
 
Joe,
I do almost all of my blade bevel grinding after HTment.
Haven't used the 3v yet but I've done S35VN, S30V and the hardest to grind was S11OV after HTment and I always use fresh new Ceramic belts, VSM or Norton Best value and dunk after each pass.
I leave the rear facing side of the blade with water droplets on it.

Sometimes I only get one or two blades per belt because I when I think they are generating to much heat I just use that belt for profiling and grab a fresh 36, 60 or 120 grit belt. I get the VSM and the Best Value from www.trugrit.com They are way under $5.00 a belt so at that price I don't mind if I only bevel grind a blade or two with each one. My blades are large culinary knives.

Good luck and I hope some of this helps you?
 
ooh putting an edge alone on my 3v knife after it came back from ht was brutal but I probably was using belts at too high a grit. go low!
 
Hi ,Joe. I too do all my blades after heat treating I had two of those 3V folder blades heat treated, but have only ground one which I believe I did with a 3M 977 or 984 with a 60 grit size. Frank
 
I've done it, I would say the blaze worked better than the 984s for grinding the bevels and then switch to gator belts for finishing. If your flatening the stock too, the 977 definitly seemed to last the longest for me. Grinding hardened 3v was really not as hard as I expected it to be
 
I have ground a lot of 3V hard and I have to say that Blaze is definitely the best that I have found so far. I have tried all the different belts so far except the 984's and nothing lasts like the Blaze. I start at 50, 80, 120, and then go to SC belt to finish. I can generally get two sometimes three 4" to 4.5" blades from each belt. The 120 grit will last the longest for me cause I am normally just cleaning scratch pattern at that point, 50 and 80 do all the hard work.
 
How big are the blades you all are talking about? I've got a few more 3V plans, and have been thinking about grinding post HT to help avoid warp. But, in my case I'd be doing around 27-28" of blade (more swords). I should expect to use 2-3 belts on that, based on Big Chris' data?
 
crimsonfalcon07 said:
How big are the blades you all are talking about? I've got a few more 3V plans, and have been thinking about grinding post HT to help avoid warp. But, in my case I'd be doing around 27-28" of blade (more swords). I should expect to use 2-3 belts on that, based on Big Chris' data?
Click to expand...

What I replied above was based off 4" to 4.5" blades. I have a sword I am working on in 3V and plan to have 3 of each grit just for it. That is not including the SC belts. They do not last nearly as long.
 
Joe, I as well grind 3v a lot in the hardened state. Personally I use 3m cubitron 2 belts up to 120 grit then gators x100 and x 65, after that its gray scotchbrite belt to make the scratch pattern uniform and lastly 280 grit cork belt loaded with black compound.

Shawn
 
I'm thinking the black compound on a cork belt, as Shawn said could be a good way to finish. Frank
 
No way on earth would I attempt a nice hand-rubbed finish on 3V without getting it to at least 800 grit pre-HT, but if you're content with a belt/scotchbrite finish, it's not as bad to grind hardened as you might think. Go for it.

I have yet to try a cork belt/compound finish like Shawn describes, but I'm hearing good things about it lately...
 
If you are looking to reduce time, regardless of how long the belt will last, Fintech Abrasives (Amazon) has some zirconia belts that work really well (they eat metal for lunch). They are cheap, and might not last as long, but they remove material very fast. My buddy and I ground the blade bevel on a M4 blade we hardened to over 65 RHS. Those belts appeared to be the fastest at removing material.
 
Big Chris said:
What I replied above was based off 4" to 4.5" blades. I have a sword I am working on in 3V and plan to have 3 of each grit just for it. That is not including the SC belts. They do not last nearly as long.
Click to expand...

Thanks for the answer. I hope you'll put up some pics of the sword. Always love to see more swords :)
 
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