Struggling to thin down some pre-hardened blanks how are you guys doing this? (basic 2x72, no surface grinder attachment).

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FloWolF

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Hi there wise ones.

The title pretty much says it all really - the last 3 knives I set out to make I chose to go with Wolfram Special for a little Petty, and Sheffcut for a Gyuto and a Santoku both of which have a hamon in there.

The steels came in 3.2mm thick minimum aimed more and the forging crew than us SR guys, and as per my usual way with my other knives, I got the drilled and shaped blanks HT before grinding, also preferred that way by my HT guy.

I need to lose a TON of thickness off this steel before I can start shaping the bevels/taper in, down to around 2mm at the thickest of the spine, and it is just not shifting! All 3 blades are at 64HRC.

I spent 2 hours on the little Wolfram Special Petty yesterday with my 36 grit ceramic belt and only managed to get a tiny fraction of the way there, and that was often using pulses of high pressure followed by a quick water dunk - quite aggressive going.

Any tips on how to get this job done for these 3? I have the ability to fire up a rudimentary pumped water trickle feed to the belt if I need to, but to be honest its usually overkill and makes a right bloody mess!

Anyway, cheers folks, and help gratefully received.

Shaun/FloWolF
 
Could be a combination of factors at play here.
My first inclination is the wrong ceramic abrasives.
I use a decent amount of Sheffcut and usually heat treatment for my blades is 63/64rc.
For the major stock removal my belt progression is 3m cubitron 967 belts in 36g then 60g as the 967 series is amazing for high pressure grinding on heat treated steel especially wear resistant steels. After that finish with your favorite 120g ceramic. I use VSM white lightning belts, and then onto the rest of your preferred finishing belts.
I would also add that using a ceramic class platen or hard backed rotary platen will help with heat mitigation along with constant water dunking.
Lastly make sure you grind your 45's to your scribed center line with a half worn belt first...then onto your fresh new belts for bevels. If you take a fresh belt to knock off the 90 degree corners you will loose half of the belts abrasive and it will be useless for bevels after that.
I actually have a honyaki Sheffcut blade to grind in the next few days. I'll try to time it all out for a comparison to what you are experiencing.
Hope that helps a little.
 
Could be a combination of factors at play here.
My first inclination is the wrong ceramic abrasives.
I use a decent amount of Sheffcut and usually heat treatment for my blades is 63/64rc.
For the major stock removal my belt progression is 3m cubitron 967 belts in 36g then 60g as the 967 series is amazing for high pressure grinding on heat treated steel especially wear resistant steels. After that finish with your favorite 120g ceramic. I use VSM white lightning belts, and then onto the rest of your preferred finishing belts.
I would also add that using a ceramic class platen or hard backed rotary platen will help with heat mitigation along with constant water dunking.
Lastly make sure you grind your 45's to your scribed center line with a half worn belt first...then onto your fresh new belts for bevels. If you take a fresh belt to knock off the 90 degree corners you will loose half of the belts abrasive and it will be useless for bevels after that.
I actually have a honyaki Sheffcut blade to grind in the next few days. I'll try to time it all out for a comparison to what you are experiencing.
Hope that helps a little.

Thanks for the complete and considered reply Tim, it's much appreciated, but I figured out the problem earlier on, just got back from the workshop about an hour ago.

The 36G ceramic belt I was using, I forgot it was a high pressure belt I use for hogging at outlines pre-HT, it hates lower grinding pressures and flat surfaces, the grains just polish instead of fracturing and cutting.

However I had some Cubitron II belts, fresh ones but only in 80 and 120g, much more the ticket so I ran it over one of these and it just did what I thought it should removed material at medium pressures and ran cool, so I carried on and shaped most of the bevel and got the spine thickness where I wanted it, with a nice taper down to the tip. I use a glass platen and have actually just replaced the old one, but I'll replace that with my padded one for the final convexing and edging of the bevel.

I need some lower grit Cubitron II's in for the two larger knives I'm sure I can't sensibly do them all 3 with just the 2x80g and 2x120g, be a waste of the belts too.

Cheers!

Shaun.
 
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Rough grinding to maybe 2mm before hardening (aka. quench) would have been a lot easier. ;)

On page 158 of "The Art of the Japanese Sword. The Craft of Swordmaking and its Appreciation" it says:

"Although the blade is well formed at this stage, with a defined cutting edge, the edge will be
left at least ¹⁄₁₆ inch (2 mm) thick to protect it during the next stages of making the sword."
 
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Rough grinding to maybe 2mm before hardening (aka. quench) would have been a lot easier. ;)

On page 158 of "The Art of the Japanese Sword. The Craft of Swordmaking and its Appreciation" it says:

'NSS' as they say. I've already kicked my own arse with hindsight, however now I've discovered my 'abrasive oversight', the panic has subsided and I'm back with my own programme again - I got all the excess steel off the petty blank using just an 80 grit, when I finally picked up the right abrasive, so when I get a couple of coarser grits of the same in I should be good to go for the larger two.

I had a few reasons to opt for doing all the grinding post HT so I know I'd weighed a bunch of pros and cons before deciding but that all went out the window with my head and my arse when the 36 grit just burnished the metal instead of biting at it.

Cheers now!

Shaun/FloWolF
 
For the major stock removal my belt progression is 3m cubitron 967 belts in 36g then 60g as the 967 series is amazing for high pressure grinding on heat treated steel especially wear resistant steels.

Would you rec. the 967 over the 984F then? It was an 80 grit 984F that managed to grind the 64HRC Wolfram Special down almost to the finish, and it cut so effortlessly. I'd planned to make an order from my supplier for the 984 in 36 and 60 grit to do the other 2 blades as the 80 did so well with quite low pressure, but if you have something to rec. the 967's over them I may have to reconsider.

Thanks again.

Shaun/FloWolF
 
Would you rec. the 967 over the 984F then? It was an 80 grit 984F that managed to grind the 64HRC Wolfram Special down almost to the finish, and it cut so effortlessly. I'd planned to make an order from my supplier for the 984 in 36 and 60 grit to do the other 2 blades as the 80 did so well with quite low pressure, but if you have something to rec. the 967's over them I may have to reconsider.

Thanks again.

Shaun/FloWolF
Hey Shaun,
I would recommend the 967 of you grind with high pressure only. The 984f is still an amazing belt for low pressure grinding...do not change your grinding style to suit the belt, change the belt to suit your grinding style.
Happy spark making,
- Tim
 
Try different belts that fit your grinding style - different brands, ones that are better for high vs low pressure, etc.

Other than that, just replace belts more often - I go through multiple 36 grit belts on a single gyuto, especially mono steel ones.
 
Hey Shaun,
I would recommend the 967 of you grind with high pressure only. The 984f is still an amazing belt for low pressure grinding...do not change your grinding style to suit the belt, change the belt to suit your grinding style.
Happy spark making,
- Tim
My supplier only had 60 and 80 grit in the 984f, so I got those, and got a couple of other ceramic belts at 36 grit to try, can't recall what now - they were out of stock on nearly all their 36 grit, must be a serious metal hogging party going on somewhere.

Anyway, thanks for clarifying - my style is neither heavy nor light really, but for removing tons of material from already hardened and tempered steel, for me I prefer fast/sharp/light pressure abrasives. I use the high pressure types like my other 36 grit for profiling the unhardened steel knife blanks out where it doesn't matter much at all if I generate a whack of heat intermittently, I can just get behind the steel with a stout push stick and hog-away with a rare dunk here and there.

Cheers Tim.

Shaun/FloWolF
 
i tried to use the flat plate before and it took a long time to get the geometry that I wanted.

i tried to use the wheel, and finally, I could get the slight convex-flat bevel and less wedging on my final product.

also, different belts act differently.
 
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