Surface grinding stainless steel

[Bladegrinder]

Hi folks, I have a Harig 612 I use for custom knife blades. when I surface grind high carbon everything goes well but when I do stainless steel I have heat problems and sometimes burn marks, when I release the chuck often the steel is warped.
I started running coolant but the stainless is still over heating. I'm using the wheel that came with the machine a couple years
ago...it's a Norton 38A46-GVBE, the steel is mostly annealed CPM-154 and AEB-L and I'm taking 2-3 tenths per pass.

So I started researching my problem and found I might be better with a ruby porous wheel to help with the heat. the wheel I'm
looking at now is a Norton 48A46-HVP2.
does anyone here grind high alloy stainless steel and tell me if I'm making a good decision on this wheel or have any recommendations on one? Thanks.

 

[eKretz]

What are you dressing with?

 

[michiganbuck]

What are you dressing with?

And what is the frequency of your dressing?
I have never found a perfect wheel for SS, it's a bugger to grind.
Perhaps call Radac and ask for wheel advice.
I see some guys recommending CBN wheels (?).
That Norton wheel and the (Norton) one you are looking at are recommender SS wheels.
I have dressed very often with a skim dress after only a few travel on SS, and overpassed at the ends of long travel to give more cooling time.
I have also had success with full wheeling rather than incremental cross-grinding on some parts, so to avoid the wheel leading edge to load-up quickly..
I remember notching a wheel OD once for a problem SS part by cutting notches by hand with a parting wheel.. can't remember how successful that was. the intention was to allow more coolant on the part.
Some parts may be better going the short way across, rather than going the full long way so less time to heat up..

 

[???]

Are you laying the parts at 45 degrees to the travel, this gives less time in the cut and less heat buildup. I know it can make polishing more difficult

I have also relieved the wheel before so there is less wheel in contact with the surface. In essence created a thinner wheel.

I have found as the wheel wears it creates a tapered cutting surface that results in a large contact surface which then causes more heat. Hence the relief on the wheel which helps with the size of the contact area.

As michiganbuck said it's a bugger to grind.

 

[Conrad Hoffman]

I had a miserable time with some 300-series stainless. Aside from having to hold it down (non-magnetic) it warped on every pass, even with light cuts. It was at least 3/8" thick, so way more substantial than a knife blade. Flipping it didn't help. Angle didn't matter. Waiting way too long between passes helped, but not enough. I swore never to grind the stuff again, just face mill it. I just did some 400-series (magnetic) and it ground like a dream, just like regular steel. It does help to dress your wheel very coarsely. Single point diamond and crank that sucker across the wheel as fast as you can turn the crank. Once, don't come back. Don't be deceived by a coarse dressing- you can still get a very fine surface finish. Also, don't think those fancy expensive blue seed wheels will help. They suck on small grinders and are a waste of money and give poor results. Don't know if ruby wheels will help. I've heard the difference is mostly color, not performing any different than the white ones. You may read that a silicon carbide wheel will help. It didn't, but now at least I have a silicon carbide wheel for my grinder.

 

[michiganbuck]

RE: anyone buying a surface grinder for Knife work, a 1/2 hp is not suitable.. 3/4 and up is needed because a slowing wheel can cause burning.
The Op's Harig 612 is likely a 2 hp.

Also grinding SS a solid setup can reduce burning (perhaps), good to tap-tap a part with a small hammer to see if the set-up is as solid as a rock.

 

[eKretz]

Going to a softer wheel can help sometimes as a bit of a band-aid with roughing/heavier stock removal too. You sacrifice some wheel life but it's a bit easier to avoid burning. Switch back to a harder one for finishing the last bit if the softer wheel won't hold up. Relieving the wheel or using an induced porosity wheel can help too. And you say you started running coolant. What kind of volume are you getting? The more the better. And yes to the very coarsely dressed wheel.

 

[Bladegrinder]

What are you dressing with?

A diamond dresser

 

[Bladegrinder]

And what is the frequency of your dressing?
I have never found a perfect wheel for SS, it's a bugger to grind.
Perhaps call Radac and ask for wheel advice.
I see some guys recommending CBN wheels (?).
That Norton wheel and the (Norton) one you are looking at are recommender SS wheels.
I have dressed very often with a skim dress after only a few travel on SS, and overpassed at the ends of long travel to give more cooling time.
I have also had success with full wheeling rather than incremental cross-grinding on some parts, so to avoid the wheel leading edge to load-up quickly..
I remember notching a wheel OD once for a problem SS part by cutting notches by hand with a parting wheel.. can't remember how successful that was. the intention was to allow more coolant on the part.
Some parts may be better going the short way across, rather than going the full long way so less time to heat up..

I had one blade approx. 9" x 1.5" at about a 45 degree angle, I just dressed the one time when I started. I probably should have dressed again when I flipped them but the heat sign was there, it bowed when I released the chuck.
I'm going to order that other wheel and see if there's any improvement.

 

[Bladegrinder]

Are you laying the parts at 45 degrees to the travel, this gives less time in the cut and less heat buildup. I know it can make polishing more difficult

I have also relieved the wheel before so there is less wheel in contact with the surface. In essence created a thinner wheel.

I have found as the wheel wears it creates a tapered cutting surface that results in a large contact surface which then causes more heat. Hence the relief on the wheel which helps with the size of the contact area.

As michiganbuck said it's a bugger to grind.

Yes, the blade was at a 45 degree angle, I'm going to order that other wheel and see if it gets any better.

 

[Bladegrinder]

I had a miserable time with some 300-series stainless. Aside from having to hold it down (non-magnetic) it warped on every pass, even with light cuts. It was at least 3/8" thick, so way more substantial than a knife blade. Flipping it didn't help. Angle didn't matter. Waiting way too long between passes helped, but not enough. I swore never to grind the stuff again, just face mill it. I just did some 400-series (magnetic) and it ground like a dream, just like regular steel. It does help to dress your wheel very coarsely. Single point diamond and crank that sucker across the wheel as fast as you can turn the crank. Once, don't come back. Don't be deceived by a coarse dressing- you can still get a very fine surface finish. Also, don't think those fancy expensive blue seed wheels will help. They suck on small grinders and are a waste of money and give poor results. Don't know if ruby wheels will help. I've heard the difference is mostly color, not performing any different than the white ones. You may read that a silicon carbide wheel will help. It didn't, but now at least I have a silicon carbide wheel for my grinder.

Thanks, I may need to start dressing the wheel more often, but I'm inclined to thing I need to at least try one of those ruby porous wheels from Norton. the mention it's good for heat sensitive steel.

 

[Bladegrinder]

RE: anyone buying a surface grinder for Knife work, a 1/2 hp is not suitable.. 3/4 and up is needed because a slowing wheel can cause burning.
The Op's Harig 612 is likely a 2 hp.

Also grinding SS a solid setup can reduce burning (perhaps), good to tap-tap a part with a small hammer to see if the set-up is as solid as a rock.

Yes, this Harig has a 1.5 hp 3 phase motor connected to a VFD. the motor is rated at 50 hertz so that's what I have the VFD set at. it grinds high carbon fine, it's just this high alloy stainless that's giving me a hard time.

 

[Bladegrinder]

Going to a softer wheel can help sometimes as a bit of a band-aid with roughing/heavier stock removal too. You sacrifice some wheel life but it's a bit easier to avoid burning. Switch back to a harder one for finishing the last bit if the softer wheel won't hold up. Relieving the wheel or using an induced porosity wheel can help too. And you say you started running coolant. What kind of volume are you getting? The more the better. And yes to the very coarsely dressed wheel.

I seem to be getting a good flow of coolant over the work piece but I might get a higher flow pump, that certainly can't hurt anything. I'm going to order that Norton ruby porous wheel, I'm hoping I see some improvement.
the finish actually looks great right now at first but then the steel heats up and starts bowing, that's when I start getting burn marks.

 

[eKretz]

I seem to be getting a good flow of coolant over the work piece but I might get a higher flow pump, that certainly can't hurt anything. I'm going to order that Norton ruby porous wheel, I'm hoping I see some improvement.
the finish actually looks great right now at first but then the steel heats up and starts bowing, that's when I start getting burn marks.

Try stopping periodically and redressing your wheel. That might be all you need. And I would recommend getting a single point diamond as well. There is some good info about wheel dressing in the sticky post at the top of this forum section.

 

[Bladegrinder]

Try stopping periodically and redressing your wheel. That might be all you need. And I would recommend getting a single point diamond as well. There is some good info about wheel dressing in the sticky post at the top of this forum section.

Thanks eKretz, I'll go read that now. I'm going to order that other wheel tonight and will post my results in a week or so after I get it. I think I'm going to replace my coolant pump too for more flow.

 

[michiganbuck]

It can be good for a repeat set-up to have a diamond that is quick and easy to go to with the least traveling.

 

[Bladegrinder]

Ok, so I got the new wheel pictured below and tried it out today.

These are the results I got on a bar of annealed CPM-154 stainless steel, I gave it a couple passes on my 2 x 72 belt grinder just to knock off some of the mill scale.
just like with the wheel I was using before I was taking of 2-3 tenths per pass. I did not get any burn marks and the steel never appeared to heat up. when I released the magnetic chuck there was no deflection, just flipped it over and did the other side.
So, I'm really glad I bought this wheel, I think this is going to work great for me. this CPM-154 was giving me fits trying to ground flat without it heating up and warping.
This was my first piece with this wheel, if I see any change in performance I'll come back here and post.
below are a couple pics of before and after.

 

[???]

Excellent, thanks for letting everyone know how it worked out. I have a couple of milk crates full of wheels that were given to me including a lot of the open grain ruby wheels. Now I know what I can use them for.

 

[eKretz]

Much better. That is a little softer wheel too. Looks like it did a pretty decent job to me. One question from looking at the grind marks. What is your cross feed step over amount? Looks very high.

 

[Bladegrinder]

I'd guess my cross over feed rate was around 3/8"