Surface grinding and wheel balancing

REK Knives

REK Knives

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Knifemaker / Craftsman / Service Provider
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Apr 3, 2011
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Hey guys, I just got a Harig 618 surface grinder, it's not completely up and running yet as I just got the RPC wired up but I'm trying to cover all my bases.

I know the "conventional" wisdom out there is that wheels sub 8" diameter do not need to be balanced (just trued and side dressed), but I want the best finish possible. Does anyone else out there balance their wheels in this size range and what finishes did you get before or after?

The balancing kit is about $700+ though so that's kinda frustrating lol.
 
kuraki said:
Define "best finish possible."

Is it measured by profilometer? By appearance? I certainly wouldn't invest $700 in a balancing stand and spindle before trying to meet your expectations with what you have.
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Basically no chatter marks and no ripples... A nice satin finish. On my old sg I tried everything OTHER than balancing the wheel (including side dressing) but still got the following finish. Ended up having someone look at it and they thought the bearings had lost the preload.

But you are right, I'll see what I can get with what I have first! I just got the rpc wired the other day and it's running now, but I have to get a fuse in the morning - the oil pump isn't working right now and I think that's the culprit.

 
Have you thought of changing diamond shape, adjusting dress speed or both? Both can change micro/finish of grind.
 
WhitleyStu said:
Have you thought of changing diamond shape, adjusting dress speed or both? Both can change micro/finish of grind.
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Yeah I've tried the latter, but my diamond is in pretty good shape so I don't think that's the issue, but I do have a new one on standby :)
 
The chatter in the video I would agree with the assessment the bearings were shot. An out of balance condition that would cause that much wheel movement would be really excessive in a wheel that size and it would be noticeable in vibration/sound.

Use a 1/2" or narrower wheel. The narrower wheel reduces the amount of mass that can be out of balance. Let the spindle warm up for a few minutes before dressing.

I've never balanced 6-8" wheels and the only time I've gotten finishes like that was when the wheel got loaded enough between dressings to start hopping instead of cutting, but in that case it also caused heat discoloration streaks.
 
I had ripples like that when I put the wheel on the wrong way, even after dressing.
I turned it around and it produced a much cleaner surface
 
I'll see how mine does but this guy had great success balancing his small wheels (6-8") on his boyar shultz 6 x 12... check out the before and after below - the latter is what I want on knife blades hehe

surfacebefore.jpg
surfaceafter.jpg
 
Does your grinder already have a balancing hub? If so you could make a stand and shaft.
 
kuraki said:
Does your grinder already have a balancing hub? If so you could make a stand and shaft.
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Not sure I'll check... but one journeyman machinist I spoke w/ said that he would just balance it with a tight fitting shaft and no hubs? as long as the shaft and stand are good it should work fine theoretically right?
 
razor-edge-knives said:
Not sure I'll check... but one journeyman machinist I spoke w/ said that he would just balance it with a tight fitting shaft and no hubs? as long as the shaft and stand are good it should work fine theoretically right?
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I don't understand what he's saying as the balancing weights are in the hub itself on every grinder I've seen.
 
ALL surface grinder wheels should be balanced when installed on the flange and dressed during use if you want professional results, but hey, feel free to not listen to me.
 
kuraki said:
I don't understand what he's saying as the balancing weights are in the hub itself on every grinder I've seen.
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apparently there are at least 2 ways to balance a grinding wheel... 1 is with weights, the other is to remove material from the wheel itself such as in the video below (8:35 or so) which is the method I was gonna use since I don't wanna fork out $700 for a weighted hub quite yet.

Kevin Wilkins said:
ALL surface grinder wheels should be balanced when installed on the flange and dressed during use if you want professional results, but hey, feel free to not listen to me.
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Thank you for confirming that Kevin, I feel the same and have heard that nice wheels even from Norton and such aren't balanced from the factory.
 
Missing link. I'd like to see how they're doing that on vitrified wheels.
 
Ok, I just wanted to hear him say "there's always a danger of breaching the integrity of the wheel..." because I couldn't envision how that was being done without possibly wrecking the wheel.

But yes, I agree with the machinist you spoke to, a tightly fitting shaft and a stand would work just fine.
 
kuraki said:
Ok, I just wanted to hear him say "there's always a danger of breaching the integrity of the wheel..." because I couldn't envision how that was being done without possibly wrecking the wheel.

But yes, I agree with the machinist you spoke to, a tightly fitting shaft and a stand would work just fine.
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Cool thanks for verifying that!
 
Once I switched to running belts all my finish issues where a thing of the past. You can get as fine a finish as you want with finer belts. Just spark it out if your worried about rolled edges.

Photo%20Sep%2026%2C%2012%2042%2006%20PM.jpg


Photo%20Sep%2026%2C%2012%2042%2018%20PM.jpg
 
JTknives said:
Once I switched to running belts all my finish issues where a thing of the past. You can get as fine a finish as you want with finer belts. Just spark it out if your worried about rolled edges.

Photo%20Sep%2026%2C%2012%2042%2006%20PM.jpg


Photo%20Sep%2026%2C%2012%2042%2018%20PM.jpg
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Wow that does look amazing. So you don't get any run out at the edges?
 
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