stone surface grinder vs belt

V

vikingGoalie

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Aug 20, 2019
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just wondering, i see a lot of knife makers do surface grinder attachments for their belt grinders.
But I have access to some auctions where I see stone surface grinders. So I could probably pick up a brown & sharpe surface grinder for under a 100 bucks.
but honestly i have zero machinist experience outside of my normal i just figure it out ;)
i'm confident i could get that surface grinder up and going. the question is more around, should I even be looking at this.
since every one seems to use an attachment to their belt grinder,i'm wondering what is it about using a stone surface grinder that blade makers shy away from?
 
I have a Harig 6x12 and love it. I use it on all folder blades and back bars and just about every straight knife I make.
 
I believe stone wheel grinders taker longer operation wise but there more accurate in measurements.
 
Belt is better for hogging off material, stone is better for getting a really clean finish and is also much cheaper. You can go through alot of belts.

Obviously the solution is to get both.
 
I think most makers buy the attachments out of convenience. There's far less moving parts, you don't need 3 phase power to run them, you don't have to buy extra consumables like ways oil, stones, diamond dressers, etc..., and while they're less accurate, they're generally accurate "enough", and usually a little bit faster to use.

In fact, that's why many makers convert their stone wheel grinders to belts: you can hog material off faster.

You say you're not a machinist; well be prepared to do some research. Surface grinding with a stone is not exactly a "plug and play" endeavor. Not if you're looking for good finishes that are flat and parallel. ;) It's almost a little bit of a lost art. You need the proper wheels (if you think there are too many options for abrasive belts, just wait...), and that wheel needs to be properly dressed and balanced. Then there's proper feeds and speeds, proper lubrication of your ways and lead screws, properly surfacing your chuck, using proper coolant, etc...
All of this can be even more precarious with a used machine, especially if it wasn't well cared for, has worn screws or ways, etc...

All that said, if you have the means to load, move and power a full sized surface grinder, and you have the patience to learn proper set up and use, it is nice to have the capabilities (and potential accuracy) of a full sized machine.

If you want to jump right into things, and you're really ever going to grind blades, a surface grinding attachment might not be the worst way to go.

Just from experience, I bought an old Reid 618p for about $450, probably spent at least $300 buying stones and oils and dressers, and then ended up converting to belts which probably cost another $300 or so. I've also had to replace a few parts on it over the years, and I'm still chasing a "perfect" finish, though it still gets the job done. I'm glad I have the machine, but it does take up a lot of room, and if I was trying to save money on surface grinding, I don't think I quite got there in the long run :D

Honestly, if somebody offered to trade me a decent SGA for my Reid, I'd probably say come and get it. hahah The extra space would be nice. Then again, it's also nice to have the extra size capabilities of a 6x18 chuck, so who knows.....
 
thx everyone very helpful as always.
just I know i need a surface grinder, space is a bit limited. but I'm watching a brown and sharpe L2 which you can see the same model in operation here:
the auto table is pretty awesome and the stone works it's way across the surface as well.

currently the auction i'm looking at the bid is at $29 bucks. (day left). I have a trailer to go pick it up, it's just one of those things is it worth the effort. because I do get the issue of old machine means hard to find parts many times. it's just incredibly tempting if i can get that for less then a hundred bucks.
 
Without actually putting you hands on it and giving it a good look over your taking a gamble. If you can put your hands on it check the spindle for runout and everything you can touch. Short of running it you won’t know till you get it home. I don’t know how you plan on getting it into your shop but mine weighed #800, I have 10 x 12 roll up doors and unloaded it and brought it in with straps and a farm tractor with a front loader. All I can say is…sometimes you run into great deals and if you let them slide you may never get it again. Im glad I bought mine but it came out of a running machine shop with eight lined up next to it. On the other hand a friend bought one off eBay, rented a truck and trailer and drove about 1200 to pick it up and it turned out good for him. It had auto feed and that is a big plus.
 
I have a surface grinder attachment for my 2x72 and as others have said, it is fine for most things, not as accurate as a stone surface grinder but how much accuracy do you require. Getting the most out of that stone surface grinder takes a lot more work. I do like having the Sin plate on my surface grinder to do tapered tangs and such.
 
For most hobby to semi-pro knifemakers a grinder mounted surface grinder is all they need. We don't need the tolerances the guys who do mass production CNC stuff need.
Like Moonie, I find the tapering and beveling options pretty nice.

Maybe it matters to folder guys? I don't know.
 
So surface conditioning attachments are not the same as surface grinders. I don't care what people call them. A legit surface grinder (with a stone) vs something you put on a belt grinder are worlds apart. One makes the steel look pretty and the other is a highly accurate piece of manufacturing equipment. If you're making knifes you really don't need a surface grinder (except for folders, then it would be nice). The belt grinder attachment will get the job done.

To be more specific the belt grinder attachment simply transfers the profile of the contact wheel onto your steel because your contact wheel is not "flat". A "surface grinder" can makes the part
"flat" within .0002" if used correctly. The reason some guys convert surface grinders to run belts is because they don't need the accuracy and belts are much lower cost.

A $13.00 ceramic belt is not going to match the performance of a $1,600.00 wheel dressed to perfection.
 
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While I agree that the tolerances of a large surface grinder are much tighter than a knife grinder attachment, I disagree that the ones we use are not accurate. Within the flatness tolerances needed for knifemaking .001" is overkill. I also suspect that the wheels on most knifemakers stand-alone surface grinders are not $1600 wheels or perfectly tuned.

Personally, as a knifemaker I am only interested on flattening a 1" to 2" wide piece of steel between 6" and 12" long. The need for a machine that does 6" to 18" wide and 24-36" long is unnecessary.

What I see stand alone SGs used for by knifemakers is flattening damascus bars and forged blades . The main work on most hand made knives is done with jigs and/or freehand on the grinders, so starting accuracy to four decimal places would be wasted effort anyway.
Additionally, the cost of a good stand alone SG is far beyond most knifemakers budget.
I would venture a guess that 95% of knifemakers who own a dedicated SG bought it used/surplus (at a low price) and adjusted it as much as they knew how. Most probably never used an SG before, or have any training in operating or tuning them.

In a fabrication shop like yours that makes multiple parts for machines that all need to fit I totally agree that a dedicated SG with perfect adjustments is needed.
CNC machinist knifemakers are also different group as well, and use high tolerance machines to make knives. They would be the knifemakers that need a $6000-20.000 surface grinder.
 
Stacy E. Apelt - Bladesmith said:
While I agree that the tolerances of a large surface grinder are much tighter than a knife grinder attachment, I disagree that the ones we use are not accurate. Within the flatness tolerances needed for knifemaking .001" is overkill. I also suspect that the wheels on most knifemakers stand-alone surface grinders are not $1600 wheels or perfectly tuned.

Personally, as a knifemaker I am only interested on flattening a 1" to 2" wide piece of steel between 6" and 12" long. The need for a machine that does 6" to 18" wide and 24-36" long is unnecessary.

What I see stand alone SGs used for by knifemakers is flattening damascus bars and forged blades . The main work on most hand made knives is done with jigs and/or freehand on the grinders, so starting accuracy to four decimal places would be wasted effort anyway.
Additionally, the cost of a good stand alone SG is far beyond most knifemakers budget.
I would venture a guess that 95% of knifemakers who own a dedicated SG bought it used/surplus (at a low price) and adjusted it as much as they knew how. Most probably never used an SG before, or have any training in operating or tuning them.

In a fabrication shop like yours that makes multiple parts for machines that all need to fit I totally agree that a dedicated SG with perfect adjustments is needed.
CNC machinist knifemakers are also different group as well, and use high tolerance machines to make knives. They would be the knifemakers that need a $6000-20.000 surface grinder.
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I totally agree. In general knife makers do not need a stand alone sg. If they find a good deal on one it doesn't make sense to keep the high dollar stone setup when a ceramic abrasive belt will do the job.
 
I have both a conventional surface grinder that uses stones and a conventional surface grinder I converted over from stones to use a belt attachment I designed. I have not used the machine with stones in about four years. Why? The surface grinder converted to belts does a great job within the areas I need in my workshop. I was very skeptical in the beginning, but the belt wins hands down.

Also, machines running stones need a balancing system to balance the stones and you need several different types of stones, etc. The machines with stones are also potentially very dangerous. I almost lost a finger in my machine before I converted it to belts. Of course modern surface grinders have safety systems most of the old machines found in a knifemaker's workshop lack.

I've never used one of those add-on surface grinder attachments so I can't say how well they work.

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Both belt sga's and stone sg's have different purposes to a degree (they are different animals). I have a stone sg (automatic) and an sga for my grinder. If I want to hog material or remove scale I use the sga. But I ALWAYS move to the stone sg (harig 618) to finish. The sga leaves little ripples in the surface or else 'runout' near the ends. I think the thing most don't understand when it comes to stone sg's is abrasives... The only way to go for hardened steel is CBN. After years of knife making someone pointed this out to me and I spent $1k on a cbn wheel and haven't looked back - it very rarely needs dressing (hardened s90v is impossible almost for alox or ceramic wheels and I was having to dress 7 times for 2 folder blades, but for cbn wheel I can get 60+ without a single re-dress of the same blade). It's been a huge learning curve... The first sg I got for cheap lost it's bearing pre-load and the parts always looked terrible.
 
I think the surface grinder attachment is good for cleaning mill scale and cleaning bar stock but for years I did the same thing by hand on a 12” contact wheel. You lose about 1/2” on both ends of the bar where it enters and leaves the contact wheel. I used to only use my surface grinder for folder blades and back bars but after using it for a while and learning how to run it efficiently I put most of my straight knives on it, that’s just me, everyone does things a little differently. I don’t find it takes that much time to clean up a straight knife, I hit the bar stock with a 60 grit on the grinder then finish on the surface grinder. But here’s the rub…. I bought it primarily for folders. If I never intended to make folders I wouldn’t have bought it. Also you have to consider the footprint of the machine and the logistics of getting into your shop. My old shop was 2/3rds of a one car garage, it would not have fit there. my new shop is 30’ x 50’ with 10’ x 12’ roll up doors. As for me, I consider my surface grinder a necessary machine in my shop for making liner locks. 😀
 
I can get 0.001” accuracy out of my SGA if I dress the belts and table. I can get within 0.003” if I throw it on and grind away. That’s plenty good for the fixed blades I make. A standard surface grinder will certainly be more accurate. I’d probably go that route for folders but for fixed blades it isn’t necessary.
 
I would argue against people saying stones provide a better finish and tighter tolerances. It all comes down to proper belt selection and when you run gator belts the life is insane. I have taken blades up to a mirror polish on my surface grinder and I’m not sure you could pull that off with a stone. But the huge advantage is you can rip material off with a roughing belt around 50grit. Removing +.010” per pass is not uncommon. I do that with a 1/8” step over. Here is a hatchet I did a tapered tang on. You would never remove this amount of material with a stone. IMG_4245.jpegIMG_4246.jpegIMG_4247.jpegIMG_3367.jpegIMG_3369.jpegIMG_3370.jpeg
 
Technique and belt selection are key with SGA's. I primarily make slip joint folders and I can achieve damn near the tolerances a stone grinder is capable of. I have debated on getting a stone unit when I build my new shop but I'm leaning on just investing in another 2x72 chassis primarily to house my SGA but it would also add more versatility to my shop vs. a big clunky dinosaur wheel machine.
 
I grew up machining since I was around 10, maybe younger....

My Dad would freak out if he saw all these makers with surface grinders.

The key to machining and good engineering, is repeatably and efficiency. Using your tolerance.
Focus on what's important.

My Dad would say...."We're not building watches"
 
I've been watching this thread about the accuracy of SGAs - with care they can be better than expected. Here's the best I've been able to do. When I took the measurements I didn't believe what I was seeing, so took them a couple more times. That time was exceptional for sure. Back in my college years (50 yrs ago) I ran rock type surface grinders and know what they can do - just amazing. BUT - it does take care with the proper grinding wheels and dressing.

Darn I didn't realize how large those photos were before posting.
Tang.jpg

Middle.jpg

Tip.jpg


That is on around a 10" total length blade. My normal is more like ±.001" on a 12" length which is plenty for my fixed blade knifes. For slipjoints over that 4" length of blade or liner it works ok. Also as other folks have said, the SGA is so much more useful in the shop, from finishing a blade with 400 grit to grinding a Damascus billet from the forge with 36 grit belt.
 
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