New purchase: 8" slow speed grinder? Your advice?

[Jerry Olexa]

Just purchased a new 8" Slow Speed (1725 RPM) Woodcraft 150780 bench grinder for an attractive price..No, its not a BALDOR but I plan to use only occassionally, mostly with plane irons, correcting damaged edge etc..I've been using a standard old DELTA hi speed grinder with no tool rest!!! Also have a WORKSHOP for regular sharpening.. So I view this as some improvement... I'm requesting your general advice on this new (for me) venture..Wobble appears to be an issue from previous threads and I have not yet assembled the tool rest, etc...My initial test shows the grinder running well with no wobble..Thanks in advance..Your general comments/advice both pro and con will be very helpful.. A grinder newbie.

[Chris Fournier]

46 Grit wheel, sorry I don't recall the bond on mine. Lee Valley grinding rests are pretty nice, I use them. Single point diamond dresser in a home made fixture that fits in your grinding rest, true your new wheel and you are ready to go.

Many folks will say that dry grinding on a bench grinder doesn't work for them and it likely doesn't. The trick is to use a very light touch and be steady on your cross feed with the tool across the wheel. When you get the feel of it you can sharpen a 2" plus plane blade quickly without ever needing to quench. The trick is light deliberate passes and look at your progress as you go, adjust your feed according to how your fresh bevel comes along.

Enjoy your new grinder!

[John Sanford]

Norton 3x white wheels. Or CBN wheels. Of course, the CBN wheels will likely cost more than the grinder. I would offer to sell you one or two diamond wheels, but diamond wheels, which have a great many strengths and uses, are NOT good for grinding tools. Apparently, once things get hot, the diamonds get greedy and steal carbon from the steel, with "subpar results." Which is why nobody sells diamond wheels to woodturners anymore, those having been superseded by CBN wheels which apparently have no interest in bogarting the carbon.

[Patrick Chase]

Norton 3x white wheels. Or CBN wheels. Of course, the CBN wheels will likely cost more than the grinder. I would offer to sell you one or two diamond wheels, but diamond wheels, which have a great many strengths and uses, are NOT good for grinding tools. Apparently, once things get hot, the diamonds get greedy and steal carbon from the steel, with "subpar results." Which is why nobody sells diamond wheels to woodturners anymore, those having been superseded by CBN wheels which apparently have no interest in bogarting the carbon.

"Norton White" and "Norton 3X" (which are blue) are two very different things.

The white ones are conventional aluminum-oxide in a friable bond. They work just like a waterstone: The weak/friable binder releases abrasive particles before they can become dull, thereby avoiding heating.

The blue "3X" wheels have 30-50% (IIRC) Al-Oxided seeded-gel ceramic particles (the rest of the wheel is conventional non-ceramic Al-Oxide just like the white ones). The seeded-gel particles themselves "shard", exposing fresh cutting points as they wear. The result is a longer-lasting wheel because you don't need to release entire abrasive particles in order to refresh the cutting surface, which in turn means the bond can be harder while still achieving sufficient surface renewal.

The downside to the 3X wheels is that it takes more grinding pressure to get seeded-gel particles to shard than it does to get a friable wheel to release abrasive, so you have to grind with a more "authoritative" touch. If you use a light touch they just glaze over, neither releasing abrasive particles nor breaking down the seeded-gel particles. You have to grind with a bit more pressure, and compensate for the resulting heating by pausing a higher percentage of the time. Overall grinding speed is about equivalent, while wear life is better for the reason outlined above.

My advice to the OP: If you're new to grinding start with the white ones. They're more forgiving, and allow you to avoid both over-grinding and heating by using a light touch.

Of course you *could* have the best of both worlds, for only $200/wheel or so... (CBN)

[Derek Cohen]

Agree with Patrick .... 36 or 46 grit white friable wheel or, if the funds run to one, a 180 grit CBN wheel. I have posted on these before ...

Article on ideal grinding set up: http://www.inthewoodshop.com/WoodworkTechniques/UltimateGrindingSharpeningSetUp.html

Regards from Perth

Derek

[Jerry Olexa]

Agree with Patrick .... 36 or 46 grit white friable wheel or, if the funds run to one, a 180 grit CBN wheel. I have posted on these before ...

Article on ideal grinding set up: http://www.inthewoodshop.com/WoodworkTechniques/UltimateGrindingSharpeningSetUp.html

Regards from Perth

Derek

Thanks Derek..Excellent article!!!

[Jerry Olexa]

Thanks guys..much food for thought...Keep in mind, I am new to this grinding thing...I realized my conventional hi speed DELTA grinder was wrong and decided a low speed grinder was a good first step. I've been doing basic sharpening with my Worksharp and years ago experimented with sandpaper and plate glass(scary sharp)..Found this to be good results but very time consuming...Have ventured a bit into waterstones but found it very messy...I'm now considering diamond stones for the next step.
Being that I've restored many older stanley planes , I still, in many cases ,find the irons in bad condition requiring in my mind, a re-grinding to get the proper angle bevel, square etc.prior to sharpening.
Therefore, the need for a suitable slow speed grinder I reasoned. So, I see the grinding need but the process is new to me...
Your posts are already helping,, I'll continue to read this thread as your ideas are posted..Thanks,

The new grinder

[Patrick Chase]

Thanks guys..much food for thought...Keep in mind, I am new to this grinding thing...I realized my conventional hi speed DELTA grinder was wrong and decided a low speed grinder was a good first step. I've been doing basic sharpening with my Worksharp and years ago experimented with sandpaper and plate glass(scary sharp)..Found this to be good results but very time consuming...Have ventured a bit into waterstones but found it very messy...I'm now considering diamond stones for the next step.
Being that I've restored many older stanley planes , I still, in many cases ,find the irons in bad condition requiring in my mind, a re-grinding to get the proper angle bevel, square etc.prior to sharpening.
Therefore, the need for a suitable slow speed grinder I reasoned. So, I see the grinding need but the process is new to me...
Your posts are already helping,, I'll continue to read this thread as your ideas are posted..Thanks,

The new grinder

If I could give one piece of advice that I wish I'd known when I started with grinding it would boil down to two points:

1. Do not grind all the way to the edge unless you absolutely have to. In normal use you want to use the grinder to speed up *other* methods of honing, by removing material so that your secondary bevel is small and therefore quick to work on bench stones.

2. If you do need to reshape the edge, for example to camber a blade, grind the edge back at a bit under 90 deg first, and then grind the bevel to restore the edge. Taking cambering as an example, you would first draw/scribe the desired profile on the back of the blade. You would then set the tool rest to a bit under 90 deg (it's unsafe to grind at higher angles because the grinder may grab the tool) and grind the edge back to the line. Finally you would set the tool rest to the desired bevel angle and grind the bevel until it almost-but-not-quite meets the face.

Both of these are motivated by one central observation: Sharp edges are thin and can't absorb or remove heat very effectively, so most burning/annealing happens when grinding along the edge. If you don't grind the edge at all (as in 1) then you won't have that problem. If you first blunt the edge as in (2) then you minimize your risk since you only grind a sharp edge at the very end (and you preferably stop before it gets really sharp, and do the last bit by hand).

Experienced grinders break these rules all the time without any trouble, but they'll keep you from disaster when starting out.

[Jerry Olexa]

Sounds like I should order "Norton White" 36 or 46 grit wheels as my starter set...
the new machine came with 2 unused 8" white wheels..Discard?
Again, thanks...I'll order later today.

[Christopher Charles]

Hello Jerry,

I have the same grinder and have been using it with the white wheels for 5+ years. I found it helpful to crown the wheels with a dresser (I use a cheap oxide bar, not even a diamond dresser) and did put wooden support platforms on the stock ones. Joel at TFWW had a very good article in FWW about 5 years ago on how to free hand grind that was also very useful. Thus, I'd say adding the LV or other upgrades to the rests would be better money spent than on new wheels. Grab an old chisel or even screw driver and play around..

Best,
C

[george wilson]

Slow speed bench grinders are TOTALLY UN NECESSARY. Another gimmick to sell to the un suspecting woodworker,or,indeed to the machinist,too.

I have never had a 1750-1800 RPM bench grinder,and have no desire to do so. I do have a 200 RPM diamond grinder which does not rob carbon from HSS tools. But,that is an entirely different issue.

I,long ago,learned how to grind tools without burning them. Plain and maybe not so simple. I grind for 2 seconds when the cutting edge has been ground very thin,and instantly quench. And,I keep a thumb or finger fairly close to the cutting edge of the chisel or plane iron I'm grinding,to feel the heat coming. And,I keep a close watch on the thin cutting edge to see the first sign of straw,brown,or blue that may be developing And,I use a white wheel of coarse grit,like the 36 grit already suggested here.(and,it happens FAST!) Actually,I have graduated to the belt grinder,which runs a LOT FASTER than the bench grinder anyway. But inherently grinds a bit cooler anyway.

By developing skill,I can grind edges quite thin. But,the word is SKILL.

A DIAMOND wheel dresser will leave your wheel SHARPER than a star wheel dresser. They have a cheap industrial grade diamond in their tip(a BORT,they are called). I advise you to use one of them when your wheel gets worn and no longer has a flat face or sharp corners. Be prepared for much wheel dust when dressing. KEEP THE DIAMOND TILTED A BIT DOWNWARDS when grinding,or the diamond may come loose. This you MUST DO. Keep your grinder WELL AWAY from your tools and machines. This is IMPORTANT.

Even if you buy the slow speed grinder,it will STILL burn your tools unless you learn to grind properly,so be prepared. Use the tips I just gave you.

I am still using my old 1963 Craftsman bench grinder. But,they made things better back then. My old grinder runs true and has minimal vibration. I like the FLAT FACE of the old Craftsman grinders. The body does not get in the way when grinding awkward tools like draw knives.

P.S.: I have NEVER had a grinder GRAB the tool. A buffer certainly will,though.

[Jerry Olexa]

I plead guilty as charged....It was a good price!! :)

[george wilson]

Don't worry!! 8" grinders run slower than 6" grinders anyway. Their wheels run faster on the periphery than a smaller 6" wheel grinder. But,in reality,you end up with about the same surface speed as a faster 6" grinder anyway. If you want a TRULY slower speed grinder with a large wheel,a TORMEK is the answer. Plus,its wheel runs in water. You then have a truly non burning wheel! They aren't cheap,though!!

[Patrick Chase]

I do have a 200 RPM diamond grinder which does not rob carbon from HSS tools. But,that is an entirely different issue.

This is nit-picky, but the carbon migration actually goes the opposite direction when the diamonds exceed 700C : Out of the diamond, into the steel.

[Patrick Chase]

I,long ago,learned how to grind tools without burning them. Plain and maybe not so simple. I grind for 2 seconds when the cutting edge has been ground very thin,and instantly quench. And,I keep a thumb or finger fairly close to the cutting edge of the chisel or plane iron I'm grinding,to feel the heat coming. And,I keep a close watch on the thin cutting edge to see the first sign of straw,brown,or blue that may be developing And,I use a white wheel of coarse grit,like the 36 grit already suggested here.(and,it happens FAST!) Actually,I have graduated to the belt grinder,which runs a LOT FASTER than the bench grinder anyway. But inherently grinds a bit cooler anyway.

Yep, and that's exactly what I meant when I said "Experienced grinders break these rules all the time without any trouble, but they'll keep you from disaster when starting out.". I use the same techniques, but I've also seen people burn tools by mis-applying them, so I recommend a more conservative approach at first. I would wager that even "long ago" you had more experience than most on this forum.


P.S.: I have NEVER had a grinder GRAB the tool. A buffer certainly will,though.

Nor have I, though I also know that it has in fact happened. Keeping the tool rest pointed slightly above wheel center isn't *that* onerous of a restriction.

[george wilson]

The ONLY way a grinding wheel is going to grab a tool is if you stupidly jam the tool down between the wheel and the surrounding guard,ir cram it down between the wheel and the tool rest. Period.

I won't say that a total idiot cannot make UNUSUAL things happen!! Some people could make WATER catch fire.:) Or,tear up an anvil.

Yes,I have been grinding since about 1952. I even wore wheels down to 3" diameter when I was a pre teenager. One time I converted a large French knife into a 6" blade hunting knife,for example.:)

Having a French knife was not necessary,but having a hunting knife was mandatory in Alaska,even if you didn't hunt! I was too poor to afford a store bought one. I must say,always being poor did help me to gain considerable experience in learning how to make my own things!

Someone had broken the tip off of the French knife and discarded it anyway.

[Jerry Olexa]

Where do I find these CBN wheels if I am foolish enough to want to order???Just want to be sure of all options. Thnx

[Patrick Chase]

The ONLY way a grinding wheel is going to grab a tool is if you stupidly jam the tool down between the wheel and the surrounding guard,ir cram it down between the wheel and the tool rest. Period.

While I agree with your broader point (it takes a serious act of idiocy to make that happen), as an engineer I have to point out that you're misrepresenting the mechanics.

To understand why you need to look at the projection of the cutting force vector (friction forces at the tool<->wheel interface) relative to the tool rest surface.

What you say is true if (and only if) the tool rest is "aimed" above the center of the wheel. In that case the cutting force has components "down" into the tool rest and "out" (away from the rest<->wheel gap) along the tool rest. If you completely let go of the tool that "out" component means that it will slide back along the rest and disengage from the wheel on its own. It's "fail safe" in the sense that it self-recovers to a good state.

If on the other hand the tool rest is aimed below wheel center then the projected cutting force has components "down" into the tool rest and "in" (towards the rest<->wheel gap) along the tool rest. That "in" component is a big problem, because it means that if you let go of the tool while grinding then there is a chance that it will be pulled into the gap on its own. I've seen this demonstrated before, so I know it's real (though please don't try to do it yourself, for obvious reasons). It's therefore "fail deadly". Again, it takes serious idiocy on the part of the user to make (or more precisely to let) it happen, but it's possible.

[Patrick Chase]

Where do I find these CBN wheels if I am foolish enough to want to order???Just want to be sure of all options. Thnx

There are a whole bunch of options by this point. Most (all?) woodworkers use electroplated ones wherein a layer of CBN particles are attached to the surface of a steel wheel. It's a similar process to the one used to create diamond plates.

Many people (Derek and I included - I did it based on his review) started out with D-Way, who make very nice but somewhat expensive wheels.

Since then Wood Turners Wonders have come out with some nice wheels, including some 2" wide Tormek wheels (D-Way's are 1.5") that use an Aluminum inner wheel to keep weight under control. They're also a bit cheaper for equivalent size/grit than D-Way.

At this point even Woodcraft is selling CBN wheels. They have an 8x1 wheel for $130 or so IIRC. The big advantage to that one is that you can keep your wheel guards on (the others are 1.5" wide, so the guards have to go).

[Archie England]

Being a grinder junkie..., I have paid for my experience: Everything works--as it is intended!

You can blue a chisel on high or low speed, with a low grit or higher grit abrasive wheel. It's learned skill, not to blue a chisel--especially the thinnest ones. Stepping down to real slow speed, I bought a Tormek (with b'day monies; and, I'm a turner, too). This is quite expensive, but given all that it can do, and do really well, makes the Tormek a great (almost) do everything machine. My friend's knife making machine is perhaps the only system (more expensive), faster and better. But, alas, Tormek doesn't like to do blade backs (yes, I've used the side of the wheel; yuck). So, there's stones (and don't we all have our favs?)!

For me, I divide my sharpening needs into these categories: (1) shaping (bad chips, broken, or unintentional skews); (2) cutting (setting the bevel and the initial edge); (3) honing (taking the initial edge to somewhere between 3,000 to 5,000 grit; and (4) polishing (refining and/or hardening an edge so that it retains sharpness longer (6000 to 13,000 or higher).

The grinder (any of them save the Tormek) accomplishes the first two quite easily. IMO, the only stone grinder to achieve honing is the Tormek (with the leather wheel), while a Knife making belt grinder can do all four.

In the end, they all work--as intended. Use what you've bought--as it's intended--and use a light touch with frequent cooling and you should be good to go, without having to become a fellow junkie. :)

[george wilson]

Sorry Patrick,engineer or not(what kind of engineer anyway?),in my whole career,whose experiences add up more substantially than what one would normally call being an "engineer",I have NEVER had a grinder grab the tool. And,I am never about to dump a tool into the wheel as you describe. Yes,as I said,an idiot can set water on fire. Grinding wheels have no "teeth" coarse enough to grab a tool unless you literally force the tool down into the gap as you describe. I have never seen a grinder THROW something at the operator either. I have even worked in machine shops where half baked "machine operators" can do silly things.

I have ended up being a bit of an engineer myself,by the "seat of the pants" as it were,from being thrust into the many "special projects" I have been assigned to do. None failed. When needed,I dug up the necessary formulae from sources such as "Machinery's

Handbook". Thus to figure out the air pressure generated by 10 men pumping the 18th. C. fire engine,and the thickness of the copper air tank,and the width of soldered joints to keep it from bursting. That included a safety factor of 6. It has never burst since 1982,despite nearly daily use for the public. Old ones frequently burst,and they wrap them in chicken wire when demonstrating to keep shrapnel from hurting someone. In the old days,they were more interested in being frugal with metal than in safety.

I wonder what engineer had the steel seat supports under the driver's seat of my 1986 Taurus bent at a sharp 90º angle,so that the seat support cracked neatly,just like a mitered picture frame? Any reasonably educated man on the street knows better. They had a recall of Escorts due to that,but had not gotten around to the Taurus yet. Or what engineer designed the socket brackets in my Craftsman tool box,so that they will not fit the sockets of the same brand?

There seem to be quite a few engineers on this forum. In England,they even call ELECTRICIANS,"Electrical engineers". I know one,and he attempts to pawn himself off as a harpsichord maker,though he hasn't even the basic knowledge of how wood shrinks and warps when drying. I have seen him use green wood on an instrument,which proceeds to self destruct.

When are you going to post us some pictures of your work?

[Jerry Olexa]

Had a friend/fellow WWer stop by today and while he was in my shop, I asked him (as he looked at my new slow-speed grinder) his opinions on grinding..His reply was quick; "I never grind, I only sharpen"..He sharpens with Japanese waterstones but says he has no need for grinding...Hmmmmm. As I pondered his response later, I concluded if your irons are not damaged or out of square, then the simple sharpening (no grinding)process is in order. In other words, Most of the time you will be sharpening and only occasionally grinding as needed (a damaged or badly sharpened iron etc)....Oh well, just my musing over a friend's comments..(He is not an SMC member but very credible in his knowledge of planes and chisels). More food for thought....:)

[Archie England]

Yes! I'm a convert to ceramic waterstones. They cut, hone, and polish like crazy. However, shaping is not one of their strong suits (if time matters). Grinders are great for speedy work, but any where too much heat meets too little blade, there's a stronger chance for drawing the temper.

[Derek Cohen]

Had a friend/fellow WWer stop by today and while he was in my shop, I asked him (as he looked at my new slow-speed grinder) his opinions on grinding..His reply was quick; "I never grind, I only sharpen"..He sharpens with Japanese waterstones but says he has no need for grinding...Hmmmmm. As I pondered his response later, I concluded if your irons are not damaged or out of square, then the simple sharpening (no grinding)process is in order. In other words, Most of the time you will be sharpening and only occasionally grinding as needed (a damaged or badly sharpened iron etc)....Oh well, just my musing over a friend's comments..(He is not an SMC member but very credible in his knowledge of planes and chisels). More food for thought....:)

There is no need to grind a laminated Japanese blade, chisel or plane, unless it is chipped. This includes hollow grinding. The soft backing is essentially the equivalent of a hollow since it wears away very easily.

Regards from Perth

Derek

[Patrick Chase]

Had a friend/fellow WWer stop by today and while he was in my shop, I asked him (as he looked at my new slow-speed grinder) his opinions on grinding..His reply was quick; "I never grind, I only sharpen"..He sharpens with Japanese waterstones but says he has no need for grinding...Hmmmmm. As I pondered his response later, I concluded if your irons are not damaged or out of square, then the simple sharpening (no grinding)process is in order. In other words, Most of the time you will be sharpening and only occasionally grinding as needed (a damaged or badly sharpened iron etc)....Oh well, just my musing over a friend's comments..(He is not an SMC member but very credible in his knowledge of planes and chisels). More food for thought....:)

There's a spectrum from "manual everything" (for example your acquaintance) to "grind almost everything" (for example folks who grind the bevel completely hollow and then hone just the tip). I mostly use the grinder to "debulk" the upper face of the bevel so that I can work the edge more easily with stones. I'd argue that's a reasonable compromise.

I would hate to have to do serious work like drastically changing the primary bevel or adding/removing camber by hand though.

[Patrick Chase]

There is no need to grind a laminated Japanese blade, chisel or plane, unless it is chipped. This includes hollow grinding. The soft backing is essentially the equivalent of a hollow since it wears away very easily.

Regards from Perth

Derek

It's also important to recognize that the brittle cutting edge relies on the softer back for support, to prevent fracturing. Hollowing out that back immediately above the cutting edge is inherently riskier on such a laminated blade than on a solid one (though I don't know where that theoretical "risk" turns into a real problem, just that it happens sooner for a laminated blade than for a solid one).

[Jerry Olexa]

Is there a good book or source that covers the sharpening/grinding process? I have the FWW(LN) book as well as Hock but they seem to focus on materials, theory rather than the process itself..Thanks guys.

[Patrick Chase]

Is there a good book or source that covers the sharpening/grinding process? I have the FWW(LN) book as well as Hock but they seem to focus on materials, theory rather than the process itself..Thanks guys.

Nah, because if I recommend anything George will disapprove and tell us he's been doing it some other clearly superior way for a long long time, so obviously that's the only answer.

Leonard Lee's book does a decent job. Also Joel Moskowitz' FWW article (I don't use all parts of his technique, but I think it's a reasonable starting point).

WARNING: IIRC (it's been a while since I read his book) Lee in particular advises against quenching in water during grinding. Don't ask about that here, because all you'll get is a ridiculous Holy War. FWIW I quench, but I'm also very careful about limiting the tip temperature, so quenching doesn't cause much thermal shock. Clearly if you're using a water-hardened steel then quenching is OK at any realistic temperature. Conversely I'd be a little nervous about quenching really hot A2 ("A" is for "air-hardened").