Sharp chisels!

[Jeff Bartley]

Sharp chisels yes! But not at the end, on the sides.

I'm just wondering how many here have been cut up by the edges of their chisels?

And does anyone purposely dull the side edges to prevent this?

Jeff (with a slice on his index finger!)

[Derek Cohen]

"Minimal" lands help to avoid bruising the edges of dovetails, but to this end it is the small chisels that are important (1/8" through 1/4"). Side bevels are a good way of reducing blade mass, and this can improve balance and feedback. Still, a chisel is just a tool. And if it is not working for you, then modify it so that it does. Overly sharp lands certainly can cut, and this degree of angle is not necessary, even for dovetails. For example, in my review of the Veritas chisels I recommended reducing the sharp edges from about 1" behind the bevel face. (I use a worn 600 grit diamond stone).


http://www.inthewoodshop.com/ToolReviews/VeritasChiselReview_html_m2689c0e3.jpg



Regards from Perth

Derek

[Al Weber]

Yes, both my inexpensive paring chisels and the LN's I have required some edge modification with a fine diamond stone to remove the sharp edges. Painful little nicks.

[Steve Voigt]

Hey Jeff,

If I'm using a chisel for mortising, I like the sides (on the back) to be that sharp. I occasionally cut myself if I'm not careful. I want the sides to be that sharp so they will cut when I lever the chisel forward. For an ordinary bench chisel, no. Yes, you can dull those edges, but I would do the minimum necessary, just a few strokes across a fine stone. Otherwise the corners won't cut.

[Derek Cohen]

I fully agree with you about mortice chisels, Steve. What a difference when the lands are truly sharp! It is one of the aspects that many may miss if they are using worn vintage chisels. I restore this area back in. Still, I do not think that Jeff was referring to mortice-, but rather to bench chisels.

Regards from Perth

Derek

[george wilson]

Many years ago I cut my finger on the SQUARE EDGE at the top of the blade of a dress sword! It must have been polished by a real master. (I was in the 4th. grade,and my hands were not yet toughened.) There was no rounding off of the 90 degree corner at all!!

Even a square edge can be sharp if it is not rounded over a little bit as they are most of the time.

Then,there are paper cuts!

And,some large grasses can cut you too!

[Jeff Bartley]

Thanks for the input! I usually don't even notice the cuts till I see blood on the work! They sure are a lot like paper cuts.....only hurt after the fact.

Steve, I thought about mortise chisels when pondering this earlier, the culprits here are those Japanese chisels that I recently aquired, which are incidently still not holding an edge! But that's an entirely different topic!

Back to work for me......

[Luke Dupont]

When I first lapped and sharpened my Narex chisels, which had some rough grind marks on them, I created sharp 90 degree corners. Well, actually - it may be that I created tiny serrations. More on that below. I went to paring with them, and after about 30 minutes I noticed all kinds of cuts on my left index finger where I'd been holding the blade.

In my case, I created tiny serrations because I did not lap the full length of the back all the way down past the original grind marks. This created a serrated edge, basically. So, I went back, removed all of the grind marks from the back, and took one pass on the stone to take off the corners.

Stop just before you get to the edge of the chisel when taking the corners off, though - you want the corners of the edge to be sharp.

[steven c newman]

And...wear a Kevlar glove on your "guide hand".....

[Luke Dupont]

And...wear a Kevlar glove on your "guide hand".....

lol.

Well, I realize that's a joke, but! Can't kevlar be cut with an edge fairly easily? Well, maybe not "cut" easily, but I recall hearing that, while it protects against projectiles, it won't actually stop a knife from penetrating.
I'd imagine it's much harder to cut into than to thrust into, granted.

On an, only slightly more relevant and serious side of things, though, I would contest the approach that I often see people taking of just "adding more protection" if there's a danger of getting hurt. The better route, is almost always, to change one's practice and retain (or cultivate) the sensitivity and awareness that working without added protection (which, incidentally, dulls one's senses and tends to give one false confidence) entails. If you're just relying on protective gear for safety, then you're just delaying an even more serious injury than if you learned to be more correct in your form, and more cautious and aware of how you handle your tools.

The above is a phenomenon/misconception that I also see surrounding the modern practice of Martial Arts, too. Rather than learning control and safe habits, people think they just need to gear up more. Meh.

Anyway, I know - none of that is what you were suggesting in earnest, but, I think it's always a good point to bring up in any discussion of safety.

[steven c newman]

Not a joke! We were issued such gloves when I worked at an injection moding factory. kevlar will indeed stop cuts. A Needle will go right through it. Knife cuts? not really. The plant was getting tired of all the cut hands and fingers needing stitches, so they issued the gloves.

They since went to a "Safety" style of utility knife. Still getting cuts, just not in the gloved hands. They also issued the new "Mechanics" style gloves to be worn when using any tools.....they were worthless around anything sharp....


Me? I just round the sharp edges off a bit. More concerned about that sharp edge hopping out and stinging me
338165
As they do tend to "smart" a bit.....wasn't any force behind that chisel, other than it's own weight.

[Mike Cherry]

On the topic of mortise chisels, are you guys actually honing the lands on your mortise chisels every once and a while? Or is it just something that you dont bevel on purpose? I can certainly see where a sharp corner on mortise chisels could help when levering a mortise.

[Patrick Chase]

Sharp chisels yes! But not at the end, on the sides.

I'm just wondering how many here have been cut up by the edges of their chisels?

And does anyone purposely dull the side edges to prevent this?

Jeff (with a slice on his index finger!)

Yes, I've been cut, once.

Yes, I dulled the side edges after that, though starting ~1" behind the cutting edge (same as Derek).

[Patrick Chase]

lol.

Well, I realize that's a joke, but! Can't kevlar be cut with an edge fairly easily? Well, maybe not "cut" easily, but I recall hearing that, while it protects against projectiles, it won't actually stop a knife from penetrating.
I'd imagine it's much harder to cut into than to thrust into, granted.

Not a joke. Aramid fibers can be cut, but not easily. The more common failure mode is for a very narrow point to penetrate between fibers.

These work pretty well: http://www.leevalley.com/US/wood/page.aspx?p=72972&cat=1,42207,45887

And these are almost bombproof: http://www.leevalley.com/US/wood/page.aspx?p=56153&cat=1,42207,45887

[Don Jarvie]

Cloth medical tape is your friend. Wrap your thumb or finger a bit and the problem is solved.

[george wilson]

I haven't had the problem of getting cut on the corners of my 1963 Marples chisels. But,if I did,I'd just hone the corners a little bit. My hands are fairly tough anyway from working all my life with tools,though.

I would NOT round the edges as badly as some of the highly polished German chisels are. Some come with very excessively rounded corners.

[Steve Voigt]

On the topic of mortise chisels, are you guys actually honing the lands on your mortise chisels every once and a while? Or is it just something that you dont bevel on purpose? I can certainly see where a sharp corner on mortise chisels could help when levering a mortise.

Mike, I don't hone the lands if the sides are already sharp. Working the back seems to keep the sides sharp enough. Bot sure if that will be true in 20 years or not, but I guess I'll find out.

I have several vintage mortise chisels that were restored from trash status, and on those I ground the sides and then honed them on PSA and stones. But I haven't retouched the sides since.

[Pat Barry]

... I usually don't even notice the cuts till I see blood on the work!
Sounds like a typical day in the shop for me, and as often as it happens its still a surprise, like, where did that come from?

[Mike Henderson]

Sounds like a typical day in the shop for me, and as often as it happens its still a surprise, like, where did that come from?
Me too. I often think that most of my work has a blood mark from me on it. The CSI people would have a field day with me and my projects!

Mike

[Mike Cherry]

Mike, I don't hone the lands if the sides are already sharp. Working the back seems to keep the sides sharp enough. Bot sure if that will be true in 20 years or not, but I guess I'll find out.

I have several vintage mortise chisels that were restored from trash status, and on those I ground the sides and then honed them on PSA and stones. But I haven't retouched the sides since.
Thanks Steve that clears it up!

[Lenore Epstein]

Thanks for the input! I usually don't even notice the cuts till I see blood on the work! They sure are a lot like paper cuts.....only hurt after the fact.
Flattening convex chisel backs as a sharpening newbie left me with a lot of those kinds of cuts, especially with narrow chisels that make it hard to keep the edges of my fingers away from the burred edges and still maintain pressure. Honing and actually using tools is less dangerous so long as I don't get fuddle-fingered, like when I recently sliced my thumb trying to catch a slipping marking knife. Using steri-strips and butterfly bandages to 'stick' the edges together once the bleeding slows reduces the pain (because the wound's edges aren't rubbing against each other) and makes for quick healing and minimal scarring (scars are more slippery than skin, so it's worth preserving the latter).

Cloth medical tape is your friend. Wrap your thumb or finger a bit and the problem is solved.
Thanks for mentioning that; cheap white athletic or medical tape is so tough and has such strong adhesive that it's the perfect defense, especially if you're like me and hate working for long with gloves on. I've used cloth tape handling rough brush, fixing all manner of back country hardware, climbing, and making mini field splints for injured digits, but I never thought about using it to avoid tool-related cuts. It's time to dig out that 1" roll floating around the bottom of the first aid box.

[george wilson]

I often super glue small cuts together. Don't let the glue go down into the wound and it will work very well. After all,wasn't super glue developed for use in surgery?

[Patrick Chase]

I often super glue small cuts together. Don't let the glue go down into the wound and it will work very well. After all,wasn't super glue developed for use in surgery?

Tissue adhesives (Dermabond, Vetbond, etc) are cyanoacrylate resins, but they're from different (https://en.wikipedia.org/wiki/Butyl_cyanoacrylate) families (https://en.wikipedia.org/wiki/2-Octyl_cyanoacrylate) than ordinary " (https://en.wikipedia.org/wiki/Cyanoacrylate)super glue (https://en.wikipedia.org/wiki/Ethyl_cyanoacrylate)". Tissue adhesives last a lot longer on skin and sting less going on (the latter helps a lot with the kids).

The cheap way to go is Vetbond, which is $15 for a multi use bottle that will seal up a lot of cuts if you're careful not to let it get plugged. The "human rated" Dermabond is $20-25 for a single-use applicator. Vetbond is n-Butyl CA, which is more irritating than Dermabond (2-Octyl CA) but it's still a lot better than non-tissue CA. Unfortunately my wife won't let me use Vetbond on the kids, so I keep both on hand.

[Lenore Epstein]

Thanks, Patrick, I wondered why regular superglue doesn't really work. It would be great to have something that would close a cut while blood is still present, so I might give VetBond a try.

[Patrick Chase]

Thanks, Patrick, I wondered why regular superglue doesn't really work. It would be great to have something that would close a cut while blood is still present, so I might give VetBond a try.

You have to at least slow the bleeding before tissue adhesive will work.

If I have a deep cut (which unfortunately happens more often than it should - my old scoutmasters would be appalled at my safety practices) I usually do initial closure with a butterfly bandage or surgical strip and direct pressure if needed, and then follow up with the CA once it slows down.

You might be able to use some of the newer anticoagulant powders instead to get the bleeding under control more quickly, but while I have some on hand I've never used them and won't for anything short of a full-on emergency. The idea of potentially introducing coagulants into the bloodstream makes me nervous for reasons that may or may not be rational.

EDIT: I learned all about the differences when I showed up at the ER with a deep cut across a knuckle that ended up requiring 6 stitches, that I had initially sealed with standard Satellite City CA. I talked the assistant into dissolving it with acetone (unpleasant) while the ER doctor wasn't looking so that they could clean and stitch it. When the Dr found out what I'd done and what I'd convinced her asst to do I got a bit of a lecture.

[george wilson]

Super glues were made so water was a hardening agent. My favorite is whatever the grocery store stocks!!:) Really,for minor cuts,they all have worked fine. I'm not recommending superglue for BAD,DEEP cuts. The glue stops the cuts rubbing together,thus eliminating the irritating pain.

If I stocked the special glues mentioned,even in the fridge,they would have hardened up by the time I cut myself,which is just not very often.

[Derek Cohen]

Mike, I don't hone the lands if the sides are already sharp. Working the back seems to keep the sides sharp enough. Bot sure if that will be true in 20 years or not, but I guess I'll find out.

I have several vintage mortise chisels that were restored from trash status, and on those I ground the sides and then honed them on PSA and stones. But I haven't retouched the sides since.

I should have replied to Mike as well.

My experience is the same as Steve's. Vintage mortice chisels are often a little rusty in the wild. They get cleaned up, but the attention is typically given to cleaning off the rust and ensuring the back of the bevel is flat. What is missed is that the back of the blade is used for about 2" of its length, and that the lands shave the side walls of the mortice when the chisel is worked back-and-forth. It is not advisable to restore the lands by honing the sides of the blade, as this will alter its dimensions. Some light work on a diamond plate can be done to smooth away irregularities, but mainly the work is done by flattening and polishing the first 2" of the back of the blade. This is what I do with the modern mortice chisels I have (all mine are based on the Oval Bolstered design). All I can add is that the difference between a mortice chisel with sharp lands and one with dull lands is like night and day.

Regards from Perth

Derek

[Steve Voigt]

Vintage mortice chisels are often a little rusty in the wild. They get cleaned up, but the attention is typically given to cleaning off the rust and ensuring the back of the bevel is flat. What is missed is that the back of the blade is used for about 2" of its length, and that the lands shave the side walls of the mortice when the chisel is worked back-and-forth. It is not advisable to restore the lands by honing the sides of the blade, as this will alter its dimensions. Some light work on a diamond plate can be done to smooth away irregularities, but mainly the work is done by flattening and polishing the first 2" of the back of the blade. This is what I do with the modern mortice chisels I have (all mine are based on the Oval Bolstered design). All I can add is that the difference between a mortice chisel with sharp lands and one with dull lands is like night and day.


Derek, I agree with you that it's better not to mess with the lands too much, if it can be helped…but I've had several chisels where width was actually a bit less at the tip than up an inch or two. Obviously, a chisel like that will be bind, and has to be fixed. It's usually not that big a deal to alter the dimensions, since old pigstickers are rarely dead-on .250", .375", or whatever dimension we were hoping for! As I'm sure you have encountered! :)

My 5/16" mortise chisel started as 3/8 chisel. The width was tapered the wrong way, and it had a hunchback of Notre Dame-like bulge halfway up. I heated it to orange, forged it flat, annealed it, rehardened and tempered it (the tempering took two tries), then reground all four sides.

I would not recommend this course of action to anyone! :rolleyes:

[Brian Holcombe]

It's rare that I cut myself, but when I do I seem to make up for lost time! The worst are Japanese crosscut saws, they make a nasty cut!

The last one I did was so bad that my wife did not stop to lecture me. She was however very angry with me for cleaning it and taping it rather than getting stitches.

[Tom M King]

I keep the little Locktite Liquid Control, and Gel Control bottles all the time. They have a neat little twist top that keeps it good for a long time after it's opened, and the squeeze things on the side work well. The liquid is good for small cuts, and the gel is holding my shoes together. The gel works good on small wood assemblies too. They're on a peg in Lowes and Home Depot where all the other glues are.
Super Glue was developed for wounds during the Vietnam War.
http://www.staples.com/office/supplies/StaplesProductDisplay?storeId=10001&catalogIdentifier=2&partNumber=886836&langid=-1&cid=PS:GooglePLAs:886836&ci_src=17588969&ci_sku=886836&KPID=886836&lsft=cid:PS-_-GooglePLAs-_-886836,kpid:886836,adtype:pla,channel:online&gclid=CjwKEAjwg6W6BRDn6v__7vzN9QkSJAC9l9C3hAfqT8Bm p7XbbIBj6nQRKBNcybUlhgku3np5SlFP1hoCvv3w_wcB

[Patrick Chase]

Super Glue was developed for wounds during the Vietnam War.

No, it was not, unless you're referring to Dien Bien Phu (and I doubt very much that the French used it there either, see below).

It was discovered in the 40s and set aside as not useful, but then came to market as a general-purpose adhesive in the 50s (Eastman 910). The wound closure variants are chemically different and came later.

[John Kananis]

The wound closure variants are chemically different and came later.

I don't know about chemically different but just about every Marine I know (that bothered to carry any first aid 'paraphernalia' at all) carried some "Crazy Glue". ;-)

[Stewie Simpson]

Coover said the compound demonstrated an excellent capacity to stop bleeding, and during the Vietnam War, he developed disposal cyanoacrylate sprays for use in the battle field. http://www.straightdope.com/columns/read/2187/was-super-glue-invented-to-seal-battle-wounds-in-vietnam

[Patrick Chase]

Coover said the compound demonstrated an excellent capacity to stop bleeding, and during the Vietnam War, he developed disposal cyanoacrylate sprays for use in the battle field. http://www.straightdope.com/columns/read/2187/was-super-glue-invented-to-seal-battle-wounds-in-vietnam

Yes, absolutely true: Cyanoacrylate sprays were *eventually* adapted to that purpose. I've said so 3 times in already in this thread.

Tom however said that "Super Glue was developed for wounds during the Vietnam War". That statement was false on two grounds:

1. CA resins (a.k.a. "super glue") were developed in the 40s and 50s, long before the Second Indochina War (the one we 'mericans narcissistically call "the Vietnam War").

2. CA resins were developed for general-purpose use as Eastman 910. Their modification and use for wound treatment came much later.

[steven c newman]

After a fellow stormed into my CP one night, and a punch broke a few of his teeth ( he had this sharp.pointy thing he was trying to stick me with) I used some Krazy Glue to close up the busted knuckle. And the cut from that .45 slide coming back across my hand....was in a bit of a hurry, was hard to get a good grip on it...

later, just let the patches wear away. ( FEB 1972, Guess where...)

[Patrick Chase]

After a fellow stormed into my CP one night, and a punch broke a few of his teeth ( he had this sharp.pointy thing he was trying to stick me with) I used some Krazy Glue to close up the busted knuckle. And the cut from that .45 slide coming back across my hand....was in a bit of a hurry, was hard to get a good grip on it...

later, just let the patches wear away. ( FEB 1972, Guess where...)

Ugh, just before some really nasty stuff (Easter). Sorry about being such a stickler for details - seems rather insignificant...

[Stewie Simpson]

Slightly off topic; the following shows my recently purchased 6 inch cnc grinding wheels (80 and 180 grit), with the Woodcut Tru Grind sliding track tool rests. The old heavy duty grinder runs at 2700 rpm. I will need to relocate those slide tracks to obtain a higher approach against the grit face of the cbn wheels. No instructions were supplied so it was all guess work setting these things up. There is plenty of existing clearance between the top of the slides and the bottom line of the cbn wheels; so most likely I resolve this issue by fitting a 1 3/4 inch packer under both slide bases. All good; easy fix.


A big thanks to Derek C. for recommending these cbn wheels.



http://i1009.photobucket.com/albums/af219/swagman001/bench%20grinder/_DSC0157_zpsrwpcyjir.jpg (http://s1009.photobucket.com/user/swagman001/media/bench%20grinder/_DSC0157_zpsrwpcyjir.jpg.html)

http://i1009.photobucket.com/albums/af219/swagman001/bench%20grinder/_DSC0158_zpsyu8gurae.jpg (http://s1009.photobucket.com/user/swagman001/media/bench%20grinder/_DSC0158_zpsyu8gurae.jpg.html)

[Stewie Simpson]

I was able to increase the height of the tool rest by moving the slide track bases 2 inches further back. With the vertical adjustment arms set at 70* and the tool rest adjusted to 32* , the hollow grinding bevel equates to 25*. ( + 7 * bias with the tool rest setting) The following photo's illustrate the before and after height difference gained with the tool rest. Job done.

Stewie;


http://i1009.photobucket.com/albums/af219/swagman001/bench%20grinder/_DSC0158_zpsyu8gurae.jpg (http://s1009.photobucket.com/user/swagman001/media/bench%20grinder/_DSC0158_zpsyu8gurae.jpg.html)

http://i1009.photobucket.com/albums/af219/swagman001/bench%20grinder/_DSC0159_zpsatnwy36d.jpg (http://s1009.photobucket.com/user/swagman001/media/bench%20grinder/_DSC0159_zpsatnwy36d.jpg.html)

[Stewie Simpson]

An additional comment; the rubber cleaning sticks used for sanding discs do an excellent job on the grit surface of cbn wheels.

Stewie;

[Kees Heiden]

That looks like a very good toolrest!

[Stewie Simpson]

The chisel shown within the bottom photo received a full 25* hollow ground on the 180 grit cbn wheel (formed a light burr to the front edge) with no obvious signs of residual heat being generated. Quite astonishing considering its a 6 inch grinder running at 2700rpm.

Stewie;

[Patrick Chase]

The chisel shown within the bottom photo received a full 25* hollow ground on the 180 grit cbn wheel (formed a light burr to the front edge) with no obvious signs of residual heat being generated. Quite astonishing considering its a 6 inch grinder running at 2700rpm.

Stewie;

I saw a paper a while back that claimed a >4X difference in heat dissipation per unit volume material removed compared to freshly dressed Al-Oxide wheels. Based on my own experience I think that's about right.

6" at 2700 rpm is ~70 feet/sec, which is a pretty good clip, about the same as an 8" grinder at ~2000 rpm.

[Stewie Simpson]

Excellent feedback Patrick; the 4x differential in heat distribution between the cbn and the Al-Oxide wheels is very interesting. The 80 and 180 grit combination cbn wheels recommended by Derek C. is an excellent pairing for grinding work. The Woodcut Tru slide tracks are also an excellent design; I use a Wixey digital angle gauge http://www.wixey.com/anglegauge/ (calibrated to zero from the top surface of the work bench) to lock in the desired angles on both vertical arms and tool rests; then slide the upright assemblies towards the grit face of the cbn wheels; lock them in position; and commence grinding to a dedicated hollow bevel (bevel angle + 7* bias). My previous grinding set up was reliant on AL-Oxide grinding wheels, with limited adjustment capabilities on the tool rests, very similar in design to the following; http://www.grizzly.com/products/Optional-Heavy-Duty-Tool-Rest/G8987?utm_campaign=zPage

Stewie;

[Stewie Simpson]

Can anyone identify the combination honing stone (shown closest to the camera); the bottom half is a medium hardness silicon carbide, the top half ??? possibly AL- Oxide. Also; is the Norton Abrasive-Queer Creek silicon carbide honing stone (medium hardness); generally regarded as a good quality honing stone. ??

Stewie;


http://i1009.photobucket.com/albums/af219/swagman001/bench%20grinder/_DSC0160_zpssjguzuo4.jpg (http://s1009.photobucket.com/user/swagman001/media/bench%20grinder/_DSC0160_zpssjguzuo4.jpg.html)

[Mel Fulks]

Know nothing about the one in front. Norton silicon carbide stones are considered good. And the queer creek side is a natural fine sandstone that was usually rated as "second line" stone.

[Stewie Simpson]

Thanks for the feedback Mel. That may explain why the original box for the QC stone is labelled " can be used with oil or water ". With regards the other honing stone; I have an vague idea these were originally marketed as Aloxite Combination Stones. I did find this early Popular Mechanics advertisement under the heading; "Sharp tools do a better job" https://books.google.com.au/books?id=vtoDAAAAMBAJ&pg=RA2-PA163&lpg=RA2-PA163&dq=aloxite+combination++sharpening+stone&source=bl&ots=Fd4f1tY411&sig=3I-pAyBoNeErUZmk5zc-bf5TRVs&hl=en&sa=X&ved=0ahUKEwj5w7fshIbNAhWBQJQKHRdMBTgQ6AEIKDAD#v=on epage&q=aloxite%20combination%20%20sharpening%20stone&f=false

Stewie;

[Stewie Simpson]

Question to the forum; if you have a 5 inch grinder that's rated at 2975rpm; what is the resulting change in rpm if you were to remove the guards and fit a larger dia. 6 inch cbn grinding wheel to it. Note: cbn wheels start at 6 inch dia; cbn wheels are rated up to 3000 rpm.

Stewie;

[Pat Barry]

Question to the forum; if you have a 5 inch grinder that's rated at 2975rpm; what is the resulting change in rpm if you were to remove the guards and fit a larger dia. 6 inch cbn grinding wheel to it. Note: cbn wheels start at 6 inch dia; cbn wheels are rated up to 3000 rpm.

Stewie;
There is no change in RPM but the velocity of the surface of a 6 inch wheel is higher than for a 5 inch wheel. The ratio of the diameters will tell you how much faster (6/5 = 1.2) 20% higher surface speed for 6 inch wheel as compared to 5 inch wheel.
\
Note - it may take a bit longer for the 6 inch wheel to spin up to rpm if it is heavier or if the weight is distributed non uniformly to the outside of the new wheel.

[Stewie Simpson]

Thanks for the feedback Pat. Excellent.

Stewie;

[Patrick Chase]

There is no change in RPM but the velocity of the surface of a 6 inch wheel is higher than for a 5 inch wheel. The ratio of the diameters will tell you how much faster (6/5 = 1.2) 20% higher surface speed for 6 inch wheel as compared to 5 inch wheel.
\
Note - it may take a bit longer for the 6 inch wheel to spin up to rpm if it is heavier or if the weight is distributed non uniformly to the outside of the new wheel.

This is 100% right. Even when CBN wheels are the same radius they take longer to spin up/down because they're heavier and have more mass at the edge (and therefore much higher rotational inertia).

[Patrick Chase]

Thanks Patrick; if you run the 5 inch grinder with a 6 inch cbn wheel on 1 side, and a 5 inch silicon carbide grinding wheel on the other side, is that likely to cause any vibration or balance issues within the grinder due to a potential difference in centrifugal force.

Stewie;

It's been a long time since I've been a practicing ME so this is probably a semi-qualified opinion, but... There shouldn't be any problem provided that the bearings are in good condition and the SiC wheel is reasonably true. What matters is balance about the axis of rotation, and you're not proposing to change that.

I ran one of my 8" grinders "unbalanced": that way (8" AlOx on one side, CBN on the other) for quite some time and never saw any trouble.

[Stewie Simpson]

Thanks Patrick; appreciate the feedback.

Stewie;