Grinding Wheels, When To Replace Them???

Sorry, Chuck. You're physics are backwards in this case. It's the reverse of what you say below. STEMO is correct. Just think about hollowing a larger bowl, for example. It takes longer to take off the same amount of wood the closer you get toward the center. Same with sanding. It takes longer to sand the center portions as compared to the rim because the rim is moving faster with a set speed at the spindle.

- Andrew

When it gets to about 7". I only use grinding wheels on my turning tools when I have to do some major reshaping or profiling. I don't use them to sharpen ... just grind/profile. One of the major reasons is because of the hollowgrind that they give the tools. I don't like hollowgrinds, although many turners do.

An 8" wheel is just barely tolerable for me if I have no other choice so I'd replace it at 7" even for profiling chores. It's tough to get rid of that hollowgrind beyond that. Actually, I'd just use it for the garden tools and farm machinery grinding tasks instead of throwing it away. That way I can use it down pretty close to the bushing.

Eventually, you'll get the diameter of your wheel down to the point where, I'd think, the hollowgrind will interfere even with those that like it. And if you're a jig user, if you have jigs that are adjustable (not static ones where you can't change the angles to compensate for wheel diameter), then you could potentially still use that smaller wheel until it's simply worn away.

- Andrew

When you get to the plastic part!

But seriously, there does come a point when it becomes difficult to maintain your angles, I suppose, although I've not reached that point yet. Come to think of it, you do stand a better chance of getting one of your tools on the "downhill" portion of the wheel and having it catch, when your wheel is a smaller diameter. I think the main thing you have to contend with is just having a smaller surface to work with. And, bear in mind the smaller the wheel gets, the more quickly it will wear, because you have less wheel doing the same mount of work.

Um, unless I've got my physics backwards, the closer you get to the center of a spinning disk, the faster the surface is going by, so in order to maintain the same surface speed (why?) you'd have to turn the speed -down- rather than up, as your wheel got smaller.

When it takes "too long" to sharpen a tool or when you feel uncomfortable about sharpening on that itty-bitty thing! I don't know, I've got the same pink wheels I started with 2 1/2 years ago, on a 6" high speed grinder and they've got plenty of grind left in them. But, I tend to do touch-up honing with diamond stones a LOT more than I do grinding. I can bring back the edge in a couple of minutes and my tools seem to be lasting a lot longer since I stopped grinding so much. One of these days, when I have more space, I'd like to get one of those belt sanders and try sharpening with that. In the mean time, though, the honing and occasional grinding seems to work pretty well.

-- Chuck *#:^) chaz3913(AT)yahoo(DOT)com Anti-spam sig: please remove "NO SPAM" from e-mail address to reply. <

September 11, 2001 - Never Forget

I replace mine when using the Woverine Jig, the gouge starts to hit the side of the grinder motor. Yes, the jig allows me to move closer to the revolving stone, but after awhile I can't get the grind I want without bumping into the motor. Glenn Hodges Nashville, Georgia

70 degrees today

I guess that makes sense...if I took the tires off my rims, I'd have to step harder on the gas to go the same speed.

Well, I never >did< take physics.

-- Chuck *#:^) chaz3913(AT)yahoo(DOT)com Anti-spam sig: please remove "NO SPAM" from e-mail address to reply. <

September 11, 2001 - Never Forget

You mean there's suppose to be tires on those rims??!?!? I've got a yard full of my "antique" cars with nothing but rims ..... protected from the ground by various chunks of walnut under the anxles of course. No wonder I don't get anywhere quick. Dang!

I took it twice ... and failed all three times. But then sold my physics prof a software program I wrote a months later that described and demonstrated (virtually, of course) the creation and motion of particles in relation to waves. I didn't get retro-credit for that one though.

Anyway, I still can't really figure out how my car works and certainly not how to fix it. Hence the "antiques" in the yard.

- Andrew

This is either an incredibly ignorant question, or perhaps just a question of definition. At the risk of appearing stupid, what DO you use to sharpen your tools? I guess I'm assuming that those white or pink wheels are "grinding wheels." What's the skinny?

Max

Not a stupid question at all. I use a round sanding disk of MDF with Silicon Carbide sandpaper on one large flat side for *sharpening*. It's mounted on one side of the grinder (actually it's an arbor that's belt attached to a 1hp motor) and turning "away" from me. The other side of the grinder/arbor is an 8" grinding wheel for profiling. For honing, I use the other side (inboard towards the arbor) of the MDF wheel that has some profiles (coves, beads) and a large flat section. I also do a lot of honing with diamond paddles and cones. Not necessarily for the finer edge honing might give me but just because it's quicker, easier, and less messy.

The MDF on that side is coated with White Diamond honing compound. I make the MDF wheel myself instead of buying one of the commercial versions. I can't see spending $30US or more for it when mine is exactly the way I want it and for under $5US including sandpaper.

I have an MDF wheel also that I carry with me to demo's/shows/etc. that has a Morse Taper attached to it. Same setup but a little smaller. I can just pop it onto the lathe for quick touchups when needed. I don't have to carry any grinder or anything else when space and weight is at a premium.

I also do everything freehand... no jigs, no toolrest. I spend less than 5 seconds honing and less than 10 seconds sharpening each time. I use a lot of different tools on many of my projects and just don't want to take the time to reset anything. I don't hone everything every time.

If I have to, I will use a grinder at demo's/shows/or workshops but it's not my favorite thing. Most people use grinders for most of their turning tool sharpening so I have to teach and demo that. I end up fixing my tools afterward but that's just the price I pay.

In my world....

Grinding/profiling = Grinder = less than 5% of the time each tools' lifetime is used on it. Sharpening = Sanding Disk on MDF wheel = 40% Honing = Left side of MDF wheel = 56%

- Andrew

Actually, the RPMs stay the same, the surface speed per minute changes, getting greater as the diameter gets larger. Or lesser as the diameter is smaller. That's what he meant ;)

-- Steve Worcester

Better Woodturning through Technology (And a hell of alotta practice)

What grit sandpaper are you using? Do these discs last a while, or must you replace them often. Sorry for the flurry of questions, but sharpening is one area that could use improvement in my particular vernacular.

Max

120 to 180 grit. Remember, I don't grind/profile or hone on these. I just sharpen. You'll get an almost mirror shine with the 180 grits if that's something you're looking for. One the big one, the one attached to the arbor, I'll often have 2 different sandpapers on one MDF disk side. One is a larger diameter than the other so that part of the larger underneath one can be used too. The aluminum oxide and garnet sandpapers don't last as long as the silicon carbide ones. I replace the silicon carbide ones about every 2 weeks. I figure that translates to about 35 bowl gouge sharpenings. Of course, it all depends on how much you turn and need to sharpen. I turn about every day for at least a few hours. I use a crepe block on the sandpaper just as I would any other to prolong the life of them too.

Sharpening is a skill just like the turning itself. I has to be learned and practiced. If you're a member of some turning club and they don't do it already, I'd highly recommend that they put on a hands-on sharpening workshop. One of my clubs did that a couple of weeks ago and it went really well. It was all very informal. We had some different types of sharpening systems and people to help others to sharpen their own tools. We were completely maxed out on space and equipment all day long. We're planning to put it on in the fall too.

- Andrew

Thanks, Andrew. I'm sure that hands-on assistance during the learning process would be a huge benefit. Sadly I'm in an area with no clubs or organizations. I'm not doing badly on my own, but I'll wager my learning curve isn't as steep as it would be with experienced help around.

One more query, if you don't mind. What is your opinion/take on sharpening systems, such as Delta's 23-710 or 23-700? These appear reasonably priced. I simply can't justify the cost of a Tormek

Max

Max

Strictly speaking in relation to woodturning only....

For a minimalist, like myself, they're all completely out of line and unnecessary. Even for a more reasonable woodturner, they're just too "much" for what you want to do (I'm assuming a lot here).

First, forget wet grinding. Second, forget horizontal grinding.

I'll interject here that people have their own preferences and do perfectly well with all manner of things. I'm just relating my own experiences (as opposed to many others' opinions based on conjecture and "somebody I know...") and what I've tried before. I have never specifically used the Tormek or the Delta systems you listed. Like I said, I prefer to use something else entirely but I realize that most don't. So, with that said, I'll continue.

Wet grinding is just too messy (rust, water everywhere) and they never work right (water holes plug, balancing is always off) for the quick and often sharpening that woodturners deal with. Horizontal grinding is difficult to get used to; not easy to find jigs, toolrests, etc. for; and are really bad about forming coves/profiles in the stone (dishing) because they are too soft. Yes, you can make jigs, toolrests, etc. yourself and I did (for my Makita) but it's just too much of a pain to do that. Holding your tools to grind on these horizontal machines is awkward at best and nearly impossible to see your bevel AND grind at the same time. Just not worth it, in my opinion. I use my wet, horizontal Makita for many things but not my woodturning anymore.

Frankly, I would recommend just a simple Delta Bench Grinder such as the DELGR350. I recommend as wide a white/pink/blue, 8" diameter, aluminum oxide, around K hardness, 60-80 grit on one side/120 grit on the other wheel as you can find. Normally, it's a 1" wide wheel but you can find wider ones. "Wider is better" It's just simply easier to keep your tool (especially the bowl gouges and wide skews) on the face of the wheel this way. You'll be paying Don't bother putting on the stock toolrests either. Either make yourself one or buy a solid one that you can adjust well for each wheel. Use a multi-diamond "T" wheel dresser regularly to clean and flatten the wheels. Even this way, you're still spending far less and you've got a better setup.

- Andrew

What does one (demo to your club) have to do with the other (a webpage on sharpening) ?

- Andrew

This brings up a question. I am trying to decide whether to give a demo on setting up and using a grinder as sharpener for our woodturning club. Would it be worth it to people for me to do it as a web page? After all, IMHO just putting wheels on a grinder is not enough. To make it into a sharpener it needs to balanced and the wheels need to be round and the jigs need to be in place whether they be larger tables or something more elaborate. Any thoughts?

Ahhh, ok. I get it now. I think it's a good idea to take the pictures and do the write up in preparation for a webpage on it while you're at it. I mean, as long as you're going to be doing it anyway as practice for the upcoming demo, you might as well document it and stick it up on your site. Or videotape it.

It helps me to be able to run through it all before hand too. The cat is going to become a fantastic turner one day for all of the prepping demonstrations I've given him. Once he gets opposable thumbs, watch out!

- Andrew

Andrew I was not thinking so much of a web page on sharpening as a web page on setting up a grinder as sharpener. The connection with the club demo is whether I want to take the pictures and do the write up for a web page as I run through the demo beforehand for practice. I hate to do a presentation without preparation.

Many thanks, Andrew, and I can't tell you how happy I am to learn those wet systems aren't really necessary. I've saved this post for future reference.

Max