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Advice on grinders – slow/fast, wet/dry?

Welcome! Forums General Woodworking Discussions Tools and Tool Maintenance/Restoration Advice on grinders – slow/fast, wet/dry?

This topic contains 13 replies, has 8 voices, and was last updated by  Dave Ring 1 week ago.

Viewing 14 posts - 1 through 14 (of 14 total)
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  • #615786

    Dave C
    Participant

    I’ve always sharpened by hand, considering a grinder of some sort for dealing with removing significant amounts of a plane/chisel blade.

    I recently dropped a plane blade after sharpening and put a big gouge in the tip, took over 3 hours on sandpaper/diamond to remove enough material to get it back to usable, so would rather not repeat that.

    I’d also like to restore some older (and much abused) chisels I was gifted, and again, would prefer to avoid spending hours on each one removing big chips/dents etc.

    I don’t know much about powered grinders though – for this sort of thing are wet or dry grinders preferred? How about low speed vs. high speed?

    Is something like a Tormek suited to that? Or is that more designed as a sharpening system?

    One final thing – it’d be set up and running in my workshop which is just a spare corner of a room in my house, so not keen any anything that’s going to send lots of sparks flying, or make a huge mess by spraying water everywhere, so I really don’t know what I should be looking for.

    Any advice/tips?

    #615826

    Sven-Olof Jansson
    Participant

    The Tormek T-8 with an additional shaping stone (SB-250 Blackstone), would do the job for you. It would of course also provide a sharpening system (in my humble: perhaps the best). As a solution it has two drawbacks: price and being comparatively slow at shaping (quick at sharpening, though)

    A friend of mine who is part of the maintenance, support and repair team at a gargantuan paper and saw mill, and who also is part of the plant’s fire brigade, recommended a belt grinder, as it produces far lower temperatures than a standard rotating grinder, no sparks, and won’t explode. He made the suggestion after having thrown an evaluating glance at the plane shavings on my workshop’s floor.

    In another thread, a grinding wheel that does not generate very much heat (or explodes) was mentioned. Unfortunately, I can’t remember neither the thread, not what the wheel was called.

    Sven-Olof Jansson
    London, UK; Cambridge, MA

    #615839

    Ecky H
    Participant

    A high speed dry grinder used with care is imho ok: cool the blade often with water, don’t apply much pressure.
    If the blade shows tempering colours as the visible sign that the steel loses it’s hardness, it’s not the end of the world. Just grind that part more carefully down.
    Here in Germany high speed dry grinders are much more common than (wet) low speed grinders and the second hand market is full of such grinders for a few Euros. I wouldn’t go below 150mm (6″) disc diameter, because the smaller discs are, the more distinct hollow the disc creates.

    But don’t underestimate the stubbornness of the grinding dust to prowl around and occupy every surface which isn’t vertically. Put blankets over the workbench, wood, tools and so on. When I have to use the power grinder, I put it on the foldable Workmate-like worktable and work outside.

    Hope that helps,

    E.

    Veni, vidi, serravi.

    Münster, Germany

    #615892

    Ed
    Participant

    Randomly ordered comments: I agree completely with Ecky H’s comment about dust from grinders, especially when dressing them. I regret the grinder I chose because there is too much runout and I’m pretty sure it is in the shaft, not a replaceable bushing. I have a sanding belt that I use for lathe tools, but it would not be good for hogging off chips: The belts I can get aren’t coarse enough grit and don’t last long enough (I’ve tried a supposedly 36 grit belt). That said, I think knifemakers take a lot of material off with belts, so maybe it is a matter of surface speed? In any case, a belt can throw sparks. That’s not to disagree with someone who says belts are less of a fire risk- I don’t know one way or another, but they can throw sparks. I was taught, if you use a belt sander for metal, never use it for wood. If you go the grinder route, learn how to ring a wheel. I’ve heard positive things about the Work Sharp sharpener, but have never tried or even seen one in person…not sure if it would be appropriate or not.

    #616073

    Dave C
    Participant

    Thanks for the advice all. I hadn’t heard of the Worksharp before, but I guess that’s another thing to consider.

    Having watched some high speed grinders I can see how the dust could get everywhere though.

    I’d be fine with slow shaping/grinding to be honest, as long as it’s quicker and less tiring than using sandpaper on glass I’ll be happy.

    The Tormek does look good, my only worry is that I’d be paying for a lot that I wouldn’t use (since I’d just be using it for shaping/grinding, not sharpening/honing really).

    #616234

    Scott V
    Participant

    I had a Worksharp sharpening system early on that I would not recommend. You sharpen (or flatten) on the top or bottom of a small 6″ abrasive disk, so the outer part of the wheel will grind (and wear) a bit faster than the inner part. You also do not evenly wear the entire abrasive disk while using the chisel port below, and sliding chisels up and down the chisel port ramp always seemed to add some fine scratches to chisel backs. There was a piece of tape there to help prevent that, but some swarf inevitably found its way in between. The cost of consumables (sand paper disks) really added up after a while. I found the whole thing to be a bit of a contraption, but it was a lot quieter than using a dry grinding wheel.

    Eventually I wanted a method that did not involve electrons, so I bought some diamond plates and was quite happy with Paul’s method. If I have to correct some tricky geometry, I might use a roller guide, but otherwise go freehand.

    Next time I have to flatten some chisel backs, or remove material fast, I would consider purchasing a really rough diamond plate, like a DMT 8″ 2X Diamond Stone.

    -Scott Los Angeles, California, USA

    #616474

    Sven-Olof Jansson
    Participant

    Hej Scott,
    I have not been entirely happy with my DMT stones. Using the xx-coarse one for re-shapening A1-steel plane blades is a slow process, and I wonder if diamond stones are better suited for A2-steel.

    Sven-Olof Jansson
    London, UK; Cambridge, MA

    #616529

    Larry Geib
    Participant

    In another thread, a grinding wheel that does not generate very much heat (or explodes) was mentioned. Unfortunately, I can’t remember neither the thread, not what the wheel was called.

    If it was a stone, the ones that run coolest are blue colored boron, followed by white oxide.
    One mistake people make is using too fine a stone. The only grinder I own now is a hand cranked model with a 36 grit stone on it. It’s hard to beat for removing metal.

    Sharpening is still rubbing on a diamond plates followed by either an Arkansas or 8K water stone, defending on the tool. And I swear the 8K water stone cuts the fastest.

    And knife makers like 2×72 belt grinders to shape and sharpen.

    The new hot thing is CBN ( cubic boron nitride) impregnated metal wheels. They are touted as the coolest running, and they don’t seem to wear out. A local knife maker, Carter Cutlery, has 2’ diameter CBN wheels made special. Large diameters run cooler because the CBN has a chance to cool down before it sees an edge the second time. In this video he starts with a CBN wheel, I think.

    CBN wheels were frightfully expensive but are coming down in price.

    #616782

    Sven-Olof Jansson
    Participant

    Of course it was Cubic Boron Nitride: Many thanks Larry!

    The belt grinders my friend uses are quite big floor standing machines. Having recently invested in a set of those water stones that don’t need be bathed before use, I think I’ll save the money and go for a slow rotating bench grinder.

    Related to that: does one need a lapping stone, or can sandpaper on a granite plate be used to keep water stones flat?

    Sven-Olof Jansson
    London, UK; Cambridge, MA

    #616785

    Ecky H
    Participant

    Before switching to diamond plates, I ground on japanese water stones (Shapton).
    Flattening on sandpaper works, but dulled my sandpaper relatively quick. Maybe the quality of the sandpaper I used wasn’t good enough.
    Then I read about another technique: just rubbing each other two sharpening stones. Works well if you keep in mind that the stones may have different levels of hardness (my 120 grit Shapton is much harder than the 320 grit).
    So I worked the 120 grit stone with the “sandpaper on granite plate” technique and the finer and softer stones with the 120 grit stone.
    But it’s necessary to often check the flatness within the process.

    E.

    Veni, vidi, serravi.

    Münster, Germany

    #617127

    Ed
    Participant

    A heads up about CBN, and probably diamond, too: Someone cautioned me that you should not grind soft steel and aluminum with CBN because it can clog the abrasive. On a regular wheel, there is wearing of the substrate that exposes a fresh surface and, also, you can dress the wheel. The CBN doesn’t allow this, so if you clog the abrasive, there’s little you can do. Has anyone else heard this and do you know if it is true? If so, it must apply to diamond plates. I’ve worked plane soles before without a problem as far as I can tell, so maybe it’s just aluminum?

    #617329

    Larry Geib
    Participant

    Yes, softer metals can clog CBN wheels. In fact, the Hurricane wood turning tools pdf on their offering states that only hard steels like HIGH SPEED STEEL be ground. A steel in that category would be A2 that the makers like lie Nielsen uses, for example, but not O1 like would be on ordinary Stanley plane irons. Another fellow adds V10, which is also a hard steel.

    http://www.thewoodturningstore.com/content/PDFs/Hurricane_CBN_Grinding_Wheels_Instruction_Sheet.pdf

    One fellow I know uses a belt cleaning rubber block to keep his unclogged and says it works. Norton makes a dressing stick like those that also has aluminum oxide, (Norton, 1X1X6 Type 54 Dressing Stick 38A150-Ivbej but I wonder how often you can do that. There are two types of CBN wheels. With one coating method, the CBN is electroplated to the wheel like diamond stones are. The other method is about a 3/16” thick layer of CBN in some sort of matrix. These can be dressed more often and is the type the video shows Murray Carter using.

    But again, this can be that you are using too fine a wheel to grind with. Large grit won’t clog as readily,removes more metal, runs cooler, and is faster. If you look at the video I posted, Murray Carter starts with a really coarse wheel to shape his knives. You can hear the wheel grinding. It’s not a sharpening wheel. In the video, he discusses that the wheel needs to be dressed.

    I have toyed with getting an old fashioned wet wheel which I see for sale from time to time. They take up a lot of room at a time when I think more about downsizing.

    #617460

    Jim Braun
    Participant

    I have been using a 180 grit Mega Square CBN wheel on a 3400 rpm grinder. A light touch works best. The 180 grit wheel shapes quickly, and from there I can go straight to the coarse ez lap plate.
    Jim

    Monmouth County, New Jersey

    #617510

    Dave Ring
    Participant

    What to buy?

    I’d go for a six inch 3400 rpm grinder with the coarsest wheel possible.

    Coincidentally, these are the easiest grinders to find and they usually come with a coarse wheel and a less coarse wheel, usually grey.

    I’d recommend buying a used one locally. (Decent new ones will cost upward of $100 and shipping will be expensive if you go the ebay route.) They are available everywhere, at least in North America. Check Craigslist and estate sales dot com.

    Baldor grinders are generally regarded as Top of the Pops but there is/was no lack of good makers. If it has good, solid cast iron tool rests it’s probably a good one. Otherwise, walk away.

    Dave

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