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Thread: Sharpening pitfalls here?

  1. #1
    Join Date
    Jan 2019
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    Fairbanks AK
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    Sharpening pitfalls here?

    I finally have my sharpening jig ready. What I have been doing is letting all my KD hardwood purchases season in my shop for another year after purchase, and now I have stock coming out of the pipeline. My shop runs about +60dF and +/- 5% RH in wintertime, even lower target EMC for the few weeks it is really really cold here. Looking for -30dF again tomorrow night, it will probably get down to +50dF in the garage/shop and the RH will be low enough I don't trust my meter.

    I cut up a piece of Ash to make a ramp for my belt sander, and a piece of red oak for the radius. These ideas are in Leonard Lee's _Complete Guide to Sharpening_ (c 1995) and I know we have learned a thing or two in the last 25 years. The guide for putting radii on plane irons he illustrated on pp 81 in my copy.

    I have a bench grinder also, but added on a belt sander after reading up on sharpening a bent gouge in Mr. Lee's book. The next boat I want to build has a bunch of joinery in it, and I need a bent gouge sharp as all heck to shape the forefoot, so I am making stuff with corners on it and learning to sharpen on a belt sander.

    I see two areas that require particular attention.

    First, since all my plane irons are slightly different lengths I am having to hold them perpendicular to the sanding belt by eye, and free hand slide them side to side on my guide. But the metal guide that comes with my Kalamazoo 1SM (no affiliation, great product) is only attached on one side, so I have to check for square right regular.

    Second, I don't know yet how much the Ash ramp will move when the humidity goes up in April.

    Third, I haven't figured out how to polish flat backs with the belt sander yet.

    The most acute angle I can get is 28 degrees in wintertime, but there is some room at the lip to rise the tail of the ramp and dial in 30-35 degrees no problem. For now I have scrubs with 3 inch radius and 7 inch radius, but if I want a five I can rough it on the grinder and bring it home with the jig I have.

    Also, if you go down this rabbit hole don't bother with a leather stropping strap. It has way too much give and will round off your edge. Just get a smooth piece of hardwood a la Derek Cohen, put some rouge on it and use that in a vise.

    What else do you suppose I should look out for?

    20200210_205438[1].jpg

  2. #2
    Join Date
    Jan 2019
    Location
    Fairbanks AK
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    FWIW I am dealing with one of the most extreme climates in North America with summer time EMCs similar to Arkansas and northern Alabama, with wintertime EMCs that are jaw dropping. There is very very little surviving casework from pre WWII.

    https://en.wikipedia.org/wiki/Fairbanks,_Alaska#Climate

    Gold was discovered here in 1901. I know of two surviving pianos from the gold rush era, both are rickety pieces of junk. I surmise they were made in the lower 48, shipped up, and then all the joinery loosened as they dried out and shrank. We just have beans for casework from before 1945, though balmy Anchorage is loaded with the stuff. I am working with the local guys about how long to season my stock before I cut dovetails in it.

  3. #3
    Join Date
    Dec 2010
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    South Coastal Massachusetts
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    5,461
    Have a look at knife grinding sites. The unspoken pitfall is overheating any given piece of steel and losing the temper.

    Most of the Big Dogs that use a grinding rig do so to get irons ready for some sort of honing (including strops).

    FYI - the current crop of plane irons has excellent steel that comes with a hollow ground.

    https://www.theunpluggedwoodshop.com...en-corner.html

  4. #4
    Join Date
    Apr 2015
    Location
    New England area
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    233
    Quote Originally Posted by Scott Winners View Post
    I finally have my sharpening jig ready. What I have been doing is letting all my KD hardwood purchases season in my shop for another year after purchase, and now I have stock coming out of the pipeline. My shop runs about +60dF and +/- 5% RH in wintertime, even lower target EMC for the few weeks it is really really cold here. Looking for -30dF again tomorrow night, it will probably get down to +50dF in the garage/shop and the RH will be low enough I don't trust my meter.

    I cut up a piece of Ash to make a ramp for my belt sander, and a piece of red oak for the radius. These ideas are in Leonard Lee's _Complete Guide to Sharpening_ (c 1995) and I know we have learned a thing or two in the last 25 years. The guide for putting radii on plane irons he illustrated on pp 81 in my copy.

    I have a bench grinder also, but added on a belt sander after reading up on sharpening a bent gouge in Mr. Lee's book. The next boat I want to build has a bunch of joinery in it, and I need a bent gouge sharp as all heck to shape the forefoot, so I am making stuff with corners on it and learning to sharpen on a belt sander.

    I see two areas that require particular attention.

    First, since all my plane irons are slightly different lengths I am having to hold them perpendicular to the sanding belt by eye, and free hand slide them side to side on my guide. But the metal guide that comes with my Kalamazoo 1SM (no affiliation, great product) is only attached on one side, so I have to check for square right regular.

    Second, I don't know yet how much the Ash ramp will move when the humidity goes up in April.

    Third, I haven't figured out how to polish flat backs with the belt sander yet.

    The most acute angle I can get is 28 degrees in wintertime, but there is some room at the lip to rise the tail of the ramp and dial in 30-35 degrees no problem. For now I have scrubs with 3 inch radius and 7 inch radius, but if I want a five I can rough it on the grinder and bring it home with the jig I have.

    Also, if you go down this rabbit hole don't bother with a leather stropping strap. It has way too much give and will round off your edge. Just get a smooth piece of hardwood a la Derek Cohen, put some rouge on it and use that in a vise.

    What else do you suppose I should look out for?

    20200210_205438[1].jpg
    I'll be blunt, your post reads almost like parody. If it's not, you need a 6" grinder with a coarse stone, a combo fine/coarse India, and a finishing stone of your choice -- surgical black Ark, fine/ultra fine ceramic, or an 8,000 grit + waterstone. Some sort of strop would be handy, but it's not exactly a necessity. A brown Kraft paper sack or blue jeans will work.

    So, a grinder and two stones with strop optional. Use the sander for something else or sell it. In the long run you'll be happier with a hollow grind. Stunning furniture has been built with less.

    Can't help you with the humidity extremes. I'd talk to a good HVAC guy about heat and humidification/dehumdification. Letting already KD'd stock sit around for a year won't help as much as you think.
    Last edited by Charles Guest; 02-11-2020 at 10:08 AM.

  5. #5
    Join Date
    Dec 2016
    Location
    South West Ontario
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    953
    I have many different sized leather strops on wood, they donít round the edge over if used at the right angle and just 3 or 4 swipes on the front and 1 on the back. It is rather subjective, but when using a 10,000 grit stone the strop is very effective. Iíve tried wood as a strop but donít get the same edge improvement, I think the leather does a better job of presenting the honing compound to the blade edge.
    Long strops used for knives can benefit from many more swipes each side with significant edge improvement. I donít sharpen knives to 10,000 grit.
    ​You can do a lot with very little! You can do a little more with a lot!

  6. #6
    +1 on everything Charles said ^.

    Seems to me overheating is the biggest pitfall, especially with the finer grits. Personally I wouldn't touch one of my tools to a belt sander like this, but in sharpening, there are many methods that work well for different people.

    Because I hand sharpen, I prefer to hollow grind chisels and plane irons, which of course requires a bench grinder.

    I think a good sharpening system (non-Tormek) would consist of a bench grinder, coarse diamond plates, water stones for higher grit, strop for polishing.

  7. #7
    Join Date
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    Longview WA
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    First, since all my plane irons are slightly different lengths I am having to hold them perpendicular to the sanding belt by eye, and free hand slide them side to side on my guide.
    Instead of having a long ramp, maybe it could have only the area near the wheel above the rest of the ramp. The back of the raised area could work as a guide if a simple holder on the blade could be used as a fence side to side. It could be as simple as a couple of pieces of wood with screws.

    The most acute angle I can get is 28 degrees in wintertime, but there is some room at the lip to rise the tail of the ramp and dial in 30-35 degrees no problem.
    Changing the underside of your ramp to an angle instead of parallel would enable a more acute angle if you would want such. My paring chisels are mostly ground to ~15ļ.

    Third, I haven't figured out how to polish flat backs with the belt sander yet.
    Even with a flat spinning disk it is close to impossible to flatten the back of a chisel or plane iron, let alone polish it.

    This is easier to accomplish by hand on a piece of glass, tile, or a granite surface plate with abrasive sheets. When you get to 3-400 grit sheets move over to your chosen stones.

    Because I hand sharpen, I prefer to hollow grind chisels and plane irons, which of course requires a bench grinder.

    I think a good sharpening system (non-Tormek) would consist of a bench grinder, coarse diamond plates, water stones for higher grit, strop for polishing.
    A hollow grind does make hand sharpening much easier. Neither of my grinding wheels is all that great. They are both powered by carbohydrates.

    My hand sharpened chisels and plane irons have flat bevels as much as is practicable.

    For many years my preference has been water stones. One big problem in my shop is it isn't heated by anything other than a small electric heater which is only on when the shop is being used. Water freezes on cold days and nights. In wintertime my blades are mostly sharpened on oilstones.

    There is no one perfect sharpening system for every person's needs.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  8. #8
    Join Date
    Apr 2013
    Location
    Stone Mountain, GA
    Posts
    491
    I have the same Kalamazoo belt grinder, it's an excellent machine and useful for all sorts of things. I use it in place of the typical bench grinder, but IMO the setup needs a little tweaking. For someone who just wants to grind woodworking blades I would recommend the usual style of slow speed bench grinder.

    For woodworking tools I only try to use it as a rough grinder, not a sharpener. Typically I grind a 20 degree primary on the Kalamazoo with a 60 grit belt, and then hone a 30 degree secondary with oil stones.

    My first attempt was to use the table inclined at a 20 degree angle (similar to your ramp but just using the stock table) but I found that the belt piled up in front of the leading edge a bit and made it difficult to gauge the grinding progress. When grinding I try to take the primary bevel down as close as I can to the edge without hitting it, leaving just a hint of the old secondary bevel. The slight dubbing from the belt makes it look like you're closer than you really are. So I reversed the motor rotation and with the belt going up the dubbing at the edge is eliminated. I ended up installing a DPDT switch next to the on-off switch so I can change rotation easily. But with the belt going up now it is trying to pull the tool up the table and climb the belt; not stable.

    So I adapted a solution Derek Cohen had written about some years back for a different style of belt sander- a steel rod is attached to the platen bracket so that it extends across the front of the belt, parallel to the platen and about an inch away from it. A block of wood is attached to the blade, the projection of the blade from the block sets the grinding angle. The block rides along the rod and counteracts the upward force of the belt. Derek's writeup is here: http://www.inthewoodshop.com/Woodwor...rinderMkI.html. My concept is the same, even a little simpler, just adapted to the Kalamazoo.

    I just grind straight across on all my blades, but if you wanted to do a big cambered grind you could probably achieve it by making the front edge of the guide block curved to a concentric radius.

    As far as keeping the edge square, basically it's judged by eye. The steel rod setup helps but it is not made super precisely, and the machine is not that rigid anyways, so you have to compensate. Usually I am starting with a square edge, so I just check the work frequently and take a little more off of this side or that to keep the grind even. If I was starting with a wonky blade I would joint the edge first on a sharpening stone or sandpaper and then grind until there was almost nothing left of the jointed end.



    I dislike the idea of power sharpening with fine grit belts, especially with a relatively high speed machine and no coolant. I doubt you can avoid overheating the steel at the very tip with a 1000 grit belt no matter how careful you are. HSS turning tools are a different story, obviously. Coarse grit belts grind much cooler for the same amount of material removed. For normal carbon steel blades I recommend just using power to coarse grind, staying away from the very edge, and then honing on stones. Less fiddling and belt changes, and if you do the coarse grinding properly honing only takes a minute, literally.


    I'd give up on the idea of flattening backs with any sort of belt grinder. There's just too much give in a belt, the edges will always dub. The best setup for back flattening is PSA sandpaper stuck down on a flat surface like a granite surface plate. I use 80 and 220 grits then move on to stones for polishing.

  9. #9
    Join Date
    Jun 2010
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    twomiles from the "peak of Ohio
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    I used to get confused....at one time, there was a Guru of Sharp....saying there should be 4 bevels done to every edge tool?

    Some are "pushing" those super high grits on others, almost as if they were the ones selling such stones....

    Biggest thing I have found over the the years.....find a simple, easy to repeat routine, and stick with it.....

    Maybe instead of charging at the Windmills of the "Ultimate Sharp Edge"......just put the thing to work...and let it tell you when it actually needs a touch up...

    Remember...you can polish a butter knife until you can see yourself in the reflection...but, will it still just cut warm butter? A highly polished cutting edge does look very nice on a store's display case....real test is when it has to go to work...

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