30 Mar 2008
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| Drastic Measures | |
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 Here is the same 1 1/4" chisel back after about two hours of flattening work. I tried several methods, coarse India oilstone, Shapton 320 grit glasstone and 800 grit waterstone. Progress was made but the amount of hard metal which needed removing was huge, due to the belly created by years of sharpening on a hollow oilstone. I was reminded of how much I dislike oilstones. The oil migrated up onto the top of the shallow chisel cross section and made a good grip almost impossible. I did not feel that the very coarse waterstone removed metal faster than my favorite 800 grit King Stone, though it was much harder and did wear much less. The whole sorry, frustrating business reinforces the good advice which I was given during my training. "Avoid bellied chisels like the plague". So, as this Pattern Maker's Long Paring chisel has lots of blade length, I decided to solve the problem by shortening it by 5/8". This was done in a few minutes with a heavy duty cutting disk in a Dremel. I cut in from both sides and snapped off the offending end when about a third of the blade thickness remained. The good part of the blade is clamped between hardwood pads in a metal working vice. The exposed tip is covered in paper towel to catch flying splinters, and given a good whack with a large hammer. The Dremel cutting disc worked very well indeed and created remarkably little heat, if used carefully. This rather drastic remodeling has worked very well and I now have a chisel with a flat or slightly concave back which will sharpen properly. There is still plenty of blade length for another couple of lifetimes. I wonder if anyone can suggest other solutions for the bellied back syndrome? Best wishes, David |
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| Sharpening | |
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| posted by davidcharl at 10:33 | comments [21] | |
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| posted by joel moskowitz [ http://www.toolsforworkingwood.com ] | 31 Mar 2008 at 03:11 |
Two solutions (maybe three): 1) Coarse diamond stone - works like charm. Don't use the same stone for flattening your waterstones it will last longer. 2) Kanaban plate and either diamond paste or 40 grit SC powder. SC powder breaks down under pressure and I saw Toshio Odate go from 40 grit sc to a flat mirror finish on a plane blade without changing grits in about 10 minutes. 3) Grinding back or trimming the chisel as you did is a reasonable option but Maurice Fraser suggested ignoring the part not flattened and if the wire edge didn't turn back when sharpening to use a burnisher to turn the edge. After a few sharpenings when the condition of the back caught up to everything else you obviously stop the burnishing. I don't know it it would make sense on your very out chisel, but when there is a tiny amount of unflatness in one corner of the chisel it saves oodles of time. BTW I don't think any of the methods you tried to be particularly effective if any amount of flattening needs to be done. - just too much work. joel |
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| posted by davidcharl | 31 Mar 2008 at 10:42 |
Joel, Thank you, I will try those methods next time this issue arises. The Burnishing technique sounds particularly interesting, seems somehow analogous to the 'tapping out' of a Japanes plane blade. Edit; Having re read Joels post I see that I completely misunderstood it the first time! But it seems unlikely to me that moving a wire edge around with a burnisher will result in a sharp edge. Mind you I have always done my best to avoid such convex tool backs! Shortening has also enabled me to get to a section of back with virtually no rust pits. As you know these can be surprisingly deep, and give one's edge a Gruyere Cheese effect. David |
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| posted by Philly | 2 Apr 2008 at 16:08 |
David I have been experimenting recently with a 12 inch disc samder to flatten the backs of irons that need serious metal removing. It sounds pretty awful but it is surprising how, with a delicate touch, you can quickly remove the worst offending areas, leaving a small amount of polishing to complete. When presenting the iron place the opposite end of the blade to the edge down first to prevent dubbing the edge. Hope this helps Philly |
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| posted by davidcharl | 2 Apr 2008 at 17:59 |
Philly, Thank you for that. Would be interested to see the results, perhaps at the Yandles Show? David |
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| posted by Gary [ http://toolemera.com ] | 3 Apr 2008 at 00:22 |
David We tend to think as woodworkers when thinking as a machinist can cut the labor. A trip to a local friendly machine shop would resolve the problem easily. Either surface grinding if the tool is valuable or a few minutes on a stationary belt sander fitted with metal cutting belts would to the trick. The thought of using a disc sander makes my hair stand up. One catch of an edge and metal could go flying in directions you really don't want. As an ex-rehab counselor, I have great respect for metal and powered equipment. When in doubt, make sure the tool is firmly held in a vise or other tool holder before presenting it to the moving belt or grinding wheel. You and your insurance company will thank you. Gary |
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| posted by davidcharl | 6 Apr 2008 at 10:23 |
Gary, I think that is very good advice. Philly is a skilled craftsman who will be well aware of the dangers, but this is not a method I would advise generally. This old Long Paring chisel would be very difficult, if not impossible to chuck on a surface grinder, hence my pursuit of hand methods. Another method which I would advise stronly against, is the use of the side of a Tormek wheel for any kind of flat side preparation. A student turned up a while ago, with completely ruined chisels. David |
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| posted by Mark | 20 Apr 2008 at 18:12 |
David, Many thanks for signing my copy of your latest book at the Yandles show. All of your books, articles and DVDs have been of great use to me. Mark White. |
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| posted by John Grossbohlin | 14 May 2008 at 00:56 |
This flattening job could be done with a mill file using the draw filing technique. The description in "A Treatise on Files" by Nicholson File Co., 1878 is how I learned to do this properly. To summarize, grasp the file by both ends and move "the file sideways across the work, after the manner of using a spoke shave." ... "when moved sideways, unless care is taken that the faces of the teeth present themselves, during the forward movement of the file, at a sufficient angle to cut, instead of scratching the work." With a bit of practice you can get a very flat surface that is also quite smooth, certainly smooth enough to clean up quickly with stones. Granted chisels are relatively hard, but with a sharp file and proper technique it works fine. Since this book is well out of copyright protection I can scan the description and send you a PDF copy if desired. Alternatively, there are a lot of copies listed in Google. Strip the obvious out of my e-mail to reach me. |
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| posted by davidcharl | 14 May 2008 at 16:52 |
John, Thank you. I tried a new file on an old draw knife, but it did not feel good. David |
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| posted by John A Grossbohlin | 21 May 2008 at 02:31 |
Filing hardened items, like flat and V-springs and tools, does take some practice and I agree it doesn't feel very good... My first experiences with this came while making parts for flintlock rifles at Colonial Williamsburg, VA. This as forged springs need "adjustment" after final hardening. The Early American Industries Association reprinted the Nickolson book in 1983 and I found copies during a Google search. I personally have one of the reprints that I bought in 1986. After my initial post I found the PDF version too. I've also used a blade sharpener, such as the Makita unit to flatten backs. It's water cooled so there is no risk of removing the temper. |
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| posted by jgourlay | 23 May 2008 at 22:06 |
I once got it in mind to own a complete set of Stanley 750 chisels, and thus faced your situation frequently. 2" wide bellied chisels are a sight to behold. If the chisel is narrower than my grinding wheel, I will orient and stroke the chisel parallel to the grinding wheel axis. If wider, I orient and stroke transverse to the grinding wheel axis. The point is to put a wide, shallow hollow into the chisel back similar to a Japanese chisel. Grind a bit, coat with blue marking fluid, and take it to the DMT black stone. When progress stops being fast enough, go back to the grinder. Use the grinder the same way one would use a fore plane: to remove the high spots. Done well, you end up with a nice flat back. Done poorly, you end up with a nice flat back with some inconsequential divots towards the middle. I find this method takes a task I despise and makes it not-so-bad. Deeply appreciate your videos, btw. |
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| posted by davidcharl | 24 May 2008 at 10:09 |
J, What a great application of engineering principles. Thank you for that interesting description. I have tried similar methods on small tools, like router plane blades and even traditional spokeshave blades. Your chisels must have taken much patient work. So pleased you enjoy the DVDs David |
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| posted by Metalworker Mike | 13 Jun 2008 at 11:32 |
Although I would probably use a surface grinder (there are ways to hold pretty much *anything* on a surface grinder), there is an alternative that would have saved you some chisel. How about just bending the end of the chisel down a bit? Clamp the end in a vise between some hardwood slips, and whack it with a mallet if you're the fearless type, or use offset slips of wood to press it to the shape you want using a vise. Either way, it should end up saving a lot of work and a decade or two of chisel life. Mike |
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| posted by mikeybabe | 8 Nov 2009 at 02:11 |
Hello David or who ever , I have purchased the DVD on sharpening one's plane blades and have ordered the recommended Norton stones. The 1000 4000 and 8000 grit. But I have not been able to track down this ( is it AGURA NEGURA or what ever the hell you said on the video. ) Unfortunately I was unable to hone in on the little label next to it to be able to read what it had to say. None the less. It is the synthetic one that I am after I THINK ??? The little chalky bobsy doo that crates the slurry on the 8000 grit stone. Can you point me in the right direction so I can purchase one and could you also tell me what it is called exactly. Kindest, Mikey |
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| posted by davidcharl | 8 Nov 2009 at 14:22 |
Mikey, The name is Nagura. You have two alternatives. A very reasonably priced one from Axminster Power Tools, or Norton's more expensive version from Rutlands Hope you suceed with the sharpening best wishes, David |
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| posted by Charles | 18 Jan 2010 at 17:49 |
Norton 60X sandpaper on glass makes short work of such projects. I've obliterated the worst of "bellies" on a chisel in less than fifteen minutes. |
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| posted by davidcharl | 20 Jan 2010 at 21:28 |
Charles, Thank you, that sounds most promising. Next time this crops up I will try it. best wishes, David |
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| posted by davidcharl | 21 Apr 2010 at 15:48 |
Thank you Lance, interesting method. Here, (Ihope) is the link which you had difficulty with. Restore chisel David |
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