What is the best way to sharpen a bench mortiser chisel? I bought the Rockler cone sharpener and tried to match an older article from FWW to sharpen the chisel (hone the flats and sharpen the points with a diamond hone), however the chisel is still too dull and burns the wood. No matter how much I hone either the external flat sides of the chisel or the points using the cone the chisel stays dull. What am I doing wrong?
Thanks
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Replies
One thing to make sure of is the ralationship of the chisel to the auger bit; the auger bit should be just proud of the chisel and can vary depending on the wood being mortised.
I believe Lee Valley has honing instructions for their chisels. If you click on the Instr. link for their 1/4" Chisel & Bit on their WEBpage here: http://www.leevalley.com/wood/page.aspx?c=2&p=41702&cat=1,180,42334. This page also describes how the cones are used.
Regards,
Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
Bob,
Thanks for the Lee Valley links. I read the instructions and believe I followed all of the steps described. One thing is the points of the chisel don't seem very sharp after sharpening. I tested the drill bit part first and it bores a clean holes without tearout so I know it is the chisel. This chisel has been used for a few projects now but did not start burning the wood until recently. Now no matter how much I sharpen it the points just don't seem to be very sharp. Could I have tempered the metal from previous burning of the wood and rendered it unusable? If so, how can I recover it?
Mortise chisel grinding cones come in different cone angles. If you've sharpened the chisel, but the points aren't sharp, it could mean that the grinding cone you have is not the right one for your chisels.
-Steve
This may be, but I have a Shop Fox bench mortiser that is about 6-7 years old so I'm not sure what sharpener will fit it. The cones seemed to mate properly with the chisel corners while sharpening.
I don't understand how the chisel could be burning the wood. If it is getting that hot you have a waste clearance problem or a problem with the auger rubbing the chisel.
................................................
Men will never be free until the last king is strangled with the entrails of the last priest.~ Denis Diderot
I don't really understand it either. I noticed this past week that while mortising the holes I smelled burning wood, and the finished square hole was square but required a good bit of clean-up around the edges.
I sharpened the boring bit and used the cones to sharpen the chisel, but the result was the same. To check the boring capability of the drill bit, I set the drill bit about 3/8" inches protruding below the chisel, and the drill bit bored a very clean hole in the wood. I then returned it to the normal setting, and the chisel part would not penetrate the wood without a lot of force from the machine arm. I suspect that the points are not sharp enough to penetrate the wood so the drill bit is just spinning after boring and burning the wood. So if that is the case, how do I sharpen the chisel? BTW, I have a Shop Fox machine from 2002 so I've emailed for tech support on the inside bevel angles to see if they match the Rockler cones. I suspect they won't know this so I will be faced with having to purchase another chisel.
If I remember right Lee Valley sells a set of diamond cones that fit the angle of the Shop Fox. It's not just the corners that need to be sharp, the entire chisel must be sharp.
................................................
Men will never be free until the last king is strangled with the entrails of the last priest.~ Denis Diderot
I set the drill bit about 3/8" inches protruding below the chisel, and the drill bit bored a very clean hole in the wood. I then returned it to the normal setting, and the chisel part would not penetrate the wood without a lot of force from the machine arm.
I think the beginning of your pursuit lies in the above. The right setting for the set your using is somewhere between 3/8" (too much) and normal setting, (whatever that is).
Oh, and when testing I'd recommend using a soft wood. If the chisel won't cut cleanly through soft woods............ The chisel is cutting/paring its way through end grain. You want the bit to remove just enough material so the chisel has enough left so it can shear away the fibers, but not take too much so the chiseled edges become ragged.
Also, honing these chisels is not the same as one would hone a plane or bench chisel in terms of how frequently done. A properly set and honed hollow chisel mortising bit set should provide good service for several years, maybe more.
Regards,
Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
Edited 4/27/2009 6:40 am ET by KiddervilleAcres
Edited 4/27/2009 6:46 am ET by KiddervilleAcres
I set the bit purposely that far to check the hole boring capability; it is not set that way normally.
Looks like the smaller LV cones are no longer on the website, though they're still in the printed catalogue. The instructions are confusing. I've had the small set for years, and the bumf that came with them suggested that one cone was for honing, the other for giving a micro-bevel, which was needed to strengthen the corners. Frankly I can't tell them apart, but use them willy nilly more in hope than in faith. The grit on both looks identical, and there's no marking on the cones to give guidance.
The large cones have 2 different grits. Perhaps the finer grit one has a slightly different bevel on it, but the instructions don't make that clear. At least it's easier to know which one to use first. The small set seems to fit the chisels that came with my SC. I used them on the chisels out of the box, and haven't had any problems with sharpness.
Jim
Thanks Jim,
I thought I might have been daft but I was also confused with the instructions. Sure glad the honing exercise isn't required very often, still waiting on the first time with them.
Regards, Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
This article may help. Burning is usually a sign that either the drill bit is dull or not set properly in the chisel. Since the hollow chisel only works as a paring tool, you need to get it very sharp and don't force it faster than the chips get cleared. Standard angle is 60 degrees. http://blogs.popularwoodworking.com/editorsblog/Hollow+Mortise+Chisel+Tuneup.aspxBeat it to fit / Paint it to match
"So if that is the case, how do I sharpen the chisel? BTW, I have a Shop Fox machine from 2002 so I've emailed for tech support on the inside bevel angles to see if they match the Rockler cones. I suspect they won't know this so I will be faced with having to purchase another chisel."You don't have to give up on your chisels just yet. The bevel on my Harbor Freight chisels was also different. I chucked the rougher Rockler cone in the drill press (on a very slow setting). Then I clamped the chisel under the cone and went to town. I machined the bevel until I got a burr all the way at the top of the points. It probably took 10 minutes. When I finished, and honed the outside, it was razor sharp and has stayed sharp for a long time. If my HF chisels can do that, surely your Shop Fox chisels are capable of it.As far as the burning, I think the other guys are right about it being a chip ejection issue. If the chips don't shoot out of the slot, they churn around inside and just get hotter and hotter. It's a good idea to smooth the inside of the chisel with some sandpaper wrapped around a metal shaft, chucked in a hand drill. Doesn't take long and makes a big different.I also occasionally spray the chisel with some lube to cut down the friction.Best of luck
David B
Edited 4/27/2009 10:30 am ET by davidbrum
Another thought: If the drill doesn't run concentrically in the chisel it will heat and burn. That would also inhibit chip ejection. Setting the chisel/bit depth is easy. Just space the chisel down the thickness of a penny. Install the bit so it is slightly (1/16 or less) protuberant from the chisel. Then reset the chisel so it bears directly on the gizmo that holds it.
Done!!
Stef
Marc, at http://www.woodwhisperer.tv did a great podcast about cutting mortices with a HCM. He address the problem of clearing chips, he uses a type of release spray, to help clear debris. He also talks about causes of burning.
Taigert
I don't understand how the chisel could be burning the wood. ??
I thought they ALL did that!
But the woods I use are kind of hard.. Hell, I can burn up a router bit on some Jatoba or Purpleheart!
OK, please slow down just a wee bit. Seems like yer shootin at a lot of variables here. I have a ShopFox HCM machine, 1671 methinks. Proper setting of the bit can make a world of difference in how the chisel performs. If it's set too shallow (closer to the chisel tips) it leaves too much wood for the chisel to remove. Thus the difficulty, read resistance. If set too proud then chips can get clogged in the chisel and cause it to overheat. There's a lot going on there.
I'm no metalurgist but tempering a hollow mortise chisel might lead me to buy another set, but that's just me. I look at it this way - time is, well, time. If you do decide to replace, I would give serious consideration to the Lee Valley sets. They are REALLY SHARP right out of the box and work on my ShopFox 1671.
No I'm NOT endorsing them but I will attest to their sharpness. Please don't ask me how I know this. :-)
Steve is right about the cones, but I believe LV only makes two of them, small and large; presumably for large and small chisels as they don't say when to use one vs the other. Your call I guess.
Regards, Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
Mortise bits have traditionally been very difficult to sharpen, requiring precise hand filing or honing due to the lack of appropriate honing tools. These diamond cones have been made to match the bevel as supplied by the manufacturer. The Conical Sharpeners (77J81.20) go with the chisels for the Delta Mortising Attachment (04J10.16+), while the Large Cone Sharpeners (77J81.22) match the size range and geometry of the Japanese-made Premium Hollow Mortise Chisels (04J11.04+).
Could you also clarrify usage/application of the two different sized cones? What I'm asking is; do the large and small cones have any recommendations as to which size they be used on? Or can you use either one on any of their chisels.
I may have missed something in Lee Valleys documentation and would like to add more sizes of their chisel sets. I bought both sized cones thinking that the small cone is used for the small chisels, large cone for the bigger chisels. Now I'm thinking that purchase might have been silly as both cones present the same angle to all bits.
Also, I have yet to use the cones; haven't needed to with these bits. I'm concerned about runout on my drill press. I should think that any runout in a drill (press) wold reak havoc with HCM bits.
Regards,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
Hi Bob,
The cones sets from Lee Valley come with the proper angle for their Japanese style chisels. The two cones in a set should have the same angle. The difference is that one cone has 180 grit and the other has 320 grit. For coarse and fine honing of the inner bevel. I have a set, they work well.
Bob, Tupper Lake, NY
Bob ,
I have a set of cones from Rockler that will do my 3/8 and 5/8 bits , I need to get one for the 1" bit. For the ones I have I just lap the sides of the chisels by hand then put them in a vice and use the cones with the screw driver handle they came with , works quite well . IMO the trick is to tune up chisels before performance degrades to where a drill press is needed.
I must say the quality of the chisels is paramount, I have no Idea what type I have as they came with the machine. I do know that they appear to be well made as they hold an edge quite well .
As for the cone sizes I do not think the smaller cones will work in the larger chisels as the diameter dose not let the cone reach the points on the chisel, Just my guess.
Tom.
If the chisel is burning the wood, it has probably lost all it's temper and that's the reason it will not stay sharp. Once the drill bit or the chisel turns blue, it will never perform well again unless you know how to re-temper it.Howie.........
Fortunately the chisel nor the drill bit were blue, and I was able to get them sharp with the Rockler cones and a fine file. I had never honed them out of the box so I guess I was lucky to have them stay sharp as long as they did.
Forrestgirl was working on this last year I think. Can't remember what she came up with. FG, you out there? Tom
OK - will give this another try and follow up. I heard from Shop Fox that the bevel angle is 60 degrees, and the Rockler cones are 60 degrees so I don't think I'm raising enough of a burr to sharpen the chisel. I did check the boring capability of the drill bit and it cuts a clean hole so I'm not convinced that the bit is dull; still suspicious of the chisel itself because the four points don't feel very sharp to the touch.
"...still suspicious of the chisel itself because the four points don't feel very sharp to the touch."
That definitely doesn't sound right. I've learned to keep my fingers away from the points of the Lee Valley mortise chisels that I have, as they very easily draw blood.
-Steve
because the four points don't feel very sharp to the touch
Ok, if that's the case then they're dull. Mine are so sharp (from Lee Valley) that your eyes will bleed just looking at them. Yeah, that's an exaguration but they will prick your finger almost just by touching them.
Regards,Bob @ Kidderville Acres
A Woodworkers mind should be the sharpest tool in the shop!
You're on the right track. The points should be sharp as needles.David B
Sounds reasonable. If you have a subscription to the FWW website, Roland Johnson did an article (and video too, I think) about sharpening mortising chisels and bits. You may want to give that a look. Tom"Notice that at no time do my fingers leave my hand"
Yes - I have the subscription and reviewed that again last night before trying to resharpen.
Success! I used the drill press and coarse Rockler cone with more applied force this time and drew burrs on all 4 of the outside faces. I then removed all the machining marks with a 250 grit paper and repeated the drill press work with a fine Rockler cone before rehoning the four burrs of the chisel with 1200 grit paper.
I also sprayed the inside with Boeshield and I used a penny to set the spacing of the mortise chisel and drill bit (+ 1/16") and the cuts look great. They are actually cleaner than they ever were so now this means I'll have to hone all of the other chisels in the set before using them. So I'll get my money's worth for the Rockler sharpener.
Thanks for all the great feedback on this problem
Good deal! I've got the Rockler cones, but haven't used them yet. Glad to know they work well. Tom"Notice that at no time do my fingers leave my hand"
If the mortiser chisel won't sharpen, Then it ain't gonna work will it?
What about drill bit sharpness, chip clearing, bit clearance?
Beats me how the downward friction of a square bit would cause burning.
I'd suggest that there's something else wrong.
Eric in Cowtown
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