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Thread: A Couple of Blade Grinding Jigs
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29th October 2006, 04:33 AM #1
A Couple of Blade Grinding Jigs
1. Flattening the back of a blade.
I always find flattening the back of a back a real pain in the whatsit. This includes both chisel and plane blades … blades that are either rounded or pitted. My strategy to date has been sand paper on glass.
I had in mind a blade that I wanted to use in my Spiers infill smoother. It had potential but was pitted on the back near the edge of the blade.
What I have now done is to basically create a surface grinder out of the disk sander section of my belt sander combo.
Sanding disks are all easily and quickly swapped over since they are Velcro backed. The sequence begins with 120 grit, moving to 240, 320, 600 (25 microns) and 1200 (9 microns). This is then polished on a leather strop disk with Veritas green rouge (.5 microns).
The idea for using the disk sander only gelled when it occurred to me that I could use the magnetic base of my Dial Gauge to hold blades securely against a fast spinning disk. Note that the right side of the sander is used so that the disks do not turn into the blade (since the 600 and 1200 could tear).
<center> <div><img src="http://i13.photobucket.com/albums/a262/Derek50/Articles/Flattening%20backs%20of%20blades/Bladerestoration5.jpg" border="0" alt="" /> <br /></center>
<center> <div><img src="http://i13.photobucket.com/albums/a262/Derek50/Articles/Flattening%20backs%20of%20blades/Bladerestoration4.jpg" border="0" alt="" /> <br /></center>
This worked extremely well. I have successfully flattened several plane and chisel backs. Contrary to what I expected, the blades do not heat up much. In any event, I dunk them frequently in water.
I was able to purchase disks up to 320 grit. The 600 and 1200 I made by gluing wet-and-dry paper on an old sanding disk.
<center> <div><img src="http://i13.photobucket.com/albums/a262/Derek50/Articles/Flattening%20backs%20of%20blades/Bladerestoration3.jpg" border="0" alt="" /> <br /></center>
The leather strop is a piece of chamois leather stretched and contact glued to another sanding disk.
<center> <div><img src="http://i13.photobucket.com/albums/a262/Derek50/Articles/Flattening%20backs%20of%20blades/Bladerestoration2.jpg" border="0" alt="" /> <br /></center>
Here is a result on a blade that was, as I stated earlier, quite pitted.
<center> <div><img src="http://i13.photobucket.com/albums/a262/Derek50/Articles/Flattening%20backs%20of%20blades/Bladerestoration7.jpg" border="0" alt="" /> <br /></center>
And finally the Spier planning a piece of Grey Gum (this has got to be the one of the most difficult woods to plane – unbelievable constant reversing and interlinked grain in a very hard wood).
<center> <div><img src="http://i13.photobucket.com/albums/a262/Derek50/Articles/Flattening%20backs%20of%20blades/Bladerestoration8.jpg" border="0" alt="" /> <br /></center>
2. Building a dovetail chisel
In a recent post Mike on WoodNet showed off his Blue Spruce dovetail chisel. Damn, I want a set!!
<center> <div><img src="http://i13.photobucket.com/albums/a262/Derek50/Articles/chiselscocobolo_lg.jpg" border="0" alt="" /> <br /></center>
Len noted that the side angles were hollow ground. This was one of the features that I found so attractive and had been giving it a little thought as I had been developing a design on rolling my own.
What I have here is the jig I built to hollow grind the sides.
Basically the idea is to use my high speed grinder. This is a 6" machine set up with the Veritas grinder rest and a 60 grit white Norton wheel. While I freehand hollow grind blades, such as those for my Gordon planes, I also have the Veritas blade holder, and I thought that I could press this into service as part of the jig.
I planned to set the side angle at 30 degrees on the practice chisel. To do this I used a Tormek angle setter (no, I do not own the Tormek - just the protractor). It is very useful.
<center> <div><img src="http://i13.photobucket.com/albums/a262/Derek50/Articles/Dovetailchiseljig-settingupgrinder.jpg" border="0" alt="" /> <br /></center>
The jig itself is very simple - just a piece of hardwood into which are set a few rare earth magnets. A section of thin steel acts as a fence for the edge of the blade. It is loose to allow for adjustment, and held firm by the clamp of the Veritas blade holder.
<center> <div><img src="http://i13.photobucket.com/albums/a262/Derek50/Articles/Dovetailchiselgrindingjig-sequence.jpg" border="0" alt="" /> <br /></center>
Note that the jig is inserted upside down here for visibility.
It is used like so ...
<center> <div><img src="http://i13.photobucket.com/albums/a262/Derek50/Articles/Dovetailchiseljig-grinding1-1.jpg" border="0" alt="" /> <br /></center>
Here is a before ..
<center> <div><img src="http://i13.photobucket.com/albums/a262/Derek50/Articles/Dovetailchiseljig-chisel1.jpg" border="0" alt="" /> <br /></center>
.. and after ..
<center> <div><img src="http://i13.photobucket.com/albums/a262/Derek50/Articles/Dovetailchiseljig-chisel2.jpg" border="0" alt="" /> <br /></center>
So the practice chisel seems to work quite well. But I couldn't proceed beyond this point. To my great frustration I only then discovered that the grinder's body projected beyond the 6" wheel and prevented the chisel body being ground in the opposite direction. I shall have to wait until I get a 8" wheel for the machine. So there we wait ..
Regards from Perth
Derek
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29th October 2006 04:33 AM # ADSGoogle Adsense Advertisement
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29th October 2006, 07:55 AM #2
I like that way of flatterning the backs.
But are you shore the result is flat......I know it have to be pretty close...... but whats stopped me from trying similar before, is the spongy velcro that holds the disks on........Does it slightly hill the blade at the corners ?.....uno, just a little daylight at the corners when rulers on .
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29th October 2006, 12:02 PM #3
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29th October 2006, 12:04 PM #4but whats stopped me from trying similar before, is the spongy velcro that holds the disks on........Does it slightly hill the blade at the corners ?..
Very fair question. In fact, my concern about keeping the blade flat was the reason I avoided using the disk sander before. However, the dial indicator base is very substantial and holding the blade flat is quite easy. I make sure that the bevel area goes on last and comes off first. The scratch pattern tells me that I am getting an even grinding. If you want you can finish off with sandpaper on glass or a waterstone. The disk sander then will just do the donkey work.
Regards from Perth
Derek
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29th October 2006, 09:03 PM #5
Hi Derek.
Sounds like nothing to worry about then.
Thanks for sharing the ideas Derek. That magnetic board idea in the jigs looks clever too.
I might pinch that idea, if you don't mind. Can see how it would grip any thin blade easily too....like uno jointer and thickness blades. small blades too no doubt.
Maybe attach a small fence in behind the row of magnets though to keep the blade square....?
My normal jigs require a clamp that extends over both sides of the blade....make its difficult sometimes because the clamp has to be kept thin to stop it running foul of the grinder wheel......but with the magnets, it looks like I won't need support from the underside of the blade, which should give more clearance....and more options. Simplifys things.
Still amazes me how reliable those magnets look (still haven't had any experience with them).... are you shore there isn't a little play ? I mean, does the occation bump shift the blade about on those magnets....cause I can't have that happening in a grind. (if that makes sense)
Goodluck with your chisel.
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29th October 2006, 09:31 PM #6Maybe attach a small fence in behind the row of magnets though to keep the blade square....?
There is already a fence - that is what the thin steel plate is for. It is just thick enough to support the chisel edge and thin enough to go under the clamp (which has a limitation for thickness).
Still amazes me how reliable those magnets look (still haven't had any experience with them).... are you shore there isn't a little play ? I mean, does the occation bump shift the blade about on those magnets....cause I can't have that happening in a grind. (if that makes sense)
Regards from Perth
Derek
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29th October 2006, 10:01 PM #7
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29th October 2006, 10:37 PM #8.
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Some good ideas Derek.
I made a slightly hollow ground sided chisel from a 6" triangular file. The sides were hollow ground by accident when I was grinding off the file teeth. Although the sides are not deliberately sharpened I have still sliced my fingers a couple of times with it. The chisel itself is quite hard and takes longer than usual to work up a burr but it stays sharp for a long time so it appears to be good steel.
Cheers
BobL
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30th October 2006, 03:56 AM #9GOLD MEMBER
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Good idea Derek, I have a couple of chisels I might try that back-flattening on...
Are you holding the mag base to the sander by hand or clamping it? I imagine that it could get fairly thrown around the workshop if things went awry. ?
woodbe.
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30th October 2006, 04:08 AM #10
Hi Woodbe
The dial gauge base is quite heavy and the magnetic force it exerts is high. Once attached, the blade is not going anywhere. It gives me the control to hold it against the disk manually. Just make sure that you approach the disk as if you were going to set the blade doiwn flat all in one go, but then set the tail end down first and the bevel end last. When you lift it up, remove the bevel end first.
Regards from Perth
Derek
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30th October 2006, 02:05 PM #11GOLD MEMBER
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Like the idea very much Derek.
Have seen pix of those dial gauges before but not sure what they are usually used for, where to get them and how much.
Thanks for a good idea.
Bob
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30th October 2006, 04:57 PM #12GOLD MEMBER
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You can probably get them at bunnies. Hare and Forbes sell them too.
http://www.hareandforbes.com.au/samp...orking/36.html
woodbe.
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30th October 2006, 05:33 PM #13Senior Member
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Great idea for hollow grinding the bevel edges on chisels, Derek I think I'll pinch that one - I find the bevel edges on chisels are often unsatisfactory. Thanks for sharing your idea
Cheers
Paul
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30th October 2006, 08:31 PM #14
Damn, now I will have to get a disk sander combo :mad:.
Great ideas Derek, and thanks for sharing them
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30th October 2006, 09:33 PM #15
Hey Derek,
I've got a Makita (planer) blade sharpener that is fantastic for flattening the backs of blades. See HERE
Because it's a water stone the finish is remarkable without the effort of a stationary stone. The only problem you might (will) encounter is practice. You need a little practice to be able to get an even mirror finish.
Without downward pressure on the blade, it actually aquaplanes and doesn't grind any of the blade. This is very handy when you come to pull the blade off the stone for inspection, just reduce pressure until the blade aquaplanes & then remove as you describe. The original unit comes with a 1000 grit stone & there is an optional 6000 grit stone that is available.
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