Chisel back flatness……?

Re: Chisel back flatness……?

Jim in Burlington On

>1" of mirror is lots for me. I do flatten the rest just don't polish it.

Re: Chisel back flatness……?

arw01

>Rob Cosman, in his class, had us flatten a couple of inches up the back. He also taught us a great trick to see if the chisel was truely flat.

If you have long flourescent tubes in your shop, hold the chisel so the tubes enter from the socket end and angle off the edge of your sharpened end. So diagonally.

Observe if the reflection of the tubes exists perfectly straight, or takes a bend link a curved mirror. Even a slight amount of bed tells you that your chisel back is not perfectly flat. I spent a GREAT deal of time in class correcting mine from poor flattening methods including scary scarp.

If this is confusing, maybe I could get a photo of flat and not flat.

Alan

Re: Chisel back flatness……?

Mike-in-Michigan

>This subject always starts a war but here goes ...

A sharp edge is just that -- the meeting of two planes at an angle. You need a flat back to get a straight edge at the point of intersection, hence a flat edge will function easier and be sharper. If you have a 0.050 bow in the chisel back or a big side-to-side dish, yeah you need to fix it, but if it's within a few thou of flat and dead flat near the time .. it's fine. Look at Japanese Chisel - they have a dished back by design - no more than a 1/4" is flat. Some will note that the edges are in the same plane, but how often is a chisel laid flat where more than the first 1/4-1/2" of the back touches the wood?

So if you've got the first 1/4-1/2" flat on the back and a flat bevel you have a sharp edge -- that simple. A Chisel cuts on that edge (intersection), any more flatness is basically so it registers against the surface of what ever you are cutting. This might be marginally more necessary if you are paring but still how many 1" or greater depth of cuts will you get on any chisel cut -- none is the right answer. Even on a long chisel you still have to be in at an angle. Choping is about 1/4" max is depth.

IMNSHO -- all this talk of getting mirror finishes to 1/4 wavelength of cadmium light and such is a waste of time by folks who probably measure wood to 0.0010 of an inch ... we are looking at precision here not accuracy .. As long as the edge is sharp from two flat planes meeting, and you keep it that way you've got repeatable precision. If you have sharp flat edge and can get a good cut -- quit wasting your time worrying about looking at your reflection and go build something. Flatten the sucker close on a good flat stone ... shape and set the bevel .. make sure the two planes intersect at a flat edge, maybe put on a micro bevel so you can sharpen faster next time. Then don't sweat a 0.0005 shaving from an 0.0002 shaving. The wood doesn't know the difference and you won't see that if the humidity changes 5% anyway, the wood moves!

Re: Chisel back flatness……?

Pam Niedermayer - Austin, TX

>Look at Japanese Chisel - they have a dished back by design - no more than a 1/4" is flat. Some will note that the edges are in the same plane, but how often is a chisel laid flat where more than the first 1/4-1/2" of the back touches the wood?

Actually, all the time, certainly every time I pare. Now I'm not one for inserting excessive precision in woodworking, but a flat back isn't excessive.

Pam

Completely flat?

Bob Hackett

>How does that explain the fact that true slicks,which were only used for paring,were always made to have some rocker to them(a back convex in one plane)?

Scrapers used in the machinist trade were also used to make metal sufaces dead flat to very close tolerances and they had both a hollow back like a japanese chisel and a pronounced curve that usually ended in a sharply pointed end.These were used more like a leaf plane than a conventional wood chisel.

If you know where the high spots are and how high they are and your control with the tool is there then you only need a relatively short area if initial flatness as long as the rest of surface of the tool rises away from whatever you are working.

If you`re going to use the back of the chisel as a jig to try to ensure flatness of the area being worked then the entire back has to be flat.

It all depends on your method of work and skill set.

Mainely,Bob

What's a Leaf Plane?

Todd O. Cronkhite Maine Native in FL. Exile :~(

>

Re: What's a Leaf Plane?

Bob Hackett

>The best thing I can say is to look in the archives there Todder.I could try to explain but I`d probably just confuse things further.

They look like a flat crooked knife and are great for all sorts of things,texturing being one I favor.If you want,when Dr. Death comes over,I can forward a pic that Manny Hernandez was kind enough to send me of one he made.

WARNING-Knowing your fondness for big chisels you`re going to want one when you see it.

Mainely,Bob

Re: What's a Leaf Plane? *LINK*

Pam Niedermayer - Austin, TX

>You can do an internet search on yariganna or yarikanna, more than you'd ever want to know. :)

The yariganna was the first Japanese woodworking plane, the precursor.

Pam


Yariganna

Re: Completely flat?

Pam Niedermayer - Austin, TX

>My Japanese slick doesn't have a curved back, nor do any of my western slicks (Witherby, Mix, Barton, Buck). Often a chisel will have a slightly curved shaft, the most visible effect being that it sits flat on the bench. I'm not saying that slicks weren't curved, just that I don't have any.

Don't know much about tools to make metal flat. The yariganna/yarikanna (leaf plane) is used a different way from chisels and planes, in a shearing action from one of the sides, which are the cutting edges.

I'm also not saying that it's impossible to do good work with curved backs, nor am I saying that greater skill is involved one way or the other; but I am saying that it's easier to get a linear, flat surface with a flat back.

Pam

Re: Chisel back flatness……?

Arw01

>The "dished back" on all three of my Japanese chisels (including a $56.00 mortise chisel that I asked Japanwoodworker to return TWICE now, and no response either time) were all arced from heel to toe of the chisel. Laying them on a square showed enough .001's to cause the chisel to not go to the same place twice depending on where in the arc it is.

I've seen how .004 in a joint shows up across the room. I work to below .002 so the joints don't show. With old stanleys and a couple sweat equity japanese chisels.

Re: Completely flat?

Joe Rogers, Northern Virginia

>Pam, your chisels are probably large framing chisels not "slicks". JR

I don't think so, they all have slick type handles

Pam Niedermayer - Austin, TX

>

Re: Chisel back flatness……?

Moses Yoder in White Pigeon, MI

>I think a straight chisel back is important. It helps me when paring, because my eyes use the line of the chisel to determine whether the chisel is being held at the right angle. The only part of the chisel back that needs to be polished in order to have a sharp edge is a very small point; perhaps .001" from the tip. But I cannot figure out how to polish just the very tip of the chisel and still have the back of the chisel straight. I usually sharpen a chisel by polishing the back first. I use a piece of 1/2" plate glass and silicon carbide sandpaper, and move the chisel across it, held flat, putting pressure at the tip. This method usually ends up polishing an inch or two up the back of the chisel. If the back is dished, I end up polishing a 1/4" or so from the tip, but the outside edges get polished an inch or two up the back.

Re: I don't think so, they all have slick type han

Joe Rogers, Northern Virginia

>If you mean that the handles are removable socket type, some timberframing chisels are made that way too. If they allow the chisel to be steered while the handle is up under your armpit then I may be "under informed" :-)JR

Re: I don't think so, they all have slick type han

Pam Niedermayer - Austin, TX

>IIRC (some of them are packed up for the workshop rebuild), they all have long, long handles with no hoops or leather on the ends.

Pam

Re: slick type handles *SLICK PICS*

William Duffield, on the Cohansey

>What makes a slick a slick is not the handle, so much as the angle of the socket in relation to the back of the chisel. Handles are replacable, and adaptable.

For example, I managed to push a marginal paring chisel over the edge into thinking it was a slick.

The socket was already raised enough that the back of this 2" Sheldon chisel lays flat, but a bit more work was needed to make it fully functional. I turned the handle and socket on two different centers, and pared a bit off the back of the socket end of the handle, thus raising the entirity of the handle above the plane of the back of the chisel.

Red outlines turning blank and socket tenon. Turning centers are in blue. This way, when working on truing a surface that is longer than the slick, I don't bump and scrape my knuckles when pushing it. The old handle at one time had a striking ring, but it had gone missing, and the handle was beyond repair. My new handle is live oak.

I have another 3" slick, J. D. Kimball, hand forged, well over a century old, that came with a handle with a striking ring, much abused, and probably not original. But, I'm sure it's a pretty old handle, as it was made from chestnut.

This one was surely made with the intent of being a slick, since any straight handle gives plenty of knuckle clearance.

It's original ring now reinforces the handle of the smaller slick, and the longer handle I put on the larger slick now has a larger ring I cut, filed and hammered from a piece of antique water pipe. My new handle is Osage orange.

The backs of both slicks are flat, and the edges of both are cambered. Both rings are rounded over and flush with the balls of the handles, so as not to detract from their primary method of work, which is pushing them by hand.

Re: Chisel back flatness……?

Mike-in-Michigan

>I don't often need to pare anything more than a dovetail, not sure what else you need to pare with a chisel where a few thou out-of-flat back is a problem. Anything larger I use a hand plane (or a router plane for a dado). On a plane then flat is the toe, the heal, sides and in front of the mouth on the same plane.

But below is a pic of the pattern I usually get. As long as the dark grey area is not convex (ie humped) that chisel work will well even for paring, if it's convex it will still work fine for dovetails, cleaning up mortises, etc.. the things most common for bench chisels. I mean how many paring chisels do you need? 1/2" is great, you can go a full 1" but you still don't need a mirror finish, just basically flat. Finish though on first 1/4" or so needs to match the bevel finish, but then I don't see why bevel needs a mirror finish either but that is another war.

If you get the whole thing flat -- thats 'great' but you sure don't need to work for more than once for 5-10 minutes max unless the beast is way way out of wack. I mean shooting for that mirror finish doesn't make it cut better.

As to joints .. don't how any wood that is not going to move 0.002 thousands (usually a lot more) over the seasons. I also agree you can see 0.004 vs 0.002 but either is good and don't see how spending 4 hours polishing the back of any chisel to a 100% mirror finish is going to make that difference.

Oh well I've caused a enough pain, just remember though are you in this to collect tools or have fun making stuff. Me I do a little of both, but I can't say I enjoy spending time flattening backs or sharpening chisels, every chisel in my collection is ready to be used, it's just not right doing it any other way .. still it's gotta be done so I do it to the extent that is required to do good work, any more is just revvin' up the engine and never putting it in gear...

Re: Chisel back flatness……?

Pam Niedermayer - Austin, TX

>I think you're reading way too much into my simple statement that a flat chisel back wasn't excessive.

Pam