chopping mortises

Re: chopping mortises *LINK*

Ted Shuck

>There was some discussion here a while back (a year ago?) about chopping end to end or with a central V. I have found that the central V method works much more quickly for me and it is easier for me to maintain square sides to my mortices using this technique. I believe the principle is similar to what you have described; ie, there is a place for the chips to go.

Jeff Gorman has a very good description of this on his website, which I have linked below.

Ted


Jeff Gorman on mortising

Re: chopping mortises

Alan Hamilton

>Bill,

Whatever works. The mortise inquisitors will not break down your door anytime soon.

I learned to chop mortises the same way you learned first. I can see where drilling a hole might speed things up a bit. As you observed, the reason the first whacks don't penetrate much is because there's no room for the chip to get out of the way.

If I understand you, I've not encountered the same problem you had--that the chisel just won't penetrate deep enough on the first few whacks. On mine, the first whack doesn't go in very far, a half inch on a good day, but the first whack has created some room so the next whack goes in a little deeper, the next deeper still, and so on. Each whack goes in deeper than the last, and by the time I get to the far end I'm usually about bottomed out.

The only areas that don't catch up on succeeding trips are the ends--but that's a good thing. With some wood left at both ends I can lever out chips to my heart's content without worrying about dinging up the end.

As I said, whatever works. (Who is that at the door?)

BTW, did I understand correctly that you sharpen your mortise chisels to twenty-something degrees?

Alam

I Wrote a Short Tutorial On It

Bob Smalser, Seabeck, WA

>Posted it here, but it never made the articles section....here it is:

http://media5.hypernet.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=008649

...and in the Coping Saw post above, I chopped those 16 mortises in less than 45 minutes.

It will now, Bob. I missed it first time around.

Garrett in Victoria BC CA

>

that's it + comments on it, improvement

Bill Tindall, E. TN

>That is the link posted earlier that inspired me to try something different from Klause approach. The author seems to like the hole drilling except the aggravation of drilling the hole. If the hole is drilled undersize then its position is not critical and it works just as well as a tedius hole drilled exactly the mortise size.

I only chop mortises occasionally, like when I have a few. Otherwise I set up the drill press and use a hollow chisel. I like the drill press because I can turn the drill slow and reduce heating relative to mortising machine.

Therefore, I never have acquired a high level of proficiency chopping. A more bullet-proof technique is desireable even if less productive.

I find the (double vee approach" hard to execute. Reversing the chiel every wack or two creates vertical orientation problems for me.

I haven't optimized details of chisel orientation and chip prying for me yet, but I am sold on the predrilled clearance hole idea for a very hard wood.

Why chop? Pare!

Don Thompson - Cutler Ridge, Florida

>Here is Adam's method:

1) Identify the datum/face side of the mortised stock.

2) Select a mortise chisel as near as possible to 1/3 the width (or

thickness) of the stock as possible. Don't forget the size of the tenon

shoulders if any.

3) Mark the near side of the mortise (nearest the face) such that the

mortise falls in the center of the stock. (Or skip this step and just

eyeball it like I do!! Works MOST of the time! :) )

4) Using the mortise chisel, mark the ends of the mortise, tapping the

chisel lightly with a mallet

5) Begin the mortise by making a series of cross grain paring cuts, bevel

down, with the top of the cannel barely clear of the stuff. (This is the

step Moxon is talking about). Work carefully, since the chisel could easily

lift a long hunk of grain right out. Just make shallow cross grain cuts.

(Lift the chisel, if you must, or for soft woods) Space the cuts maybe

1/4-3/8" apart. Work from one end of the mortise to the other. Then turn

around and work your way back, this time removing shallow triangular chunks.

At this point, your mortise looks like shallow saw teeth. Repeat this

shallow paring until your mortise is at least 1/4" deep. Only then (or

maybe not even) will your mortise be deep enough to register on the sides of

the chisel. Once you get to this depth and beyond, the sides of mortise

will keep the chisel tracking straight and square.

Re: Why chop? Pare!

Bob Smalser, Seabeck, WA

>Why?

Slow, that's why.

I chopped 16 mortises in this dense, 20 rings per inch madrone in 45 minutes. No drilling, and no rushing.

Tutorial

Bob Smalser, Seabeck, WA

>In a small response to years of subtle but predatory marketing on PBS that has newcomers asking about mortising machines for their early projects, I prepared a short primer this morning in the shop to answer a younger man�s question. The entire session, including stock preparation and photography, took 30 minutes. The actual mortise chopping took 4 minutes, and I wrote this up on my lunch break.

First, you need mortise, not paring or firmer chisels. These Japanese ones below I bought from Highland Hardware when they first opened more than 2 decades ago to replace the badly worn family ones.

Note the flat bevels in the photo above; not hollow ground and no secondary bevel. These are laminated blades designed for striking, and they come in the exact width of your intended mortise, �, 3/8, and � inches.

Also note that the backs are hollow ground to facilitate easy flattening as you hone them during their life. You can see the hollow above the edge.

Their bevels should be touched up on the hone every time you use them; your stones ready for use should be a permanent fixture on a corner of your bench. Honing these is easy; just index the flat bevel on the stone. You also need to hone the back dead flat, and I also hone the sides lightly on the fine stone to remove any burrs. I use a set of 4 Arkansas stones all the way to the finest �black� grade, but you can use what you normally sharpen with. I wiped the oil off the stone and chisel for clarity; don�t hone them dry or the stone�s pores will clog.

I do a final stropping on the stitched muslin wheel with Knifemaker�s Green Rouge. Hard felt wheels are the best for this, but they are expensive.

Then I lay out the mortises on the prepared stock. First, the mortise gage double tines are set to the width of this half-inch chisel. Then the mortise gage fence is set for mortise location on the stock, and lines scratched. Want to have the mortises dead center? Simple, just run the fence down the opposite face of the stock, compare the marks, and adjust the fence until the marks are identical.

It�s a simple matter next to mark your mortise width with try square and marking knife. I�ll cut a simple blind double mortise and have used a pencil to make the lines clear in the photograph. You need to leave your pencils in the drawer for this and other joinery marking, as they are insufficiently precise.

Index your mortise chisel plumb in the end knife cut, and strike with a wood mallet. Do all four ends.

Continued on Part II

Re: Tutorial Part II

Bob Smalser, Seabeck, WA

>

The next chopping sequence is from the center of the mortise, and the waste merely levered out�splitting rather than cutting the wood along its long grain. My training aid today is a 2 X 2 of sopping wet Douglas Fir from the scrap pile out in the weather�. hard, tough and splintery. Your dry cabinet hardwoods will be easier. When working with highly figured wood such as Birdseye Maple you are afraid to split, then simply strike the outline of your mortise lightly with a paring chisel, first.

I repeat chopping from end and center, levering out the waste until I reach the desired depth; then I reverse the chisel and use it bevel-down to clean up the mortise bottom.

The final result is a little furry because of the wet wood, but entirely satisfactory. There is a small chip-out at the top of the right mortise, but this will be completely hidden by the tenon shoulder when assembled.

Frankly, even working in large, commercial, 3-phase shops, I never found many mortising machines that were entirely satisfactory. The bits are difficult to sharpen so you need two sets of them for production work, and the over arm design likes to flex under pressure, especially when the bit is getting dull, which also tends to pull your work piece out of alignment with the fence.

Why bother? These few simple, inexpensive tools and a shop-made mallet are all you need to do mortise and tenon joinery on one-off projects for the whole of your lifetime.

Step 5?

Bill Tindall, E. TN

>This looks interesting but I don't understand step 5. Anybody got a pictorial description of this approach?

Re: Step 5?

Ted Shuck, Centennial, CO

>The way I interpret this is that the chisel is placed as for a "normal" mortising cut. It is then tilted back with the bevel down so that the bevel is just above the level of the wood surface. The chisel is pushed to make a lower angle paring cut at an angle of about 40 degrees (?). A series of these cuts are made, then another series are made in the opposite direction (180 degrees).

I think the key point here is that the chisel is not held vertically and pounded. The chisel is held at a lower angle and pushed. Since the cut is not directly across the grain, it is not so difficult to make the cut and the chisel need not be pounded.

Another key point (that just came to mind) is that the chip is not being forced horizontally by the chisel bevel. The lower angle attach causes the chip to lift up, relieving the horizontal chip pressure in the mortise. This is related to origin of this thread where a hole is drilled to relieve horizontal pressure.

I haven't tried this method yet, but after thinking about it, it does seem to have some advantages.

Ted

Re: Step 5?

Bill Tindall, E. TN

>what you say I can follow, but the original directions refer to a "cross grain" cut. I would interpret "cross gain" as across the grain, orthogonal to the length of the board. "Cross grain" and "saw tooth" left me confused. I'll have to try it, but I'll bet it doesn't go quickly unless the wood is mellow- not oak. Of course one could do this operation with taps of the mallet as well as pushes of the hand.

Re: Step 5?

Ted Shuck, Centennial, CO

>I found that "crossgrain" terminology confusing as well. I itnerpreted this to mean "cutting across the grain" in a similar manner to a conventional mortising cut. I think what makes this cut possible in hard woods is the angle of the cut. If you go straight across the grain, you have to use a mallet. If you angle the cut so that it is only at about 30-40 degrees across the grain, sort of a miter cut, then it is possible to push the chisel. I think this is why he referred to it as a paring cut.

Ted

Re: Step 5 explained

Adam Cherubini, NJ

>Sorry for the confusion, Bill. I'll bet this technique would be more popular if I were able to explain it better.

The key to this technique is the beginning series of shallow cuts. The chisel is held orthogonal to the long grain as you say, the same as you would if pounding. Instead of driving straight down, you work as Ted has said at the lowest angle possible.

You make a series of incisions, producing no chips, on the first past. The next pass, making identical incisions but from the other direction, makes chips. The result is a shallow saw tooth.

Once the depth of the mortise is 1/4" or 3/8", you can stop making careful incisions and start simply paring away. At that point the sides of the mortise help guide the chisel. The process picks up speed then, but I've never made a mortise in the softest of wood faster than 5 or 10 minutes.

I don't feel strongly that this is the only way, the best way or even the old way. I only mention it because it makes some sense and is never discussed.

Folks that wish to try it need a mortise chisel with a huge handle (because you push the tool not with your hand, but with your shoulder). Bob's chisel wouldn't work well for him. This technique probably explains two cherries' and the old english mortisers' handle shapes that many complain about being too large.

Adam

that was clear to me

Bill Tindall, E. TN

>and indeed it may explain the huge, round, handles on some chisels. (I find the butcher knife handles to be easier to steer with the wacking approach)I will you technique in something less recalcitrant than oak and see how it goes. I can anticipate it may be more satisfying to perform than wacking with a mallet. I think I would like wacking out robust barn mortises but I have never found pounding out fine ones very staisfying. I have a bunch of cherry mortises comming up and they are too big to do with hollow chisel machine. So, I can try a few things.

Oops. Left out half the instructions

Don Thompson - Cutler Ridge, Florida

>1) Identify the datum/face side of the mortised stock.

2) Select a mortise chisel as near as possible to 1/3 the width (or

thickness) of the stock as possible. Don't forget the size of the tenon

shoulders if any.

3) Mark the near side of the mortise (nearest the face) such that the

mortise falls in the center of the stock. (Or skip this step and just

eyeball it like I do!! Works MOST of the time! :) )

4) Using the mortise chisel, mark the ends of the mortise, tapping the

chisel lightly with a mallet

5) Begin the mortise by making a series of cross grain paring cuts, bevel

down, with the top of the cannel barely clear of the stuff. (This is the

step Moxon is talking about). Work carefully, since the chisel could easily

lift a long hunk of grain right out. Just make shallow cross grain cuts.

(Lift the chisel, if you must, or for soft woods) Space the cuts maybe

1/4-3/8" apart. Work from one end of the mortise to the other. Then turn

around and work your way back, this time removing shallow triangular chunks.

At this point, your mortise looks like shallow saw teeth. Repeat this

shallow paring until your mortise is at least 1/4" deep. Only then (or

maybe not even) will your mortise be deep enough to register on the sides of

the chisel. Once you get to this depth and beyond, the sides of mortise

will keep the chisel tracking straight and square.

The technique I use for this step is Moxon's. Hold the chisel blade between

your fingers using your dominant hand, with two fingers behind the blade

(last two or first and last), and two in front. Hold the handle (helve)

with the other (I wrap my thumb over the end). Push the handle using your

dominant hand's shoulder. Support your upper body using your dominant hand.

The tool slides through the dominant hand's fingers. Oh boy! I hope you're

getting this! Anyway, this is a better technique than driving with a

mallet, since your are in complete control and you're not dulling your tool

needlessly. The key is your connection to the stuff and thus to the bench

directly. Much better than baring down on a tool, hoping it won't slip and

ruin your project or bench (yikes!)

6) Continue with your paring cuts using the same technique but with less

caution. The mortise will keep the chisel straight allowing you to cut

deeper and faster. You can make vertical cuts from time to time as

necessary to define the ends. No need to work to the full length of the

mortise. A sharp, carefully used mortiser can easily pare the end grain at

the end of the job.

7) Inevitably, I end of with either a mountain in the middle, with valleys

on either side, or a deep valley on one side, and a high mountain pass on

the other. Regardless, I resort to working bevel up paring the snow off the

mountain's slope, taking a piece of the top away with each stroke.

8) At last you have a deep mortise with flat sides and tapering ends. Only

now do I flip the mortise bevel up and reach for the mallet. Its my goal to

use as few and as light mallet blows as possible.

1/4" x 2 x 2" deep mortise in white pine takes me 5 minutes. Harder woods

may take 10.

9) Set your mortise gage to the mortise you just made. In your mind, rename

your mortise gauge "tenoning gauge".

==========

It might be worth mentioning things not to do:

1) Don't try to "clean up" the mortise sides with a paring chisel. Correct

your tenon if you must. The key to a good mortise is its parallel sides.

The moment you pick-up that small mortiser or paring or firming chisel,

you've relegated yourself to an ill fitting mortise.

2) For the same reason, avoid the temptation to start your mortise with a

series of holes. First, the holes will likely not be perpendicular to the

face you're mortising. Second, your mortise chisel won't work as it should.

You'll be forced to pare out the sides, banging away needlessly. Might be

okay for a barn.

3) Lastly, try to limit how often and how hard you hit your tools. Few 18th

c tools can stand up to routine banging. They're not still around because

someone (Mike Dunbar) wailed on them and used them as pry bars to "lever out

the chips". (OY!)

The key to this technique is the beginning series of shallow cuts. The chisel is held orthogonal to the long grain as you say, the same as you would if pounding. Instead of driving straight down, you work as Ted has said at the lowest angle possible.

You make a series of incisions, producing no chips, on the first past. The next pass, making identical incisions but from the other direction, makes chips. The result is a shallow saw tooth.

Once the depth of the mortise is 1/4" or 3/8", you can stop making careful incisions and start simply paring away. At that point the sides of the mortise help guide the chisel. The process picks up speed then, but I've never made a mortise in the softest of wood faster than 5 or 10 minutes.

I don't feel strongly that this is the only way, the best way or even the old way. I only mention it because it makes some sense and is never discussed.

Folks that wish to try it need a mortise chisel with a huge handle (because you push the tool not with your hand, but with your shoulder). Bob's chisel wouldn't work well for him. This technique probably explains two cherries' and the old english mortisers' handle shapes that many complain about being too large.

====================

Final word- I could be wrong, but it works for me, is demonstrated at

Wmsburg (not that they know everything) but moreover fits into an

archeologically revealed framework- a sensibility really. A kind and gentle

way on wood, body and tool. How this all fits together, I'll leave for

someone else (Eugene Landon? www.oldemill.com).

Adam Cherubini

Q for Adam

Stephen in Ottawa

>Adam,

I tried this technique on my last project. I had to make twelve mortises in red oak. It went very well and I much prefer the technique to pounding the chisel. The accuracy of the mortises, I might add, was better than I'd ever been able to achieve using the traditional pounding or the drill-and-pare techniques that I'd used before.

Now on to my question. When you take the initial shallow cross grain cuts, approximately how deep is each cut? I suspect I was taking too deep a cut ( about 3/32" or so ), which would require a fair deal of force, and consequently some loss of control of the chisel.

Thanks,

- Stephen