Tips for cutting mortises?

[jarrett]

So, I decided I'd try to cut out some mortises, and to start out, I tried to make some half blind (?) joints. But, after putting three pieces together, I noticed that I made them a little crooked.



Closeup of the tilt in the wood...


and the end result...something getting close to an MC Escher piece.


So, some questions:
1. Is there a way for me to correct this twist? Do I just turn the legs around and recut it? :gar-La;

2. Any advice on cutting these straighter? I guess I should buy a mortise gauge, for starters.

3. I'm working on the balcony of our rental, so I don't really have a good work surface. I've been cutting things sawbench style--a la sticking it on a table and clamping it with my knee. But it seemed really difficult to cut out the tenons out that way. Anyone ever try it, or is the sawbench style good for just less precise cuts?

4. I'm cutting everything using my Veritas dovetail saw--since it beats that cheapie saw that came with my miter gauge hands down. It seems to cross cut decently--is there any harm (in the wood, in the saw) continuing that way?

5. Anyone know a good deal on a work sharp 3000? Dull chisels are partly to blame, I think. But after spending an afternoon on sharpening one of my chisels, the missus actually told me to buy one! Someone here posted about it being $160 at one point, and now I can't convince myself to pay full price.

Sorry for some of the newbie questions. Thanks!

Jarrett

 

[Len]

Jarrett,

Having been in limited work space situations myself, I would suggest you take a look at the Black & Decker Workmate 425:

http://www.blackanddecker.com/ProductGuide/Product-Details.aspx?ProductID=7812

I have an earlier version that came with some accessories that don't appear to be available any more. But 90% of the time I use the top/vise or swivel pegs to hold things anyway.

It doesn't look like much, but it beats the heck out of using a knee to hold the wood when trying to saw a straight line. You can cut a piece of plywood or MDF to make a tool shelf in the in the lower opening. And it folds up so you can stick it in a closet when it's not in use.

The Workmate even has it's own chapter in "The Workbench Book" by Scott Landis! I believe the full retail is in the $120 range, but 've seen them on sale at Target for under $100 now and again.

I'm a newbie to cutting mortises myself. I just attended Roy Underhill's 'Woodwright's School' class on dovetails and mortise/tenon joints, and it was a matter of user preference whether a dovetail or tenon saw was used to cut the tenons.

If you spent a whole afternoon sharpening one chisel, I would suggest a quick Google search on "Scary Sharp". It's quick, and it works.

Len

 

[froglips]

I won't say much bout the Worksharp, other than to say when learning to sharpen, in my early days I spent boat loads of time.

As I got "better", it went much faster. I opted for sandpaper on glass and then waterstones.

The real break through I had was going up too quickly in grit size. I just couldn't wait to get to the next stone, and that ended up costing me. I'd spend all this time on a polishing stone, when I really needed to be back on an 800 or 1000 grit.

Another tip, most videos they start out with tools already in really good shape. 5 minutes start to finish? My left foot. I have mostly older chisels and plane blades that appear to have lead lives of hardship and jar opening. In some cases, hours are the only way to get it done.

Using your dovetail saw as a tenon saw should be fine. It just limits your tenon depth and the cut might be a bit rougher than a dedicated tenon/back saw. The other gotcha is the handle. A dovetail saw handle is much different than a tenon saw. It will put your hand at a very awkward angle. Again, not impossible, just a bit awkward.

Mortise guage is really key in getting those straight. But, also a flat datum surface (reference face). If your face isn't flat, the marking won't be right.

Well, flat enough.

For your twist, you could tweak the tenon by shaving top of one face and bottom of other face then shimming with veneer or paper. It'll be a lot of fuss'n, but doable.

On the table I'm with Len. I've got a workmate, can't live without it. I'd look at the other models too. I've been mostly unhappy with the excess features and weight on my 425. But the X-frame one is less stable.

Never seen anyone sit on their work while tenoning, but no reason it won't work. Might look at how the Japanese work, they tend to sit a lot vs. western folks who stand at a bench.

One unsolicited idea for working in an apartement (or any shop) is an L frame. I have a few I keep around for quick benches or extra support stands. 2x4, 2x6 doesn't matter. I made them to go on a porch railing. Clamped to the railing, and shimmed on the floor, they worked quite well. As it was a rental, I did protect the porch railing and didn't do anthing wildly forceful.

Lastly, I applaud your efforts! If we can keep you away from the Dark Side (lathe), you have a bright future in the 18th century

Jim

 

[LeftyTom]

Jarrett, in reference to the pics: make sure the mortise & tenon are centered on the stock. Draw them on and cut to the lines. It is easier to trim them to fit. For the slant like you have, you can try shimming the tenon, to press the slant in the opposite direction.

 

[jarrett]

Hm, there was a workmate for $50 on craigslist, but someone just bought it this morning. Ok, fess up, which one of you got it? :gar-Bi

I've always been wary about the stability of a table that is advertised as lightweight and one you can fold up and hang on a wall. But it sounds like it's a good first step and a useful tool even down the road.

I have been trying the scary sharp method, but it's just taking too long for me. Buying a sharpening tool is the difference between having a piece to show the missus vs. having a sharp chisel to show her (you can guess which she'd be more impressed with). Anyway, I just bought a worksharp 3000 (you guys are a bad influence here). Good to know I don't have to buy another saw for now! :gar-La;

But, I think a mortise gauge is in the picture soon. The tenons actually fit pretty decently into my mortise, it was just that they were crooked. I guess my arm just wants to do dovetails. But, I will try shaving down the tenons and stuffing them with paper. Thanks for the advice.

BTW, these pictures of Christopher Schwartz is how I'm trying to use my little table. It's about the same height, but it's a lot harder to cut a 2x2 this way than a 1x8 that's in the picture!
http://blog.woodworking-magazine.com/blog/Using+A+Sawbench.aspx

 

[SSuther]

Regarding the workbench end of the questions, I've used Workmates quite a bit, and they are quite useful. However, if you are going to be chopping mortices, be sure to place the mortice directly over a leg of the bench to provide the most solid base and least bounce of the workpiece when it is being struck. This makes the chisel strike most effective. I've done a lot of work with two old Workmates acting as a base for a small but thick top attached to the Workmates with cleats screwed to the bottom of the work surface. Altogether, they provide enough heft to resist bounce and even do OK with planing. I even attached a small woodworking vice to the front of the work surface. When I need to, it all breaks down into a relatively small space.

 

[willarda]

Jarret: I am conducting a Beginining Mortise and Tenon workshop on May 23. I have two signed up but space for one more. Give me a call or email if you are interested.

 

[Len]

What I have is an old Workmate 400. It looks like the 425, but without the extra top piece, or the interlock to make both screw handles turn at the same time.

It also came with a 1/4" hardboard tool shelf in the lower open space seen on the new model 425. I replaced that with some 1/2" plywood so it would hold some of my heavier 'home built' accessories when I have it set up.

As Jim mentioned, it is heavier than the smaller versions. I actually consider that a plus, as I find it helps keep it from moving around when edge planing boards, etc.

Since I'm getting into doing hand cut mortise & tenons myself, I've been thinking about the problem of support SSuther mentions.

:widea:I'm thinking a 4x4 post cut so the end comes out flush with the top of the Workmate when stood on end will work. The 4x4 post would be clamped in the Workmate jaws, and the area where the mortise is being chopped out centered over it. This would keep the force of the chopping from being applied directly to the Workmate at all. And the Workmate is low enough that the workpiece could be held in place by sitting on it.

I think I'll give it a shot this weekend. I'll let you know if it works, or not.

Len

 

[froglips]

Boy, this is a fun thread! Workmates, can't live with them, can't live without em.

As if someone is watching us, this months Woodworking Magazine just arrived. It has an article on....... fitting tenons.

Looking forward to your update Len.

Jim

 

[Len]

:icon_cheers:icon_cheersIT WORKED!!:icon_cheers:icon_cheers

Considering:

It turns out I didn't have a scrap 4x4 laying around, so had to use a couple of scrap stips of plywood clamped together for the striking post.

I don't own a mortise chisel, so ended up using an old 1/2in Stanley paring chisel passed on from my dad long ago.

And this is just the second time in my life I've hand cut a mortise.

I'm just a bit amazed that it actually worked.

Now if I can figure out the picture thing-a-ma-bob...

The first thing I did was clamp the two pieces of ply together, and into the WorkMate. Then I got out the ryoba saw and cut them off flush with the top of the table as seen here:

Since the WM 425 doesn't come with the hold-fast accessories the 400 came with, I used a quick clamp to secure the workpiece. It's a little hard to see the pencil lines, but I deliberately made the mortise slightly longer than the strike post is wide. I wanted to see how the fixed table top would do if the majority of the force was taken by the post.

My driveway wasn't quite level where I had set the WM up, and the workpiece drifted a bit with only one end clamped. So I added a second clamp as shown, which probably wouldn't be a bad idea in general:

Since this was a "proof of concept" test I only went a bit over half way throught the workpiece, and didn't flip it over to finish a through mortise.

Besides, it was starting to get dark out. And I was in such a rush to try this, I forgot to mark the mortise on the other side. Oops!:eusa_doh:

At any rate, it is possible to use a striking post in combination with a WorkMate 400/425 to hand cut a mortise. I'm not sure the smaller WM's would do it though, given the differences in height and sturdiness.

And I'll bet it'd be even easier with a real mortise chisel.:gar-Bi

Len

​

 

[jarrett]

Len,

Very inspiring...I need to find a workmate now, it sounds like it'll help my situation (Right now I'm setting it against the floor and a door jamb, and bracing it down with my knee--my muscles aren't too happy about that). Do you find that using this setup is a big improvement over using the built in vise over one of the legs?

 

[jarrett]

Well, this past weekend I cut out 18 1/4" mortises using a Stanley beveled chisel I bought from Lowes. The result is the frame of a bedside table (haven't take any pictures yet), and it is standing on its own, but it isn't pretty.

One problem I had was deepening the mortise. The first 1/4" was fine, but when I got deeper, it got a lot more difficult. It felt like my work at the top was just compressing all of the wood at the bottom, making it tougher to chop through cleanly perhaps? I'm dealing with whitewood here, so nothing that tough.

Another problem was that the wood was just really stringy. I guess I don't understand how the sides are supposed to be cut when the blade is only chopping perpendicular to the sides. So, I would have a lot of waste at the bottom that I had trouble cleaning out. Am I not chopping it hard enough?

Also, I've curved over most of the shoulder corners when trying to lever out wood at the bottom. Is there a better technique? It made the fit of my tenons bad since it at times lengthened the mortise.

Not sure if I'm explaining myself well here, but I'll try and get some pictures if people are confused.

Are there any good videos online showing the chiseling out of a mortise from finish to end? Most of what I've seen show the starting of one, but not the complete mortise (essentially, the hard part for me!)

 

[froglips]

Boy, this thread just gets better and better.

Len, one word. SWEET!!

Jarrett, here is a video you might have seen. Its St. Roy filming the man Frank Klausz chopping a mortise.
http://www.popularwoodworking.com/article/mortising_under_glass/

Three things pop to mind. White wood/pine is going to be harder to mortise. Poplar might be a better compromise.

Crushed ends of a mortise, if I follow, can come from levering waste at the ends of the mortise. You do not want to do that. Leave a bit of wood, say 1/8" on both ends. Use that 1/8" to lever against/crush. You want to pair or chop straight down on the ends. Never lever against the final ends.

I'm going to also guess your chisel sides are not parallel. Which is just fine for a bench chisel but not so good for mortises. Here is an exaggeration.

Imagine a mortise chisel is a perfect rectangle. You chop down, it cuts straight, parallel sides in the mortise. Now, picture a bench chisel as a V (I'm looking at the top face, not the sides). The further your drive the bench chisel, the more the V will crush the sides, like a wedge.

What you might try is figure out the widest width of your bench chisel and make your mortise just a hair wider than that. You will end up paring a bit more, but might get you there. I'd not go this route though.

Instead, draw bore. By draw boring mortise and tenon, the fit and machine like precision is not needed. What matters most in draw born M&T is the fit of the shoulder of the tenon.

Draw boring can save you a lot of frustration in the learning stage. As you progress and get the "right" tools, then work on doing more precise work. Otherwise you are pulling out hair and having to spend lots of money on hats.

Jim

 

[McRabbet]

Jarrett,

I usually "hog" out my mortises with a Forstner bit before I attack them with a chisel. If you want to stay with all hand tools, use a brace and bit. Just be sure to stay inside the layout lines when drilling. Then I shave the ends and corners of the mortises with a sharp narrow chisel, working almost entirely in the vertical to avoid damaging the edges; the sides are also pared vertically with a wider sharp chisel. I also avoid levering against those edges.

Here is a video link on cutting haunched mortises by Franz Klaus -- he is using a mortising chisel, but his technique will work with a bench chisel, too.

 

[Len]

Jarrett,

Without the striking post I find the WM tends to hop around a bit. With it, the majority of the mallet blow force transfers to the floor instead of the WM, so it stays in place. I believe a larger, heavier, striking post would have been even better.

The WM also put the workpiece at a very good height for making solid mallet strikes, without getting a back-ache in the process. I believe that also translated into getting a relatively clean mortise, even though I was using the wrong kind of chisel.

I also found with the WM I didn't have to keep flipping the chisel around to keep the bevel side facing the direction I was moving toward in the mortise. I could just walk around to the other side of the WM holding the chisel the way it was, set it in place, and start cutting the opposite way.

A couple of things I discovered about using a paring/bench chisel instead of a true mortise chisel during my test, but forgot to mention as I was focused on whether the WM set-up would work out:

The bench chisel is sharpened to a shallower angle than a mortise chisel. So it tends to go straight into the wood, creating parallel vertical cuts, rather than riding back and creating a chip the way a mortise chisel does.

I found that if I leaned the pariing chisel away from myself about 5 degrees or so it would slice back a bit, creating chips as it went. Just make sure the first cuts at each end are with the chisel held vertically, and about 1/8" in from your end mark. I wish I'd had someone around to take pictures as I was working so you could see the difference.

I didn't start clearing chips out until my 3rd pass. I didn't lever them out the way a mortise chisel would be used because of the thin edge on the paring chisel. Instead, I flipped the chisel so it was bevel down and pushed it from the near end of the mortise toward the far end. Slicing the chips off and lifting them out was I went. Then I switched ends and went the other way. This worked well, and left a smooth bottom to start the next run of chips on.

As you mention, the edges were a bit rough, but a paring chisel used for it's intended purpose smoothed them up quite a bit. Just be careful not to overwiden your mortise.

Len

 

[willarda]

I find it useful to use a sliding t-square, the 4" variety. Set the blade to be just shallower than your shoulder depth on the tenons. You can then set the body of the square on the good face side of your tenon material and hold this up to the light. You should be able to carefully evaluate the degree of twist or undercut in your tenon by gauging how even the light is between the blade of the square and the cheek of the tenon. For those areas that deviate, mark them with a pencil and plane (rabbet plane) or shave (chisel) these until your tenon is perfectly square on the face side (that is the outside face of an apron, for example). Now fit your tenon to the mortise, but do all of your adjusting (planing and shaving) on the opposite cheek. This assumes that your tenon is not too thin to begin with. If it is too thin after straightening the face cheek, then glue your cheek cut-off back on, or glue on veneer to the opposite cheek, and resume your fitting. All of this assumes that yourmoritse is parallel to the length of yur stock and that the mortise cheeks are square to the face of the stock.

A mortise gauge is invaluable. You use the same settings to lay out your tenon and to lay out your mortise. More importantly, you set th emortise gauge to the width of your mortising chisel. When you make your cuts, you cut the tenon cheeks on the ouside of the scribe line and the mortise on the inside of the scribe lines.

 

[Gofor]

First off, my hat is off to you for getting the mortises that close in that wood using the tools you have.

As you have seen, several things are very important:

Securing the wood so it doesn't move
Accurate measurements
Sharp tools.

Securing the wood: Chopping mortises requires the wood doesn't move sideways (front-back or edge-edge) and doesn't move down when you chisel. This will take some sort of clamp. Workmates work in one dimension (front-back). To prevent edge-edge, a couple of scrap boards clamped on each side will help. To prevent down, block it with a stool, chair, (if good furniture, cover with a piece of scrap ply) concrete block, etc. This also applies if you clamp it with a c-clamp to the balcony rail (I used a porch rail once, and have been known to use a step ladder).

Accurate measurements: A marking gauge is the best. Using a combination square as a depth guage is also a player, and use an exacto or pocket knife to scribe the lines. A pencil is not accurate enough, all tho a 5mm pencil to fill in the scratch line may make it easier to see.

Sharp tools: You cannot chop out a decent mortise with a dull chisel. the "scary sharp" method is initially less expensive. However, using wet-dry paper is slow and most store-bought chisels have mill cutter marks on the back and bevel that will take forever to clean up. I have found that a having a DMT diamond stone set (one side blue/coarse and the other red/fine), greatly reduces the time. Northern tools has a butterfly pocket sharpener for about $25 that can get the chisel usable quickly (I mention DMT brand because they are flat, a characteristic not found in some of the cheaper ones). The fine will get it sharp enough to chisel white-wood, but honing with 600 and 1000 grit wet-dry afterwards will greatly improve it.

With soft wood, leave 1/4" on the end of the mortise to receive the "lever-out" crush. Lightly hit the sides first with a straight down tap and then work only to the depth of that tap. With soft wood this will reduce the tear of the fibers.

For tuning up the fit, don't forget the old standby: A flat block of wood with a piece of sandpaper wrapped on it. With 80 grit, it is a rasp. With 150, it smooths the side for that slip fit. if it has straight sides, it can also even the shoulders of the tenon.

Good luck

Go

 

[jhreed]

I HAVE TWO WORKMATE 425S AND AM WILLING TO PART WITH ONE. NOT AS CHEAP AS CL BUT WILL GIVE A DEAL. I THINK I PAID $117.00
GIVE ME A CALL IN GOLDSBORO IF YOU ARE INTERESTED
JAMES H. REED
e-mail reed6605@bellsouth.net
919-583-8475

 

[McRabbet]

I HAVE TWO WORKMATE 425S AND AM WILLING TO PART WITH ONE. NOT AS CHEAP AS CL BUT WILL GIVE A DEAL. I THINK I PAID $117.00
GIVE ME A CALL IN GOLDSBORO IF YOU ARE INTERESTED
JAMES H. REED
e-mail reed6605@bellsouth.net
919-583-8475

James -- you need to put this info into a Classified Ad as not many people will find this here. Just click on Place an Ad on the right side of the Brown menu bar.