Chopping mortises-perpendicular

oops

John Pappas

>Should have said ..keeping the chisel perpendicular...not chopping perpendicular...sorry

Re: Chopping mortises-perpendicular

paul womack

>Any and all aids can help;

* a clamped on guide piece can help

* a visual reference (e.g. square standing on the bench)

* standing "in line" to get a good "sighting"

* using long mortise chisels (long tools are easier to line up)

People who've chopped hundreds of mortices most likely need none of this.

But I ain't too proud.

BugBear

Re: Chopping mortises-perpendicular

joel -( tools for working wood)

>the traditioanl was (as described by Moxon ) is to chop fast and hard - possibly inaccurately, and then using a paring chisel on the scribe line to size the mortise. but in any case with or without paring all you do is just site the chisel to hold it square - no jigs or gizmos needed - just a little practice.

Re: Chopping mortises-perpendicular

Derek Cohen (in Perth Australia)

>John

In addition to the recommendations made by Bug Bear, I would add:

1. Place tape around the chisel's blade to act as a depth gauge.

2. Try using Oval Bolstered Mortise Chisels (there Joel, the correct name!) if you can, or another chisel of a similar thickness. These provide the best registration to the side walls of the various mortise chisels I have used, making it easier to maintain a straight line.

3. Use the longest chisel possible since this also helps you gauge how close to vertical you are.

Regards from Perth

Derek

Re: Chopping mortises-perpendicular

Jack Guzman from Maine

>I find if I alternate which end of the mortice I'm chopping from I can check on my perpendicularity(that's a big word).It makes it a little harder but I hate it when I get a mortise that's at an angle.---Jack

Re: Chopping mortises-perpendicular

joel -( tools for working wood)

>Thanks Derek,

In a small way I feel I've accomplished something this year.

Happy Holidays,

joel

Most of the time

Wiley Horne--Glendora, CA

>you can use the work itself as the reference (Bugbear's third item). Usually the work is parallel sided. You're standing over the work looking down the chisel. The projection of the chisel on the work will form an angle--make the angle the same on both sides of the chisel. Only have to do this a coupla three times to get started right.

It's kinda like edge jointing--there are lots of visual cues to what is plumb and what is square.

Wiley ...... who nevertheless uses a paring block for dovetails

Re: Chopping mortises-perpendicular

Adam Cherubini

>This is just one reason I reject this technique

Paring the sidewalls as Moxon and Joel mention isn't exactly easy either. And you have the exact same problems with that operation as well.

So I think its a good idea to try to do this job accurately the first time. Here are a few tricks:

1) Aligning the chisel for the first blow is tricky enough, but if your edge isn't 100% square with the blade, every subsequent blow will cause additional inacuracies. Holding the handle tighter isn't a solution.

2)Like sawing, I find a relaxed grip to be best. But as you bang away, you need directional control. So you want to start with a relaxed grip, then tighten during the mallet blow. How you ask? Here's a hint; Traditional firming chisels including mortiser all have tapered handles.

3) Long makes straight. What i do is make a groove and lay the chisel down as low as possible in the groove. In this way I have a lot of the chisel's precision ground sides registering inside that groove. (if only the first 2" of chisel was ever inside the wood, why do you think makers went to all the trouble to draft the whole length and precision grind the whole length?) But you can use this same philosophy when you chop. We should ask Pam what Odate says, but I'm pretty sure he digs a nice square hole then just lengthens it into a trench by incrementally working the walls into the pit he's dug. This way, he's using the first hole to guide the squareness of the trench. If he's wrong, he's wrong the whole length which is reasonably easy to fix. In any case, he only needs to worry about square for one hole, not the whole trench.

4) I don't think most furniture makers with the exception of chair makers (who I don't think could have possibly used this technique) produced joints suitable for tite bond. I think their joints were sloppy and hide glued or pinned or both. I suspect you guys who can chop these perfect mortises quicly are simply better than the old timers. And I think this isn't the only joint some you are just superior at producing.

adam

Re: Chopping mortises-perpendicular

joel -( tools for working wood)

>Adam,

paring the sidewalls was the way I was taught - and the entire class of fairly inexperenced students did it pretty easily. Just place paring chisel on scribe line, stand at the end of the mortise, sight the paring chisel sqare, and push down.

but I think it's really a matter of practice on the whole thing. After the first few mortises holding the chisel square isn't really a problem and the real reason for paring is to get very smooth sides so that you get a great fit with thin, very secure gluelines.

THe basic concept of sighting a tool, also feeling it sit square as you are holding it is a very important concept. It's not only for chisels, but also for sawing, and drilling that being able to see and feel if stuff is square is important, and of course with planing - the high cenrter of gravity of a wooden plane makes it much easier to hold a plane square and planing square is also an important skill to develop.

Question re applied theory of glue

Wiley Horne--Glendora, CA

>Hi Joel and all,

Joel, not to argue with you at all, but I want to raise a question regarding glues that stemmed from something Adam said some time back.

I've begun shifting a lot of gluing over to hide glue (folks, Joel sells excellent hide glue). Including using hide glue for M&T joints. As I understand it, yellow glue wants a tight fit to develop its best bond--think a clamped edge joint. Whereas if you load up a mortise with hide glue, the glue will fill all small nooks and crannies and get a death grip on whatever is in its environment. So I figure that (a) if I make the tenon a tight enough fit to make a real good yellow glue bond, then there's a considerable risk it'll be a little out of square, and (b) on the other hand, if I use hide glue, I can leave the sidewalls a little rough off the mortise chisel, and it works because the hide glue will get an even better bite.

I'm not suggesting using hide glue to make a sloppy M&T joint--I'm still talking about a joint that needs a little malleting to go together.

So I'm asking: If you use hide glue, is it just as well to leave the sidewalls a little rough off the chisel--this is what I'm doing--rather than arrange to have a smooth sidewall. And more generally: Does your M&T strategy depend on what glue you're going to use, or no?

Wiley

Re: Question re applied theory of glue

joel -( tools for working wood)

>"I'm still talking about a joint that needs a little malleting to go together."

THen you sill have some sort of interference fit.

Hide glue isn't gap filling. it can easily stick to a peice of glass, and there should be no reason for roughing up a surface. THat being said you want a surface with open pores and no dirt or dust because if the pores are closed or there is dirt what the glue will stick to is dirt, dust, or thin whisps of wood that have no structural strength.

Over time a glob of glue in a joint will crumble, play will develop in the joint, and eventually it will pull out.

The entire purpose of glue in a mortise is to keep the parts from sliding apart. A great fit is important to long term longeviety of the joint.

As for rough off the chisel I was trained to pare the sides. when I do it right the joint slides together like a piston. It's much easier than trying to get a pretty smooth mortise by chopping alone. Gauge the mortise to whatever. Select the next smallest mortise chisel you have (which is why mortise chisels were always sold in 1/16" increments unlike bench chisels which were almost always sold in 1/8" increments)

Chop the mortise as fast and deep as you can. You can be a little sloppy. don't worry about the sides you have a lot of wiggle room.

when done use the mortise chisel on the scribe line to define the length of the mortise. Use a wide paring chisel - of ideally the width of the mortise length. and put in on the scribe line and push down. The wood (1/32" or so will just peel off perfectly. THis is even more important on through mortise where the joint is visible.

(note: I didn't invent any of this technique it was how I was taught by Maruce Fraser, and how it is described in Moxon).

Re: Chopping mortises-perpendicular

Warren in Lancaster, PA

>I guess we are talking about several different techniques here. If you chop vertically with a mallet you can learn to feel when the blows and the chisel are straight. Typically the mallet is hit several times without withdrawing it. If everything is lined up there is a much more solid feel when you hit the mallet.

I think that in 18th century work there are more through mortises than used today. If you lay the mortise out nicely and chop halfway from one edge then chop from the other side the chisel finds the mortise and there is an improvement in accuracy. This is particularly useful in making sash or paneled doors.

Re: Question re applied theory of glue

ThomD

>I went down the hide glue trail myself for a variety of reasons. I never changed the fit of my joints, and while I am not all that interested in antiques, my impression of them is not that the joints were gap filled. Epoxy has some hide glue features like reglueability and it is a happy gap filler, but both hide and epoxy can also be used to lubricate joints as they go together. That's all you get with epoxy, with hide it can go either way, but there isn't any necesity to leave excess clearance if one is blessed with enough heat.

Re: Chopping mortises-perpendicular

ThomD

>I don't mind paring through mortices, I think that is easy to do properly, but I don't feel confident about paring blind ones, or at any rate confident relative to the alternatives.

I like to rest the chisel on it's edge, and feel how it ballances on the wood, this doesn't tell me anything much about square, but it makes repeating the same set-up on subsequent cuts easier. I don't care if the edge is square, but if it bothers my sometimes I tape the chisel tentatively to get it set for the first wacks. I sight the chisel against the wood behind it for alignment. I try to hit is square. It's like golf, there is no jigging affect at all, just alignment and execution. Over time the results get better.

Apparently my Grandfather had non-electric morticing "machine" in his joinery shop, about the only machine he had. I have two power mortisers in my shop, the small English one is for sale. One still needs to know how to cut them freehand since there are so many situations where that works better or is the only way. I have cut them with routers and just hate it.

The only thing I know of that is different about Odate's technique from what I see in the West is the fact that cuts are taken from the center out, alternating the bevel direction, to excavate a triangle, and then the the ends are taken with vertical cuts. I like that technique, but there is a lot of chisel manipulation which is not convenient with the massive handles one sees on Western chisels. Also Japanese chisel handles taper so they are wider at the chisel end, allowing some weight to be placed on them, without driving the handle into your hand with each wack of the hammer.

hide glue properties

Adam Cherubini

>Hide glue IS gap filling and actually requires a gap to develop adhesion and full properties. Hide glue won't "wet" the surfaces like yellow glue. A tight joint will just push the hide glue out- just like epoxy.

Yellow glue requres 150-250 psi to develop full bond strength. This pressure cannot be produced by a tight fitting and unclampable mortise and tenon joint. That said, PVA (yellow ) glue probably has sufficient unclamped properties for tight fitting M&T.

Otherwise it makes sense in my mind to use glues with gap filling properties when you need them and PVA when you want an invisible butt joint.

Re: hide glue properties

Joel

>I'm going to check with the factory next week but before I posted I asked a few people and I got 100% not-gap fitting response. Also a rub joint is essentially a non-gap filling joint and is and was of course a very common use of hide glue.

I'm not personally that picky on glue. I like hide glue because it's transparent to finishes and reversible - and I use it for everything without much thought (which is why I first asked around)

Re: hide glue properties *LINK*

Don McConnell

>What Joel has been told is consistent with the information on adhesives in the _Wood Handbook_ published by the Forest Products Laboratory. In their listing of the main adhesives commercially available, only four are listed as "gap filling." Those are construction adhesive, epoxy, hot melt, and polyurethane. Hide glue is not so listed, which agrees with all my other references.

The _Wood Handbook_ is available for download in pdf format. Not all chapters are relevant to everyone, but some chapters are well worth downloading for basic information - the chapter on adhesives being one of them. In addition to listing the characteristics of the various adhesives, there is information on surface preparation for the various adhesives, etc.

Don McConnell

Eureka Springs, AR


http://www.fpl.fs.fed.us/

Re: hide glue properties

ThomD

>Most glues don't really wet very well. Maybe the water content goes in there, but the particles of the adhesive are usually pretty much left on the surface. Thining glue often creates the impression that it wets better, for instance thinned epoxy looks like it really penetrates, but all the solids stay on top. It's takes special epoxies where the molecules, or whatever, are smaller, to penetrate and actually saturate.

Was Forest Products thinking of liquid hide glue the stuff in a bottle? You can get pretty thick hide glue. In fact it's not unlike hot melt glue, in smell or properties. I can see it binding things together, but I don't use hot melt either. It may be gap filling, but it's a different mater getting it everywhere one wants it in a joints, so that it really fills the gaps.

I prefer good wood fit, and properly thinned glue of whatever type. I used to use hide glue for repair, and also speed, and rubbed joints. Now I really don't think anyone is going to bother to repair furniture with hide glue. So I only do it on my own stuff.

Clarification: 'gap filling' or 'bridging'

Wiley Horne--Glendora, CA

>I think terminology is getting in the way of understanding in this discussion. I did some google-level research, which admittedly is the lowest form of research. However I found something interesting. There are these two groups of authorities who differ on 'gap filling' in regard to hide glue:

Group A: Several highly-respected woodworking practioners, masters in their fields, who are quite convinced that hot hide glue has gap-filling properties, and

Group B: Materials engineers who say that hide glue does not have gap-filling properties.

Are these leading practioners and materials specialists really coming to opposite conclusions? I think it is more of a terminology problem. Here is what seems to be happening: The materials specialists equate 'gap filling' with the property of a polymer glue to form strong crosslinks, meaning covalent-bonded crosslinks. Epoxy does this, and the (poly)urethane glues do this; so they are the glues which are said to be 'gap filling' in the Dept. of Agriculture table. Collagen, or hide glue, is a polymer which is much more weakly crosslinked, and so it is deemed to be not gap-filling.

The Group B woodworking masters (I'm speaking of folks like Patrick Edwards) say that hide glue is 'gap filling', but I THINK they are speaking of a bridging property--the property of bonding across small interstices to hold two things together. That is, two reasonably well-mated objects--but with some irregularities-- held together with little or no pressure, will bond and bond well. Well, what's the difference between 'gap filling' and 'bridging'? The difference is the size gap that the different glues will bridge across. Yellow or white glue wants boards which mate well to be clamped together at high psi levels--no gaps. Epoxy will bridge considerable voids to glue things together--big gaps no problem. Hide glue is somewhere in between, in that it will reach across small voids--so small gaps for hide glue.

What's small? That's what this discussion should be about. Quantifying differences within a continuum, as opposed to yes/no, on/off, either/or, it is or it ain't.

Wiley ...... whose M&T joints are good enough off the mortise chisel and saw to be held by hide glue. Real small gaps.

Re: Clarification: 'gap filling' or 'bridging'

Don McConnell

>While I agree that terminology can obscure as well as clarify, my concern is of a much more practical nature. It seems there is an emerging perception that one need not be at all concerned about appropriately matched/mated bonding surfaces when one is using hide glue. While hide glue, along with most adhesives, will "bridge" small gaps, I feel it is misleading to encourage the notion that an ill fitting joint can be "fixed" by slathering on/in a lot of hide glue.

One may get away with that for a while, but in addition to excusing sloppy workmanship and undervaluing the development of skills, it seems likely to eventuate in disappointment and frustration.

(I'm not suggesting that you, Wiley, are encouraging this. I'm responding to my perception of a general undercurrent in such discussions.)

When the older woodworking literature addresses this topic, it usually stresses that hide glue does not have gap filling capabilities (so it isn't just engineers). While this may seem a bit dogmatic, I believe this was stressed in order to encourage the development of skills and learning techniques to produce results which would use hide glue to best advantage. So, I'm "sticking" with the Forest Products Laboratory on this one. :-)

Don McConnell

Eureka Springs, AR

Re: Ebanistonics

ThomD

>If you could jam enough compressed sawdust into a mortice along with an ill fitting tenon you could probably make a durable joint. Basically a version of holding everything together with a "gap filling" wedge.

Epoxy is an example of a gap filling glue where you could lie two pine boards down on a plastic covered table separated by a 1/4 gap, dam up the ends, and pour in the epoxy, and bonding wise get a really strong joint stronger than the joined materials. That's gap filling and isn't a mater of definitional niceties. In a cold enough environment you ca do the same with water.

The issue to me isn't whether or not hide glue has some range of gap filling properties, it's about whether it's an "art nad mystery" that loose fitting joints are a great thing to be filled in with hide glue, or whether that is "artless". The epoxy example, of what is sometimes called "liquid joinery", is real world and a comon practice. I don't believe that gap filling mortise joints was a cmomon practice among competant ye olde woodworkers. I have seen plenty of very tight joints in old work that leads me to believe otherwise. I think we are going down the path of woodworking ebonics.

To pare or not to pare mortise sidewalls

Wiley Horne--Glendora, CA

>Don,

Thank you. I understand you are trying to encourage sound practice. Also, Joel is on hard ground by citing both Moxon (as a reference to period practice) plus his own professional training. I just have a personal preference not to pare the sides of mortises, unless it truly is essential to a sound joint.

So let me try again on the mortise and tenon joint. No one encourages sawing tenons fat, and shoulder planing them to final size. Instead, we say 'learn to saw'.

But in the case of mortises, Moxon's account plus Joel's professional training say to chop thin, and pare to the scribe lines. For me, chiselling the sidewalls thin goes against the grain, just like sawing fat. (Of course, you have to protect the end lines of the mortise and pare them to final dimension.)

But setting aside personal preference, how do we analyze the situation? The mortise chisel is pretty sophisticated. Deep enough in cross-section that if you start plumb, you'll finish plumb. Parallel in the back edges which do the sidewall cutting, so that the mortise can be a consistent width. And sharp back edges which leave a fair surface (but not as good as pared) on the side walls of the mortise.

Can we pare more plumb than we can chop? Let's say we're talking about a 1-1/2" deep mortise. An error of one degree in the paring chisel orientation will translate into a slope of a little more than 1/64" from top to bottom of the mortise. 1 degree= 1/64"; 2 degrees = 1/32", approximately. These variances seem to me to be in the gap-filling range, not the bridging range.

The choice is not a no-brainer, in my opinion, because of the precision required of the paring cut. I feel like it is just as well to go for plumb off the mortise chisel, as opposed to trying to pare to both plumb and width at the same time, and altering the sidewall slopes with every paring cut. Remember, the mortise chisel will hand you the correct width for free--you just have to work on plumb. But if you pare, you're putting both plumb and width up for grabs.

There is the tradeoff that the paring chisel will leave the smoother sidewalls. No question about that.

The original question was to pare or not to pare mortise sidewalls: I'm seeing the overall tradeoff like this:

'Paring' will leave smoother mating surfaces for gluing, but requires very high handheld precision to execute accurately for both plumb and width. 'Not paring' will leave a rougher mating surface on the mortise walls, plus you only get one crack at plumb, but you do get the consistent width that comes with the mortise chisel. I like the odds better to 'not pare', provided that the glue will cope with the rougher mortise walls. Otherwise, it seems better 'to pare'.

Wiley .... who ordered a Moxon last night after reading Joel's account.

Re: To pare or not to pare mortise sidewalls

Joel

>I understand your math but holding a paring chisel very plum never seemed a big deal to me - (or for that matter most peple in my class back then) I mean big wide English Paring chisels. Try it and see. I might be harder with Japanese paring chisels because English paring chisels are top heavy so it is easier to feel plumb.

As for sizing - that's the best part. I can make a mortise to any exact wide because by paring on the scribe lines whatever I scribe to mortise and tenon - that's what I get - exactly.

Re: To pare or not to pare mortise sidewalls

mikew

>I think this discussion is sorta like which sharpening system is better--to each their own. Or, tails or pins first.

Or maybe, mortises or tenons first.

But, like everyone here, I also have a preference. That is to pare the mortises. Why? For the same reason I make [fairly] smooth tenons.

I simply trust the fit over a couple assembly/disassembly runs as I fit other parts to the whole. Less compression of the rough mortise walls to the tenons, which has happened to me on Mahogany, a wood I use frequently.

And--of course it was the way I was taught. Including laying out and chopping the mortise using a slightly smaller mortise chisel, paring to the scribe lines. Gauging the tenons from the resultant mortise, and sawing as close to the line as I can--but still cleaning the tenon off. Most often with a couple swipes of a rasp or file.

I've worked alongside people who cut tenons first and create the mortise from the tenon. As well as people who have left each M&T pretty much as the come from the saw or chisel. Each did really good work, but not really much faster or slower at the end of the day.

So for me, there is nor right or wrong way, just whether it produces the intended results in an acceptable amount of time.

Take care, Mike