I built the 12x16ft shed described in the sobon book. I did it all with hand tools,using a chisel and slick to make the tenons. I used a handsaw for the shoulder line. If I do a larger project, I would like to gain speed using power tools. I assume to make the tenon, a skilsaw is used. The end is squared and the saw is placed on the endgrain and two rip cuts are made with the saw. Is this correct? What size saw is needed ( 16"?)and are there sources for used equipment. Same question for the mortise. I used boring tool and 1.5 or 2." auger bits. Can a chain mortiser be acquired used or is it likely to be burned out from use? Any leads appreciated.
Thanks,
Bob

You can do it as you mention but be sure to leave enough to pare to the line. Very often I see beginners think they can cut to the line and then they make the tenon too small/thin. As to what saw you use, use the one you have and then finish with a hand saw if needed.


From time to time used chain mortisers do become available. Recently I helped two different framers sell two machines to two others. I can watch for one for you....

You may be surprised at how small a circular saw you can use for tenon cheek cuts. Even if it's just over half the depth of the timber, it will be effective. Make four cuts (each side of the tenon, top and bottom). You'll leave a "widow's peak" of uncut wood. If the grain is straight, a light tap with a mallet will usually knock of the waste. Clean it up with a slick. Or use a hand saw to cut the widow's peak. Jim's advice about thin tenons is spot on. CB.

A 7&1/4 circ saw is usually enough depending on the size of your timber. You draw out the cuts for the tenon on all 4 side of the timber with proper layout technique. Then lay it out again, this time scoring your layout cut lines with a utility knife. Roll the knife to the scrap side. This will leave your shoulder or face nice and square/sharp. With the timber set so the tenon is horizontal, set the depth of your circ saw by holding to the side of the timber and make your depth about a 16th short of your tenon face. Cut the shoulders to this depth staying 1/16 to 1/8 away from your score line. Roll your timber 90 degrees and reset the depth of your circ saw deep as you can but not so much that you will run into your good wood. Now cut along the sides of the tenon staying 1/16th or more away from your final score line. Note: always check your circ saw for the blade being square to the foot before any cuts. Once you've cut as much as you can with the circ saw, you can try whacking the scrap portion with your mallet. If your cuts were close enough, the chunk will break out and then you will chisel and pare to your score lines. Remember not to try to take more than 1/32 with each chisel&mallet pass. Use your combination square to check your shoulder and tenon for square as you pare. If your circ saw cuts were not close enough, use a hand saw to finish your cut, but be careful to keep your saw square and don't overcut into your good wood. You can even just get close and then whack it with your mallet. The 7&1/4 circ saw is an important tool for large chunk material removeal. I was also taught that when using a large 13 inch or 16 inch beam saw, first make cuts on either side of your piece with the 7&1/4 saw, then come back with the beam saw and use one of those kerfs as a guide for the beam saw. This also reduces the amount of material the beam saw has to cut, so it's not straining so much in the cut. Use the larger saw for it's cutting length, not to necessarily cut more material in a pass.

I'll stick my ole neck out and say CUT TO THE LINE!!! work slowly if you need to and have a pair of safety glasses so you can see what you are doing.
Gabel makes a great point about this when he says watch BOTH faces that the saw is entering.
your circular saw skills will NOT improve if you stay off the line.
In fact, they may even get worse....

Hi Everybody!

if you are going to drop cut the tenons with a circular saw make sure the end of tenon cut is nicely done. for instance if you have a four inch tenon on a tie-beam, make sure you lay-out the end of tenon cut parallel to your shoulder. If this cut is accurate then when you drop cut the 4 inch cut the base of your saw will have a nice plane to ride on. This really helps with control of that cut. Sometimes people don't worry about the end of tenon cut because it is waste but then those people usually are not thinking of their next cut.

Another good rule (if you are precise with lay-out) is to take both the lines on tenons and mortises. It seems like to much time is taken to fit-up sometimes.

Do you all really think that if a tenon has a 16th of a inch on each side between the mortise and tenon (non-bearing faces) it really makes a difference. And if so why. Thanks, mo

Thanks for all of the comments,espeeecially Jim Rogers saying use what you have and have fun. Thai is advice I can relate to.
Bob

Bottom line is sloppy joints are bad....
There shouldn't be a business card thickness between the mortise and the tenon....
What happens when things dry out... they shrink... Will that 16 of an inch be a 16th after drying?
No it will be much larger....
If you're building an outbuilding such as a garage, barn or shed that's one thing but if you're building a house that's another...
I don't want big gaps and sloppy joints in my house.....

Mark, from my experiences watching beginner students trying to cut to the line with a skill saw, is that they can't do it and they usually make a wrong cut, making the piece two small.
I prefer they leave the line and then pare to the line using a chisel. If the line is scored then putting the chisel in the scored line is accurate and precise.
A power skill saw in the hands of an inexperienced student can be a bad thing, and mistakes can be made very fast...

Jim, I'll just toss back that I've seen plenty of undersized tenons cut with a chisel in my classes here...
What I tell my students now is that if you can cut to the line, by all means do it. If you can't cut to the line, then by all means stay off a bit and pare down. But a beginner paring down with a chisel or slick is often just as inaccurate as a beginner going for the line with the saw. So why not start developing your saw technique by going for the line? Also I am using primarily hand tools in my classes and only hand tools for the introductory classes.

Personally, I like to go for the best possible fit with the least possible fuss. I get there by keeping mortise and tenon guages handy at all times and developing my sense of what a finished mortise and tenon look like. I think a joint should slide together easily but not be loose enough to 'wiggle'.

derek, you need to get clear oil.... 10w30 for example, or hydraulic fluid
( - ;

Amen Jim. I was taught recently "Perfection and Grace puts a smile on your face", corny but true for a craftsman. You do want precise, tight joints as shrinkage will cause a gap to open up even if the joint is perfectly tight when done with green wood. 1/32" of shrinkage gap you can live with in your home. 1/16th or more looks like poor crafstmanship. And if it's your home, you will notice. That is why I said (as I was taught), leave 1/16th when using the saw, then chisel and pare to your scoreline and use your combination square to make those tennon shoulders and mortises dead nuts. It's amazing how much precision you can get with good layout/score lines and a sharp chisel. You should spend as much time surveying and laying out your timbers as you do cutting. That will save you lots of problems in the end.

I would never suggest leaving a exposed mortise with a 16th on either side, nor would I leave excess room above and below the tenon in a frame, however a tie beam is wider than a two inch tenon and the sides of the mortise will not be seen, don't let my question convolute my thinking on precision, Precision is the way to go or you will pay the price ten fold down the line. That being said, again what is the problem in a hypothetical bent where all critical points are on then noses and bearing points not the side faces where plates, joists and purlins leave that tie beam in the right place?

I pose this question because most people who work in a shop do not all have the same degree of precision, so.. if the shop takes the attitude of having a more narrow tenon than fit up will proceed more efficient. To some up long winded post to explain reasoning I still ask the question.

Are there any problems with having room on each side of the tenon in a mortise (when it is concealed, therefore disregarding the aesthetic debate)?

Mo:
If you feel your using too much time in fit up then the joints cut that need extra work during fit up aren't being cut right in the first place.
Making sloppy joints to save time during fit up isn't the answer. Making correct joints in the first place is. If the joint is cut correctly then fit up shouldn't take a huge amount of time.
As far as your exact question about a beam with hidden shoulders, my first thought was the possibility of some rotation, although very little, I would imagine. But also, load goes to stiffness, if a joint isn't stiff then the load shifts to where it can and this could put added stress or load to another area.
Of course this is my opinion.

If you are having fit up problems (more than a quick parring touchup on a percentage of the joints), perhaps your layout technique is not sufficient. What is your layout technique? Do you score as I described in an earlier post? Do you do your layout referenced from one side of the bent, outside faces, basically two reference surfaces? how square are the beams you are starting with?

I saw to the line as well, with hand tools and power tools. I only score in hardwoods. If you look at the shoulders of old frames you don't generally see chisel marks (because they were sawn). One advantage of square rule framing is the housings (girts, braces, studs, all non-through housings that is) hide potential shrinkage. Drawboring takes care of some as well, and then you don't need 15 comealongs (or any really). I'm still practicing with the chain saw on the end of tenon cuts.

thanks for you all's insight. Personally I do not like to or do leave room on any joinery. Just wanted to see the consequences if any that people might think of with said areas.

BB, my lay-out technique depends upon the wood and/or design. Sometimes Mill Rule, sometimes datum line square rule, sometimes edge rule square rule, sometimes french scribe, sometimes sauterelle lay-out (bevel), mechanical pencil, framing square, ruler from combination square, tape measure, 20/16 vision, always attempting dead on replication of design, spans and heights within 1/16th of an inch.

mo

that's an interesting concept to use chainsaws for cutting joints. my background is log building, but i set aside the saw after felling and hewing because i thought it wasn't appropriate for timber framing. but the skil saw isn't seeming that accurate with the uneven surfaces, and i'm ending up chiseling all the cut offs anyway. i wonder if it would be easier just to rough everything out with the chain saw and make a clean cut surface with a slick and chisel.

a friend mentioned using a plywood jig to support a skil saw on a hewn timber. does anyone have experience with this?

we use olive oil as bar oil when quartering moose. only COLD PRESSED extra virgin though. ;>)

use the tool that works the best!
probably safer to use a chainsaw on hewn timber, rather than have the circular saw baseplate hanging up in the air most of the time.
sharp chainsaw and good eye can be an awesome combo.
olive oil is actually good for bar oil, doesn't dry out. I also use canola, bit cheaper.

I'm with Mark - cut to the line with your saw! Life's too short, oak's too hard, and there are too many variables beyond my control to imagine that all of my joints are going to end up with less than 1/16th gap after assembly and drying. House all of your joinery if you don't want any visible gaps.