Mortise and Tenon Joint

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About: hgv driver but only because it pays more than I can make otherwise

As part of another project I needed a door, I decided to make this myself. I decided perhaps rashly mortise & tenon joints would be in order.
Having never made one before I decided to do a practice one first I am not a regular wood worker, a few wood work lessons for one term back when I was 13 is all the instruction I've ever had, but I'm prepared to try my hand at pretty much anything. I've made this instructable in part to encourage others to have a go, and in part to get advice as to how I could have done it better from more experienced woodworkers.

please note a few of the photos are taken from the construction of the door, not my first actual attempt at doing this, even then they are only my next six joints.

Step 1: Tools

I already had access to some good quality chisels, and a carpenters square.
Whilst I've cut halving joints and a fair few beams to size with a cheap hard point saw in the past I invested in a new cheap tenon saw, just £5 I liked the feel of this one the handle fitted my hand better than some more expensive budget ones, I also brought a cheap combination marking/ mortise gauge, this I could have done without but once set up it makes doing repeated joints much quicker. I also used a pencil, a Stanley knife,& Steel rule for marking out. A hand brace with a1/2" flat woodbit to remove the bulk of the wood from the mortise (I subsequently added a pad saw to my tools to save on chisel work).
My work bench was mostly an elderly folding work bench with clamping jaws salvaged from a skip more than 20 years ago.

Step 2: Set the Marking Gauge

measure the thicknesses of the timber devide by 3, set the fixed tang to 2/3 the thickness the moveable one to 1/3, lock and make a test mark on the timber swap sides check the points line up with the test mark adjust if needed.

Step 3: Marking Out

I laid my 2 pieces of wood in the T form and lightly marked the edges an end of the joint with the pencil.
I then positioned the carpenters square on these lines and marked them more firmly, I then checked theses lines were where I wanted them to be, happy they were I again used the square and pencil to mark around all 4 sides of each piece.

Hindsight 1) mark the orientation of the joint and use the marking gauge from the same side on each section unsurprisingly my set up wasn't as accurate as it should have been but matching the orientation means the error is in the same direction on both parts.

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Once happy with the lay out in pencil I went over the lines again with a stanly knife still using the square for guidance. Now I remember we used marking knives at school the explanation was it made a cleaner cut than just the saw, I didn't used to bother with using a knife, but I noticed on occasions when I've not had a pencil to hand and just used a knife not only are my cuts cleaner they seem to be more accurate, I'm not sure if it needs more care to follow just a fine knife cut or if it some how guides the blade as it starts or if it is just an incorrect impression I've got

Step 4: Cut the Mortice

using a flat wood bit and a hand brace I chain drilled the mortise cavity taking care not to go all the way through to avoid splintering the exit side.I then drilled through from that side ( hindsight 2) this is probably what caused the ridge that stopped the joint closing those last 10 to 12mm see later step) I was able to trim the remaining webs out with a sharp knife I've taken to using a pad saw for this on followed up with a chisel.

The workmate tm (folding bench) is not substantial enough to stand the blows on the chisel so I worked on the ground with a scrap block under my work, hammering a chisel into the concrete won't do it any good, also keep your free hand behind the blade blood stains wood something terrible

Step 5: Cut the Tennon

Whilst it is perfectly possible to cut a tenon joint with any hand saw a proper hard backed tenon saw makes it easier, possibly in my opinion as a novice, a good hand grip is more important as good control of the cut is essential.

I started with the shoulders I cut carefully down to the edge of the tenon on both sides.
I then cut down the end grain along the faces of the tenon, this would have been easier with a vice that would hold the work vertical. I found I got best control by fixing my work horizontally in my work bench and sitting on top of it whilst making the initial cuts, once down to the shoulder of the tenon I turned the piece over and cut down to the shoulder of the tenon on the other side, once this was done it was possible to mount the piece vertically and cut squarely through the remaining triangular web of wood down to the shoulder, this was then repeated for the other side of the tenon

Step 6: Test and Trim

With the mortise and tenons cut it was time to do a trail fit.
The tenon would start in the mortician about 3mm(1/8") from either side so I pared a little off each face of the tenon with a chisel this allowed the joint to fit about a third of the way in, it was visible at this stage that my joint was off set and that the un-cut sections would not meet with a flush join it was also apparent that one way up the off set was less pronounced than the other.
At this point I marked the orientation of the joint something I should have done when marking out.
By removing wood only from the face of the tenon that was under flush with the mortise frame and later from that side of the mortise socket I was able to bring the joint together almost flush. After a little more wood being pared off the tenon from just the one face another fitting I noted the marks on the face of the tenon evidence of some tight spots in the mortise and cleaned up the inside of the mortise, this allowed the joint to almost close about 12mm short on a 63mm section.(on adding the photos I note part of the reason for this is I assembled the joint in the wrong orientation when I tapped (ok whacked it rather hard) it with a mallet
I thought that "tap" with a mallet would close the joint and leave witness marks where the joint was still tight. Whist this was the case it also split the wood around the mortise .
Paring more wood off the face of the tenon and the inside of the mortise did result in a joint that closed reasonably flush and without opening up the split made by hammering the joint together.

Step 7: Next Step

Happy with my first attempt, I proceeded to make the frame for a simple two panel door.
The complete how to build a door may appear later as a stand alone instructable or as part of how I designed and built a shed.

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