The difference in the bridle joints mortise and tenon is in the length of the tenon and the depth of the mortise. The tenon on this joint is as long as the depth of the timber it is being inserted into and the mortise is cut the whole depth of the timber.
This allows the two pieces to lock tightly and you can also see the end grain of the tenon unlike on the mortise and tenon joint which makes it a little less attractive.
Because of this woodwork joints increased interlocking area more adhesives can be applied which creates a joint that may be marginally stronger than a regular mortise and tenon joint although it isn't quite as aesthetically pleasing because the end grain of the tenon can be seen.
Step 1: Start by marking out the tenon by drawing a line around the entire piece of wood to create the tenon length. The length of the tenon will be the same depth as the width of your other piece of timber which has the mortise.
You must now mark your tenon width which should be around 1/3rd the thickness of the timber. Check to see if the tenon matches the closest size chisel or mortising drill bit and if it doesn’t modify the lines to match the chisel or mortising drill bit.
Step 2: Now you cut the tenon and there are two methods of doing this the first being with a tenon saw. Put the piece of timber in a vice on a slight angle to create a neat and straight cut and then carefully cut along the lines.
Next put the timber back upright in the vice and mark 5 millimetres in from each end although it can be slightly more with larger tenons.
Now cut straight down where you marked to create small cut outs on both sides of the tenon, the reason you do this is to create a neat and flush joint but it also hides any gaps you may have from your mortises if they are cut slightly to wide.
The second method of cutting tenons is with a band saw and all you have to do is cut along the lines like you do with the saw.
This method is usually better because the band saw has a guide rail making the cuts quicker and more accurate. Remember to cut the tenon shoulders before cutting the rest of your tenon.
Step 3: For this step you need to mark out the mortise and decide where you want to position the joint.
Next you can use your recently cut tenon as a guide for the width of your mortise and you do this by resting it across the timber that will have the mortise and drawing lines along the two edges of the tenon.
After you have the width sorted you must put two more lines in between the ones you have already drawn to create the thickness of your mortise.
The thickness will be the same as the tenons thickness and you can use it again as a template if you need to but remember to measure the space on each side of the mortise to ensure it is centre.
Step 4: Now cut the mortise and once again there are two methods the first involves a mallet and chisel. If you use the first method you need to put some timber in a vice to rest your timber against and then you clamp the two bits of timber together to hold them steady.
Now you get your chisel and hammer it straight into the wood with the mallet. Apply some pressure away from the chisel bevel and repeat this on the other side of the mortise to create a V shape.
Work from the centre to the outside of the mortise and be patient meaning do not remove too much timber at once but also remember to cut the mortise the entire depth of the wood to house the tenon.
The second method of cutting a mortise involves the mortising machine and what you must do is set the width and depth before you use it. Once they are set simply drill into your timber bit by bit to remove the excess wood.
This method is also the faster more accurate one but remember not to drill too much at once and make sure the gap in the drill bit is facing the empty space of the mortise so the excess timber can escape when it is removed.
Step 5: After you have completed the mortise and tenon check to see if they interlock neatly. If your tenon won’t fit you can shave a minimal amount of timber off with the band saw but do it to both sides.
Step 6: Once you are happy with the joint and it fits flush and neat you can now bond it together with clamps and an adhesive.
Always do a dry clamp first to ensure everything fits and always keep checking for squareness while clamping plus remove the excess glue or you will have glue spots which are hard to remove later.
Tip: Remember that on a bridle joint you will be able to see the end of the tenon because your mortise is cut all the way through the timber. The back of the mortise may need some sanding if your tenon is slightly long but remember it is better slightly longer than shorter.
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