Wednesday 11 July 2018
1 Any bandsaw will do as long as the all-important blade is sharp. I use a basic 12in machine for all my joint cutting
2 While not essential, a substantial mitre guide makes the job easier. Mine is made from a piece of thick MDF with a perfect right-angle on one corner. Use it as a fence to feed work into the blade
3 The blade must cut dead straight or the tenon will vary in size along its length, so make a test cut to see how the current blade performs. For most work a 3/8in x 6tpi wide blade is more than adequate but change to a 5/8in if there is a lot of serious ripping to do
4 If the blade is in good condition, but pulls away from the rip fence, it may be that the fence is out of alignment and needs adjusting to compensate for the 'lead'
5 Use an engineer's square to check that the table is dead square to the blade. Be aware that the stop bolt underneath the table, that allows you to reset it back at 0 degrees after tilting, may need minor adjustment to get the alignment spot on
The key factor is getting the length of the cut for each of the tenon cheek identical on either side.While you can do this by eye, every joint must be marked out individually. A much better and quicker way is to use a repeat stop. If your machine doesn't have a tenoning stop make one from a scrap of wood and a G-clamp fixed to the fence. For setting purposes mark out the first tenon then make all the other cuts just using the stops.
6 Start by carefully cutting the first cheek to stop dead on the shoulder line. Leave the timber in this position and switch off the bandsaw
7 Slide the tenoning stop up against the end of the timber and clamp it in position on the fence
8 Note how the end of the stop is angled away slightly so that any sawdust build-up ahead of the sliding workpiece won't interfere with it engaging on the stop
9 Now the stop is set in the correct position, start up the saw, withdraw the timber, turn it over and make a cut for the second cheek. At the end of the cut leave the timber in position for a few seconds to allow the blade to move forward slightly off the rear thrust bearing, otherwise the length of cut may vary slightly. Repeat the procedure for all the workpieces; none will need marking as you are working against the fence and stop every time
10 The shoulders are cut using the mitre guide, so make a few trial cuts first on scrap to ensure it is actually cutting at 90 degrees to the blade. Use your block of wood and clamp as a spacer, but keep it well forwards of the blade
11 This gives you the correct positioning for the timber as you start, but as the cut is made the block of waste falls away well clear of the fence
12 This procedure should produce a perfect tenon with square shoulders that are all lined up properly, essential requirements if the joint is to be strong and look neat