Replies

1. 
   Danford_C_ | Jun 06, 2002 02:49am | #1

   CGREEN36,

   Interesting that you should ask.....

   "Consistent" mortise and tenon joints begins with "consistent" stock.  Assuming that you are doing them by machine, that would be followed by precise lay out, and equipment set up.

   After the stock has been four squared and final dimensioned, I'll begin the joinery operations, in this case the tenons.  For production runs I prefer the table saw and tenon jig or on longer pieces the tenons will be milled out on the flat.

   Regardless, each size should be run in single separate operations to insure consistency, using a "master" or single measuring device also goes a long way in consistent layouts and equipment set up.  Little if any trimming will be required.

   As to the second question, no, I've never checked with a vernier caliper. Generally, I lay out my mortises from the finished tenon using a marking knife, make a test mortise, then proceed with the rest.  My idea of a good fitting mortise and tenon joint is that it requires firm pressure to fit the joint by hand and a couple of "taps" with the mallet to separate.  FWIW.

   Dano

   "Form and Function are One" - Frank L. Wright

   
   

   ---

   Edited 6/5/2002 7:51:20 PM ET by Danford C. Jennings

1. 
   DonStephan | Jun 06, 2002 04:41am | #3

   As indicated by my not infrequent requests for help, a consistent run of prefect joints is still more goal than reality. Seems like every time I learn an additional source of error to be addressed the next time. But I also don't expect the same degree of accuracy routinely obtained by a machine shop. Wood is much more dynamic than metal. Bought a shoulder plane last month with the thought that if I intend the mortises and tenons to be tight, a couple swipes with a plane and I have a good joint; when the joint comes off the table saw a bit looser than intended it is good without the plane touchup. Don

1. 
   chairmake1 | Jun 06, 2002 11:34pm | #4

   You hit the nail on the head with the purchase of a shoulder plane. You just gotta have one in order to do the kind of work needed for the mortise and tenon joinery. I use a Delta mortise jig to cut the shoulders of the tenons I always - I mean everytime - use my Stanley #93 to clean up and fit the tenons. Moderate pressure to push in and also to pull apart. The high humidity in Central Texas will play with the fit from day to day so sometimes a little tap from a small hammer is in order. I have put the tenon parts in the oven for ahile and then pressed them into a "wet" leg mortise that has been steam bent and shaped. An 1/8" dowel thru the connection and I've had no failures or any other problems.

   Robert

2. 
   StanleyNiemiec | Jun 06, 2002 04:41am | #2

   I don't know about others but I have been using both venier and dial calipers for almost 20 years now.  I could not function in my shop without 'em.  I cannot understand how someone can measure planer thicknesses without 'em; and basically I use 'em for 99% of all measurements <3".

   For T&G/M&T joints on door frames, I most often use my shaper to cut both the groove, and the tenons.  I want them to hand fit together so that I will have sufficient glue contact on all surfaces.  I try to have the tenons 0.004" smaller than the mortise and will shim the spacer on my shaper spindle assembly to obtain this.  But this is also a function of the adhesives I use (Liquid Hide glue or slightly thinned Borden's PVC white).

   For longer tenons, I have a shaper spindle adapter that accepts router bits.  I will cut the face dimension first on the tenons (using a fixture board with hold-down clamps) and then will reset the height of the spindle to machine the back side.  If I am cutting a bunch of deep mortises, I will set up my Legacy machine that uses a plunge router.

   If i feel it needs it, I am not adverse to using a rabbet plane, file or sandpaper to adjust the fit.  I will likely beveling the corners on the tenon anyway.

   Part of the key to good fitting, secure joints is doing the assembly as soon after machining as possible.  Older joints are generally not as strong (surface oxidation so says the FPL) and I don't want to have the wood changing dimension due to changes in MC.

3. 
   JimGG | Jun 06, 2002 11:43pm | #5

   Having a thickness planer is a big help. Run all your rail and style stock through at the same time which makes them the same thickness (say, 3/4"). Then if you use the table saw to make the tenon by removing material (say, 1/4") from both sides, then a centered 1/4" tenon is left on all tenons (at the same saw setting). If rail and style stock is not the same thickness, then the tenons will be of different thickness. If you make the tenons a hair fat, you can fine tune them with a file. A plunge router with mortice jig can make centered mortices of accurate width. You can get good joints right off the machine. Dial calipers are good to check yourself. Imports are only about $20, and good enough for this.

1. 
   domermatt | Jun 07, 2002 05:52am | #6

   I have to throw in my vote for the horizontal router table in issue 147. Start with properly thicknessed stock and work will proceed smoothly. I cut the mortises first (making sure they are centered), then the tenons (which center automatically). Sometimes they need a cleanup with the shoulder plane but usually if I have cut all my pieces to size accurately the joints are ready to glue right away.

   When people 100 years from now see my work, they'll know I cared. --Matt Mulka

1. 
   Elcoholic | Jun 08, 2002 12:21am | #7

   I like a fit between hand tight and a couple of smacks with a mallet.  If I dry fit a chair and can sit in it without too much wobble I'm a happy 275# camper.  Glue, 3/8" dowel pegs and corner blocks will do the rest.  I do mortises first with a hollow chisel mortiser.  I cut the shoulders 1/32 to 3/64" (yes I use a dial caliper) deeper than the tenon dimensions and cut the mortises an 1/8" deeper  than the tenon length.  This allows quicker fitting of the tenon thickness with just a block plane and gives any small splinters off the mortise walls a place to go.  I have to force my self not to clean up the relatively rough walls of the mortise left by the HC, but I'm learning.  If you touch them at all you can pretty much kiss repeatability bye-bye and count on lots of grief with the tenons.  I cut the height of the tenon an 1/8" shorter than the mortise length for a little adjustment room.  Any part of the joint that's end-grain doesn't really even benefit that much from glue anyway.  Good shoulder contact adds a lot to the M&T so I clean them up as needed with a shoulder plane (the small LN).  Even after accurately thicknessing my stock (planer and drum sanding) I have some trouble with the most critical fit - tenon cheeks to mortise sides.  That's were the only long grain to long grain contact is and therefore the strength of glue bond.  The freshly milled wood just doesn't sit still for very long 2 miles from the beach.  I used to use the Delta jig on the TS and flip the piece for centered tenons.  On my current run of chairs I experimented using the outer blades from my dado set (CMT) and spacers instead of flipping.  It only took a couple of test cuts to shim them for the most consistent fit I've ever had and it took 1/2 as many cheek cuts!  My spacers were fairly crude being made of muliple thickness of 1/8" BB ply and I used the CMT plastic shims.  I'm seriously considering buying a matched set of 10" blades and having a machine (saw?) shop make a set of precision spacers made for each of the std. hollow chisel sizes.John O'Connell - JKO Handcrafted Woodworking

   Life is tough.  It's tougher if you're stupid - John Wayne

1. 
   theRev | Jun 08, 2002 01:15am | #8

   Elco-man,

   I've heard of that technique and have wanted to try it myself but haven't gotten around to it. This person was using CD's as spacers. Once you get your setting just right, save the spacer set, label it, and hang it on the wall. Ready to go next time.

   Scott