Router Plane

Monday, July 22, 2019

FLW Cabinet - #9 More Leg Problems, Cutting Mortises & Peg Holes


Doing some layout work on the legs is next or at least I thought it was going to be.   Checking one last time to see if any of the legs had moved uncovered a bit of a problem with two of them.  Below you can see the gap at their center.  What was once a set of nice straight edges had developed a bow.  Naturally these two legs are the front ones where the door goes.  Trying to put a straight square door into a curved opening is not a good plan.

Straightening them required a bit of setup.  Since the legs are tapered, I could not work off the opposite edge.  Using the router with a ½” carbide spiral bit run along a known straight edge is the solution. Below is the setup.  Three legs are clamped together to make a level surface and my straight edge in this case the 8’ level is clamped down so the router will take off nothing at the low point of the curve.  That ended up shaving of just under 1/16” at the high points.

After a couple passes with the router the two legs have straight edges and fit together with no gaps.

NOW, I can start working on the leg layout.  Up until now all the legs are the same.  From here on they will be split into left/right legs and also front/back legs.  I need to carefully mark which is which as ending up with too many of one type of leg is not that hard – that’s the voice of experience speaking.  As you can see, I do put a lot of information on pieces to make it easy to keep track of what’s what.

The top photo below is the layout for the mortises and the square holes for the pegs.  To speed things up and make sure the layout is the same from piece to piece I made a jig with master layout lines.  The bottom photo shows the bottom end with the jig in place with the mortise and square holes laid out.

Since the 3/8” mortise chisel is already set up the through mortises will be cut first.  Here is the setup for cutting the mortise into the tapered face.  The machine is set so it cuts the mortise dead center and slightly more than half way through the piece.  A stop makes sure that all of the mortises start at the same point.


The order of cuts is to make one at each end then cuts between them followed by cuts to remove the remaining material.  I use full cuts because it equally loads the chisel.  A three-sided cut could cause the chisel to drift stressing the chisel/drill assembly.

After all the pieces have this cut made the piece is flipped end-to-end so the same face is against the back of the clamping assembly.  That’s so the cuts are all registered against the same face and line up perfectly.  If I were to just flip the piece over and make the cut any difference from the mortise being absolutely centered would keep the cuts from lining up and that’s a problem.  There is one other little quirk in cutting this face and that’s the taper.  Since the tapered face is now down the mortise would not be square to the first setup.  It’s not hard to fix, a short piece from the original tapered offcut is put under the leg which squares things up.  With that done the second half of the mortise can be cut so it ends up aligned with the previous mortise.  Because the leg top and bottom mortises are not the same distance from the end of the leg the whole procedure needs to be done with different start and stop points.

Once all the mortises have been cut a little interior cleanup using a rasp and occasionally a chisel was needed to smooth the surface left by the mortising chisel and clean up any small irregularities.

Cutting the square holes for the pegs in the legs is next.  Here is the top half of the cabinet to give you and idea of the leg pegs.  
 
Changing the mortising bit from 3/8” to ½” is first.  That is followed by setting the distance the pegs are from the inside face on the mortise machine because it is the same for all of the holes.  Last is to set up a roller stand on each side to support the leg when it is cantilevered way out beyond the edge of the table.  The center photo shows that except the left stand is out of the photo.  The right photo shows one hole cut and my small square being used to align the edge of the bit with the layout line.  What does not show up in any of the photos is a 3/8” spacer that fills the through mortises so when the peg holes are drilled the interior side does not blow out when the chisel exits.

After drilling 64 holes for pegs the legs can be set aside until later.  They well underway now but still need; a stopped rabbit for housing the back, final sanding and putting a small radius on some of the edges to soften them.  Below are the legs and a closeup of the bottom of the leg.

Next up are the cross pieces or rails that go between the legs at the top and bottom.  First is to sort through the blanks to decide which ones will be used in the front, the back, which will be the show face, its up/down orientation and marking them accordingly.

Since the rails are 1 1/8” thick and the legs are 1 3/8” thick and I want the inside faces flush means that the tenons are not centered but offset.  Add to that the bottom tenons are not centered vertically means there will be lots of places where things can go very wrong very fast.  Looks like I will be doing a lot of measuring and double checking before cutting.

Next up – Starting the Leg/Rail Tenons

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