Monday, June 15, 2009

Exterior Wooden Door Part Two

A Closer Look at Mortising using a Brace and Bit

I had a few comments from my last post and thought it would make sense to answer them here. Been busy this week so I apologise for the delay. To start off with, no...I won't be publishing the address of my clients home where this door is destined so you can do a 'drive by'...they may not think that's such a good idea! :) As for a template, I tried to get some shots of the one I made; sorry for the quality but with the low ceiling in the basement shop I can't get the entire template in one shot so I'll try to sketch a diagram for my next post. I basically just cut out a piece of luan to match the finished door size and then carefully drew to scale all of the elements of the finished piece...joinery, rails, stiles etc... I was asked about the process I've been using to cross cut the rails with a inadequate size back saw. I actually took a few approaches to this and will describe it here; for the bottom rail as well as the mid-locking rail I started the cut on the board edge to establish a square kerf on either side. I then proceeded to make two passes working in from each surface. This worked well and the edge kerfs gave a track for my back saw to follow. The upper rails are thinner in width so I just made the two surface cuts meeting somewhere in the center of the board. When I lay out these lines I'm careful to work off of only my reference face and edge to keep things as accurate as possible. Once the sawing is complete I'll use a large paring chisel when it comes time to square off the end; if I was working with thinner stock then this would be accomplished on my shooting board but for 1 3/4" stock I prefer a chisel to say a low angle block plane. (Just my personal preference-either way works.) I hope that explains the cross cut system I follow; I should say that I used my bench hook as well as my miter hook for these large timbers...you can see my set up in the first photo. I considered my saw bench and did a test cut with my panel saw but with my limited shop space and the nature of this Oak I had better results with my large Lie Nielsen back saw. (still waiting for the 'Bad Axes' to arrive...won't be soon enough!!) With everything cross cut, ripped and surface planed square I lay out the mortises. These will be 5/8" thick and range from 2 1/2" to 3" deep. They all have 1" deep by 1" wide haunches but will be later cut down when the door panels get introduced. The 3" ones are on the stiles and wider lower rails and the 2 1/2" for the top 5" rail. The upper window rail gets a relatively shallow 1" mortise. I actually started with that one to get into the feel of the Oak and get a rhythm for the work. I have a great old Millers Falls brace I cleaned up about 4 years ago and it's been my daily user ever since. It's a standard 6" sweep but I don't have any issues with this smaller size. A sharp, straight bit really helps as well and I'm using a vintage Irwin auger bit I purchased for a couple of dollars at a local antique dealer. It only has one spur and is a perfect size...9/16" so I'm left with a small amount of waste to clean off the inside cheeks of each 5/8" mortise after drilling. This is a good thing-I'd never want to use a bit the exact size of my finished mortise due to the slight tear out and human error involved in the process. Even after I clearly define a center mark to register my bit some holes seem to drift ever so slightly. I figure this is mainly due to fatigue and mind meandering while performing the task. A reader mentioned using a brace with a 10" sweep...I would love to find one sometime; I can only assume it would make this process a little less demanding on the arm muscles but again, my old Millers Falls seems to be up for the challenge. When starting out the hole I'll check for plumb with a small engineers square placed along side the bit. I'll slowly get into the wood fiber and check again on the opposite axis. Begin working down and stop frequently to remove the waste. I just blow this off and never have to back out the bit. I should also mention my elaborate system of depth gauge...the ball of blue tape around the bit is it...nothing could be simpler. I should probably drill out a long piece of wood and cut it to length again placing it on the bit while I drill...this would indeed result in more accurate depths but these mortises don't have to be exact. Close to about 1/32" but not exact. It's only end grain meeting down there so as long as they're deep enough I don't worry too much.
The following is a quick clip of my process...one thing to notice is which hand I'm using where. I'm right handed so this goes at the top of the brace; I think the natural tendency would be to use your stronger arm for the turning motion but this is inaccurate. Use your leading hand to hold the brace secure and square and your other hand to turn. A bit of practice and you'll be reaching for the 'ol brace all of the time.

"Unplugg the drill and wrap your hand around the words of working man..."


video

5 comments:

  1. Come visit my house, lots of asthetic work need to be done.
    Cheers !

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  2. I will indeed...
    see you soon cousin!

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  3. Okay I saw it but I don't beleive it. I heard the singing but your lips didn't move once other than to blow the chips away. Not only quality workmanship but also a performer of magic. I can't waite to see what you do while trimming the tenons. Sorry waiting for my students to show up for night school and thought I would drop in to see what you are up to.

    Dan

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  4. Pulling a rabbit out of that mortise would be somethin' now wouldn't it?
    Thanks for the comment.

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  5. Hi Tom,
    I find myself humming your Working Man song while I'm in the shop lately.

    Thanks for the video! :-)

    Stephane

    ReplyDelete