Perfect Miters...
Every Time

By David Knipfer
August 2005

Well...   when I am exhibiting my little boxes at a craft show, the WWs who stop by usually have 3 questions...

Question #1:  Where do you get your wood?
Answer:  Trees usually.

Thats always good for a chuckle before I fess up and tell them my local sources.

Question #2:  How do you finish these?
Answer:  Rude and Crude.

Then I tell them about shellac first followed by oil.

Question #3:  What do you use to make these miters?
Answer:  My homeowners tablesaw and a miter gauge.

Thats the point they usually stop believing me.

I suppose lots of folks think there is magic somehow in cutting perfect miters...  I'm talking about gap-free, crisp, perfect miters.

Anyways...   I'm writing the section in my book about building box carcasses...  so I figured I'd share a few of the photos that speak to making perfect miters...

There is no magic at all here...   just paying attention to the basics...

Here is how I go about it...

If you aspire to make truly perfect miters...   then IMHO you need to square away:
  •   your tablesaw,
  •   your accessories and
  •   your timbers.

  • Then perfect miters are a cakewalk everytime.

    Lets speak to each of those points individually...

  •   Your tablesaw needs to be in tune.

  • If you have any doubts about how to tune your saw...   then I recommend to you the great book "Mastering Woodworking Machines" written by Mark Duginske.

    Duginske is best know as a Master of the bandsaw...   but this is a fine text and describes in clear language how to tune and maintain all the power tools in your shop.

    Paraphrasing from Duginske...   a properly tuned tablesaw will have the following characteristics...

    1.   The table top and extensions are flat.
    2.   The cradle and arbor assemblies are secure.
    3.   The arbor turns smoothly without excessive runout.
    4.   The miter gauge slots are parallel to the blade.
    5.   The blade is at 90 degrees to the table.
    6.   The miter gauge is at 90 degrees to the blade and to the table.
    7.   The rip fence is parallel to the blade and at 90 degrees to the table.

    Duginske covers how to check and adjust all of those items...  and that's part of what I was doing yesterday.

    Unless your saw is in tune...  forget the rest of this post.

    You can't get to perfect miter heaven with a sloppy saw.

    OK... so your saw is squared away?
    Good for you.

    Now, take a look at the two accessories that you need to make perfect miters...  your sawblade and miter gauge.

  •   Your blade needs to be clean and sharp.

  • I use a Freud 80-tooth cut-off blade for making miters.   It is clean and sharp.

  •   Several years ago I purchased a Woodhaven miter gauge
  • because it has the ability to be adjusted to fit the miter slot perfectly without any play.

    You can get there of course as well with a stock miter gauge...   I recall dimpling the edge of the bar with a punch to get the fit proper.

    Either way...   side-to-side play in your miter gauge is a no-no.   Correct it.

  •   I add a scrap wood extension to my miter gauge.
  • It gives me some backup to the cut to prevent tearout...   and also allows me to see exactly where the cut will be made.

    You have those accessories squared away?
    Good for you again...   you're almost there.

    Last required element...
  •   your timbers themselves.

  • I hope it goes without explaining, that whatever you are trying to miter, it needs to be flat with parallel edges.

    If you have all these things in place...   a tuned saw, squared away accessories and properly prepared timbers...   then you are ready to cut perfect miters with your tablesaw alone.

    Photos are next.

    I start by getting the blade angle close to 45 degrees and checking it with a drafting square...

    This is by no means the final check...   but it gets me closer to start.

    A few tips here...   raise the blade as high as you can, and be sure to measure against the blade blank...   not against a tooth.

    Adjust the blade angle until it makes a perfect 45 degree fit to that triangle.

    Then...   make a pass at the scrap end of your stock.

    Here, I'm ready to shave just a little off to recheck the angles after an adjustment.

    Then, we get a little more accurate in our angle checks...   I don't know how anybody does precision work without an accurate adjustable square.

    My Starrett 12" adjustable square is set so that I have all the blade extending out to one side...   then I check the 45 degree angle.

    With 10" or so of blade sticking out there...   your eye can see any error to a fraction of a degree by looking for a visible gap along the blade.

    Stop and take the time to adjust the blade angle if you need to...   make another test cut and check this again.

    Make it just right...   perfect.

    Then...   don't forget that miters are actually two angles that need to be correct...   that 45 degree angle we just set and also the 90 degree crosscut.

    So I check the crosscut angle as well...

    Once you feel you two angles are correct...   then we make the acid test...

    Cut the other end of your plank...   flip one over and lay them next to each other on a true flat surface.

    I use my tablesaw top...

    This is the final test...   if you have perfect miters it should look like those two pieces are one...   no gaps...   either at the miter or along the crosscut face...

    In my book, you'll see all the steps to make the carcass...   but fast forwading here a bit...

    This is the goal...   perfect miters.

    No fancy jigs...   just a tablesaw and miter gauge...   and a little attention to the basics.

    You can make them this way as well...   everytime.

    It's just a matter of taking care of the basics.

    That's it.



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