Sunday, September 26, 2010

Using the KM-1 on a Table Saw

The Bridge City Toolworks KM-1 is a clever instrument for perfectly sizing a dado, groove, half-laps, or anything, really, if you treat it as an instrument for perfectly calculating an offset.  Visit the linked page for Bridge City's description of it, or, if you're not the type to "read it for the articles", watch the video of how it's used.

I'm currently making a simple cabinet for inside a closet.  This will be a wonder of plywood case construction with plywood shelves dadoed into plywood sides.  That said, I will be using the KM-1 liberally to ensure that I get exact dados for the "nominal 3/4" and "nominal 1/2" ply.

In the demonstration video, the KM-1 is registered against a stop block on a fence used while cross cutting to create the half-laps.  Naturally you can do the same on a table saw crosscut fence, but what if you're using the rip fence as I will since these sides are 4-5' long by 22" deep?  All you need is a stop block of sorts for the KM-1 to register against.

This is my stop block for the table saw along with a MagSwitch from my magnetic feather board and the KM-1 (I feel as though I should have anodized my MDF jig, but I digress...)

The MagSwitch has two flat sides so I get a very snug fit and it locks the jig to the cast iron like a rock.  Use the shoulder of the jig to register the KM-1 for the first cut...

...the flip the KM-1, move the fence, and make your second cut that will finish the perfectly fitted dado.

I have a router table in the extension wing so the MagSwitch won't work out there.  However, my fence rail is steel so I can move the jig there when I need to be out 22" or further.  Here it's shown with the KM-1 ready for the first cut...

...and flip it and move the fence for the second cut.

When I documented how I did a walnut inlay into cork flooring, I described how I used the KM-1 with the Festool OF-1400 router to make the inlay groove exactly match the inlay pieces.  Basically all you ever need is a stop block of some kind.  This MDF jig for the table saw will definitely make the KM-1 easier to use when dealing with the rip fence.


  • Anonymous said...

    Thanks for sharing
    I used the KM-1 yesterday for the first time and spent hours trying to figure out on how to use on a long board with repeat dado.
    I will try your jog.

  • Anonymous said...

    I just purchased a TM-1. How did you
    come up with your stop block size and set up? I am trying to use mine on the BS and can't figure out how to place the stop block to get the cut. I am sure it's just a senior moment ;-) . How did you figure out the distance to set the stop block?

  • HalfInchShy said...

    Hi, Charlie,

    Do you mean the KM-1 or TM-1? I'm actually in the shop right now recording a video on using the KM-1 on a tablesaw, bandsaw, router, mitersaw and the JMPv2. It should be out early this week.

    If you mean the TM-1, I do have one, but haven't posted anything about it. The jig I used for the KM-1 is detailed in the video and likely will work fine for the TM-1.

    There aren't a lot of hard numbers to the jig; my jigs are all of the easiest kind :)

  • Anonymous said...

    I have the TM-1. I must have tried
    hundred different ways and I can't get my head around it, probably be one of those"AHH HA!" moments, but until then it's a head scratcher.
    How do you set the stop block? I mean, how do you come up with that initial distance before you insert the TM-1. That's the head scratcher.
    I am sure I am "over thinking" it.

  • HalfInchShy said...

    Works the same way as the KM-1. Set your fence for the first shoulder cut for the tenon. Then you put the TM-1 on the saw deck against the fence and clamp a stop-block on the other side. Make the first shoulder cut. Now flip the TM-1, bump it to the stop-block and slide the fence over to bump the TM-1. Make the second shoulder cut.

    The only difference between the TM-1 and KM-1 is that the TM-1 leaves something the size of the calibration whereas the KM-1 removes something the size of the calibration.

  • Anonymous said...

    AHH HA!

  • HalfInchShy said...

    Excellent! But do watch for the KM-1 video this week as the method of use is very very similar to the TM-1. You'll likely get some tips you can apply to the TM-1 there until I do a video of that.

  • Anonymous said...

    I will definitely keep an eye out
    for the video. The problem I was having was that I was not only flipping the TM-1 but also the work
    piece... a little flip happy ;-0
    After I picked it apart it all came
    together, thanks again for the advise!