Making and Using Tools - Layout and Measuring Tools
Twist-Lock Marking Gauge by Jim Hendricks
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received a beautiful old rosewood twist-lock marking gauge.
I thought that this would make a superb tool to build. Something
simple, yet deceptively clever.
First we will discuss stock selection, show how the original was
measured and how these dimensions are transferred to the raw
What You Will Need
You can use off-cuts and even if you don't have anything
suitable, you can get even expensive exotics fairly cheaply from
woodturner suppliers as you won't need very large pieces at all.
The best wood for this type of tool is a species which will
withstand the rigors of constant use. Most of the value of a
homemade tool is the time spent making it, so it does not make
sense to use a soft or unsuitable wood.
Traditional stock includes boxwood, ebony, rosewood, beech,
maple, hornbeam and many more of the hard exotics too numerous
to list them all.
I have chosen English boxwood which is available in "the round".
Since you will almost certainly start with squared stock you can
ignore the first part of this article, just size it as follows:
1 block 3"x2"x1" for the head
1 piece 3/4"x3/4"x9" for the bar
This is slightly oversized but we are aiming to get a bar
diameter of 2/3", so bear this in mind.
This is the original "twist-lock" marking gauge made out of
rosewood and using a simple screw as the cutter.
I will also use a screw in our new gauge but then I will show
how to make a cutter from O1 tool steel (gauge plate) or from a
piece of old bandsaw blade and a brass wedge if you want to make
your gauge a bit special. As you will see however, this simple
solution works very well indeed!
The principle of the "twist lock" mechanism is simply a cam. The
hole is comma shaped, being a true circle with an extended curve
key. The bar is the same shape so it will fit easily into the
hole if you line it up with the comma.
A simple twist however, will bring the thicker part of the bar
into contact with the thinner part of the head hole and thus
lock it in place, very firmly indeed! And that is it!