I needed to measure the depth of some big wide mortises and the only thing I could find that worked was my marking gauge. Worked quite well actually but felt kinda lame. Made me think I needed a “real” depth gauge so I bought a nice old Lufkin. These old tools are nice because they have a “tension” spring that keeps the rule from falling out when the nut is loosened. I like it but I wanted something bigger so off to the shop!
The base on this one is 4″. I used a 6″ flexible rule (another Lufkin from some combo old tool deal), which feels too thin but seems to work fine. The most work was rule holder but it was the quickest to make (go figure). I fiddled and faddled with shapes for the wood and finally wound up with a series of ellipses, which I bandsawed out of Jatoba (with lots of tear-out removed with a hefty round over). I milled a slot for the rule and used a forstner bit to drill the cavity for the holder. Wood done.
The rule holder consists of five parts: the brass and steel gizmo the rule slides through, a #10×24 screw, a spring, a thin brass washer (to keep the spring from digging into the wood), and a brass nut. The rule is locked in place by the outer brass face pressing it against the wood.
Only the spring and screw were “off the shelf”. I made the gizmo by taking a ¾” steel rod, milling a slot in the face and then drilling, tapping and countersinking a hole for the screw. I brazed on a brass cap and drilled a access hole for the screw (I pretend it is a window to the rule). The nut has a spring recess (~ ½ spring length) so the spring can compress but not get smashed. I just sorta winged the shape, using files to do most of the curvy stuff (on the lathe, under power). For the “rope” knurl, I hand held the knurling tool and rotated it around the “rope”.