Thursday, August 15, 2019

Dedicated Mortise Gauges

I've thought for a while about making a couple dedicated mortise gauges.  The Marples and Veritas mortise gauges I have work well, but I have some scrap material to use up and this is a nice project for scrap.  It seems like most of my mortises are either 1/4" or 3/8", so having dedicated gauges for these sizes might be helpful.  And I can space the pins just right for the chisels I use.

The 3/8" gauge is made from cherry.  After squaring up a piece of wood, I laid out some lines, then bored out and pared the mortise.  Adding a smaller, angled mortise for the wedge was a piece of cake.  I made the smaller mortise about 1/16" larger on one side of the 1" thick fence than the other side.  This gave the wedge a nice angle to do its job of tightening the beam to the fence.
The fence blank with two mortises
One detail to consider is how large you want the beam to be.  I made a single-pin marking gauge a few years ago and the beam is 7/8" square.  It is a great marking gauge, but it seems a bit bulky.  So on the 3/8" gauge, I decided on 13/16" square and it looks and feels great.
The parts of the gauge
I like the pins of the gauge to run catty-cornered, so I chiseled a little flat in that area to accommodate the pins.
The beam, showing the flat area for the pins
For the pins, I used ordinary nails (with heads cut off) and I filed the ends to make a sharp rounded end.
Pin shape in profile
Pin shape straight on
To hold the nail for filing, I'm using a little finger vise that I found at a garage sale last year.  I love this thing - it really comes in handy for small duty filing.
Stubs finger vise (that's a 3/4" dog hole behind it for size reference)
I took a torch to the nails to harden them, quenched in oil, and then pounded them into the beam and got them set at the same height.  I have no idea whether the heat treatment will have had any beneficial effect on the type of steel used for the nails, but it seemed like a good idea.  Actually, they still seemed fairly soft after that.
The bevels are set to leave any bruising between the pins
Finished using Watco
This Watco had been in this jar in my cabinet for years.  I thinned it a little with turpentine and applied it with a rag, wiping the excess 15-20 minutes later and repeated this the next day.  After several days, the wood still had a tacky feel to it, so I won't be using this stuff again.  I did wax the front face of the fence after a few days, but it still didn't feel right.  It performed fine on some test marking, so I'll see how it goes when I need to use it in the future.

The 1/4" mortise gauge is from a design I saw in one of Bob Rozaieski's videos.  For this one I made a prototype in poplar, thinking I would make the real thing from some harder wood.  But the poplar one came out so nice that I'm keeping it.  If it doesn't hold up, I'll make another.

This one has the wedge oriented differently from the gauge above.
Layout on a squared-up blank - note the "x" for the smaller wedge mortise on the near edge
Note the angled layout line for the wedge.  The wedge mortise overlaps the beam mortise by 1/16".
Bored from both sides to remove the bulk of the waste
Then squared up the mortise with chisels
Then bored and chiseled the smaller mortise
I made a sacrificial beam, which I put in place while cutting the smaller mortise.  This prevented any blowout in the areas where the mortises overlap.
The sacrificial beam showing the mortise overlap chopped away
The smaller mortise was a challenge to get cleaned up - it's long and narrow (5/16" wide, I think) and it took a lot of careful paring to flatten the walls.

For this gauge I made the beam 3/4" square.  It seems fine, but I think I like the 13/16" beam better.
Test fitting the beam.  Temporary wedge in place.
I made the pins for this gauge the same way as the other gauge and spaced them just a tad wider than my 1/4" chisel.
This pic makes the pins look too wide - the chisel actually fits a little better than it looks
All fitted
I love this style gauge.  The orientation of the wedge makes it so easy to loosen or tighten with a tap on the benchtop.  I only wish it had more fence surface area to ride along the piece being marked.
Getting finished
Unfortunately I finished this one with the same Watco "Danish Oil", so it's not as slick as I'd like on the front face of the fence.  I've got some projects coming up where I'll be able to use one or both.  Can't wait to see how they perform.
Glamour shot 1
Glamour shot 2