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Marking and Cutting Gauges

 

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Figure 1. A freshly made set of marking and cutting gauges, ready for use.
 

 Have you ever had a favorite old tool that you have used absolutely forever, and weren't willing to give it up even though it's worn far past the point of usefulness?  I have two such tools - both, unfortunately, happen to be marking gauges.  One is an old Stanley #97 wheel marking gauge, the other a Stanley #77 mortise gauge.

This errant devotion to these old tools finally led to frustration when I realized that on the #77, the pins had worn down to the point that there wasn't enough pin left to mark anything with.  Over the years I had filed them down to tiny little nubs - there simply wasn't enough of them left to do the job anymore.

Something else - I didn't have a decent cutting gauge, something that I am going to need for my radio cabinet project.  Very similar to a marking gauge in construction, they use a knife blade rather than a pin to cut rather than mark the surface, and are often used when cutting veneer parallel to an edge when installing inlay.

I could buy all the gauges I wanted, but getting all I wanted would cost a bit of cash, and the way things are I figured it might be cheaper (and funner!) to make them myself.  Besides, I had all this brass stock laying around and also had this one, perfectly quartersawn piece of coco-bolo I have been hording since I found it years ago that was just begging to be used for some small tools just like these.


     Wooden Marking Gauges I own

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Figure 2.  My old #77 with a $12 HF marking gauge right below.  Note the lack of pins on the 77 and the uneven pins on the lower.
 

 The Stanley #77 marking gauges are some of the best designed marking gauges out there, but unfortunately are no longer available.  Mine (which is scores of decades old) has been used for so long the the face of the fence (including the brass) has actually worn down about 1/16"!  If you don't use it at the proper angle, the line it draws can actually vary up to that much.

There are several manufacturers out there today making them, but they either suffer from high price or from low quality.  In my opinion, the high price commanded for these tools are well worth it, as they are surprisingly complex to make for such simple tool.  Of course, a stick through a hole in a board with a nail in it will work, but when you are working a precision joint, it's nice to have a tool that is consistently up to the task.

I did purchase an HF mortise gauge (made in India, see Figure 2) for about $12 to get by with, and while it is certainly serviceable, it has one major flaw - the two pins on the mortise side are completely mis-matched.  There's simply no way it will work as-is for marking a mortise as the difference in height between the two pins is so much that you could never even get the interior one to touch the wood!  Yes, you could file the outer one down to work, but that not something a person should have to do on a brand new tool, not even a low quality one.


     Preparing the fence

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Figure 3.  Mortising the fence for the shaft.
 

 After cutting the fence out approximately square, I drilled a 3/8" hole and superglued a piece of brass rod (see the brass circle in the fence in Figure 3).  The purpose of this is to provide an embedded metal "nut" in the wood for the clamping screw.  Later, I would drill a hole and tap it to 1/4"-20 TPI threads for a brass thumbscrew.  Realistically, it should have  been a 1/2" in diameter, but I had the 3/8" on hand so figured it was close enough.

Then, it was time to mortise the hole in the center for the shaft, which is about 3/4" square by about 7" long, though the exact size isn't that important.  Ironically, the best tool to mark this hole out with is another marking gauge...  That way you can accurately mark out both sides of the fence and then use a chisel to square up the hole after drilling it out with a 3/4" bit. Keep the shaft handy, so that you can use it to size the mortise - eventually it will fit through, and if you have done it correctly it will fit squarely into the mortise.  I left the fit so it was much too tight, as I would later sand down the shaft and could do a final fit for it at that time. 


     Routing For the Brass Strips

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Figure 4.  The shafts for all of the gauges are routed to accept brass strips.
 

  I decided at the same time that I was making these marking gauges that I would build a pair of cutting gauges based on Steve Latta's design, first published in Fine Woodworking some time ago, and later used as a basis for the design Lie-Nielsen's inlay tools use.  I won't get much on their design as that is documented elsewhere and may be subject to copyright laws, but the processes are much the same, and you'll see photos of them included.  One change I made to Mr. Latta's design was to use an Xacto #19 blade rather than the standard #11 - it made routing a channel for the blade much easier as it is a consistent width (3/8").

For the standard gauges, the brass I'll use is 1/4" wide by an 1/8" thick, and for the Latta gauges it will be 3/8" wide (only because it looks better than the 1/4" on the wider shaft).  The original Latta gauges did not have the brass strip in the shaft, I added it to reduce wear on the shaft, where the tightening bolt introduces wear.


     Drilling the End of the Shaft

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Figure 5.  A drill-chuck mounted in the lathe makes accurate end drilling in the shaft a breeze.
 

  A couple of the gauges have a screw threaded into the end.  The best way to make sure this is square with the world is to use a drill-chuck in the lathe (see figure 5), though its certainly not the only way to do it.  If you are good with a drill, by hand is certainly possible as well.

This particular shaft is one I drilled out to accept a pencil - that way I could use at least one of the gauges with a pencil, for those times when you just don't want to scratch the surface. 

Again, when finished, I tapped the end for a 1/4" x 20 TPI bolt.  brass knurled-head screws are available from Lee Valley and Rockler, and 2" knurled head screws are available from Rockler only - it's the only place I found where they are available in lengths longer than an inch.

Paddle-style thumbscrews can be purchased from most metal supply stores like MSC Direct or McMaster Carr, but be ready to pay a premium to get them in brass,  Your local hardware store will have an economical alternative if you are happy with standard steel thumbscrews. 


     Making and Mounting the Knife

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Figure 6.   A home-made knife is mounted into the end of the shaft
 

 For the knife in the standard cutting gauge, I didn't want to use an Xacto blade like for those in the Latta-design gauges, as the main goal of this gauge is not for slicing veneer, but for marking across grain.  I wanted a thicker, more substantial blade that could easily be sharpened and modified to my needs.   To make the blade, I scavenged a used-up lunchbox planer blade, shaped the end of it to the correct size and snapped it off the the appropriate length in the vise - then finished grinding it to shape. 

It's handy to have a water cooled grinder such as a Tormek for this step - it's too easy to overheat the steel so it loses its temper otherwise.  I don't know what kind of steel is used in the planer blades, but it keeps a good edge and is a great source of metal for small blades - I've used it many times previously including when making a marking knife in a previous article.  However, if I would have make it from new material, a piece of 1/8" thick O-1 tool steel 3/8" wide and and 1-1/2" long would have sufficed, and I would simply harden and temper the steel using my gas forge.

In figure 6, you can see the end result - a small knurled screw through a piece of 3/8" wide brass mortised into the end of the shaft, drilled and tapped using the method previously mentioned.  The brass is held in place with both epoxy and 4 1/16" brass rods, which are inserted into holes drilled through the entire assembly.  It won't work with just epoxy, and larger pins tend ot break out of the end of the endgrain. 


     Placing the Brass Face

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Figure 7.  Setting the brass plates - a gimlet is handy to start the threads.
 

 The brass inserts are placed into the mortises and held in place with CA glue.  Epoxy just makes for a mess here, and the CA is plenty if the slots are sized properly.  For the parts that are to slide, if they don't slide freely I use a file to slightly narrow them until they do, being careful not to remove too much so they feel sloppy.  

For a "handle" on the sliding mortise piece, I simply epoxy a short piece of brass rod into one end.  One potential flaw here is that these slides can fall out, but as they are generally held in place with the adjustment nut, it's a flaw I can live with.  A T-slotted piece could be done (and is what's done on well-designed retail gauges) but since I don't have the machining available, I forego it.

I also route a slot for the brass wear plates on the face of the gauges, where I use more of the 3/8" x 1/8" brass I have on hand which is super-glued into place.    A 1" piece of brass is used for the face plates of the Latta gauges, which are held in place by epoxy and by brass screws (see Figure 7).  Here's an old trick you might already be aware of - when first threading for the brass screws, use steel ones in their stead.   Then replace them with the brass screws after - that way, you aren't as likely to strip out several brass screws trying to get them into place. 


     The Brass Endpiece

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Figure 8.  After cutting to approximate size with a hacksaw, 60 gritsandpaper gets the end of this shaft into shape.
 

 Once all the wear plates are in place, it's time to fit the end pieces for the Latta gauges.  After screwing a slightly oversized piece of brass onto the end, I hacksaw off the majority of the waste and file the corners to close, then finish off using sandpaper laid out flat on top of the table saw, stopping when it gets close enough.

I thought at first that the Xacto blades would have a tendency to slip with this design (see the slot for the blade in figure 8), but after putting it together it seems to fit quite tightly - I don't think slippage will be an issue.  It's important the slot for the blade is ever-so-slightly shallower than the thickness of the blade to allow it to be clamped into place by the brass endpiece.

I used steel screws here, as the only way to replace the blade is to loosen the screws - and brass, over time, would have more of a tendency to strip out.  

To get the rest of the brass inserts to fush out with the face of the wood, I used the same method, placing sandpaper on the table saw, working up through the grits until about 220 or so.


     Sharpening the Pins

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Figure 9.  A drill is used in concert with a grinder to put a point on the new pins
 

 The pins for the two mortise gauges are two different sizes, 1/8" and 1/16".  I wanted two different sizes for a couple of reasons - one, a set of pins large enough that I can later file to a cutting profile rather than a point - and a finer set for work as pointed pins that will work well with finer settings.

For the 1/8" pins, I used some 1/8" drill rod I had, with the ends already hardened and tempered.  For the 1/16", I used some drill bits I had on hand - the steel is good and hard, excellent material for pins.   I pointed the ends by mounting them into a drill, and used the grinder to put a point on them (see figure 9).

 Once I had the point established, I cut them to length using a pneumatic cut-off tool, making sure the mortise pins are of equal length.  They are then glued into place with CA glue or epoxy.

 


     The Finished Gauges

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Figure 10.  The finished gauges.
 

 For a finish, all that's needed is a good waxing.  It's the beauty of coco-bolo and brass, ang they are the perfect materials for these gauges.  Any finish other than oil is going to wear off and look ugly in a short time, and oil simply isn't necessary.

Anyway, here's the finished products.  Hopefully they work well, and give me as many years of satisfaction as my old Stanley #77.  Look for them being used in future articles... 

 

 

 

  

 


 

 

Comments

Comment: 

cheekyhow do you get the pdevilinty thing in the woodmail