Mr. Rick has some good forum threads running on various aspects of Greene & Greene style construction details. One of those is making the square mortise holes for the accent "plugs" that appear everywhere in G&G makings.
What I am attempting to show is the method I use. Works for me and I'm sure there are plenty of other ways that work as well or even better.
Also in order keep the approval of the ever Ganderly LBD, this single blog makes for a good place to spell it out.
So, let us begin.
The key ingredient is the Lee Valley mortise punch. A variety of sizes available, but my most used is the 3/8" version.
Basically, this is just a hollow chisel mortiser head with a basher head that screws to the back.
Common problems using this tool is making for consistent and precise depth mortises and more so, locating the hole to the exact position wanted.
For controlling the depth, a drill press, Forstner bit, and using the presses depth stop will make for perfect and consistent depths.
The process I will show is on a scrap of red oak.
Locate the center of the hole, use an awl to locate the bit, and drill.
Voila! No one anywhere will find this new! The flat bottom from the Forstner bit will create the platform for depth. I use a bit smaller than the punch dimension so the square mortise border won't get all squirrely. 3/8" chisel and I used a 8mm bit (.315")
Why the metric? Plenty of clearance from the .375 mortise border and it was the only bit I had that was between the common 3/8" and 1/4" bits that come in sets.
Now for locating that mortise and keeping the square hole square to your project.
There is a hole bored through the LV tool, Since it it is probably a common "business end" of standard hollow mortiser bits, it is usually for the drill to clear waste wood when used in a mortising machine. The tool I have will allow a 21/64" bit to reasonably pass through without a lot of slop. A "Q" letter drill (0.323") probably would fit better. Go ahead and find a 21/64" bit in your drill index and skip to the end. I wanted a better fit so I did a little more work.
Seeing that LV is a Canadian company, I figured that the tool hole was a metric standard. Measuring showed it about 8.5mm (.335") best as I could tell.
I save parts from printers, etc. I take apart, especially bearings and shafts. Ya never know when that scrap will come in handy, like for this!
I happened to have some short sections of 8.5mm HSS rod. Almost would slip through the tool, but slightly large. I used some strips of abrasive cloth and a Cotter pin for a make shift hone to bore out the tool so my 8.5mm would fit. Only took a few minutes to hone it out so the shaft would have a piston like fit.
8.5mm is close to the 8mm hole I drilled in the beginning (duh!) and I wanted that shaft to align with the hole. Solution? Order a metal lathe or reduce one end of the shaft to 8mm.
Chuck it up in the drill press and use the Horrible Freight diamond hone block to cut a reduced tip. It worked!
Tight and concentric fit with my 8mm hole in the wood.
So now I have a shaft that will align the tool with the crosshairs I used for drilling.
Slip the tool over the shaft and make square. I could cut the shaft down flush with the end of the tool since I will be bashing that and don't want to be hammering my drill hole base needed for depth, but no need. I just slip a deep socket that fits over the shaft and rests on the beating end of the tool.
Whack, whack, until the arch in the tool meets the wood surface. So the need for the 8mm hole is to have some place for the wood being displaced by the tool to go. It is a chisel (4-sided albeit). Better to have the wood squish inside that mess up the nice square exterior!
A 1/4" chisel is perfect to pare away the excess and then a 3/8" to fit with the border lines and get the edges square based upon the tools marks.
All done! Exactly the outer dimensions of the LV tool and no distortion from the wood pressing outwards. Centered and square!
Same process for the other size chisel mortiser tools available. Just check you drill bits and select one that fits nicely (or use your collection of bits 'n' pieces and do a I did for this 3/8")
Well done Mr. Splint, thought this out well for an accurate design method for centering, executed it perfectly, and proved it works. Now you just need to apply for a patent & start making the components.
I've never been a fan of G&G... reminds me of zits on my face as a pubescent... however, a good write up can always give ideas to people, though to other it may be obvious, but individuals never think of. I have used sandpaper on dowels mounted in a chuck, but never considered a diamond stone on metal,
If your first cut is too short... Take the second cut from the longer end... LBD
Thanks everyone! Ross, I actually thought about that! Turns out I also have the LV 1/2" and 1/4" and several fractional drill bits fit those nicely.
LBD: I had originally tried a flat file but was getting nowhere. This diamond block was under $10 and already worn out. The four sides (200, 300, 400, & 600 grit IIRC) made for a great way to get a square cut in the metal while I slide the block back and forth on the table. The blocks edges still had some grit, but this work (no water) seemed to take care of that. Just another worn out tool that I kept around in case something came up (and it did!) Fun thing about using drill index bits is many have the shanks turned down to 3/8" for bits > 3/8" diameter. Perfect since you can find a good fitting bit, then put it in shank first to mate up with a 3/8" Forstner depth hole.
Thanks for the info Splinter. I tested my drill bit sets to see what would fit in to my 3/8” square mortise bit. The 13/32” fit almost perfectly. The mortise bit is about 1” longer than the drill bit. Next time I’ll try it. This is why I always make my ebony squares a little bigger that the holes.
I'm a bit lazy and do the process backwards then use a hand drill to clear out the inside of the LV tool then clean things up with a chisel and pick. Keeping the LV tool square with the world is the challenge.
Yes - I'm still lurking about and making things. Working on mid-century nightstands for my daughter at the moment.
There is a sliver of missing grain (lower left side) Anyway, yep, I always go for about 1/64" over so the hole sides get compressed slightly.
Can't tell you how many I've biffed with using a 3/8" bit and having a slight hole radius peeking out the side of a plug.
I used to locate and tap the punch to establish the four corners, mark diagonals corner to corner to establish the center point for drilling, then lay the punch back in the corner dents and hammer home. Thins were much slower then with marking the offset for the chisel from the desired center and drawing the diagonals.
Looks good Rick. Having a flat-cut drill bit of a good diameter to fit the punch hole and using a stop like that would be awesome. Maybe an endmill or old straight router bit (finding the right diameter will be tough).
I like to have the center cleared out before the punch, gives the waste somewhere to go with the wedge chisel shape to avoid it scooting slightly back over the exposed wood. Of course small bites work too!
Thanks Rick. Yeah, the problem is the bit size required for a close fit to the punch hole. Standard point bits are easy to find in 1/64" increments, maybe some quality time regrinding the tip into a brad point style. I believe a letter drill "Q" is a perfect fit for mine, but the 8.5mm rod and taper to an 8mm tip works perfect and I didn't have to but anything new. There is also the possibility of finding a section of tube that has an ID fit for a Forstner and OD modified for the punch, but that's getting complex. I'd assume if the punch hole is polished (Cotter pin in a drill with some 400G), one could just wrap a drill bit with tape for a good fit.
Yesterday I used my drill press with a Forstner bit and then used a transfer punch to precisely align the square punch over the drilled hole. It worked like a charm!
