Making Metal Things

I've been lucky in that both of the woodworking schools I've attended have had horizontal mortising machines with XY tables. Once you've used one of these it's impossible to go back to either a chisel mortiser or cutting mortises by hand. About a year ago I was looking into buying a horizontal mortiser and thought 'maybe I'll just make one'. I had made a crude horizontal mortiser out of wood a few years back while I was working at a timber framing shop, and while it worked well enough it was far from a precision machine. Let the scheming begin! One of the things that I found frustrating about the couple horizontal mortisers I've used is that cutting angled mortises means you have to shim your work up to the appropriate angle. And if you have several identical pieces you have to be able to duplicate that setup exactly each time. Why not make the table tip? I also preferred the motor to move in relation to the workpiece, it seems like it would be easier if you had large pieces, like a door, to hold it steady while the bit moved around. Without much inital planning or drawings, I went to work.

The first thing I made was a base. Cast iron makes for superior machines, period. The grain structure and density of cast iron compared to that of cold or hot forged steel makes for superior dampening properties. Unfortunately the advancements made in production sheet metal stamps and welding have made most modern machinery pale in comparison to the heavy cast iron giants of the past. Someday I'd like to do some experimenting with investment casting, and I'd love to get to the point where I can make my own castings for machines, but for now I'm like Taiwan - stuck to hot forged steel and an arc welder.

I tend to be a bit nomadic, and never stick to one location for very long. Therefore all of my machines except for the very largest have grown wheels to ease the constant moving they have to endure. The base for my mortiser was no exception - consisting of a 2" flat bar box with a sheet of 3/16" plate welded to the top. I found a piece of 6" heavy wall square tubing at work to use as a column as well. To accomodate the tilting top I built a pair of supports that can rotate almost 90 degrees and be clamped tight to the column. The table will be bolted to that.

In order to increase the weight and density of the machine, and to reduce any resonant vibrations, I've considered filling the entire column with concrete. I waste a great deal of time at work reading the forums at www.practicalmachinist.com and have read good things about a mix of epoxy and lead shot. I might give it a try, we'll see.

So, just to recap, I'm making my mortising machine so that the workpiece sits stationary on a 16"x24" table (that can tip front to back) and the motor will move back and forth on an XY table. This means the XY table will have to be exceptionally rigid to stand up to the torque generated by a 3hp motor. At least, that's what I assume.

I got to the point where I had the base and column figured out but was unsure how I was going to raise and lower the motor. I didn't want to have to manually lift the motor because it's heavy as hell but I needed something that could lift the motor smoothly, be rigid enough to hold the motor securely, but also had to have tight enough tolerances that moving it up or down wouldn't effect the geometry of the motor in relation to the table. I found the answer in 1922.

My dad used to work as a millwright and he has an old friend from out in BC who still deals in the sawmill business. His name is Snuffy Stapleton and his place in Cranbrook is like the place where old machinery goes to die. The last time I was there I almost came home with a 24" jointer, but decided it was way more work than it was worth. A few years back Snuffy showed up in town with an old drill press, from 1922. I'm not sure where he got it but it's massive, seized up solid and pretty much useless. The arbor assembly on it though is in fairly good shape and has a very ingenious 2-speed feed control. Out came the cutting torch and I 'salvaged' it for my project.

I needed a table. Those shiny surfaces of a new wood or metalworking machine are ground, not machined. Surface grinding leaves an incredibly flat, accurate surface. Tolerances of modern grinding machines are measured within .00001". The only other way to ensure those kinds of accuracy is hand scraping, and there's no way I was attempting that. I cut the material for the table from a sheet of 1" plate and sent it off to Sharp-Rite Technologies in Edmonton. Unfortunately plate steel is far from straight and the acetylene torch I used to cut it out only added to the warpage. By the time I got the table back it looked great but cost almost as much as a new mortiser. Damn.



So there she sits, and has for several months. I started on the XY table last spring, but didn't really like my design for the linear bearing seats and journals. I've recently aquired some better bearings, bearing blocks, and rails and am hoping to get some work done on it this weekend maybe. I have a great deal of money invested in this project and don't like seeing it sit in the corner of my dad's shop collecting dust. Perhaps writing about it in this blog will brew up the motivation to finish it up. Here's hoping.