My Christmas break project has been to finish refurbishing the old Powermatic 66 cabinet saw that I bought this past summer.
TL/DR version: Aside from some minor odds and ends of fixes and improvements, the main work has been to a) remachine the miter gauge slots, b) make a new miter gauge and bar from scratch, and c) revise and attach a t-square style fence that I had previously made (had to cut the "square" part from the fence and re-weld it with a larger spacer in-between). The results have exceeded my most optimistic hopes - the miter gauge is a snug but smooth sliding fit in the slots, and the pre-set holes (e.g., for 90° or 45° or so on) seem to be dead-on accurate.
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If you want all the gory details, read on:
For those of you not familiar with the Powermatic 66, here is a nice tribute to the species:
https://www.woodworkerssource.com/b...f-excellence-powermatic-66-table-saw-retires/. According to this source, the Powermatic 66 was the "iconic" cabinet saw, heaviest in its class. New, more-or-less equivalent models sell for $3000 or more, depending on how they are equipped. Used, they generally start at $1000 and go up from there.
I saw a Craigslist ad for one this summer for $200, and jumped on it immediately. It was well-worn, having been in a school, and the motor was of unknown condition - a 5hp 3-phase motor (!!), and the seller had no way to run it, and thought it didn't work. It did come with a matching but dismounted Biesemeyer fence, also worn and missing the scale and indicator.* It did
not come with a miter gauge. Most important, though, is that the bearings and trunions seemed smooth and free of wobble, and did I mention it was only $200?
I got it home and began to assess what I had. First order of business was the motor. It turns out to be a Baldor that looked brand new - very promising. I wired up a plug for the motor and tried it out on my 3hp phase converter - yes, theoretically too small to start the 5hp motor, but figured I'd give it a shot. Voila, the motor started right up and runs smooth as silk.
Next order of business was to assess the top. I knew it had plenty of wear from years of use in the school ... but it is a table saw for woodworking, not a machine tool for metal, so absolute flatness is not essential. As it turns out, it really is generally pretty flat. But there was a definite problem when it came to the miter slots. Not surprisingly, the left-hand slot was significantly worn, while the right-hand slot had just a bit of wear. The total wear was a little under .015" in places ... unevenly in places. While .015" is not much in woodworking terms, the miter slot is a critical component, and even a little slop there can greatly affect the quality and squareness of a cross-cut. The fact that the wear was uneven, and the two slots didn't match, meant that I couldn't just use an expanding miter gauge bar to take up the slack.
Thus began a lengthy and pucker-inducing process to re-machine the slots and make a new miter gauge and bar with precise fit. I wish I had taken pictures of the machining setups as I went - too late now - but if you are still reading this lengthy tome and want more, I will describe below.
I was not sure how well I would achieve either one, but I gave it a go. First I put the saw table on my Bridgeport mill and aligned it with the slots as best I could (averaging out the dips and bumps). Then I machined each slot to a total width of .765, just cleaning up each side. Sounds simple enough, but the problem is that the table is 28" long, while the maximum X-travel on my BP is 24". Rather than moving the saw table on the mill table - potentially creating all sorts of opportunities for messing up the alignment of the slots - instead I left the saw table secured to the mill table, and instead extended and swiveled the ram to each side. I still had to be very, very careful to match up the previously made cuts, but with much care and concentration, I succeeded. There might be a tenth or two variation (.0001 - .0002") at most, as best I can measure. Whew!
Then I had to made a miter gauge bar, and I wanted to make it as long as possible. I started with a bar of hot-rolled steel, approximately 1.25" wide by .5" thick, around 26" long. I wound up milling it down to size held in the vise, with machinist jacks and clamps at either far end. This left a little waste at each end, but produced a very long bar. I was also able to take advantage of the jacks and clamps to carefully tweak the bar to get the machined sides as close to perfectly parallel over the long length as possible. I left the bar around .002" oversize, and then spent a couple of hours carefully and tediously "grinding" the bar to final size by hand - i.e., I secured a strip of 120-grit cloth-backed emery paper to the flattest section of the saw top, and carefully worked the bar back and forth, measuring frequently and testing for fit. I was surprised that this worked as well as it did. To ensure that the grind was as even as possible, I had to pay close attention to the placement of my hands to vary how and where I was pressing down. The final result was so much better than I could have hoped - again, maybe a couple of tenths of variation, but it fits into both slots snugly yet slides smoothly, with no discernable play. Another big Whew!
Finally, I had to make the head of the miter gauge. I started with a piece of 1/4" thick 2" x 3" angle iron, but had to weld on an extension to widen the base to > 4.5" - because I had decided to make this oversized. Most miter gauges seem to be based on a 3" radius, but I made this one on a 4" radius. Nothing too unusual involved in machining it flat and square. I reamed the central hole 10mm and made a very precise post to use as the swivel. I made an adapter plate to go on the rotary table so that I could cut the various features without cutting into the rotary table itself. I used the rotary table to position the preset holes, cut the slot, and to attempt to cut the outer radius ... but that part did not go well; there was way more pressure on this cut than I had anticipated, and it seems that the worm gear in my rotary table chipped a few teeth as a result.
Accordingly, I finished the outer radius on my 2x72 belt grinder.
The only other thing of note is the way I put the angle scale on the miter head. Rather than grooving the degree markings it on the rotary table (which by now was no longer a possibility) and then stamping the numbers, I worked up the design in Inkscape and used that in my cheap laser cutter/engraver along with ceramic marking coating to bond the design to the steel. If you're not familiar with marking coating, here is the product I am using:
OMTech Laser Marking Spray (no affiliation other than satisfied customer). Cermark is the original "brand name" for this sort of thing (as best I can tell), but is about 4 times more expensive - I wasn't sure how well this cheaper stuff would work, but it turns out that it really does work extremely well, creating a strong bond that doesn't rub off. It
can be sanded off if necessary ... and I found it necessary to do so twice, since it took me three tries to get everything lined up perfectly. I haven't yet made a pointer, but based on how the markings sit with respect to the rim and to the preset holes, I am confident that the third time was the charm.
Finally, to cut some wood and check the results. I dialed in the fence - the whole point of a fence like this is that you can adjust it to be perfectly parallel to the blade, and you can adjust the indicator to give highly accurate results. I adjusted until, when the fence was set at 2", ripping a piece of plywood gave me a caliper reading within +/- .003" of 2 inches - absolutely phenomenal accuracy for woodworking! And then I used the presets for 90° and 45°, and the resulting cuts were as close to perfect as I could measure with a pretty accurate square. (All of this is after first aligning the table slots to the blade, which I had done a few weeks ago.)
Needless to say, I am ecstatic - I now have a powerhouse of a table saw that cuts incredibly smoothly and accurately! Meanwhile, if you have read all the way to the end of this lengthy discourse, you are truly a glutton for punishment!
*On edit: I forgot to mention that I wound up selling the Biesemeyer fence that came with it, and instead used the fence I had made years ago to use on the Craftsman "contractor" saw that I had up until I acquired this Powermatic. Somewhat to my surprise, the Biesemeyer was considerably lighter in construction, and my fence has proven to be extremely accurate and reliable, so I removed it from the Craftsman and sold the saw with its original (crappy) fence, and also offered the Biesemeyer as a separate accessory - wound up selling both together