Miter Slots and Other Important Measurements

A comment commonly heard is “my Delta tenoning jig doesn't fit my Craftsman saw.” There are a couple of reasons for that, and they have to do with the actual dimensions of the miter slot in table saws (cabinet or contractor) and to a lesser extent, the distance from the flange on the arbor to the left hand miter slot.

The subject of Delta tenoning jigs and Craftsman saws comes up often in a threads on the woodworking forums and usenet, and it's well known that the Sears slot/gauge dimensions are smaller than those of other manufacturer's. I vowed to go to a tool supplier to settle, maybe once and for all, the issue of miter slot sizes and other measurements for the popular saws. There was a Home Depot just five minutes away, and a Sears about ten minutes further up the road, so hitting all the major players was relatively easy.

With vernier caliper in hand (I don't have a micrometer, but this should do), I set about measuring the distance from miter slot to arbor flange, the miter slot width, and the width of a typical miter gauge bar laying about the store. I recorded all the information on a convenient scrap of paper and then encoded the whole thing in HTML for your viewing pleasure.

In the table below, I don't have specific model numbers, because for the most part, different model numbers on a particular line of saws (PM66 or Unisaw, for example), don't denote anything different about the basic construction, but merely identify accessories, motor hp, etc.

Saw	Miter Slot	Miter Bar	Flange -to- Slot	Blade Tilt
Powermatic PM66	.755"	.753"	5 ½"	Left
Powermatic PM64	.755"	.753"	5 ¾"	Left
Delta Unisaw (LT)	.755"	.752"	5 ½"	Left
Delta Unisaw (RT)	.755"	.753"	4 3/8"	Right
Delta Contractor	.755"	.753"	4 3/8"	Right
Jet Cabinet Saw	.755"	.751"	4 ¼"	Right
Jet Contractor	.755"	.753"	4 3/8"	Right
General 350	*	*	4 3/8"	Right
Ridgid	.750"	.746"	5 1/16"	Left
Craftsman	.750"	.742"	5 1/8"	Left

* (Unable to mike the slot or bar, although a Powermatic miter gauge was a snug fit as in a Powermatic saw. Measured at Superior Distributing.)

So, some folks are nearly right, that the Sears (and Ridgid) slot is .750" and the bar is slightly smaller for a snug fit. The bar on others' saws is ≈.750", but the slot is slightly larger, also for the snug fit. In other words, it's like the bar is undersized to fit the slot on the Sears (and Ridgid) and the slot is oversized to fit the bar on the others.

Who knows why Sears selected the slightly smaller combination when they spec'ed the original design (and it may not even have been Sears—they may have merely adopted an existing design), but a guess may be to force purchasers to buy accessories which depended on the miter slot from Sears. My guess is also that when Sears spec'ed the miter slot to whoever is supplying their table saws now, they kept the old specification rather than get on the Delta/Powermatic/Jet bandwagon to acommodate the same inventory of miter slot based accessories they continue to market.

Similarly, Emerson, the long time supplier to Sears until the mid '90s and current supplier of the Ridgid line of tools to Home Depot, probably saw no need to change their machining just because they changed outlets. They also no doubt had an established manufacture and inventory of miter slot based accessories.

I also found the distance from slot to flange interesting. Although Jet is generally considered a clone of Delta, Jet's contracter saw mirrors the same dimension as Delta, but the cabinet saw is an eighth narrower. Sears/Ridgid is nearly the same as Powermatic.

Delta's jig has gone through a couple of iterations. In its original form, it was set up for the Delta tools. A later version had an additional set of holes to permit moving the bar to accomodate the miter slot to arbor flange dimension of other saws. I noted that the current Delta tenoning jig that I saw at the tool store not only had the two holes in the base for repositioning the bar, but has a t-slot washer on the bar as well. Mine does not.

I didn't measure the distance between the two sets of holes, but I should have, because as I reflect on the flange to slot dimensions, it should have only been about an inch, but I seem to recall it more than that. I wonder if left tilt/right tilt has something to do with that (Sears/Ridgid/PM are all left tilt saws).

Okay, make of this what you will. And if any of you that actually own iron not represented in the chart (General 650, General International, Jet left tilt–contractor and cabinet, SawStop, Grizzly) and want to measure yours and forward the info to me, I'd be happy to have it. Now that this is on my webpage, we'll have it for posterity...or as long as I pay my host bill.

Last updated: 23 August 2010