Rethinking the RAS table - comments?

[Richard Sextro]

I have a venerable Dewalt 7730 10" radial arm saw that I bought new a lotta years ago. I've decided to build a new base for it to replace the Dewalt 'trapezoidal' metal base that came with the saw. I also thought this would be the time to rebuild the saw table itself using the "Mr. Sawdust" approach of sandwiching ~1/8 x ~3/4" metal bars (mounted vertically) between two pieces of 3/4" plywood (his book is: Wally Kunkel, "How to Master the Radial Arm Saw" available from his family - a must have for RAS users).

However, in drawing up what I want to do in Sketchup, I realized that with a saw table base basically the same width as the RAS table itself, the ends of the saw table could be supported directly. Kunkel's approach is based on the fact that most RAS tables are supported by - and attached to - the metal framework to which the vertical saw arm support is attached. As such, that means that ~8 to 10" of the saw table is essentially cantilevered out from that frame on either side - hence the need for a rigid table top. I've attached a pdf of my current sketchup drawing - the green pieces illustrate how I envision supporting the saw table (and no, I didn't draw the RAS in my drawing - its a result of the library of drawings in the 3-D warehouse available from sketchup and someone else with more drawing skill, patience and time than I have...). The supports would have short vertical slots for bolts so that the flatness of the saw table could be adjusted (Kunkel's book shows how to check this using the saw arbor).

Has anyone else done this? Are there any downsides/limitations to mounting and supporting the saw table this way?

- thanks, Rich422781
422781

[Richard Sextro]

Hmmm -- I'm not sure why a) the attachment doesn't show up as some sort of thumbnail picture and b) why there are two pdf links...??

[Dave Cav]

I think the picture doesn't show up because it's a PDF, not a picture file. It does open if you click the link.

I've built a couple of tables like that; it works fine. I've also built a large Mr. Sawdust table. It also works fine, but it's a fair amount of work to build, and a REAL pain if you ever want to shorten it.

[John K Jordan]

Hmmm -- I'm not sure why a) the attachment doesn't show up as some sort of thumbnail picture and b) why there are two pdf links...??

Here's a thumbnail and JPG if that's easier for someone to view:

422794

[Charlie Velasquez]

After you make your table you will need to mount it to your base.
Now here is one rub... as you pull the saw out you exert a lot of torque on the point where the arm connects to the column. That torque is transferred to the place where the metal base and column connect . That connection and the metal base will flex, especially in the 7730, 7740,7770 models, they were made with less robust stamped steel after Black and Decker took over to compete with the cheaper Craftsman models.

One of the most important adjustments for the RAS is to adjust the table to be parallel to the travel of the motor in the arm (actually, I shouldn’t say that, they are all important). That flex will bring the front of the arm downward as it travels. I just moved recently and my Kunkel book and my Jon Eakes book (a better book than Kunkle’s if you’re just concerned with setup) are packed away and I don’t have access right now. (Edit: found my Eakes book, page 47)
But look through it and find the section on setup. If you keep the green supports you should consider making the holes you have for the screws attaching it to the base of your wooden stand slotted at a radius and to use machined bolts instead of screws so the table can be aligned as to the method in your Kunkel book.

In the setup you have diagramed the green supports are used to both support the table and keep it from sagging.
That flex will translate to your wooden base differently than the saw’s metal base. I am not sure how it will affect those green supports but any effects will impact your alignment.

Your saw’s original setup has two angle irons that bolt to the sides of the saw’s metal base, so the angle brackets will flex in the same manner as the saw’s base.

Additionally, a single layer of ply may be prone to twist or warping. All your other alignments are based off your table. It is important to keep it as flat as possible.
It might be better to keep the two functions separate. A table that will remain flat as one function, and a system to attach it to the saw, and only the saw, as another.

[Tom M King]

I built the base my first RAS is still on in 1974, after I opened the box. I used 2x4's, plywood, all bolted together. It even still has the same casters under it. The locking casters are on the front. It's eight feet long. The doubled 3/4" Birch plywood top is bolted to the top of the RAS base through the bottom layer. The top layer is held to the lower layer with screws, and has been replaced a number of times, and the old tops, once the groove gets eroded out too much, have always been used to make shop fixtures out of.

It must have been a pretty good design, because it's been moved at least 40 times, in and out of the back of a pickup, and I'm still using it exactly like I built it that day in 1974.

Just dumb luck, but it's exactly the same table top height as the sliding miter saw stand, with wings, that I use these days too, so they stand side by side, and help to handle any length board.

[lowell holmes]

You can attach 1x12 outriggers to the saw top with hinges.
I built a cabinet of drawers that my saw sits on. There are drawers in the cabinet.

[John K Jordan]

I built the base my first RAS is still on in 1974, after I opened the box. I used 2x4's, plywood, all bolted together. It even still has the same casters under it. The locking casters are on the front. It's eight feet long. The doubled 3/4" Birch plywood top is bolted to the top of the RAS base through the bottom layer. The top layer is held to the lower layer with screws, and has been replaced a number of times, and the old tops, once the groove gets eroded out too much, have always been used to make shop fixtures out of.

It must have been a pretty good design, because it's been moved at least 40 times, in and out of the back of a pickup, and I'm still using it exactly like I built it that day in 1974.



I did almost the same thing with my RAS, but in 1972. :) I made the base a little wider than the saw top with legs splayed outward for stability, and a second nearly identical base with a vise in a worksurface top the same height as the top of the table for the RAS so it could support long boards but could still be moved around if needed. Heavy carriage bolts secured the saw base frame to the wooden base. Very sturdy.

The saw table was a piece of 1" MDF with a sacrificial piece of 1/4" ply tacked on top with tiny finishing nails, easily replaced when scored too much.

I loved that saw and kept it until just last year when I gave it away. So versatile.

JKJ

[Richard Sextro]

Thanks everyone for your comments. Charlie, thanks for the tip for the Eakes book - I just downloaded it and will use it and the Kunkel book to figure out the alignment. You raise an interesting point about the RAS arm sagging a bit as the motor is pulled out along the arm. Isn't most of this compensated for in the alignment process, as it relies on using the motor arbor as a test point for ensuring that the table is flat. So as the saw motor is pulled out away from the fence, the 'sag' is calibrated into the set up, is it not?

I should have said in my original post that I intend to mount the saw table top to the 'usual' mounting rails that are attached to the metal base of the RAS in addition to the 'green' supports. And my intention was to have vertical slots in the 'green' supports that would accommodate something like a 1/2" carriage bolt mounted in the hole in the supporting base. I thought I'd try to get the center portion of the saw table aligned first, using the mounting angle irons that attach directly to the metal saw base. Then I'd try to use the 'outriggers' to align the left and right edges of the table. I suspect that it won't be quite that easy and I'll have to do an iteration or two on the whole alignment. This is my only saw (besides a circular saw) and it, along with my router table, gets used the most for the woodworking that I do, some of which can pass as "fine woodworking". So I'm hoping that this won't be one of those 'if it ain't broke, don't fix it' outcomes.

[John K Jordan]

... interesting point about the RAS arm sagging a bit as the motor is pulled out along the arm. Isn't most of this compensated for in the alignment process, as it relies on using the motor arbor as a test point for ensuring that the table is flat. So as the saw motor is pulled out away from the fence, the 'sag' is calibrated into the set up, is it not?...

I thinking of this and not knowing the details of the support structure, I wonder if the "sag" might not be in a straight line, i.e, describe a slight curve as the motor weight was moved towards the end of the arm. This could be a problem for precision crosscut dados, one of my favorite things about a RAS. Just guessing, of course. A dial indicator fastened to the motor carriage could easily measure things.

JKJ