The saw table is an accessory for the Myford lathe. It bolts to the cross slide, and a slitting saw is clamped on an arbour and driven between centres (I had the arbour already.) I decided that I needed it mainly to cut out blanks from sheet material that would go on the mill or be sawn by hand to the final shape.
I chose to use the saw table kit from Hemingway. It was my first really sizable accessory, and not only was it something I needed, but it does not require high precision for most dimensions except a couple of bores, unlike, say, a dividing head, so I thought it would be a good first project. The challenge was that since I lack a large vertical mill, all the castings would have to be machined on the Myford. The table was the main problem, being about 180 by 110 mm, which is large for a Myford. Kirk at Hemingway assured me it could be done, but the more I thought about it, the less I liked his idea which seemed to involve holding the casting at one point only while machining the top surface. So I thought up my own solution. I don't think it could be done without an extended cross slide because the standard Myford cross slide would not have enough travel to cover the whole surface. Even so, it was tight.
This is mostly about how I machined the castings. The rest of the work proved to be fairly standard turning and did not pose any unusual problems.
I started with the foot that, on the finished table, is clamped to the cross slide and holds the pillar on which the table is mounted. To obtain a reference surface, it was mounted base outwards in the four jaw chuck and turned flat. It was then reversed, clamped to a faceplate, and the hole for the pillar was drilled and then bored to size.
The casting was then mounted on the vertical slide and the pad for the attachment bolt was machined flat, and as this hole did not have to be fine tolerance, it was drilled using the bench drill. It went back on the vertical slide to be slitted so that it would clamp the pillar. Finally the hole for the pillar clamp bolt was drilled and tapped.
The saw table is the trickly one, because of its size. It had to be machined flat on the top surface, and a hole for the pillar drilled and tapped in a boss on the lower surface. In addition to the boss, there are also supporting ribs on the lower surface that make the whole thing difficult to clamp. I began by creating a reference surface on the bottom of the table. This was done by mounting the casting, top surface away from the headstock, vertically on an angle plate bolted to the cross slide. The face of the angle plate was carefully set with the dial gauge to be parallel to the direction of travel. You can see in the photo the large top overhang, and a toolmakers clamp being asked to do more than it should. But by mounting it first one way up and then the other, I was able to machine two flats, one on each end of the the table.
The casting was then removed, and I bolted two angle plates, one at each end of the cross slide. After lots of tedious work with the dial gauge, I got their vertical faces parallel to the direction of travel and aligned with one another. The table was then clamped with the top side facing the headstock, and parallels between each flat on the lower surface and the angle plates. I had to use two angle plates instead of one, because the casting was too long, and because the boss and ribs got in the way.
The table was set just high enough (on more parallels) that I could cover half the surface with a pass of a largish fly cutter. The top slide travel was just enough for the purpose, and I just managed to get the clamps out of the way of the cutter. Once one half was done (using light cuts not to disturb the set up), it was unclamped, reversed, and the operation repeated on the other half.
Of course, in spite of all my efforts, the angle plates weren't exactly aligned, and this process left a small step at one end at the interface of the two cuts. This was only a couple of thou, and I was able to remove it with a file without too much effort, but that means the table surface doesn't have that nice "machined all over" finish that wins medals in model engineering competitions. But it is flat enough and does its job. It was finished with slots for the fences and the saw blade. It was clamped to the drill table, boss upward, checking that the table was normal to the drill, and the boss was drilled and tapped for the pillar, an operation which ensured that the pillar is normal to the top surface.
After that, the rip fence was a straight forward piece of machining in the four jaw chuck and in the vertical slide, only requiring attention to ensure all surfaces were square with one another.
The cross-cutting fence requires a circular profile where the boss and clamp bolt go, and I could not think of a neat way to do it with the Myford equipment. However, it was small enough to fit my rotary table on the Sherline mill, and to my surprise (I probably should not have been) the mill coped with it without the least grumble.
The final photo shows the completed saw table, with fences and clamp. I decided to use toggles for all of the screw clamps, to give a more unified appearance than the mixture of toggles and knurls that the kit recommends. The exception is the foot where the pillar is clamped. I used a clamp bolt for this on the basis that I'm not likely to keep adjusting the height of the table.
Nick Baines Model Engineering