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Making an angle plate
Having made two cylindrical squares it is possible to make an angle plate from a casting. On a vertical milling machine it is only practical to mill a large flat surface if it is parallel to the milling table.
An angle plate needs two flat surfaces at right angles to each other. To start with there are two rough surfaces. The first surface is cleaned up with a file so it will sit flat on the cylindrical squares. This surface is clamped to the cylindrical squares. The second surface, which is now horizontal, is machined so it is flat. The angle plate is removed from the cylindrical squares. The flat surface is now clamped to the cylindrical squares. The top surface is now machined. This surface will, by definition, be at right angles to the other surface. The result is two flat surfaces at right angles to each other – an angle plate.
553 cylindrical squares 5
Fig. Using cylindrical squares to hold an angle plate casting 553
Fig. Finished angle plate 563
john f's workshop 
Hi John
I am looking for a method of holding a slab of aluminium to the mill table so I can skim it flat with a fly cutter.
Any ideas? Cheers, John
Try using side clamps. That is, a fence at one end and one or more side clamps at the other. But be careful the pressure from the clamp does not cause the plate to flex upwards.
john f
Hi John
The plate is 8″x5″ and 5/8″ thick. What is a side clamp? Can you give me a lead? I don’t want anything to protrude above the plate.
cheers….
The problem using side clamps is exactly what has happened to you. The clamp is too high. If you are using a fly cutter you want to go from being completely to one side of the workpiece to going right over to the other side so the pattern that is formed is uniform over the workpiece.
One soltion to this is to make a side clamp that consists of a flat long plate say 150x 20×10. This has holes in it so it can be clamped across the table.
This is fitted across its width with grub screws that are pointing slightly downwards. There might be, say, 6 of these.
The workpiece has a fence one side and the side clamp the other. The grub screws are tightened so pushing the workpiece down and towards the fence.
There is something here on side clamps but I will try and expand it but that will have to be thurs at the soonest.
john
I have made a special low profile fence and side clamp and put photos into my web page on side clamps if you are interested.
john f