You have the classic problem of an entrepreneur; too much optimism and not enough capital. Still optimism is good thing and ingenuity and hard work can compensate for lack of capital. Here is how I would approach this problem.
I have shown a cross section of the fixture I would make. The red block is fastened to the machine table and has two dowel pins and two threaded holes for the bolts that attach the blue block which is the body of the fixture; these bolts and dowel pins are not shown. The blue block has dowel holes in faces 1, 2 and 4 and has holes for bolts to attach it to the red block on either face 1, 2 or 4. 3 will be mentioned later. The green block is a clamp to hold the stock (pink block) using bolts located adjacent to where each part will be machined. Notice the clamp is relieved on either side of the clamping bolts and also in the root of the lip that clamps the stock. This is needed for efficient clamping particularly for the stock which would only be held at the bottom corner due to deflection in the clamp if this relief was not there.
Obviously the stock held within the clamp cannot be machined. Very often it is more efficient overall to use material that has excess size simply because this makes clamping possible. The material cross section needed for the part is shown approximately by the black rectangle drawn in the pink block.
The base and body would both be machined out of hot rolled mild steel and the clamp cold rolled mild steel.
The machining sequence is best described by referring to your picture. You show the first operation as the two very small holes and the profile around them. These holes and the full profile, full depth, would be done with the fixture holding the stock as shown in the picture; face 1 bolted to the base.
The body of the fixture is repositioned with face 2 against the base and the profile and bearing hole shown in the right hand part on the second line in your drawing are done. This time the profile is done just past the mid point.
The partially machined stock is taken out of the fixture, the fixture body is attached to the base by face 4 and a filler piece cut from a length of the stock is put in the stock clamping location and the clamp bolts tightened.
Now the inverse of the profile done in the second operation is machined into the joint plane 3. After this is done a few thou are machined off the clamp face so the clamp will close firmly on the profile not just on the unmachined faces.
The partially machined stock is now clamped into the profile sockets and the parts are fully machined and at the same time separated. Further up I mentioned that the clamp has a bolt adjacent to each part location. This is so that when the final operation is done each individual part has its own clamping bolt and is held firmly even when separated.
If I wanted to economize on material I would not machine away all the excess but would do operations one and two with faces 2 and 4 against the base. Then I would remove the stock which now has parts along both edges, split it along the middle on a bandsaw and then finish machine and separate the parts from the two halves. |