This was a project I had never thought about from the aspect of the fabricating stand point other than machining and carving a block from solid.
But a question by a member of our forum got me thinking on this line and brought about this article.
Recently I had been working on articles about fabricating anvils and many of those methods fit this subject as well.
Like many DIY projects this one is labor intensive.
It also requires a lot of welding which may cost as much as a good small block.
Do not overlook the cost of electricity when doing such projects.
1) Small cut off saw, bland saw or hack saw
2) Angle grinder(s).
3) Arc welder (Stick or MIG).
5) Cutting torch (optional).
6) Drill Press (optional for small holes).
The drawing above was my initial response. It was not very well thought out.
The square and round holes are too close together. They should have thick walls or spacers between them.
However, it shows the basics of construction.
Pieces of angle, pipe and bar all cut the same length are welded together to make a solid block with holes and forming shapes.
Heavy bar strengthens and spaces the shapes apart. These have 45° weld preps for joining the parts and fill.
Where there are odd shaped holes to fill pieces of round bar of various sizes are inserted then welded over.
Bars 1/2" and larger can be full length with weld preps.
Shorter fill bars would want to be about 1/2" short (1/4" on each side). Bar down to wire size (1/16" welding rod) can be used.
Besides using structurals and holes built up from flats a fabricated block can also have solid pieces with drilled holes and milled slots.
Very small holes should be in a plate much thinner than the block with a larger opening underneath.
A fabricated block could also have shallow bowls or other impressions created in thick plate.
Blocks can also have various curved surfaces.
The most difficult thing to obtain for this project is the pipe sizes you may want.
Note that standard threaded pipe is sized on its OD for a nominal ID. The wall thickness varies making the ID smaller.
So if you have schedule 40 and schedule 120 pipe, the 120 will have a much smaller ID.
Many hardware stores carry standard pipe "nipples" threaded at both ends. The maximum length is 6" (with threads).
However, some places also carry short lengths of pipe starting at about 18".
I would start with 1/8" pipe (.269" ID) and get every size up to 1.5" (1/8, 1/4, 3/8, 1/2, 3/4, 1, 1-1/4, 1-1/2").