I came across this idea in a 20 year old copy of Model Engineer Magazine and it seems worth passing on - I have not seen it posted elsewhere..
The original article explained that this method is commonly used in industry but does not seem so well known amongst model engineers.
I am posting this in the hopes it may prove a useful aid for a "quick and dirty" method for setting up a large item on the mill table.
It is a really simple, yet effective way of clamping larger items (provided they have two parallel(ish) sides) on the mill table, without the interference of strap clamps or similar.
The clamped workpiece is thus clear to machine over its whole surface without re-setting.
The attached photos should be self explanatory. I have "posed" a steel plate in the "clamped" position between the two wedge ended blocks on the left and the stop block on the right.
The three blocks would be held by straightforward studs/nuts/washers into T nuts (not shown).
My blocks are from 3" X 1.5" X 1" mild steel.
The "wedge" angle on the two blocks is 10 degrees, with a 5mm "straight" at the top of one and the bottom of the other.
The "angled" faces should be a very clean finish - polished on a stone to remove any machining marks if possible. Nice and slippy/slidy against each other.
Set the "stop" block first against one edge of the work.
Set the other two together, with the slotted block proud against the other side of the work.
As the nuts are tightened on the middle block, the wedge drives the middle block hard against the work and the fixed wedge.
The clamping force on the work-piece is very powerful so excessive force on the spanner is not required!
The centre block has T slots to allow for movement as it is screwed down.
Very simple to make in an hour or so and worth the effort?
I hope this idea may be of help to someone.
Peter
