On 2021-01-06 04:25, Bruce Layne wrote:
Why don't you just install a spoil board and machine it flat like most
people do with a CNC router?
When I converted my mill, I followed some published instructions for an
identical mill, and added ballscrews. That involved machining a shallow
'trench' on the underside of the bed. I know machining a casting is
always risky, but I trusted the instructions and figured the bed must be
sufficiently well seasoned or stress relieved, so I went ahead.
Of course the bed bowed along the Y axis, quite noticeably. I then took
it to the only machine shop in this area and spoke to the foreman. By
pure luck, they had a grinder with a large bed, and the foreman was
sufficiently interested in my attempts to convert my mill that he used
the job as an example for the apprentices. I got a beautifully flat bed,
nicely finished, and they got a box of prizes for their annual golf
competition.
A couple of months later, the big grinder went in the skip, along with
all the other manual machines. The factory concentrated on CNC machining
of toolheads for the oil drilling industry. With the downturn in recent
times, the factory has gone, so no more machine shops in this area.
In the absence of someone to do a surface grinding job, I would do one
of two things.
First, as Bruce suggests, I would mount a plate on the bed and flycut it
flat. If you drill an array of holes, tap some and ream others for pins,
you will have a handy way of securing work, holding your vice, jig,
fixtures etc. It may be difficult to reach the whole of the table, so a
good alternative is to mount a couple of blocks parallel to Y and flycut
the tops of those, then bolt a plate to the tops. Even with my flat bed,
I use this arrangement as it locates the work a little higher. The top
plate has bolt holes and pin holes and I use those to hold a selection
of fixtures for various jobs. I seldom remove the sub-plate and revert
to the bed. You may be able to buy T-slotted table tops from other mills
(SEIG table tops are available in the UK in small and large sizes at
reasonable prices). Mount one of those on the blocks.
A second approach, developed because of a particular job that keeps
reappearing, is to mount a long SEIG table top on L-shaped legs using a
tilting arrangement which pivots the table near the top front, along the
X axis. That gives me a table large enough to hold large-ish plates so
that I can machine one edge at an angle. It has been useful for other
jobs too. Adjustment is from -5 to a positive angle which depends on the
height of the legs.
Marcus
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
