I finally got my spoil board attached to the main surface of my Altmill. There are somewhere around 40 or so screws holding the spoil board on. Now this spoil board is probably already spoiled in a way - it is particle board that came off an old work bench, probably 20 years old. Based on my surfacing path, it is either bowed or possibly uneven in thickness. I did one pass of 1 mm, some areas were not touched and other areas had maybe 2 mm removed. I ended up doing a second 1 mm pass to make sure that material was removed over the entire surface.
Based on the front edge of the Altmill table, the spoil board is tight to the board beneath it in some areas but in other areas it is floating maybe 1 mm above the lower board. I assume the surfacing pass made the entire thing flat BUT what happens if I use a downcut mill for my job putting pressure on the spoil board. I have visions of the workpiece being forced down by the force of the downcut bit. If that would happen then profiling cuts would have to be made allowing for the spoil board flex and I would have to cut into the spoil board by way more than I would like (1 mm vs less than 0.1 mm)
Is this something I should worry about or am I overthinking this? Taken a bit further, one could also have the board below the spoil board being slightly warped.
Should I forget about trying to re-use the old particle board and spring for new, shiny and hopefully flat sheet of MDF?
I am used to working with 3D printers and a 1 mm flex is simply unheard off.
I would recommend replacing, if for no other reason than the older one may warp/flatten more over time and cause additional work or possibly mistakes on workpieces.
@Jens Short answer. Yes you should scrap the scrap particle board. That said, even with shiny new MDF, you should still surface it.
Thanks guys! I will do ‘experiments’ for now (since I can’t use it anywhere else) and replace the particle board with new MDF before I do anything that requires accuracy.
Yes, I realize that surfacing is required even on brand new MDF … but I assume only on the top of the spoil board and not the first/base board. Is that assumption correct?
If you are able to force the slab flat against the machine, you can surface it, flip it, surface it again and maybe have a better fit?
I have my machine bolted to an mdf slab fitted with inserts and use custom made waste boards that fit the project size. When I make signs I use a wasteboard that is only 10 inch by 46inch with wholes corresponding to my instert pattern for clamping. It has its own fence system and place to go where its flat to the machine axis.
You don’t always need a machine wide waste board. Smaller works fine too, if your project allows.
This might be an idea for you, untill you get a full blown wasteboard.
“If you are able to force the slab flat against the machine, you can surface it, flip it, surface it again and maybe have a better fit?”
"I have my machine bolted to an mdf slab fitted with inserts … "
I have no clue how you would force a slab against the machine … I knew that the spoil board I was going to use was warped a bit and figured that once I screwed it to the base board it would conform/flatten but screws into MDF have very little holding power before they strip out and that did not work out. Inserts will hopefully fix that. I am still working on how to best make sure the insert pattern and spoil board hole pattern match up and that there are enough bolts used. I will use a master CNC file for that. My spoil board is made up of two 24*48 inch boards and there are no T rails.