Spoil board for 25x25 using bed slots

[thadamsv]

I wanted to use the on-bed slots for hold-down on a 3/4 inch MDF spoil board so designed the attached in Sketchup. Anyone versed in Sketchup can download from 3D Warehouse and adjust dimensions as they see fit (search for "shark" and "spoilboard").

[jimily]

Super useful, thanks! Sketchup is great, nice job!
Jim

[bill z]

Where do you get spoil board material that is the pressed paper looking stuff?

I like your idea here because not all of the slats will need to be replaced (theoretically).

[jimily]

Hey bill z
I've been pondering your question-do you mean MDF? It's just the regular stuff at the box stores. I too am in the middle of making a spoilboard and have some of the blond MDF for this. I'll make a post once completed, I'll watch for yours too.

On design: Ralph B had posted one too very similar to this but his main bed was MDF not aluminum. It's on youtube: https://www.youtube.com/watch?v=iyt8zOJUQJ4. And to reduce the resurfacing of your spoilboard I like Peter Passuello's techniques: https://www.youtube.com/watch?v=Q-Q1o16Ux-I and most of his other videos.

Good luck!
Jim

[bill z]

Please understand that I am new to this hand have ideas more than practical sense. I am thinking that the glue that holds the MDF together is harder than the wood dust it holds and can do damage to a bit. Just thinking with no real proof.

The stuff I was looking for and did find is made more of paper. In my local builder's box store, they use similar stuff to cushion the fine paneling from the rack they set the bundle on. It is like the cardboard back on a writing pad of paper except thicker.

While watching the 2 videos that jimily posted, I'm now rethinking all of this. Seems most are not worried about the hardness of the glue in the MDF, so why should I. Also, I live near the coast where the humidity is frequently very high. Humidity will be absorbed by the paper cardboard quickly and distort the smooth sacrifice board defeating the main purpose of having a flat surface with respect to the Z axis.

Lastly, I am new to CNC and this forum but I really like it here. Nice people with great ideas.

[meb]

If you zero on the spoil board and make sure the thickness of your material then you will rarely cut into it. If you cut a lot of MDF for projects then yes it is hard on bits but the slight cuts you make when cutting out other projects won't make much difference.

[jimily]

I think somebody used oak planks for their slats instead of MDF. I would suppose there would be some movement still from humidity but potentially less with a hardwood instead of MDF. Obviously more expensive though initially, potentially.

Oh yeah and peeps use mdf on the 3d puzzles and for jigs and nah I don't see anyone really concerned about their MDF spoilboard being hit, trying to lessen it yes, repairing it sure, but otherwise it's is better than scraping that nice aluminum table with an expensive bit.

Jim
PS so far all I have been doing is sliding a scrap piece of wood underneath if I am cutting through in this time while I am making my permanent nice spoilboard.

[jimily]

If you are still working on this I have finally finished mine off. I used the screws and nuts meb suggested. I made it from 3/4" MDF and countersunk the bolts 3/8". The heads of the bolts fit neatly into the t-slots without having to fool with shaving them down at all, and sheared off easily when I did final planing.

Super happy to have that done. I already have ideas for improvements and additions-inserts, fences and such.

Thanks all for posting your info here for others to follow. I did post a video over on our facebook page under the name Jimily Farms if you would like to see it.

Seeya!
Jim

[rsetina]

I used oak on mine and only surfaced it twice so far. The second time I re surfaced it I took off so little the cost of using them is quite low, in my opinion.

[NewAgent45]

See the attached post/link for details on my spoilboard. http://www.cncsharktalk.com/viewtopic.php?f=7&t=4069

Note that mine in slightly smaller (24 X 24) to allow for surface planning the MDF using an oversized pocket toolpath. 25 X 25 inch is at the maximum for the machine.

I have never seen any excessive bit wear on the carbide or carbide tipped bits from cutting MDF. It does make a lot of fine dust and I recommend using a dust boot to collect as much of the dust as possible.

Hope this helps and have a great day!

... Rod