ShopBot Decking Material

[dttworld]

I recently redid mine, and I used.

2x 5x5 sheets of 3/4" baltic birch plywood cut to make an oversize support board spanning between the table legs, measuring about 104" long. I joined the two sections using biscuits. I bolted this "support board" to the table using every available bolt hole, which was somewhere in the neighborhood of 50.

I was wondering about the bed size. In the assembly manual there is a CAD drawing that shows the mounting of a 4' x 8' sheet of decking for the PRS Standard 96-48-6. For your 10' x 5' deck did you need to move the table cross supports on each end farther out to support the bigger deck? Also, do you think a 4' x 8' bed is good enough?

[dttworld]

Danh

I second the Baltic birch recommendation... It's the most stable material I have used. I don't have a vacuum hold down and use Baltic birch even for my spoil Board. Unless you intend to Air condition 24/7, you'll need to resurface an MDF spoil board every time you use it due to uneven swelling (and even some times in the middle of a long day!)

Steve

I just bought the most expensive piece of plywood I could find from Home Depot. It is "3/4 inch Birch Hardwood Plywood". Cost $47. Don't know if it's Baltic but that's all they had. Sounds like the MDF could be problematic in my garage. Maybe I'll go with another layer of plywood. Wonder if the resurfacing might leave behind surface splinters.

[Brady Watson]

Maybe I'll go with another layer of plywood.

Danh - please do not reinvent the wheel when it comes to the table layup. You will be disappointed...

ShopBot officially recommends 'cabinet grade plywood' for the support board that bolts to the chassis of the machine. Then, MDF for the next layer, which will be called your 'spoilboard'. Both can be sourced from the big box stores, although I must say that it is not my preferred choice.

Glue both of these together, clamp all around the edges and put weight (lots of weight) in the center and let it sit overnight.

On my personal machine, I use 3/4" MDO from HarborSales.net, and Medex moisture resistant MDF as my spoilboard, also available from Harbor. I *always* sand the MDO paper to give it tooth before I glue anything to it. Epoxy would be best, Titebond and even white glue will work, as will Gorilla polyurethane. Use what you KNOW will work, or what pros have recommended to avoid getting the sawzall out and starting over again...

Drywall screws are the devil - when used on ANYTHING other than drywall, and should NEVER be used on your CNC for ANY reason.

-B

[rcnewcomb]

Drywall screws are the devil - when used on ANYTHING other than drywall, and should NEVER be used on your CNC for ANY reason.

I agree. It was pretty sad to watch the sparks as a drywall screw destroyed the very expensive bit we used for surfacing the spoilboard.

We ended up tearing everything out and re-doing the setup as ShopBot recommends.

[dttworld]

....I use 3/4" MDO from HarborSales.net, and Medex moisture resistant MDF as my spoilboard, also available from Harbor .....

I should be ok with the Birch plywood because it's also recommended by ShopBot. How much was freight from HarborSales.net to NJ for something like a 4'x8' sheet of Medex MDF? May not make sense for me if I don't buy in bulk to offset freight charges.

[Brady Watson]

I should be ok with the Birch plywood because it's also recommended by ShopBot. How much was freight from HarborSales.net to NJ for something like a 4'x8' sheet of Medex MDF? May not make sense for me if I don't buy in bulk to offset freight charges.

You'll be fine with the Birch.

Overnight shipping of any qty sheet good(s) is free...You need to set up an account to get pricing etc.

-B

[dttworld]

You'll be fine with the Birch.

Overnight shipping of any qty sheet good(s) is free...You need to set up an account to get pricing etc.

-B

$55 for the Medex MDF. Not bad with free shipping. I'll get 2 for the ShopBot and 1 for my mill. Formaldehyde free is probably safer than the stuff I was buying from Home Depot.

[michael_schwartz]

I should clarify. I used 2 5x5 sheets worth of material, but I cut them down so that I could make the support board as large as it could be. The actual size was not 5x10. I can't remember the width off the top of my head, but it spans in-between the table legs leaving about 1/4" of clearance. I did this for a number of reasons. Mainly to keep dust from falling to the floor under the table,and to have something sturdy on the sides of my actual spoil board to accommodate various means of hold down, because I don't want to screw into my bleeder board when not using vacuum.

Personally I would use either MDO, or Baltic Birch. I didn't have the time this time around, but the next time I rebuild mine I am going to coat the baltic birch support board top and bottom, with a generous amount of marine epoxy.

I no longer buy any sheet goods from home depot at all with exception to construction material such as CDX, OSB, and of course Drywall, and perhaps underlayment grade particle board, or melamine in a pinch. From my experience they just do not sell any cabinet grade material that I would be comfortable using for anything. The last time I was there there were at least 3 skids of their higher priced material material improperly supported leaving all of the sheets with 4-6" of bow. My guess is that they do not even try.

Its worth taking the time to do a nice job with a support board, since you can keep using it for a while. I did not do a good job with the spoil board I built when I setup my machine. At least it was easy to rip up when I had to rebuild it.

[gwstephens]

I am assembling my Prs Alpha 120 after some delay. I was going to snug the deck in tight between the rails but every photo shows a gap of a few inches either on one side or the other. I can find nothing in the instructions that cover this. Any ideas?

[steve_g]

My deck goes the full width, minus maybe 1/8” because MDF swells…
I wanted to minimize the debris underneath the machine because I use that area for lumber storage.
I don’t have vacuum hold down.
You can’t surface the spoil board the entire area, so I made mine separate
pieces around the edges.