Bora Centipede Top w/ Hold Down Dogs & Connectors

Instructions

I break down sheet goods with a track saw on a Bora Centipede using a pocket-holed 2X4 frame, clamped on the Centipede, with a foam board on top. The 2X4 frame is unwieldly and difficult to clamp down. When I looked at the Bora top, I had two issues: 1) Thee 2’X4’ sheets are ¾” MDF, so a bit heavier than I wanted to deal with, and 2) I don’t need the all the dog holes for my use case. So, I decided to make my own top using ½” thick 2’X4’ MDF sheets. I designed a corner treatment for the MDF sheets with dog holes aligned with the Centipede mounting holes to hold down the sheets. I also included connector recesses with dog holes for the 3D printed connectors. Since I have the original single hole corner supports on my Bora, I could only use the connecting dogs on one edge of each sheet, so the connectors were required to keep the boards aligned and provide rigidity to the Centipede. (The connector recesses aren’t required on the outer edge of each end piece, which saved some routing time.) I used the Shaper Origin along with the Plate to cut the corners. But this can be done with a router and templates. I 3D printed the hold-down dogs and connectors. I realized after I put it all together that the dogs on the connectors were unnecessarily long, so in the model and 3D files I posted I reduced them so they are just a bit proud of the bottom of the MDF sheets. The only surprise in the process was that I assumed that since MDF is exactly ½”, the length of the sheets would be exactly 48”. NOPE! I cut my first end sheet, using the ends of the sheet as my Plate reference. Then I cut my first middle piece to do a test fit. I couldn’t get the connectors to align. I then realized the first sheet was 47 7/8”, and the second piece was 46 13/16”. So, I added a 1/32” offset on the recess to address the 1/16” difference. If I had checked first and trimmed all the sheets to the same length, I could have eliminated the offset. I’ve posted the 3D print and Shaper files on Printables, Thingiverse and the Shaper Hub in case anyone has a similar need. https://www.printables.com/model/923623-bora-centipede-top-with-hold-down-dogs-and-sheet-c https://www.thingiverse.com/thing:6674833 SHAPER NOTES Since you are referencing from the edges, make sure in advance that you have confirmed your sheets are the same length. If not, trim them down or add an offset on the connector recess to accommodate the differences in the lengths. The offset should be 1/2 of the difference between your longest and shortest sheet. You don't have to adjust for the hold down dogs since the swiveling mounts allow you some wiggle room. Hold down dog head recess depth: 3/16" Connector recess depth: 1/3" Through hole depth: .52 (This will ensure you go all the way through the MDF) Process: I cut the recess for the hold down dog using a pocket cut first at full depth. Then I used a pocket hole cut in the center of the through hole to make sure I didn't have a bump sticking up. I just plunged to the full .52", wiggled a bit, then retracted. Then I cut the through hole w/ an inside cut using auto pass. Since the recess was there, the first 2 passes were easy, but you should be going slowly so when you get to the bottom of the recess you don't ram into the material with an abrupt bump. Then I cut the recess for the connectors. I started with a pocket cut. I did the pocket cut in 2 passes w/ a 1/4" bit - .16 first pass, .34 second pass. Once that was done, I did an inside cut. Since my boards turned out to be different lengths, I added a 1/32" offset. Then I cut the through holes the same way as I did for the hold down dogs. Since MDF is so dusty, I work a face covering and vacuumed out the cuts often.