Butt clamps

Alright calm yourselves. Yes, with my job you might expect something for my colleagues in colo-rectal surgery but no this is a pressure clamp for my x-carve.

Since the x-carve has an open frame on the y axis you can carve very large objects and unlike the Glowforge there is of course force involved in carving so while the regular clamps that screw into the wasteboard do a good job of applying pressure they really just push the edges down (and if you’re not careful bowing the piece). Even worse when you part is cut out of the stock it is no longer held by the clamps of course and one touch of the end-mill and your project is destroyed. So normally you leave tabs in the profile cuts (ugh). They work but mar the finish at their points, no matter how well you sand. So what folks will do is the “tape and glue” method where you stick blue painter’s tape to the sacrificial piece and the brim of your stock and the CA glue them together (essentially making your own cheap double stick tape that is more easily removable) and that works great (you put the clamps on the sacrificial board underneath) now you won’t cut through the clamps and no warping. But that tape isn’t super strong if you’re turning a big tool (like a 1/4” 90 degree v-bit) you need a lot of lateral holding power. So this clamp is a modification of Phillip Lunsford of Paw Paw’s workshop on YouTube’s design. His are made of birch ply but getting back to the pass-through you need guides to keep the piece square as you push the stock through (and square means to the actual machine square not the printed lines on the wasteboard - pro tip just engrave 2 thin lines one up Y and one across X for 750mm to indicate the actual squareness. Then this clamp of course can be secured parallel to those lines (it can tilt probably 20-25 degrees) and the reason I wanted acrylic is it is much more slippery for sliding the stock along for sign making. Not having a guide is terrible with tiled signs since even a 1 degree error is huge over. 6-8 foot sign.

Now I do realize the irony of cutting acrylic on the Glowforge for a machine perfectly capable of cutting acrylic for itself. But the edge is smoother with the laser and less nasty dust to deal with. So 1.4” black acrylic it is left over from another project. and yes the dust shoe is proof grade thick clear on the Glowforge with a 3D printed hose adapter on my prusa. And apparently I am a bad man and made puppies cry by printing it in PLA and not PETG. Geez. Like seriously how much force do you put on your dust hose? Enough force to tear apart the PLA would also pull the X-carve out of the path so the answer should be as little force as possible! The bigger issue is the snap tabs that click into the acrylic wear down more quickly with PLA but since this is a quick part to print and costs like $0.20 who cares.

I will upload the file if anyone is interested. The bolts need fender washers for best holding without cracking the acrylic. The bolts are M5 and the fender washers are 1/4” and there is a M5 washer above it to make sure the head doesn’t slip through the 6.5mm hole.

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butt-plate.svg.zip (1.1 KB)
Note, the red square is to provide a perpendicular center mark so that gets engraved. (feel free to not use it. on the black acrylic it is almost impossible to see - may put some white paint-marker in there). And yes I realize the top has square edges on the front and the bottom has fillets. I had an idea of one versus the other and didn’t decide. Probably should be both filleted to prevent sharp edges cracking and scratching work pieces, but doesn’t really matter in practice. As you can see if you need REALLY high clamping force it will accommodate 2 sets of bolts. (but then you can’t angle as much). The slots have a deliberate amount of clearance to allow for alignment as needed.

I’d suggest against clear only because it is easy to forget it’s there if it’s clear. Honestly if I had 1/4" orange I would have used that instead.

Link to the original video from Paw Paw’s workshop:

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Walked in the door just 3 minutes ago, after getting a colonoscopy. And yours is the first post I see. Thought I might benefit from what you made.
Will have to wait for the drugs to wear off to figure that out.

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Oooh, I’m going to have to design and build some of these.

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Hey, what people do with the clamps in the privacy of their home isn’t any business of mine!

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I must say that this subject matter was way over my head and not something of real interest to me, but your title gave me a good laugh. :joy:

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looking at the setup it occurs to me that a the used (or in your case due to availability, not) cpap hose would push things along furthur and not need a clamp to hold the rubber end to the printed piece. Being less obstructive visually might be a minor point, but as long as it gets through the start it is an observation that despite the increased resistance per CFM, lt moves things along faster.

Ok, but not sure what problem that solves for me? The hose setup moves a lot of air and I’m connected to the metal inside this hose (most cpap tubing has no concern about dust explosions) to ground. My prior hose was carbon impregnated for even more static dissipation but was a bit too stiff. This hose also matches the hose diameter of my cyclonic separator.

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Only because you’re not an ER doc.

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