Here is a 3D printed custom attachment for my Makita multi-tool that I designed myself.
The attachment is designed to cut 90-degree V-grooves into the back of plasterboard sheets (also called drywall/rockwall/gyprock etc) so that the sheets can be bent to exactly 90 degrees without needing the typical metal edging.
Because the front of the plasterboard is never cut through, there is also no need to fill and sand to finish the corner. This attachment makes a perfect, sharp corner with a minimum of time and effort.
These photos show a small piece of 13mm plasterboard I cut and bent, just to prove the attachment actually works, and to test the finished quality of the corners.
Next I plan to make attachments for 45, 30 and 15 degrees so that I can form corners that are closer to smooth curves.
Great idea, but I bet you find if you didn’t put the corner bead on over time you’ll be doing repairs. Corner beads plastic or metal are also there to take the abuse from normal use. Could that be used one the fiberglass duck work in Hvac systems, that’s what it reminded me of but you can just use a utility’s nice for cut the notch.
@Mike_C1
Good point about the abuse of corners. Without reinforcing these will be weaker.
My intention wasn’t to make corners on standard walls, but to use smaller cut-offs to make tidy boxes and trunking to cover pipes, ducting etc.
I have a built-in wardrobe that has an air-conditioner drain tube running through the back, and my first real use will be to make a 10cm X 10cm plasterboard cover to hide the tube, with a minimum of time and fuss.
@Mark_MARKSE_Emery
If there is a proper way to cut V-grooves in plasterboard with an oscillating multi-tool, or anything else, then I know nothing about it!
But then I am new to cutting plaster anyway, so this little attachment is only a very naive attempt.
I was actually pleasantly surprised that this attachment actually worked. For 3 hours of messing around with Sketchup plus my Printrbot, it’s a fair result.
Most of my time was spent sizing the adapter holes and getting them in exactly the right place so that it locked good and tight in the multi-tool head.
The rasp at the business end was pretty easy to draw and get right.
3D printers really rock - I would not even attempt to do this without one.
Also, the multi-tool speed was set to the slowest speed. Any faster and a lot of the cardboard facing comes off as well. That isn’t too important since it’s the inside that gets messed up, but it seems to cut slower when that happens.
I am going to make some small changes to the design before the next cuts. I want to round off the front a bit so that it rides over the cardboard facing much easier.
I will make a new post here when I have done that.
Sweet. And there are lots of applications where durability wouldn’t be an issue (and where the local extra thickness of the corner bead is). I am wondering about interior and surface treatments to improve toughness. People don’t put multiple coats of sealer on any more.
@paul_wallich
Regarding the toughness of the corner, I was planning to try something very simple - run a bead of PVA wood glue (white glue?) in the grooves of my little test sample to hopefully set and strengthen the corner.
After it dries I will bash my test sample around and see how much abuse it can accept.
@Joe_Spanier
After I make some adjustments to the design and test a new cutter I plan to post details on Instructables to describe the cutting process.
Just briefly:
I slice away most of the cardboard above the V-groove with a knife prior to the actual cut.
Then I cut by making several passes to deepen the groove with the nose of the attachment touching the groove but the back raised. (It can’t cut the groove in a single pass.)
The non-cutting part of the attachment needs to be re-designed with a rounded, bull-nose front to stop it gathering the cardboard beside the groove on each pass.
Regarding the Sketchup models and STL file of the cutter - what is the generally accepted place to post those design files?
