TableSaw Dado Tool : Use multiple 1/8 jigs to create Dado cuts by indyToronto

Last crawled date: 3 years, 4 months ago

If you want to cut grooves or dadoes wider than the width of your table saw blade, you will find this jig useful.
Parts Needed :
1x M5 hex nut and 1x M5 bolt (20mm minimum, the longer the bolt, the more pieces you can stack up.
The jig is basically constructed using multiple copies of a single 1/8" high (3.175mm) piece about 3.5" long and 5/8" wide. It was designed to be used on a sliding sled with a T track and a swing away fence stop but you can use them in anyway you need by stacking them.
The time saver here is that if you print (say 7) and get a 30mm M5 bolt and nut, you can selectively rotate each piece one by one. For example, to get a 1/2" wide groove on your stock, you start with 2 pieces down, cut the first groove, move 3rd piece down, cut again, and then the 4th piece, cut, and then 5th piece and you've cut 4 slots of 1/8" right next to each other to make a 1/2" groove.
To get this to work with your 3D printer however, you have to first print one and measure how close it is to 3.175mm (1/8"). There is almost zero chance this printed piece will be 1/8" exactly. The object in the design is exactly 3.175mm high (1/8") but the printer does not have the resolution to get the vertical height exactly correct --- even with adaptive height the Z-stepper is unlikely to be accurate enough to get that 0.005mm resolution correct so you can't even get close to 0.01mm or 3.17mm or 3.18mm with just the printer itself. You will need to play around with this a bit. For example If you are off by 0.3mm, add 0.3mm to the Z height in CURA.
So manually scale the object (in Z direction only) and print until you measure the printed object as close as you can to 1/8". An alternate way it to use a waste piece of wood, cut the groove and make sure the printed piece fits very tightly inside the groove. You can do this by using 0.1mm layer height and then rounding up (for example to next 0.1mm or 0.2mm - or even 0.4mm or more in some cases) until you are satisfied. If your printer is calibrated exactly, this won't take long to get to but it is very difficult to get more than 0.1mm accurate in height differences, so don't despair, no consumer grade printer will get you to within 0.005mm which it would have to if you really want exactly 3.175mm. Alternately, you can always print 3.2mm or thicker and use fine grit sandpaper to remove 0.025mm (LoL - good luck with that).
Be aware that with consumer grade 3D printers, the Z movements are never perfectly accurate.
Once you have the right setting that makes the piece come out at the 1/8" height that you're happy with, print as many copies as would fit on your longest M5 bolt that you have.
I've included a simple M5 knob that I find useful for my own use. It takes a M5 hex nut and includes a small stopper to close the top and keep the nut in place. the stopper is tight but a persistent force will push it in. Or you could use superglue to keep the stopper in and prevent the nut from coming out but I didn't have to.