Alright, on to building.
First up, The frame.
The legs on my model are a about 35 3/4ths as opposed to the design's 99cm. Why? Because I used old 2x4 legs I had cut out of one 12' 2x4. Saving money here. The side bars for the frame were cut around the given 45cm at 18". Now the measuring and math come into play. The plans call for a 69.5 cm drive shaft, thats a 27.4" shaft. Now I said forget it and went with a 24" shaft, less cost, no cutting and no weird measurements. This means I had to change the length of the cross members on the frame. Good news, they come out to a nice even 26 inches. Screw everything together like in the plans and you're done.
One thing to note, do yourself a favor and get some nice 2x4s. Mine are slightly warped and pretty rough, they do not make getting everything square easy. I did manage it though, the bar clamps I have are reversible and let me spread and clamp until everything was in line.
Next up, Break into the goodies. Truth be told you need to do this earlier to take measurements for the drive shaft and such to find the cross member length.
All the goodies from mcmaster laid out on a arrow tapering jig to be. You can also see three parts of the MDF drum. I went with a 3/4th shaft because it is plenty thick and costs less for the shaft, bearings and pulleys. I forget but it was something like a 20-30 dollar difference between 3/4th and a 1" shaft and components.
Now is the time where I start using my brain and the calculator sees some heavy use. It comes out that with my cross member length at 26" I'm left with 20" between bearings and just enough sticking off the end to fit my pulley. So, lets say we give a quarter inch clearance on either side of the drum and the frame, thats 19.5" of working drum. It also works out to 26 MDF circles to make the drum. But, that leaves me with a solid drum and no room for expansion due to humidity. so we take out one disk and add 1/16th space between every four-five disks. This makes the drum a bit over 19" allowing for some space between the pillow blocks and the drum, which will come in handy later for dust collection. Now that we have all that figured out, its on to disk production.
First up, I needed to figure out how to cut circles. I don't have a lathe, so turning the drum isn't an option. So, the solution, make a jig and do it on the band saw. What you'll need, two scraps of MDF or plywood, one nail, and two wood screws, plus some of the equipment above. Heres what I did. I took a nice thin strip of MDF and screwed it at an about a right angle to a larger piece. The thin strip sits into the miter track, and is used to guide a cut to the center line of the larger MDF piece. Then I measured down the centerline 2" and 9/16ths, marked it and drilled a 1/8ths hole through the piece. Counter sink the underside and put a nail through it and this is what you'll end up with.
Notice the little mark on the mark on the table by the bottom right corner of the miter guild? This lets me know when the blade is cutting at the centerline of the jig as the blanks cover up all of it. That brings up blanks. The fence on my bandsaw is set up to make roughly 5.25" cuts. When I make the disks I rip the MDF sheet through to make a plank of sorts, then crosscut using the fence as a stop and the miter gauge to make squares. I run lines from corner to corner, and drill a 1/8th hole in the center of the square blanks. Then they go through the jig and come out as discs. Heres how they go through:
This is before cutting with the jig loaded. The blank isn't so square but it works.
Straight cut in, lining up the jig with the mark on the table.
And most of the way through the cut. I'm using the crummy 3/8th blade that came with the saw, not the best blade for the job, but better than my nice ripping/resawing blades.
Now something of note, if you must reset your fence mid project like I did don't forget to make sure you do it properly. I forgot and set my fence at 5" as I'm aiming for a 5" diameter drum... yeah I screwed up the 16 or so blanks I cut before realizing it. And that is how I ended my day, on a low note. But made up for it with dinner out with the fiancée and some friends.
Another note, if you use a smaller nail diameter its easier to get a nice center bore with the forstner bit. I ran three test pieces and spent considerable time making sure the holes are not off center, a smaller center hole would make this easier.
More tomorrow. Any questions?
Topic: Thickness Sander Buildalong (Read 885 times)
