Okay, I'm having trouble creating little flat "rings" (like washers) of plexiglass... I started out by cutting a rough shape with a small hole in the middle. I used the hole to attach the plexi to a dremel in the same way you would a cutting disc. I then spun it round and used a file to make it round. So far so good, but I need to make the hole in the middle quite large (10mm maybe) and the total size of the ring is only about 25mm. I can enlarge the hole with bigger and bigger drill bits, but it's really hard to get it perfectly centred. 10mm drill bits are too big for a dremel so I can't use my drilling rig. If I make a 10mm hole first (before filing down to a disc) I can't fit the plexi to my dremel... Catch 22? MoJo
Im not real familiar with mm's, so forgive me if Im way off, but couldnt you clamp the ring in a vice and use the sanding drum attachment on the dremel to hollow it out with? Should that fail, a good round file may be your best bet.
Well if you want the hole perfectly centered then I would guess that you'll have to drill that first. Can you not use the old bodgeit way of using masking tape or sumat to make the dremel bit thicker until the ring fits snug?? might slip but worth a shot maybe?!
one of these works pretty good: http://www.reamers.com/tapered-reamers.htm But it's all hand work, so centering it up takes a bit of patience.
well, couldnt you just use a drill, b/c the tiny hole for the cutting bit has to be in the center now, just make sure you get the tip of the drill bit in that hole, and go from there
Drill the center whole to your desired size. Put in a long bolt, use a nut to hold it tight and put the extended bolt thread into a drill. Use the drill to spin it like you did with the dremel.
Probelm with that is that if he's doing what I think he's doing, the desired size is about 3/4". So getting hold of the right bolt isn't easy, nor is drilling a 3/4" hole in the center in the first place. I just buzzed away at mine with a dremel bit 561 and shaped it by hand when it got close to being big enough, cause my reamer is only up to 1/2" anyhow.
if you are just making a small hole (i.e. just big enough for the arbour) you can use a spade bit at the right size (or just under). I have had good luck with those, as it cuts the outer edge before cutting into the center, and since it tapers down on the center of the bit, it centers itself in the original hole. I have done this for several icemouse wheels. Works nicely, if you ask me.
1 inch = 24.6mm 10 mm = (just over) 3/8" The center hole drilled to size, then put a bolt through it idea is good. Then just put the end of the bolt into the chuck in the drill, and spin it from there. You'll probably want a corded drill No need in killin your batteries
Yes! Thank you, it's so obvious now I feel a bit dumb for not thinking of it! It worked perfectly. Thanks a lot mate MoJo
A bit late, buuuuut... 2 hole saws. Clamp stock to board, drill center hole with hole saw, don't go all the way thru the board you're clamping to, then drill outer hole with larger holesaw. Done, D...U...N, Done!
Hardware stores may have 'em, I know they go to at least 3/4, cause I have one (That'll teach me to post before I read all the numbers LOL) Failing that, a plexi-point drill bit, or a reg bit dulled a little, you should be able to use the center of the drilled hole as a pilot to start the hole saw pilot bit, keeps everything nicely centered. Wichita, linear...
1cm 'holesaw' = 10mm drill bit. Why not buy your acrylic disks perfect, ready made and nicely polished: Disks! Then just mark the centre and drill a hole with a normal drill. No muss, no fuss. Edit - to mark the centre of a disc (if you didn't know): 1) use a compass set to the radius of the disc. 2) place the compass point on one edge of the disc and draw a small arc over the centre of the disc. 3) repeat a couple of times placing the compass point further around the disc edge each time (3 lines with the compass at 3 equally spaced points around the circumference of the circle seems to work well). 4) where the lines touch/intersect is your centre. Mark it - drill an accurate 2-3mm pilot hole (drill press or LOT of care to get it exact). Then drill your 10mm hole with a drill bit (plexi-point or dulled as Sportbilly suggests will avoid damage), slow and careful. Perfect plexi 'washers'. Professional look with minimum work.
Here is my method. It's not perfect but it does work. Start out by marking a circle the size of your washer, and cut around it with a Dremel leaving at least 2-3mm gap. No need to be neat at this point. Then, drill a small (1.5mm) hole in the center and affix the chunk of plexi to the Dremel like you would a cut-off disc. Hopefully, it will be a tight fit because if the plexi can wobble at all this won't work. Spin the Dremel up to maximum speed, and use a large metal file to grind the plexi down. Don't use too much pressure, just be patient. When the disc is a nice round shape slow down to medium speed and finish the edge off a little. Now, you have two options. You can either try and enlarge the hole accurately, in which case you need to end up with the disc being the right size in the last step. Alternatively, you can enlarge the hole and then fit the plexi on to a 10mm bolt, and fit that to a drill and file it down like before. In that case, you need to leave some plexi to file in the previous stage. If you go for the latter option, it is again important to make sure you have a really right fit. Any wobble and you won't get a perfect circle. Some electrical tape wrapped around the bolt can help. A good quality drill is also useful. You should end up with really nice washers. I am aiming to make some lit control knobs, like these: http://www.bit-tech.net/article/113/9 Beleive it or not I did actually have the idea independantly ages ago, I just never got around to doing it with my old case. Actually, rather than copying Macroman I was copying the radio in a Toyota, which has a lit volume knob. It looks like Macroman used some really bright LEDs, and sure enough my tests with normal LEDs seem to indicate that they might not be bright enough. MoJo
