I've been thinking that a disc sander would improve my pattern making, I'm not particularly well set up for woodworking and making a decent pattern seems like a basic requirement for casting.
I made a bicycle-powered potters wheel for my daughter's birthday earlier this year, the throwing head is 12" diameter so I decided to use the same pattern and make a 12" disc for the sander.
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After machining the rough-as-guts casting, I made an arbor and set it up on the balancing rail for my surface grinder wheels. Had to drill out a fair bit of material from the heavy side to get it nicely balanced.
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Used the shaper to cut the internal keyway; I drilled a hole at an angle to intersect the bore near the bottom, so the slotting tool has somewhere to run out at the end of the cut.
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When I bought the vice for my shaper, the previous owner had it bolted down to a piece of .600" thick plate that has a machined surface both sides. This piece of plate was just the right size to become the table for the disc sander.
I milled a recess in the plate so that the sides of the plate extend forward of the disc face; this enables the pivot point for the table to be close to the same plane as the front edge of the table so the gap doesn't become change too much as the table is tilted. I then rebated the underside of the table to 45 degrees as the table will be able to tilt to that angle. Setting up to rebate the plate took a bit of imagination as I don't have any kind of tilting fixture; fortunately I have a dirty great angle plate and plenty of room in the Z-axis of my mill.
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I needed a 1/2" wide by 1/4" deep slot in the table to accept the mitre guide from my cheapy bandsaw. I found a 1/2" x 5" side-and-face cutter amongst my collection; it looks like it's ready for the bin
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but a visit to the surface grinder with my almost-finished sharpening jig and it was good to cut.
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The table is now ready to go.
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I'm using a 3hp 3-phase motor that has been hiding under a bench for a few years. I have a RPC but I want this sander to be more portable than the 3-phase wiring in my shed will allow. I put together a static converter, mostly with bits left over from my RPC build although I had to fork out for the capacitors and the plastic box.
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I don't know how much power a 415v 3 phase 3 horsepower motor will put out when it's being fed 240v single phase power but hopefully it's about right for a 12" disc sander. Given that every other build I looked at on the internet was running 3/4 to 1hp, I reckon it should do.
My least favourite metalworking activity would have to be fabrication. After a lot of cutting, grinding, welding etc I got the frame together and gave it a couple of coats of ford tractor blue.
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I had to fit the vertical head to my mill to slot the tilt adjusters. This is one of those times when two crappy mill vices are better than one good one. I left the stock long so I could cut the two slots between the vices, gripping the 10x40 bar stock where the slots aren't.
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I got the thing assembled today. I'm waiting for a couple of sanding discs to arrive in the mail as no-one seems to stock anything bigger than 9".
Also I put a ground finish on the tilt adjusters, I'm going to have to give them some kind of anticorrosive finish.
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The table can tilt about 10 degrees upward and 45 degrees down. It pivots on M8 socket-head capscrews, the diameter of the heads of these means they are below the surface of the table.
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still to do are add feet to the underside of the frame- I'll probably use discs cut from some delrin stock- and screw a sheet of 19mm flooring to the top of the frame members. The feet will enable my fridge trolley to easily get under it for portability and standing on the flooring to use the sander will anchor it when in use. Once in use I'll be able to decide whether it needs a shield and dust extraction; the main reason to keep it portable is to be able to take it outside, or by the door in bad weather- I've never actually used one of these things so I guess I'll find out how much mess it makes once my sandpaper arrives.