Linear motion
I found this site: www.contraptor.org. It's something I've really been looking for. I want to do linear motion, but 8mm steel rod is expensive, and hard to cut (It's beyond my table mounted jigsaw so I would have to hack saw it by hand). Linear bearings are expensive too, and that's before you consider the mounting blocks. This is great: aluminium angle will do as a track. You can buy the bearings in quantity extremely cheaply.
Contraptor itself is imperial, so no good for me, uses really thick angle, which I don't have around, and also uses tapping to make some parts. That's almost certainly for good reasons, but I'm going to improvise...
My bearings have 3mm bore, so I'm going to fix them to the angle using m3 nuts and bolts. The nuts will set flush against the angle. The nuts are 5.5mm. The angle I have is 1/2" x 1/16", or 3/8" x 1/16". In the first instance, the 1/16" = 1.6mm is relevant. The hole will be a minimum of 4.35mm from the edge. The bearing OD is 10mm, so that works nicely. I'm going to measure from the inside of the angle, so I'll measure half a nut. This is beginning to sound like more precision than I can really do, but I'll use a fence so that at least I'm consistent... I can set my callipers around a drill bit that's about the right width, and see how that goes.
Which angle? Well, neither can be used with maker beam - the hypotenuse is more than 10mm either way. Bigger will be stronger, so I'll go with the 1/2" angle.
I think drilling a hole in the top with a standard bit, which will leave a tapered hole, and then fixing it with a countersunk machine screw will be easiest. I'll go with M5, which means that hole needs to be 10mm at it's widest. That'll intersect at 7mm down the side. Once I've got one right, I can set the stop to drill the rest. Contraptor use only one screw for each unit, which I guess is so you can tighten it parallel. In fact, during assembly, they wedge an allen key in a gap to keep it parallel. I should probably do the same thing. Actually, is this counter sunk thing wrong? It won't allow any play in the position. A flat base and a washer would, then you can adjust the position. Again, I should copy contraptor. That means I need a milling bit though.
I wonder if I put the small angle flush against the large angle, the bearings will clear it? I guess it's really time for a cad drawing. Actually no: the bearing is only about 3mm from the outer edge of the angle, so it would have to be < 3mm thick but it's 4mm and there will be a shim too. No matter: the allen key trick looks like it will work well.
Anyway, I need the end mill, and I think I'll start by practising the holes in the corner of the angle. I have another idea that uses this, which I'll write up in my next post.
Contraptor itself is imperial, so no good for me, uses really thick angle, which I don't have around, and also uses tapping to make some parts. That's almost certainly for good reasons, but I'm going to improvise...
My bearings have 3mm bore, so I'm going to fix them to the angle using m3 nuts and bolts. The nuts will set flush against the angle. The nuts are 5.5mm. The angle I have is 1/2" x 1/16", or 3/8" x 1/16". In the first instance, the 1/16" = 1.6mm is relevant. The hole will be a minimum of 4.35mm from the edge. The bearing OD is 10mm, so that works nicely. I'm going to measure from the inside of the angle, so I'll measure half a nut. This is beginning to sound like more precision than I can really do, but I'll use a fence so that at least I'm consistent... I can set my callipers around a drill bit that's about the right width, and see how that goes.
Which angle? Well, neither can be used with maker beam - the hypotenuse is more than 10mm either way. Bigger will be stronger, so I'll go with the 1/2" angle.
I think drilling a hole in the top with a standard bit, which will leave a tapered hole, and then fixing it with a countersunk machine screw will be easiest. I'll go with M5, which means that hole needs to be 10mm at it's widest. That'll intersect at 7mm down the side. Once I've got one right, I can set the stop to drill the rest. Contraptor use only one screw for each unit, which I guess is so you can tighten it parallel. In fact, during assembly, they wedge an allen key in a gap to keep it parallel. I should probably do the same thing. Actually, is this counter sunk thing wrong? It won't allow any play in the position. A flat base and a washer would, then you can adjust the position. Again, I should copy contraptor. That means I need a milling bit though.
I wonder if I put the small angle flush against the large angle, the bearings will clear it? I guess it's really time for a cad drawing. Actually no: the bearing is only about 3mm from the outer edge of the angle, so it would have to be < 3mm thick but it's 4mm and there will be a shim too. No matter: the allen key trick looks like it will work well.
Anyway, I need the end mill, and I think I'll start by practising the holes in the corner of the angle. I have another idea that uses this, which I'll write up in my next post.
