Idea for Simple Circle Projection Tool

[larry cottrill]

Here's a proposed design for a tool that will project circular arcs on the surface of tubes, cones, slanted plates, etc. so you can mark them for cutting holes with a scribe or marker or some such. You'll need a lathe with a standard 3-jaw chuck to hold and spin the tool. Just adjust it to 1/2 the desired circle diameter and cinch the lock nut.

Such a tool will not be error-free, of course, but the error will be small if you align it carefully while tightening and if you don't try to use it by projecting clear across the room!

L Cottrill

[Rossco]

Ah, for marking the side of any shape or suface, for an intersecting pipe!
Not bad, too fiddly for me, but not bad. You can put a lot of time into designing such a cut.
I would think a solid stand for a drill with the same attachment could be more flexible!
Thanx Larry, you just keep coming up with them dont you!

Rossco

[ZSartell]

Great idea! That could come in handy that's for sure. Not that it would really be necessary but instead of using a threaded bushing, you could use an unthreaded bushing and a nut on each side. That way you are not limited to increments of the TPI on the bolt. Although if you used a fine threaded bolt I doubt it would need to be any more accurate. I know that my unsteady hand would mark it off at least that much anyway. Maybe a more powerful laser would solve that problem. It could just burn a mark into the material. :)

[larry cottrill]

Thanks, gentlemen.

A couple of other things I thought of:

Another way to make the tool, simpler for some, would be to make the shaft out of a big bolt or big piece of hexagonal bar, and drill and tap from one flat face through the opposite face. Or, as Zach has suggested, just drill through and use two jam nuts.

Another way of using the tool would be to wrap a piece of suitably ruled graph paper around the curved or sloping piece you're wanting to perforate, and mark the paper. This would give you a full-size template you could re-use or share by scanning to a file. If you're comfortable with darkroom work, you could even set it up with a piece of film or enlargement paper wrapped around the target area, expose it briefly to the laser projection and develop it. Let the laser do the marking!

And, you could make an interchangeable set of laser bits set for different angles, projecting a conical pattern! Note that in this case, though, carefully measured spacing from the tool to the target area would become a critical part of the setup.

L Cottrill

[Mike Everman]

I like the conical bit, that's friggin clever. Perhaps you should spend a few minutes a day on alchemy and antigravity, Larry. :-)
With solidworks, you can model it very quickly, unroll the surface, print it and wrap the piece of paper around the tube or cone you want the hole in, but not everyone has $5k worth of software!

I got a combination laser pointer/ballpoint pen at the liquor store for $4 that comes with extra batteries. Hard to believe. China is going to ruin us.

[Bruno Ogorelec]

China is going to ruin us.

I believe it's horses for courses. Everyone should find out what his strength is. Chinese are good at turning out cheap stuff by the million. But, frankly, I don't see them coming up with very original, inventive stuff. Same with the Japanese. The threat that one day, they would be flooding the world with invention, not just mass production, has still not materialized.

I think the two are incompatible. You either have invention or you have mass production. Look at historical examples. The moment the US started mass production of automobiles, they became uniform, started losing the technological edge and left invention to the Europeans.

The moment the British car industry died, the specialist cottage industry developed into the most formidable force around. Just look at the British Formula 1 industry -- it is all small and individual and the technology is very probably above the NASA level.

The US has a single 'serious' motor cycle manufacturer -- it is just not a notable player on the international scene -- but turns out some of the most inventive motor cycles in the world from hundreds of small individual outfits.

Look at the US aerospace industry. The big manufacturers are tottering, but the general aviation industry is in a huge boom, powered along by small new inventive teams. Look at Lancair -- from a small hangar to the biggest GA manufacturer in the world in a decade or so. Had someone asked you ten years ago whether a garage guy could defeat Cessna in the field of small private aircraft, would you have believed him?

Look at Burt Rutan. Small US industry is going to space. Can the Chinese say the same? Or the Japanese? No. they just don't seem to have what used to be known (rightly or not) 'Yankee ingenuity'.

The real threat is going to come from India and Pakistan. Maybe Russia. They have long been knowledge-driven.