Tracing Round Objects for Lathe Template

[Jared Greenberg]

I am looking at making some templates, but need to know a good way to trace a round (cylinder) object. I have seen a tracing jig before that was a block of wood coming out of it and the point of the block ran against the object being traced and the pen scribed the line on the template to be cut out.

Does anyone know of any tried and true methods? Or does anyone know of this jig that I am talking about. The person who showed it to me said he found it in a woodworking magazine and I am kicking myself for not taking a picture of it.

[Jared Greenberg]

Anyone????

[Christopher K. Hartley]

Are you wanting templates to cut bowl blanks?

[Jared Greenberg]

No, a stair spindle/baluster.

[Christopher K. Hartley]

No, a stair spindle/baluster.

Sorry, just my one track mind.

[Bill Stevener]

I think for what you wish to do, a simple compass would work well. You can also go and buy a pin form tracer, they are fairly cheep. But I guess a pointed stick with a hole drilled in one end to except a pen would do the trick also.

[Andy Hoyt]

One small (highly technical) drawing for Jared

One full hour to create it for Andy

Hoytinator.jpg

[Ken Fitzgerald]

Jared,

I've done a lot of thinking about this since I turned 8 spindles for the steering wheel on Dave Richards sail boat.

You could do it by a couple of methods.

1. Use a dial caliper and measure strategic points on the spindle/ballister. Use a light and place the sample spindle between the light and the paper. Adjust the distance between the spindle sample and the light until the shadow on the paper has the same strategic measurements as you earlier measured. Draw it freehand using the shadow as a pattern. Cut the pattern.

2. Make one sample. Find the exact middle. Cut it so the middle remains on the edge of one of the cut pieces. Use it to draw and cut a pattern.

Good luck! I'll be interested in what others suggest!

[joe greiner]

I think the shadow method could be inexact, because the light from a single bulb fans out across the boundary. BUT, if the light source is the sun, it's far enough away to produce substantially parallel light rays. A little more difficult, though, unless your lathe or other mounting is near a large window or door.

A contour gauge (like this: http://www.toolking.com/greatneck_cg6c.aspx ), with multiple adjustable wires can be used to transfer varying shapes to a drawing, using strategic diameter measurements at specific points, like Ken suggests. I've used it to make almost identical members of a pair, without the drawing. For longer than about 6 inches workpiece, you'll have to make several transfers.

Another stunt I've used is to place a sheet of (whatever) at the equator of the original, mounted reasonably solid. Then, I tape down narrow pieces of card stock or paper to reach the original, and continue along the profile. Finally, tape all the strips of card together, flip upside down, and trace along the edge to the pattern material, fairing any irregularities freehand.

Joe

[Ken Fitzgerald]

Joe,
You are correct. However.....if you moved your light source up and down the length of the spindle, it would be exact as long as the distance from the light to the sample remained consistant. That's why I suggested measuring the shadow and insuring it meets the measured reference points before tracing it.

Maybe use a flourescent tube so the light was constant without moving it.

[Jared Greenberg]

This is what the jig looked like...

[Richard Madison]

Have one of those countour gauges that Joe suggested, and am pretty sure I have used it a time or two. Unknown source, as I did not buy it. But it's one of those things that every few years it's exactly the thing you need.

Lacking the above, do you have access to a copy machine, or a scanner and printer? Suggest making a copy of the original and tracing onto the material that will be your template. Something to try at little or no expense.

[joe greiner]

This is what the jig looked like...

Jared, that looks like a pretty slick way to do it. With the original mounted on the lathe (or a lathe-like support), clamp the pattern stock (as you say mdf, or masonite, or heavy cardboard, or whatever) to the lathe bed, and put the follower point at the same height as the lathe axis. I think it'd work best with the pen vertical, and in fact the pen could just be taped to the vertical edge of the tool, e.g. filament tape or duct tape.

It may be tricky to keep it perpendicular to the lathe axis. A Q&D solution could be to place the far edge of the pattern stock in line with the edge of the lathe bed. Then clamp a small framing square to the tool itself, with the blade horizontal. As you trace the pattern, hold the framing square parallel to the far edge of the pattern stock. For something more durable, attach a small piece of plywood to match the framing square arrangement.

Joe

[Jared Greenberg]

Jared, that looks like a pretty slick way to do it.

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It is..the person I saw use it knew that the masonite stuck 1" into the template holder on the lathe. He then marked that point on the masonite, then measured the initial point on the object on divided it by to to know where to set the object on the masonite. He then stabilized it from rolling and used the jig to trace the object. It was traced in maybe 20 seconds.


I guess my question is...He said that the pen and tip of the block of wood come to the point together (the pen is then held by a set screw). So that where the object is lying the pen line would come directly below it to get an exact tracing. Would that block of wood be on an angle (sitting back a little) when tracing it?

[joe greiner]

.

It is..the person I saw use it knew that the masonite stuck 1" into the template holder on the lathe. He then marked that point on the masonite, then measured the initial point on the object on divided it by to to know where to set the object on the masonite. He then stabilized it from rolling and used the jig to trace the object. It was traced in maybe 20 seconds.


I guess my question is...He said that the pen and tip of the block of wood come to the point together (the pen is then held by a set screw). So that where the object is lying the pen line would come directly below it to get an exact tracing. Would that block of wood be on an angle (sitting back a little) when tracing it?

I don't see why that extra complexity would be needed. The vertical pen would be at a constant horizontal distance from the surface, by being at a constant horizontal distance from the tracer. Use a caliper to measure the diameters at two significant locations near the ends of the prototype. Divide each of them in half to locate the lathe axis in plan, offset from the traced pattern, and strike a straight line to locate the lathe axis on the pattern. Even so, the lathe axis doesn't contribute to the production process because you'd just be checking the shape with the pattern. UNLESS you're using a tracing cutter; then you need to mount the pattern accurately. I hope that makes sense.

Joe