Need a book recommendation

[jgourlay]

In the June addition of Popular Woodworking there was an illuminating article on an old layout tool called a "Sector". This is one of those old implements that does the job of a (calculator + ruler) in about 1/10 the time, but requires some level of understanding. Because of the understanding piece, and the fact that they need to be made out of light, stiff, cheap materials (aka wood) with a high degree of precision, nobody uses them anymore. They are rare as hen's teeth on the used market, and expensive.

So, I want to make one. There is one skill in the process that I don't have, and that I can't find anywhere in my books. That is the skill of 'ruler making'. I need a book that address a few fundamental issues. For example, what is the right technique and what are the right tools for making every mark with exactly the same spacing? What is the right tool and technique for actually making the mark? Sectors for my use need to be 24" to 36" long. What are the right tools and techniques for graving a perfectly straight, 36" long line from the centerpoint of a hinge to the end of the arm to which that hinge is attached?

Note that I have a small lathe, but not a mill. I'm not sure that generalist machine tools are even the right tools for a one off project like this. Sectors were common at least as early as the 15'th century, so I know machine tools are not even close to necessary.

Do you all know of any books that could guide me through this?

[danlb]

There are many ways to do it with varying degrees of accuracy.

For simple repeatable spacing of drilled holes: Use a fence to keep the distance from the edge consistent. Use a peg in the table (the same size as the holes) to locate the most recently drilled hole while you drill the next.

For a simple rule, use a computer printer to print a 1:1 picture of a ruler. Laminate it to the surface.

For a linear rule, you can use dividers as scribes and walk them down the edge.

There are other ways. How accurate do you need?

Dan

[Dr Stan]

What are the right tools and techniques for graving a perfectly straight, 36" long line from the centerpoint of a hinge to the end of the arm to which that hinge is attached?

I could see this being done with either a table saw with the blade tilted @ 45 degrees, or with a router mounted on a router table.

As to the divisions an old pantograph would work well, but probably the "best" tool for making any and all of these marks/divisions is a laser cutter/engraver. Check around at the local trophy shops to see what's available.

[jgourlay]

There are many ways to do it with varying degrees of accuracy.


For a linear rule, you can use dividers as scribes and walk them down the edge.

There are other ways. How accurate do you need?

Dan

For layout, the dividers method is the way to go for me. The more befuddling problem is the actual scribing. Here's the thing. One line, no problem. Two lines? Not so bad.

But when you think of the numbers of exactly identical and precisely spaced lines a simple ruler denominated in eighths' takes, it becomes daunting. How to prevent that little slip, that little wiggle or wobble that ruins the whole thing? Reminds me of a project where I had to cut 42 dovetails (164 cuts!) #'s 1 through 40 came out fine. #41? Not so great.....

And what's the right tool? A carbide scribe? A graver? Is it pushed or struck? Two or three gentle strokes (all with an opportunity for error) or a single authoritative whack?

Here's the question: how did great grandpa Starrett get it done back in the day?

[H380]

Take a broken 1/8" or similar end mill and sharpen to a point. Or a replacement scribe point. Mount your soon to be rule in your mill vice. Move your mill table left/right .125 for each 1/8" mark or what ever graduation you want. Vary the amount of in/out movement for the heights of 1/4", 1/2" etc...

[danlb]

It always helps if you can create stops or fixtures to prevent going too far. If you have a mill you can set the 'y' stops for a certain length line, then move the X axis 1/4 or 1/2 or 1 inch (as appropriate) until all are done, then do the next increment( longer line).

Interestingly, your standard ruler (in eights) has the 1/8 marked every 1/4 inch, and the 1/4 marked every 1/2 inch. You only have the 1/2 and 1 inch marks every inch.

If you are doing it on wood, it will not be all that precise anyway.
Dan

[Gary Paine]

Sounds like a fun project. Without a long bed mill to do it for you, I suspect your main issue to be indexing of the lines and numbers. I suggest you think homemade leadscrew. Since this is basically a one off project, you do not have to get fancy. Think, maybe of a 3 foot long bar (sturdy metal or even wood). Attached to each end of the bar would be a bracket that holds the ends of a 3 foot piece of threaded rod (1/4 – 20 would be good). Now we need a carriage, basically a fitted yoke or carriage to ride the bar. It is driven by a captured nut on the threaded rod. Your workpiece would register against the opposite side of the bar than the rod is. Fashion a crank handle and index away. 5 turns for ¼ inch, 20 for an inch, and so on. The yoke is where you can get creative. It could have slots that register a line punch and number punches at the same Y position on the workpiece as you index the X axis. I believe all the old rules, commercially made of boxwood, were stamped. Stamping crushes the fibers, but doesn’t cut them, so the strength isn’t compromised excessively. Make the line stamps from mild steel flat stock, tapered to an edge with a blunt tip. Try to use quartersawn stock as it will be much more stable with temp and humidity. If you could find old wooden yardsticks, they might make good stock after planed smooth. Experiment on scrap to find the right smack on the marking tool and when marking the final piece, resist the temptation to strike twice.

[aostling]

In the June addition of Popular Woodworking there was an illuminating article on an old layout tool called a "Sector".

For the benefit of those of us who don't know what one looks like, can you link to an illustration of one of these "sectors?"

[form_change]

One method I've heard of for making out divisions accurately is to use a (universal) dividing head to drive back through a gear train to move a mill table ever so slightly.
I've never done it or even set up to try it, but the idea is that the dividing head will enable small but precise repeatable movements. If you thought about it, you may be able to adapt a semi-universal to drive the table and get the same result.

Michael