Only three points of reference are required to define the radius of a circle. New technology available today along with new design breakthroughs make it possible to build an inexpensive tool capable of handling the high tolerances required for measuring arcs by using these three points “A”, “B” and “C”.

ARC MASTER  Radius Gauges are indispensable in the rolling of round pipe handrails for spiral staircases.

Are you creating advertising signs, or drafting, the Variable Arc will come into its own. The Variable Arc will allow you to draw and accurately scale any sized arc to any sized drawing. Does your business have a metal rolling machine? Without an Arc Master Radius Gauge producing irregular shapes such as parabolas, S curves, etc. can be a daunting affair. By breaking these shapes down into a series of identifiable sections, each section having its own specific radius and arc length, you end up with a accurate rendition of the required overall shape.

## Bump-Rolling Steel Plate

For bump-rolling plate or rolling sheet, you can get an accurate measurement of the radius without the hassle of making cardboard arcs or having to remove the work-piece from the machine to check its curvature.

However, taking the guesswork out of adjusting your radius is where the Arc Master (without the Variable Arc) really proves its worth. Under normal circumstances, setting a brake to bend any angle can at best be set and measured to around +/- 1/4 degree. A sample bump-roll will have to be made. When you use a sweep (sample arc) to check the arc radius you have just bump-rolled, and it shows that its either small or large, a best guess is all you have when it comes to accurately adjusting the bend angle for each bump. Knowing the exact radius will tell you exactly how much you should be adjusting the angle to get the desired radius.

To do this, here’s a sample adjustment:

For a radius of 36 inches and with a bump every 1.5 inches, the angle per bump is 2.39deg.. After your first 8 of bumps you measure the radius and you find that the radius is 40 inches. (NOTE: The Arc Master IRG-3600 requires 12 inches of arc the take a measurement.)

• 36″ / 40″ = .9
• .9 x 2.39deg. = 2.151deg. (This is your actual bend angle.)

You now add .24deg. to your angle, re-hit the bumps and continue on with rest of the arc confident that your radius is now accurate.

The formula is as follows: