Calculating Location of Grooves on Cylinder

[Flute Maker]

I have a cylinder (a piece 3” long and a little over 1 1/2” in dia. that I turned ) I want to put some decorative grooves equally spaced length wise) This is sort of an experiment for a repair. . I usually just mark them and experiment how many and how far apart…. I know there should be some math to calculate let’s say 8 grooves on a 1 1/2” diameter piece putting them from one end to the other lengthwise…I hope this makes sense lol!. I would be cutting grooves using a “v” bit with my mini mill ….

 

[RickR]

if you have an indexing ring on your lathe, the easiest way would be to use it to make layout marks 45 degrees apart (360/8). Lacking that, the spacing can be calculated as 3.14 times diameter divided by 8. The spacing is measured on the surface of the cylinder.

 

[mdbuntyn]

Draw a line from top to bottom and use a set of dividers and step off the placement of the grooves

 

[bob vaughan]

Wrap a piece of masking tape around it. Mark the tape or razor cut the tape. Take the tape off and divide by 8. Mark the segments. Split the tape and wrap around the ends. Mark the stock with a straightedge. A 1.5" diameter should have marks about every .589" on the strip of tape. There's a trick with a T-square and a ruler at an angle but I can't figure out how to quickly convey that trick.

 

[smallboat]

What Bob Vaughn said.

 

[kserdar]

Think of your cylinder as a flat piece of paper rolled up.
You already know one dimention - the length of your piece - 3” long.
Other is circumference (C = 3.14 x Diameter) - 3.14 x 1.5 = 4.71
4.71 / 8 = 0.58875"

37/64 = 0.5781"
19/32 = 0.5937"

4 23/64" = 4.7187

 

[PeteM]

4.71 / 8 = 0.58875" = 14.95425 mm
37/64 = 0.5781" = 14.68374 mm
19/32 = 0.5937" = 15.07998 mm
4 23/64" = 4.7187 = 119.85498 mm

No matter how you measure it that's too much math.
Much easier to take that flat piece of paper you just unrolled, fold it into eighths, wrap it back around the cylinder, and transfer the creases to the cylinder. No measuring. No mistakes.

 

[kserdar]

No matter how you measure it that's too much math.
Much easier to take that flat piece of paper you just unrolled, fold it into eighths, wrap it back around the cylinder, and transfer the creases to the cylinder. No measuring. No mistakes.

After learning Hex, Octal, Binary, Etc ....

Why can't we just switch to the Metric system and be done with it.

 

[bainin]

8 equal spaces on a 360degree circle.. every 45 degrees. Thats a pretty easy angle to get in the shop.

b

 

[Flute Maker]

Thanks guys I got it…Sounds good to me!