Simple trick for laying out 180 degree holes in cylinders

[Monahan Steam Models]

Here’s a quick and dirty simple trick for quickly laying out holes to be drilled in a cylinder that need to be 180 degrees apart.



First take some painters tape and wrap it around the cylinder making sure the ends of the tape are cut exactly 90 degrees to the length and don’t overlap like this.



Next remove the tape from the cylinder and fold it in half with the adhesive side opposite of each other making sure the cut ends match up to each other.



Take one half of the cut tape and wrap it around the cylinder.


Like so.



Another view



Now take a right angle square and line up the edge of the first half of the cut piece of tape with the square to place the other piece of the cut tape at the other end of the cylinder.



Now you can use a template to mark out the centers of your holes 180 degrees apart like this example.

Hope this helps someone

[rwtdiver]

Nick,

That is a very good idea! Very simple, and it works. Thanks for sharing that information with us!

Rob
"Firemen can stand the heat"

[Bob Gato]

Great tip Nick... If you don't mind I'd like to add don't use any tape you have laying around like masking or fine line tape- masking or fine line tape easily stretches and will throw off your measurements.-BG

[Monahan Steam Models]

Great tip Nick... If you don't mind I'd like to add don't use any tape you have laying around like masking or fine line tape- masking or fine line tape easily stretches and will throw off your measurements.-BG

Excellent point you make BG!

[He Who Shall Not Be Named]

Or make and use a GRP tubular template:

[Monahan Steam Models]

Or make and use a GRP tubular template:

David,

That is a slick and clever tool for laying out multiple cylinders! I like it.

Really I was too lazy yesterday to set up the dividing head in the mill to make the four holes in the one off ballast cylinder so I chose to use this tape method that I came up with on the fly. Prior to that, I was considering measuring the diameter and then using Pi to determine the length of the template needed and dividing by two. Instead I was like duh, just use some tape dumb***! LOL

Production tooling like you share is an absolute must when creating multiples of the same part.

For me personally, my production days have come and gone and I have very little interest these day in getting back into that kind of work. I still think production when designing some stuff because old habits are hard to break.

Nick