Center line on a pipe?

[Chasboy1]

Hi Folks, I'm hoping I'm not too far off topic.
I want to make a straight line along the length of a piece of tubing.
The project is our patio swing where the seat base/sling is falling apart and I have patio chair webbing to replace it. The webbing his held by a screw at each end that goes thru the webbing at regular intervals. I want these holes to be in-line along the length of the frame(tubing) but working on a curve is not easy in this direction. The tubing diameter is about 3/4".
thanks in advance!

 

[magpens]

The tubing is straight, presumably.

Use a long length of 1/2" masking tape (eyeball the straightness of the tape !). . . Measure and Mark the positions for screws and drill.

 

[jttheclockman]

Quite easily. I will try to explain. It is basically the same method I use when marking a pen tube. Lay the pipe on a flat surface. The flatter the better. Make sure the pipe does not roll. You can tape it to the surface or chock it in some manner. Now lay a flat piece of angle iron or a straight edge board making sure it is straight, next to it. I like to use a piece of aluminum angle. This has to be less than the thickness of the pipe. Now mark a line straight down the angle. If it is not long enough just move the angle down some and continue till you get to end. Hope you understand that.

Here is an example of a pen tube.

Look at the tube in the back ground laying against the piece of wood. I draw a line down the length of the wood onto the tube it is straight down the center. You basically do the same with a larger pipe and longer pipe and straight edge.

 

[lyonsacc]

Hold the pipe vertically up against a door frame/jam. Draw the line using a piece of the framing as the straight edge.

 

[Curly]

You said there is a curve to the tube. If it is a two dimensional curve (will not lay flat on a table) then I have no suggestions.

If the curve is in one plane (will lay flat on a table) and you can take it apart then do so and use a block of wood half the thickness of the tube to follow the tube, marking as you go with a Sharpie. If you want the screws below the front edges so they don't catch the back of your knees, use a thinner block. Should you not be able to take it apart turn it upside down and clamp a straight board across the tubes, moving and marking it as you move the board along.

A picture or two of the patio swing would help with better advice.

 

[jttheclockman]

You can do as I suggested and make 2 marks one on each end of the pipe and snap a chalk line between them. Now if you have a curve in the pipe. Need to lay the pipe flat and use a short piece of blocking and just follow the pipe from one end to next. I think we all are saying the same thing here. Straight edge against the pipe and keep the pipe from moving when marking. I think when you are saying curve you mean the radius of the pipe. Again I could be wrong. But you got the drift of what needs to be done.

 

[Curly]

John without more info curve to me, having occasionally had my butt in a swing, is a bent tube from the back of the seat sweeping around across the front and back again to the back of the seat. In fewer words the seat has round corners at the front. Some have a additional curve front to back along the ends to contour the seat into a more backside friendly shape. New pew style over the flat bottomed and straight backed of old. Not that I'm any kind of pew expert. :wink: That's why pictures would clarify what the problem looking for solutions is. Marking a straight tube is a snap but it gets tricky if the tube is bent into shapes. Should it be a straight tube then disregard my babbling. :biggrin:

 

[leehljp]

Hope this works ok.

I drew a quick center line maker, based somewhat on some above comments.

If the round bar is straight OR curved in one dimension, lay the bar flat on a level floor if you can.

NEXT, take a 1 inch square piece of none grainy wood such as poplar, maple or cherry (or other) and cut a half circle on one side as pictured below. Drill a hole the size of a pencil (with no slack).

If the rod/bar is laying flat on the floor, place the cutout onto the bar, make sure the pencil is in contact with the bar and trace it from one end to the other.

 

[Curly]

Hank your jig would be a little easier to make and work just as well by cutting a "V" instead of a round cutout.

 

[leehljp]

Hank your jig would be a little easier to make and work just as well by cutting a "V" instead of a round cutout.

"Duh" to me! It sure would! Thanks. My head is in the clouds today! Aging does that!

 

[magpens]

Don't think it's only you, Hank .... happens to all of us !!!

I am constantly reassessing my ideas and methods to avoid over complicating my approach.

 

[dogcatcher]

Is the piece of pipe straight or does it have bends in it? A picture would help.

 

[Curly]

"Duh" to me! It sure would! Thanks. My head is in the clouds today! Aging does that!

I think of aging like hanging beef. Makes us better. Just don't tell the cannibals. Let them think the young ones are tender. :tongue:

 

[pshrynk]

I often worry about cannibals here in Eastern Minnesota... :tongue: