How can I lay out/ mark up this shape?

[Scott Winners]

What I have is a milspec 5 gallon fuel tank. I actually have four of them.

The problem is one of these lids is so tight I need a wrench to open the lid. It is a 10 ponted star shape, with rounded points. I have made a positive pattern in brown paper, a positive pattern in paste board, started a negative pattern in paste board and I am wasting my time.

Have one of you all a CNC pattern already you could cut out of half inch plywood and drop in the mail to me for some dollars?

What is the smart way to get this shape onto a scrap of plywood so I can leave the line when running my jigsaw?

What is an efficient way for me to make a pattern of this fool thing so I could upload a data file here that others could download, print, mark up a plywood scrap and leave the line when they get out their jigsaw?

Thanks


20210604_233127[1].jpg

[Mike Kreinhop]

I wouldn't bother trying to make a cap wrench unless you are interested in the process. Instead, I would buy a wrench made for these cans:

https://www.amazon.com/Miltary-Wrenc.../dp/B074V7DC7L

[Lisa Starr]

I just use a strap wrench if one of ours is too tight.

[Bill Dufour]

Or switch to a NATO can. gas cap technology has improved in 90 years.
Bill D

[Doug Garson]

Cover the cap with painters tape, cut the outline with a sharp knife, peal off the tape and stick it on your plywood, cut along the outline of the tape. Done.

[Scott Winners]

First thanks to Mike Kreinhop for linking me to the correct ready made wrench. If I had found that product online last night I would have just ordered one.

Now that I have come this far I think I want to see it through. There is always going to be stuff on backorder and I would much rather figure this out than play tetris.

Next time I have a new problem like this I want to come at it with the additional skills I am about to learn.

I do think a strap wrench would work. I used to have one, but it ended up so oily I gave it to a mechanic friend and haven't needed to replace it yet.

I am going to try making a blue tape pattern here in a little bit, with some reservations because of the curved top to the cap. And I will call the guy with the CNC router who PM'd me today also.

Thanks for your input so far.

[Jim Becker]

Since you have a trace of the caps, transfer that shape to a piece of plywood, dril some round holes in the places that make sense to follow the shape and cut out the remainder with a jigsaw or fret saw. It should be "not tight" when you put it over the cap and be sure to ease the edges with abrasives. You can have the handle as long as you want for leverage. Think of it as a plywood, for-purpose wrench.

[Bill Dufour]

scanner/printer

[Scott Winners]

Since I have 4 identical cans, I was able to remove the lid from one of the empties. From there I marked up and cut out a working tool in half inch plywood and will be sending the removed lid out to a CNC guy in the next couple days.

Thanks for your inputs.

[Keith Outten]

Scott,

IMG_1509.jpg IMG_1510.jpg IMG_1511.jpg IMG_1512.jpg

I traced the wrench outline and then used my CalComp board to convert the tracing to a digital file for machining.
Because of the strap that connects the cap to the gasket I had to notch the wrench and add a cap to the wrench to prevent the wrench from breaking. Many of the point areas have been damaged, rounded over but it didn't affect the fit since the pressure area is on the long radius area. The two small indents were sanded to fit the small edge protrusions every 120 degrees, the third one is in the cutout area. Made from scrap Corian countertop.

The pictures are self explaining from there.

Enjoy!

[Bill Dufour]

The older style had ears sticking out to hit with hammer. I believe they are 2" NPT.
Bill D

[Scott Winners]

Keith, that looks great! Thanks. Attached is the best I came up with using blue tape / razor knife/ drill/ jigsaw. It is serviceable, but not sure how long the one I made will last.

[Keith Outten]

I considered using 3/4" PVC but decided against it because it is a bit soft and over time the wrench would have a sloppy fit. The Corian is harder than the plastic can lids so it will keep the tolerance and fit for as long as you use the wrench. Secondly I have plenty of Corian scraps in my shop and a couple of out buildings since I don't throw it away. When pieces get very small they become pen blanks.

Converting the trace to a digital file was the most interesting part of the project. Most of the radius's are worn and far from perfect so I picked a set that was in the best condition for the trace. Once I had the digital trace in my software I did a little editing and created an array around a circle of major diameter to create the final vector. I was a little tight on the machining so a little spindle sanding was necessary to adjust the fit.

I rarely get the chance to make any custom tools, lots of jigs and fixtures but not many tools and I enjoy the work.

[Edwin Santos]

If what you were looking at was basically a hex nut, you could imagine cutting up a piece of plywood in the shape of a large hex wrench. Where I grew up we called it a spanner.


So what you really have is a decagon with concave sides, but the "dec" wrench idea should still work. You might start with striking two parallel lines the correct width apart, lay the cap over it to trace the convex shape onto your wrench jaws and freehand draw the rest of the "wrench". You could glue coarse sandpaper to the convex jaws of your wrench for more grip. Make it with a long handle and you would have lots of torque.

What you have made already is the equivalent of a socket wrench, but since side clearance is not a problem I can't see why the correctly sized open ended wrench would not work. Just another approach. Hope it makes sense. This would be 10-15 minutes at the bandsaw.