Plastic Gas Cap Threads

[jim18655]

Unscrew before the putty fully hardens and that should cut the threads around the cap

 

[eric.grulke.79]

Rather than a cap could you just plug it with a bung?


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[kd4gij]

What make is it?

 

[Wreck™Wreck]

That's actually where I was foreseeing the problem -- in unscrewing the part from the mold. If the thread helix is interrupted as it winds around the neck I don't know that it could be unscrewed? Perhaps I'm looking at it wrong.

-frank

You will notice the dirty line along the part this is where the mold parts, the threads do not cross the parting line and appear to have a sort of Higbee start and end. I would not be at all surprised if this were a two start thread much like plastic beverage bottles.

 

[Groundhog]

Did the original have a vent? That will increase the difficulty of making one if so.

I recently needed to replace a cap for an old chain saw. Discovered that the local small engine repair shop keeps a bunch of salvaged caps, found one for a couple of bucks. That's what I'd try first!

 

[John Hasler]

same thread as a plastic gas can...

I've got half a dozen plastic gas cans. None of the caps are interchangeable.

 

[Billh50]

John Hasler,
I have the same problem. That's why I said earlier they are not all the same. Even some plastic bottles have slightly different threads so no other caps quite fit right. I know this from when I used to make blow molds for plastic bottles many years ago. Some have 2 or 3 starts. Some have interrupted threads on the bottle but not on the cap. slightly different minor or major diameters. They do some strange things for whatever reason.

 

[Ebel440]

I lost a cap for a chainsaw I had a while ago. I just went through my house and garbage trying every screw top I had until I found one that fit.

 

[chips&more]

To single point that kind of thread on a lathe in plastic is not easy, maybe not possible. I would mount a Dremel with appropriate cutter/burr in place of the single point cutter on the lathe and machine it that way. And turn the headstock spindle by hand. Would probably have to make several passes to get the correct thread form…Dave.

 

[TOOLMASTER]

EVEN IF YOU FIND A CAP THAT GRABS A COUPLE THREADS BEFORE IT CROSS THREADS, JUST REMOVE THE OFFENDING THREADS AND USE THE FIRST TWO