If you have a GM series yanmar with the kw tranny and your dipstick has the yellow plastic threads you might be interested in this. I have had the threads stripped to the point that the dipstick needed replacing. I'm pretty careful when threading being that the soft plastic is going up against an aluminum housing. After a little research, I found the problem to be fairly common.
To avoid plastic altogether I found an iron drain plug that would fit but I gave up on trying to drill a 1/16" breather hole in it. I finally found an aluminium plug made in Germany for Porches. See link: http://www.5150motorsport.com/oil-drain-plug-m18-x-1-5mm-900-219-020-31.html. It's around $8 with shipping. Fits perfectly and was easy to drill the breather hole. Came with aluminum gasket. Even if you don't need one now would be useful as as a spare. I kept the old stick for measuring.
To avoid plastic altogether I found an iron drain plug that would fit but I gave up on trying to drill a 1/16" breather hole in it. I finally found an aluminium plug made in Germany for Porches. See link: http://www.5150motorsport.com/oil-drain-plug-m18-x-1-5mm-900-219-020-31.html. It's around $8 with shipping. Fits perfectly and was easy to drill the breather hole. Came with aluminum gasket. Even if you don't need one now would be useful as as a spare. I kept the old stick for measuring.