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General control line discussion => Open Forum => Topic started by: Randy Cuberly on February 27, 2018, 01:21:21 PM

Title: Metric tap!
Post by: Randy Cuberly on February 27, 2018, 01:21:21 PM

Hey guys. anyone know precisely what the thread is on one of the OS muffler pressure hole fittings.  The thread appears to be 3 mm and the standard 3mm thread is 3 x .5 mm but it seems to be a finer thread than that.

My reference books on that material are currently on loan to someone who is unavailable so any help would be appreciated.  At any rate I need a tap and the standard thread tap seems to be finer than the pressure fitting.  I have several of these things and would like to use them on tongue mufflers but need to make the dam hole!

Tucson seems to be a desert in more ways than one.  It would seem that most of the small tool suppliers have dried up and left!

Please help!

Randy Cuberly

Title: Re: Metric tap!
Post by: Tim Wescott on February 27, 2018, 09:04:57 PM

Looks like M3.5 standard thread (0.5mm pitch)

Edid:  Yup.  3.5 -- it fits in an OS carburetor mounting screw hole, which the instructions say is 3.5.

Title: Re: Metric tap!
Post by: Roy DeCamara on February 27, 2018, 10:55:45 PM

Hey Randy----------------if you cannot locate one in Tucson,  Micro Fasteners lists a M3.5x.6mm tap, P/N TAPM35 @ $5.80 + $4.00 S&H.  Order at microfasteners.com  On second thought,  Jim Lee might have them at the VSC.....................

Title: Re: Metric tap!
Post by: Mike Haverly on February 28, 2018, 09:32:53 AM

McMaster-Carr has them also.  https://www.mcmaster.com/#taps/=1brngya

Title: Re: Metric tap!
Post by: Randy Cuberly on February 28, 2018, 07:18:36 PM

Thank You to everyone who offered assistance in the matter with the Tap!  Turns out it was in fact a 3 x .5 mm thread and I actually found one among my assorted taps left over from my serious motorcycling days (long ago).

The mysteries one uncovers when scrabbling back among mementos from 40 years ago is mind numbing!..Several tool boxes full of mind numbing memories and Triumph and Yamaha parts!

The good news is I've solved the problem!

Thanks again.  Hope to see a lot of you soon at VSC!

Randy Cuberly
PS:  More Good News is that I seem to have the new Colossus working fairly well.  It's going to be a good airplane!
       Biggest problem of course is my 77 year old body and lack of flying for the past couple of years!  Not much to
       do about that I suppose but try to have fun!

Title: Re: Metric tap!
Post by: Dave Harmon on February 28, 2018, 07:56:20 PM

Quote from: Randy Cuberly on February 28, 2018, 07:18:36 PM

       Biggest problem of course is my 77 year old body and lack of flying for the past couple of years!  Not much to
       do about that I suppose but try to have fun!

Hey Randy....I can certainly relate to that!!