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Older OS engine head and backplate screw sizes

Old 08-23-2018, 11:30 PM
iskandar taib
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Default Older OS engine head and backplate screw sizes

I seem to recall seeing information about OS's head and backplate screw sizes on the web in the distant past, but three hours of fruitless searching (and scrolling through this forum) did not bring up any information. I'm mainly interested in changing the cross-head (Phillips) head screws with socket screws, since the ones OS supply are rather soft and easily damaged - apparently they require JIS B 1012 standard drivers for assembly and disassembly - the use of American Phillips screwdrivers is the usual cause of the damage. I'll list the engines I'm interested in below - I seem to recall some rather weird sizes (M2.2 or M2.3 or M2.6), which might actually be hard to come by. On another note - the .15FP used 5/16x28 UNF for the prop nut, I remember going crazy trying to find one from OS parts (finally found some from Thunder Tiger), and then I find they're readily available from the likes of in bags of 100!

The engines I am interested in "fixing" are:
OS .10LA
OS .15FP
OS .15LA
OS Max III .15 (old iron piston engine)
OS .25FP (don't remember - this might already have socket head screws)
OS .35FP

Also looking to obtaining a set of JIS drivers. I'm wondering if those nifty anodized screwdriver sets RC King et al. sell might be JIS B 1012 compliant, since they're made to disassemble Japanese-made model helis and cars. Some of the engines are old and I'll probably need to heat them up before attempting to remove the screws.


Last edited by iskandar taib; 08-23-2018 at 11:32 PM.

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