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Set Screw for Pinions

Set Screw for Pinions

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Old 05-12-2009, 12:31 AM
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Default Set Screw for Pinions

Does anyone know the size of the of the set screw used for the Pinions?
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Old 05-12-2009, 02:28 AM
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Which brand of pinion?

All the non-US brands (RW, Kawada, Tamiya etc.) use an M3x3mm set screw. The US brands might use an imperial equivalent, I'm not sure.
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Old 05-12-2009, 04:12 AM
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Originally Posted by sosidge View Post
Which brand of pinion?

All the non-US brands (RW, Kawada, Tamiya etc.) use an M3x3mm set screw. The US brands might use an imperial equivalent, I'm not sure.
I do know you wont fit a traditional sized grub screw in one of the 48dp american pinions I have, the allen driver I use is smaller, and so is the grub screw within it.

Sorry to sound vague, but the grub screw is definately smaller, not good when you strip the said grub screw
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Old 05-12-2009, 04:44 AM
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Robinson racing 48pitch pinions that are steel use a 5-40 imperial grub screw
Robinson racing 48pitch older alum purple pinions use a 4-40 imperial grub screw
Robinson Racing 48pitch new dark grey alum pinions use a 3mm metric grub screw.
(so there are some u.s. pinions that use metric grub screws now)


Hobby works use a imperial grub screw in there pinions which i think is even smaller than the above ones (not sure what it is but it uses a .05" imperial hex driver. It could be 4-40 but im not 100% sure


RW, Kawada, atlas and most other brands all use a 3mm metric grub screw.

if you have a metric 3mm tap its easy to tap out an imperial alum pinion to accept a 3mm grub screw.

Last edited by LOSI123; 05-12-2009 at 04:32 PM.
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Old 05-12-2009, 09:40 AM
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bvoltz,

My PRS and ROBINSONs take either 4-40 or 5-40 (Older ones take 4-40, the newer ones take the 5-40)

The wrench size -

.050 = 4-40

1/16" = 5-40

from Tower Hobbies


4-40 set screws

http://www3.towerhobbies.com/cgi-bin...?&I=LXEX08&P=7

5-40 set screws

http://www3.towerhobbies.com/cgi-bin...?&I=LXEX09&P=7


and 4mm Set Screws

http://www3.towerhobbies.com/cgi-bin...?&I=LXURT6&P=7
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Old 05-12-2009, 10:32 AM
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Originally Posted by LOSI123 View Post
if you have a metric 3mm tap its easy to tap out an imperial alum pinion to accept a 3mm grub screw.
That would be at best a bodge to "get home".

1. If the pinion is hard steel is not easy to tap (if possible at all). You will most likely destroy both tap and pinion.

2. If the pinion is aluminium, you will be able to cut the thread but it won't hold for long (if at all). I have done it, it's a waste of time and it will let go at the worst time.

The problem is the M3 thread pitch is 0.5mm i.e. finer than both 5-40 and 4-40 imperials. It is also shallower (if that makes sense; I mean the depth of each thread is less than the imperial sizes; think about it: to cut a thread at M3 you need a hole at dimaeter 2.4mm. That leaves only 0.6mm for the thread on the diameter. The thread depth is half that, i.e. 0.3mm). This means what you will do is basically scratch the imperial thread to a M3 thread (pitch/depth) which is not sufficient.

On top of that, some materials give in after a while even when they start with a M3 thread from factory (some of the pinions I bought have stripped the thread after taking out and tightening the grub screw a number of times) so this thread is at best fragile (in normal aluminium). Overtighten it and you'll strip it straight away. Proper materials (good duraluminium, aircraft grade, etc) are good, but not too many manufacturers do use them. Steel holds very well if it starts with a M3 from factory but even then I wouldn't overtighten it. Hard steel is very good but then you might strip the grubscrew.

If you just want to finish a race, you can bodge a thread, but then use loctite if you want to get somewhere. If you're looking for replacements, Robinson black pinions 64 pitch are very good quality and really smooth finish so they last forever and don't chew the spur either. Kawada is the next best thing, their dural being a bit softer. The Kawada spurs however are on the par with the Robinson pinions.
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Old 05-12-2009, 04:29 PM
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Well i have tapped a couple of alum pinions with 3mm tap , I think it had a 4-40 thread before, I since have had no problems at all and i have taken them off and on heaps of times.

they where older hobby works pinions which the alum seemed soft, maybe this helped.
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Old 05-12-2009, 05:21 PM
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Many thanks, I pretty sure that they are 5-40 or 4-40 the reason, the 3mm do not work....

Thanks again....
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