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Filing flats on retract pins


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I've filed flats for undercarriage legs before, but never very accurately or neatly and usually just on piano wire legs. As I am installing Electron retracts with beefy pins I'm looking for pointers of the best method and steps involved to do a decent job please. The units have single set screws for the connecting pin on both sides of the trunion and dual set screws on both sides of the legs.

 

Any advice most welcome, TIA

 

Charles

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Thanks for the filing tip. As I'm setting some "toe in" what I'm also interested in is once I have set/adjusted the 4 flats on the leg side, how best to mark the spot to make the first flat through the set screw hole on the trunion side of the pin, once the leg has been offset slightly? I think once I have a decent flat on one side, giving the correct angle of offset, I can use calipers to make the opposing flat match it?

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+1 for the use of the Dremel. Personally, I wouldn’t bother with a flat on the second side. When you tighten the first set screw against the flat, you are trying to clamp the pin to the opposite side of the hole. Don’t then overtighten the second set screw or you can end up with the pin effectively ‘suspended’ on the points of the two set screws!

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I have lost count of the number of these I have done over the years. I find it one of the most tedious jobs to do on retracts, and this how I normally go about it:

Mark the leg or stub with a felt tip and push it into the retract unit, then firmly fit a grub screw which should leave two marks from the concave tip. Place the leg in a vice about 2mm from the centre of the mark and with a 4mm thick file cut a fairly deep groove. Re coat with ink and if you have got it right the grub screw should now trace a complete circular mark. Repeat for any other grub screws until with the first one tightened they all trace a circle on the ink.

I recommend at least two screws since a single one will crush the softer leg in no time and allow it to twist. Rather than Loctite it is better if you can use two short screws in each position so that one locks the other.

Best of British!

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