Glow Engines Discuss RC glow engines

Heli-coil

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Old 02-14-2012, 06:34 PM
  #1
telejojo
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Default Heli-coil

I bought a used Saito 1.20 on flea bay and the guy forgot to tell me the glow plug was stripped out,what size is the glow plug and where's a good place to get a heli-coil?
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Old 02-14-2012, 07:22 PM
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Default RE: Heli-coil

The glow plug is 1/4-32. For what you spend to by all the tools for one heli coil installation you would be better off to send it to Clarance Lee for repair. The kit will be north of $60 or more.

Just googled this from Amazon..... I was a bit shy of the price. Looks like it will do several repairs, but the coils are the cheap part.

[link]http://www.amazon.com/HEL-5425-Heli-Coil-Airplane-Motor-Repair/dp/B00408H90M[/link]
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Old 02-14-2012, 07:51 PM
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Default RE: Heli-coil

Yes they make 1/4-32 heli-coil kits for fixing stripped out glow plug holes. But one big caveat, is that some four stroke engines have the valves really close to the glow plug hole. You may or may not have room to drill it out and insert a heli-coil or not. So you want to check that carefully before you drill the hole and tap it.
I think what Clarence and others do in that case, is they machine and thread a bronze insert and the blind drill the hole down short of going all the way through. You can look at a 4 stroke glow plug and see the machined smaller unthreaded tip on them. They then use a bottoming tap and thread the partially drilled hole, and then insert the bronze insert and use permanent threadlocker on it. They let that set up overnight then drill the inside hole all the way through to fit the glow plug tips. Then they drill part way through and using a bottoming tap thread it for 1/4-32 glow plugs. Anyway, that is about the only way I can see someone doing it, if the vales are too close together.

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Old 02-14-2012, 08:34 PM
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Default RE: Heli-coil

Clarence Lee advertises in the back of Model Aviation Magazine.

C.F. Lee Manufacturing Co.
10112 Woodward Ave.
Sunland, Ca, 91040-3342
818-352-3766
leecustom@msn.com

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Old 02-14-2012, 08:53 PM
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Default RE: Heli-coil

I don't know about the 120, because I have not done one. But the other saitos I have done are drilled thru and tapped thru for the helicoil insert. But earl is correct some 4 strokes do have the valves to close to go all the way thru W/O hitting them so a method very much like he pointed out is what is used.
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Old 02-15-2012, 03:23 AM
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Default RE: Heli-coil

Thanks..................................
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Old 02-15-2012, 05:00 PM
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Default RE: Heli-coil


Quote:
ORIGINAL: w8ye

Clarence Lee advertises in the back of Model Aviation Magazine.

C.F. Lee Manufacturing Co.
10112 Woodward Ave.
Sunland, Ca, 91040-3342
818-352-3766
leecustom@msn.com

Ditto.............Clarence just blueprinted a couple engines for me and fixed a head bolt that was factory stripped...........4-40 is way smaller than i thought possible to fix. and gee, he charged me a whopping 5 bucks...............
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Old 02-15-2012, 05:21 PM
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Default RE: Heli-coil

Mr Lee is still working for wages that was present back in the 60's *L*
Just kidding , he does a very fine job and does not charge anything for his work not to many left that are like that now days.
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Old 02-15-2012, 07:13 PM
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Default RE: Heli-coil

Clarence Lee is the best in the business.
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Old 02-16-2012, 11:21 AM
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Default RE: Heli-coil

I have done a few Saito engines(and other 4 stokes) with stripped glow plug holes, you must be very careful not to damage the valve seats when drilling and tapping for a repair coil. If you are not confident you can do it without problems I would send it to someone, as others have mentioned.

For example, I repared a pair of stripped Saito 82s for a guy, I had to change the angle of the glow plugs slightly when I prepped them for the coil repair to avoid getting into the valve seats. I did the work on a small milling machine, which was considerably more accurate than a drill press. I have also put an insert into a blind hole so I didn't have to drill all the way through into the combustion chamber. This also involved a mill, with and an end cutting end mill.


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