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Engine basics => Engine set up tips => Topic started by: RknRusty on December 05, 2015, 12:54:44 PM
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One of the head bolts in my fp40 is stripped. I want to ask before I assume the right thing to do. I'm thinking either bore and tap it for a 3.5mm bolt, or install a helicoil for the original 3mm bolt. The latter would be my preference. I don't know anything about thread pitch so I want to make sure I can get a bolt back in after fixing the hole. Any suggestions would be appreciated. Thanks.
Rusty
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Hi Rusty, I'm assuming it's an allen head bolt that stripped? If so aren't small size easy outs available. Maybe a little heat, a little break oil and the easy out would be a viable way to go.
Rich
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i assume u mean the case is stripped ,i would tap it out to the next bigger size bolt. not a fan of helicoils
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I'm going to tap it for a 4-40 since I don't have a metric tap. Thanks for the replies.
Rusty
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I'm going to tap it for a 4-40 since I don't have a metric tap.
Ewwww.
I'm not sure that there will be enough meat in the hole for a 4-40 tap to do much good -- you may just end up ruining the case completely.
'course, they're still available on eBay for not too much, so it may not be that bad of a deal.
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I think there's enough, but I can look at it and tell before I foul it up.
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You will need tap for a 5-40 or a 3.5mm a 4-40 will not work
Randy
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DO WHAT RANDY SAYS!!!!!!!!!!!!!!!!!!!!!!!!!
not enough meat there for a 4-40 tap to bite into.
ask me how I know,,,,,,,,,,,,,,,,,,,
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Rusty, pm me your address
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Dane, PM sent.
Randy, I know enough around here to pay attention to you on engines. I'll talk with my local engine man more about this before I proceed with the job. Thanks for your input.
I wish I had a 5-40 tap, I have plenty of black oxide hex bolts. I use them for deep reach prop bolts on my Cox engines.
Rusty
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Rusty - I'm pretty sure I have a 5-40 tap if you need one.
For what it's worth, I have done quite a few heads with 4-40 helicoils and never had a problem.
Bob Z.
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Rusty - I'm pretty sure I have a 5-40 tap if you need one.
For what it's worth, I have done quite a few heads with 4-40 helicoils and never had a problem.
Bob Z.
Okay, thanks Bob. If you'll bring it next time we fly, I'll put this plane aside and finish the job at the field. What do I need for a drill bit, 3/32, 7/64, in that neighborhood?
Rusty
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Okay, thanks Bob. If you'll bring it next time we fly, I'll put this plane aside and finish the job at the field. What do I need for a drill bit, 3/32, 7/64, in that neighborhood?
Rusty
My helicoil chart shows a #31 or a 3mm drill bit for the hole size.
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My helicoil chart shows a #31 or a 3mm drill bit for the hole size.
Bill, I just re-checked and that's about right. It was too late last night to be trying to think, when I posted my drill size guess. I was looking at the wrong row on the chart.
Thanks for the reply, I think I've got it from here.
To prevent my saying anything else dumb, I'm closing the thread.
Rusty