Question about helicoils
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Postmaster
Joined: Oct 2005
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From: Clarksburg WV
Question about helicoils
I've never used helicoils before, but a recent problem has gotten me to think about using them, but I'm wondering if they will work.
Here's the story-
I had a flange with four studs in it that were 3/8"-16. I tapped it out for M10-1.5 studs, then went to put it together and it wouldn't fit because the holes it was going into were too small, and I can't get a drill in there to drill out the new holes.
So, I ran the tap back through for 3/8"-16, and they will thread back in but they fit kinda loose.
I would have to drill this hole out to fit a helicoil, right? I'm not sure if I wanna do that or not, I always seem to chew up drill bits when I try to step up a size on a hole that's already there. I'm probably just gonna weld the studs around the top anyway.
Here's the story-
I had a flange with four studs in it that were 3/8"-16. I tapped it out for M10-1.5 studs, then went to put it together and it wouldn't fit because the holes it was going into were too small, and I can't get a drill in there to drill out the new holes.
So, I ran the tap back through for 3/8"-16, and they will thread back in but they fit kinda loose.
I would have to drill this hole out to fit a helicoil, right? I'm not sure if I wanna do that or not, I always seem to chew up drill bits when I try to step up a size on a hole that's already there. I'm probably just gonna weld the studs around the top anyway.
Logistics Pro
Joined: Aug 2005
Posts: 3,884
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From: Morgan Hill, CA
To drill it out for a 3/8-16, you'd need an "X" drill that measures 0.397", an STI tap for the oversize coil, the coil, and an install tool. If you are cool with welding it, it's probably easier and cheaper to do so.
Cargo Master
Joined: Apr 2001
Posts: 2,220
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A trick I found out about at the Shop Floor Talk forums is to use a piece of rag soaked in lubricant when drilling a hole oversize. Cut a piece about the size of a shotgun bore patch, and put it under the drill bit. Works for me.
Elder User
Joined: Nov 2003
Posts: 963
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From: wichita kansas
If you can get a drill in there to drill out for a helicoil then why can't you get a drill in there for the metric? Helicoil are OK unless you need to take the bolt in and out very often especially with a impact. I'd want to try the metric first and leave the helicoil for a plan B.
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Postmaster
Joined: Oct 2005
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From: Clarksburg WV
I can't drill the OTHER side of the flange that the studs are going through.
Besides the fact that I'd need a right angle drill or adapter to get at it where it is, it's old cast iron and I just know it'd chew up whatever drill bit I put in there. I haven't had much luck in the past drilling out old cast iron.
I'm working on some creative solutions right now with the 3/8" studs. No biggie, I'll get it figured out.
Besides the fact that I'd need a right angle drill or adapter to get at it where it is, it's old cast iron and I just know it'd chew up whatever drill bit I put in there. I haven't had much luck in the past drilling out old cast iron.
I'm working on some creative solutions right now with the 3/8" studs. No biggie, I'll get it figured out.
pedant
Joined: Jan 2008
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From: EXTREME southwest CT
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Elder User
Joined: Feb 2004
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From: Ocean Park WA
We use Helicoils all the time for major repairs in power plants and really it's the best wat to go and the basic kit for say a 3/8 is less than $25.00 at any autoparts store and gives you the tap, insertion tool and all. If it's a one time deal do that. if it's going to come back apart multiple times buy the better kit and get extra inserts. we replace maybe 2 a turbine every 4 years and we do inspections every 12 months. I've also used them to repair heads and blocks with no problems. Aluminum blocks and heads use them at all high stress areas and they use them all over in the aircraft industry for new components. My $0.02.
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Postmaster
Joined: Oct 2005
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From: Clarksburg WV
Well right now I'm planning to use a slightly longer stud, with a jam nut on one end, and put a couple tack welds on to hold it, should be fine. Only really doing that because I'm not sure if regular bolt head will fit down in properly since I would have to thread it all the way through and there's some stuff in the way.
It's not a big deal, it would end up with tack welds on it anyway because I want to make sure the studs don't back out, and if I weld a jam nut on top that'll make doubly sure it doesn't back out.
It's not a big deal, it would end up with tack welds on it anyway because I want to make sure the studs don't back out, and if I weld a jam nut on top that'll make doubly sure it doesn't back out.
Postmaster
Joined: Apr 2004
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From: Bossier City, LA
To each his own on thread repair, do what ever is successful for you. Helicoils are just as good if not better if installed properly. Every Lycoming and Continental aircraft engine come from the factory with them in every hole, including the pipe threads.
Posting Guru
Joined: Nov 2004
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From: sunny fla sometimes windy
Helicoils will make a thread stronger than it was brand new if properly installed!!
Just be sure to drill it straight and dont wallow it out, clean the hole with alcohol
use plenty of the red locktite to hold the insert in place, and always always ALWAYS
use silver antisieze on the bolt!! It will be in there forever if you follow these and the
manufacturers instructions.
Just be sure to drill it straight and dont wallow it out, clean the hole with alcohol
use plenty of the red locktite to hold the insert in place, and always always ALWAYS
use silver antisieze on the bolt!! It will be in there forever if you follow these and the
manufacturers instructions.
Cargo Master
Joined: Apr 2001
Posts: 2,220
Likes: 26
"Where possible - I would use a keysert NOT a helicoil."
Pratt and GE aircraft engines frequently use keyed inserts. They are common in military aircraft airframes too. Helicoils are fine repairs for infrequently swapped hardware, but for items that require frequent removal over a very long lifetime the keyed inserts reign supreme. Helicoils are less expensive though.
Pratt and GE aircraft engines frequently use keyed inserts. They are common in military aircraft airframes too. Helicoils are fine repairs for infrequently swapped hardware, but for items that require frequent removal over a very long lifetime the keyed inserts reign supreme. Helicoils are less expensive though.
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