Maximum Length of Helicoil
#1
Melting Slicks
Thread Starter
Maximum Length of Helicoil
Not a Corvette question per se but I need to repair a stripped M14x1.5 bolt hole with a Heli-coil or similar thread insert. The length of the threaded part of the bolt is 40mm (a bit longer than 1.5"). Does anyone make a thread insert that is that long? Seems like most a less than 1"
#2
Tech Contributor
Member Since: Aug 1999
Location: At my Bar drinking and wrenching in Lafayette Colorado
Posts: 13,652
Received 4,917 Likes
on
1,929 Posts
HeliCoils come in lengths as a function of the diameter of the thread (D). In standard (inch) sizes, standard HeliCoil lengths are 1D, 1.5D, 2D, 2.5D and 3D. In metric, the standard sizes are 1D and 2D (your M14 is available in 2 lengths: 14 and 21 mm). If the parent material (the hole that the bolt is going into) is the same as the bolt, the bolt achieves full strength with a threaded grip length equal to the diameter of the bolt. Any threaded insert longer than the diameter of the bolt becomes overkill. 2X the diameter is considered the max needed for any application. Having a 40mm long thread for a 14 mm bolt is pointless, so no such insert is made.
Lars
Lars
Last edited by lars; 01-18-2019 at 01:52 AM.
The following users liked this post:
jim lockwood (01-18-2019)
#3
Team Owner
HeliCoils come in lengths as a function of the diameter of the thread (D). In standard (inch) sizes, standard HeliCoil leghts are 1D, 1.5D, 2D, 2.5D and 3D. In metric, the standard sizes are 1D and 2D (your M14 is available in 2 lengths: 14 and 21 mm). If the parent material (the hole that the bolt is going into) is the same as the bolt, the bolt achieves full strength with a threaded grip length equal to the diameter of the bolt. Any threaded insert longer than the diameter of the bolt becomes overkill. 2X the diameter is considered the max needed for any application. Having a 40mm long thread for a 14 mm bolt is pointless, so no such insert is made.
Lars
Lars
#4
Melting Slicks
Thread Starter
HeliCoils come in lengths as a function of the diameter of the thread (D). In standard (inch) sizes, standard HeliCoil leghts are 1D, 1.5D, 2D, 2.5D and 3D. In metric, the standard sizes are 1D and 2D (your M14 is available in 2 lengths: 14 and 21 mm). If the parent material (the hole that the bolt is going into) is the same as the bolt, the bolt achieves full strength with a threaded grip length equal to the diameter of the bolt. Any threaded insert longer than the diameter of the bolt becomes overkill. 2X the diameter is considered the max needed for any application. Having a 40mm long thread for a 14 mm bolt is pointless, so no such insert is made.
Lars
Lars
This application would be for a brake caliper bolt. The original called for 104 ft/lb of torque. I can get a 28mm Time-Sert. If I used this, can I still torque to the recommended value safely?
Also, the caliper bolts are AL and the steering knuckle is AL. THe Time-Sert insert is presumably steel. Will I have galling issues with this? If so, should I use anti-sieze or is that a bad idea on something like a caliper bolt? Am I better off with blue Loctite?
#5
Safety Car
In aluminum blocks, and other applications, 1 or 2d just won't cut it. They make extended length Helicoils for many threads in your case 14x1.5x42. The question is how bad do you want them. I only see them available in packages of 50. I have used extended length Helicoils in many repairs. LS and Cadillac 4100 head bolts are 2 such cases. If you used a standard Helicoil to repair those i seriously doubt they would hold torque specs. They do come with extra length inserts but they are a different size. In some cases I have put 2 in the hole for extra length but make sure if you can't use a full length in the second Helicoil you screw in shorten the first before you install it. The Helicoil doesn't have to be one continuous piece.
https://www.globalindustrial.com/p/s...-of-50-inserts
https://www.globalindustrial.com/p/s...-of-50-inserts
Last edited by Robert61; 01-18-2019 at 12:07 AM.
#6
Tech Contributor
Member Since: Aug 1999
Location: At my Bar drinking and wrenching in Lafayette Colorado
Posts: 13,652
Received 4,917 Likes
on
1,929 Posts
I can get a 28mm Time-Sert. If I used this, can I still torque to the recommended value safely? Also, the caliper bolts are AL and the steering knuckle is AL. THe Time-Sert insert is presumably steel. Will I have galling issues with this? If so, should I use anti-sieze or is that a bad idea on something like a caliper bolt? Am I better off with blue Loctite?
Lars
Last edited by lars; 01-18-2019 at 01:59 AM.
#7
Melting Slicks
Thread Starter
HeliCoils come in lengths as a function of the diameter of the thread (D). In standard (inch) sizes, standard HeliCoil lengths are 1D, 1.5D, 2D, 2.5D and 3D. In metric, the standard sizes are 1D and 2D (your M14 is available in 2 lengths: 14 and 21 mm). If the parent material (the hole that the bolt is going into) is the same as the bolt, the bolt achieves full strength with a threaded grip length equal to the diameter of the bolt. Any threaded insert longer than the diameter of the bolt becomes overkill. 2X the diameter is considered the max needed for any application. Having a 40mm long thread for a 14 mm bolt is pointless, so no such insert is made.
Lars
Lars
In aluminum blocks, and other applications, 1 or 2d just won't cut it. They make extended length Helicoils for many threads in your case 14x1.5x42. The question is how bad do you want them. I only see them available in packages of 50. I have used extended length Helicoils in many repairs. LS and Cadillac 4100 head bolts are 2 such cases. If you used a standard Helicoil to repair those i seriously doubt they would hold torque specs. They do come with extra length inserts but they are a different size. In some cases I have put 2 in the hole for extra length but make sure if you can't use a full length in the second Helicoil you screw in shorten the first before you install it. The Helicoil doesn't have to be one continuous piece.
https://www.globalindustrial.com/p/s...-of-50-inserts
https://www.globalindustrial.com/p/s...-of-50-inserts
#8
Safety Car
The Time Sert or Helicoil will handle the torque. However your failure is not the result of the thread repair. Aluminum doesn't have the same strength obviously as steel. Your threads failed because the parent material let go. Im sure the engineers that designed the brackets calculated the proper torque. Since yours failed and I have no idea if they failed because the aluminum sheared or if you had some type of thread damage, i.e cross threaded or a few threads messed up. I wouldn't go back to 104 lbs. it's your car and you do as you decide. I would probably stop at 85 flbs. this is only my opinion you make your on decision here. I just finished rebuilding my LS1 and the torquing procedure is crazy for them. It calls for an initial 22 flbs followed by two additional steps of 90*. I don't go the full 90* on the second step because it gets very tight and I'm not stripping out my block. I hate torque to angle bolts. I posted a pic of head studs and a standard Helicoil. They are both for a small block Chevy, one for iron blocks the other for aluminum. You can see they extended the length of the threads double for the aluminum. If you were to install either the standard stud or Helicoil in an aluminum block the threads would fail they might reach torque a time or two but they would fail. I worked in aircraft maintenance for 18 years both Helicoil and Time serts are approved for thread repair. In aircraft maintenance you don't just say oh I'll fix it this way, you have to follow manufacturers instructions. When you strip a thread in aircraft it almost always has a Helicoil in it already. The normal procedure is to use what is called a Twinsert. This is a Helicoil that you install in the repaired original hole and then install the original size Helicoil back in it. This allows you to use the original size fastener, they are very picky about using the correct fasteners. You are allowed in some cases to go to a second or third size fastener.