I'm in the process of reinstalling a transmission in a 92 NSX after swapping in shorter gears and FD.
Last night I tried to torque the bolt that attaches the upper A arm to the rear subframe and the threads pulled out!
The rear subframe is aluminum, the bolt is M10x1.25 and the torque value is 43 ft lbs.
What is the best way to make this repair?
1. Helicoil
2. Timesert
3. Keensert
4. Replace the entire subframe
Pic of subframe-missing bolt is the one sans threads:
It is going into a casting, which is good, but there does not seem to be much metal around it. A Helicoil would remove the least amount of parent metal and will still be plenty strong.
Would a thread chaser fix the threads?
If no, helicoil it for a has to be done today repair.
Helicoil is the answer there. Make sure you get the correct drill bit. I always buy a good bit, and keep it with the kit.
Like the others have said - Helicoil. Plus . . .
If you have to remove the part consider doing the others while it is out.
In reply to Streetwiseguy :
You can buy thread repair insert sets that will even come with the correct drill bit.
Two people to eye the drill when you go in to make sure it's as straight as possible. Actually learned that years ago while.gping thru JLR training and it works well.
The nice thing about a helicoil drill is that you already have a straight hole, so unless you're really leaning hard on the drill, it'll be hard to screw it up (get it!? Hah!).
I'm a fan of Time-Sert over Helicoil for more critical thread repairs.
enginenerd said:I'm a fan of Time-Sert over Helicoil for more critical thread repairs.
Time-Serts are nicer, but often more difficult to get if you need to get to work the next day :)
RonnieFnD said:Two people to eye the drill when you go in to make sure it's as straight as possible. Actually learned that years ago while.gping thru JLR training and it works well.
I don't know if you have enough room, but my trick for drilling a straight hole against a flat surface when you have to do it by hand is to first take a piece of square tubing and drill through it with the exact same size drill bit you'll be using but on a drill press. Then attach that piece of tube against your surface by whatever means you can come up with and start drilling. The 2 holes in the square tube will guide you straight.
So, I just bought a helicoil kit for m10*1.25 and of course you can only buy like 10 inserts or whatever but since I only needed one - I've got a lot left.
Let me know if you need one haha.
In reply to A 401 CJ :
That is a very timely tip. My son's car has two exhaust manifold studs broken off flush.
Not for a head stud but how much more depth of material do you have. Can you just go deeper and use a longer screw. Heh, Heh...shut up Bevis!
Longer bolt after cleaning the threads out?
Helicoil is a good answer if you can get to it with the drill.
If possible, if nothing else - drill all the way thru and use a long bolt with a nut on it.
Helicoiling a dead end hole like this is probably one of the easiest drill jobs in the world, it is just opening up an existing hole by less than 1mm. Even if you did manage to make it go in less than straight, the difference will be so minor that you would never notice it.
If there is not room underneath for a straight shot, a right angle drill or right angle adaptor will work just fine. One can also cut the base of a drill bit down to make it shorter.
In reply to Robbie (Forum Supporter) :
Haha, if you bring 2-3 spare helicoil inserts to the challenge i'll trade you 3 of the mini-maglite repair kits I have.
I had to repair 1 flashlight and had to buy 12 kits?
You all are absolute princes-many thanks for all the suggestions.
One more question. If the depth of the stripped hole is 28mm, what length of insert should I get?
From this chart it looks like both 20mm and 25mm are option:
CrustyRedXpress said:You all are absolute princes-many thanks for all the suggestions.
One more question. If the depth of the stripped hole is 28mm, what length of insert should I get?
From this chart it looks like both 20mm and 25mm are option:
I bet it doesn't matter. The bolt wouldn't be designed to bottom in the hole, so you're not using all 28mm of thread. You're probably only using about 20mm of thread.
Robbie (Forum Supporter) said:CrustyRedXpress said:You all are absolute princes-many thanks for all the suggestions.
One more question. If the depth of the stripped hole is 28mm, what length of insert should I get?
From this chart it looks like both 20mm and 25mm are option:
I bet it doesn't matter. The bolt wouldn't be designed to bottom in the hole, so you're not using all 28mm of thread. You're probably only using about 20mm of thread.
Agreed, and since you only really need three threads of engagement for max strength, at one thread every 1.25mm, a 20mm would give you 16 threads of engagement. Go with that one, less tapping to do :)
I would only use the super long ones for head bolts or the like.
I have had to helicoil all twelve head bolt holes in a Subaru EJ255 engine after someone used SOHC head bolts in it, which are shorter, and ripped all the threads out of the block. oops.
Also all of the main cap bolt holes in a Northstar after someone reefed them with a 1/2" impact and sent it. Not it, that time.
Do the threads start at the face of the subframe, or does the bolt have a shank that extends into the subframe to act as a locator? It would suck to put threads where there should be no threads.
Pete. (l33t FS) said:Do the threads start at the face of the subframe, or does the bolt have a shank that extends into the subframe to act as a locator? It would suck to put threads where there should be no threads.
Bolt has a small shank that wouldn't extend past the flange that the A arm is attached to in the first picture. I haven't taken the assembly off yet, but I'm pretty sure the threads would start on the face.
New question! Helicoil has a chart that explains what length of insert to use, but it depends on knowing the sheer strength of the parent material and the tensile strength of the bolt. It looks like the sheer strength of cast aluminum is about 180MPa, but I'm having trouble finding the tensile strength of the bolt based on the marking on the head.
Here is a pic, does anybody know what this symbol (10? 01?) indicates on a metric bolt head that is from a early 90's Honda product?
Keen Serts and Helicoils appear very similar, I always understood a Time Sert to be stronger. Find articles like this before committing.
Plan B? Weld the hole up and punch in new hole & threads, remove the subframe first for accuracy. (cheaper than buying a subframe).
You won't really see any benefit in strength beyond 1.5 time the diameter of the fastener. Combine that with the limits of tapping a blind hole and I would use a 15mm or 20mm long insert.
When I did the recent repair on the exhaust manifold in my jeep, I wasn't able to get at it with a drill so I used just a chuck and turned it by hand. I used a couple bits to go from the original hole to the new one without having to take too much material at one time.
914Driver said:Keen Serts and Helicoils appear very similar, I always understood a Time Sert to be stronger. Find articles like this before committing.
Plan B? Weld the hole up and punch in new hole & threads, remove the subframe first for accuracy. (cheaper than buying a subframe).
You are way overthinking it. Welding it would be traumatic to the aluminum and make it weaker. A Helicoil is actually stronger than what Honda put there.
Helicoil it and done.
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