Stripped Threads??

[Lazzman]

While wrenching a bolt into an iron manifold I stripped the inner threads and the bolt does not go in easy anymore or flush.

Is there anyway to fix this? I onces stripped the threads on the sway bar bushing clamp and the dealer used a bigger bolt to solve the problem. Don't know if it was a lot of work to do this but they certainly charged me a lot of money.

Any tips?

 

[shamaal]

If you have a Haynes, there is a discussion in the maintanance techniques, tool and working facilities - How to repair damaged threads.

If the bolt does not go in easily, it's probably not stripped -just cross threaded. You may be able to get a tap, (use cutting oil), chase the threads and use a new bolt. Autozone, and probably others, loan tap and dies sets. Inspect the kit before leaving the store, they're not well kept up. There is a difference between metric and SAE.
If it's truly stripped, I use heli-coils. These come in kits that contain a bit, tap, insertion tool and five coils. You drill the hole larger, tap the hole, insert the heli-coil and use the same size bolt. They are pricey, but you get everything. There is a knock-off kit at Autozone, that works as well as heli-coil and, in my opinion contains a better insertion tool.
Alternately, you can drill the hole larger, tap and insert a bigger bolt. I've always used heli-coils because I like using the same bolt. Respond with the part (exhaust manifold, intake?) and the bolt size and I'm sure someone can recommend the next larger size to use. Also let us know if you have used a tap before and someone can provide directios. They are simple, but there is technique.

 

[marragtop]

In addition to what shamaal said, make sure that your problem isn't with the threads on the bolt. It's a lot easier to buy a new bolt than chasing new threads or going with a heli coil. If you need to go heli coil, you may have a problem getting a straight shot on it with a drill motor.

 

[Lazzman]

Thanks for the informative replies.

I have never used a drill and tap. Don't know if it is the bolt or threaded bolt hole that has the problem. I just forced the bolt in as hard as I could when it would not go anymore, I know I shouldn't have but was loosing my patients with this project.

Its a straight on hole so I think I could use the drill and tap set. What is the autozone one called?

 

[BrooklynBay]

AutoZone sells them in a black carded package by a company called OEM.

 

[spindlecone]

Just don't break the tap off in the hole Lazz, than you have a real nasty problem

 

[BrooklynBay]

Walton makes a tap extractor set in the event of a tap breaking off. Here are the instructions:

 

[BrooklynBay]

Tap Drill Chart For Some Common Sizes:
Tap Size Drill Size Nearest Fractional Size (inches)
#4-40 #43 3/32"
#6-32 #36 7/64"
#8-32 #29 9/64"
#10-32 #21 5/32"
#10-24 #25 5/32"
#12-24 #16 11/64"
1/4-20 #7 13/64"
1/4-28 #3 7/32"
4 mm x .70 #30 1/8"
4 mm x.75 1/8" 1/8"
5 mm x .8 #19 11/64"
5 mm x .9 #20 5/32"
6 mm x 1 #9 13/64"
7 mm x 1 15/64" 15/64"
8 mm x1 "J" 9/32"
8 mm x 1.25 17/64" 17/64"
9 mm x 1 5/16" 5/16"
9 mm x 1.25 5/16" 5/16"
10 mmx 1.25 11/32" 11/32"
l0 mm x 1.5 "R" 11/32"

 

[shamaal]

All right,

If the bolt goes but doesn't tighten, it is considered stripped and must have a heli-coil or redrilled to a larger hole and re-tapped. You did not mention what part the hole is in so we'll assume you won't need a bottoming tap.

If the bolt is hard to screw in, it may be cross threaded. Go to a hardware/Auto store and purchase a replacement bolt. Take a similar bolt with you and use the sizing charts in the store to determine what size bolt you have. It will probably say something like 10X1.25. Obtain the right size tap, put some oil on it and screw it into the hole as far as it will go by hand. Use cutting oil. When you meet resistance, back off a half turn then advance it 3/4 turn. Continue this advance and backing off until correct depth is reached. Clean hole and try your new bolt.

If stripped, purchase heli-coil size kit for the replacement bolt that you sized. Drill hole using bit in kit (or size identified in kit) to correct depth. Insert tap, turning one full turn to start, then proceed as above. 3/4 turn forward, 1/2 turn back. Use cutting oil and keep tap perpindicular to work. You'll develop a feel for it after a couple turns. There is a tap holding handle in the tap and die set. I just use a small wrench to hold the tap. Insert heli-coil per directions until flush with surface, then insert your screw.

If stripped and you don't want to use a heli-coil, go to the next larger size bolt after you have determined the original's size. Using BB's table, drill your hole and tap as above. Make sure that the next larger size bolt fits through the connecting part, if not you'll have to drill that hole larger also.

Breaking the tap should not be a problem unless there are unusual circumstances; take your time, use oil, ask questions.

I just did 12 of 14 holes on my son's auto transmission pan. The techs used an air wrench and after they stripped the holes, filled them with an epoxy. It held until the engine overheated and the pan started leaking.

 

[BrooklynBay]

Did you use Heli-coils on all of those holes in the transmission, or did you just tap them out to a larger size, and use larger bolts?

 

[BrooklynBay]

Check this link about using Heli-Coil repair kits: http://www.automedia.com/Cruising/the/Strip/res20050401th/1
This link is from the same website. It has additional information about repairing stripped holes: http://www.automedia.com/Thread/Repairs/101/res20021201tr/1

 

[shamaal]

Heli-coils in all 12, once I had the kit I just bought extra coils at a tool store. The authentic heli-coils come with a crummy nylon installation tool. They used to have a good insertion tool but I think they changed to a new design when their patent ran out. The knock-off kit at autozone has the old type insertion tool.

 

[aldive]

Where is the hole/bolt located?

 

[Lazzman]

Its on another vehicle in the aluminum Manifold.