# Need help with tapping new threads



## darcy32171 (Nov 28, 2013)

My starter bolt holes are stripped. The original bolts are a 1/4" 20NC. Can a guy safely go up to a 5/16" 18NC or will there not be enough meat for threads? I don`t think there is a wide enough ledge on the motor to go to a 3/8" bolt. Even if there was a happy/medium in metric I`d be fine with that. I have a brand new 4 year old tap/die set here. Thanks,Darcy


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## darcy32171 (Nov 28, 2013)

I guess I might be buggered either way. The city I live in more than likely won`t have a "Heli coil inserts" or a "bottom hole tap". I compared the 5/16" 18NC tap to the original bolt length and I would not even really be starting to cut threads before it bottomed out. Might have to make the 2hr round trip to a bigger center. 
Thats what I hate about living in a 11,000 populated oil booming city.....can never get anything you need.


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## UNDERTAKER (Dec 30, 2013)

you can go up to 5/16 NC-18. that is what most are any way


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## Blue Hill (Mar 31, 2013)

If your block is aluminum, use kerosene or WD40 as cutting oil, and don't be stingy. 
If it were mine Darcy, I might go with 5/16" NF fine threads. Less likely to strip again. Removable lock tight too.


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## td5771 (Feb 21, 2011)

Another thought would be to follow all the great advice above but then use automotive studs (they come fine or coarse thread) so they can stay in for good with the new threads and some epoxy or permanent loctite.

studs sticking out and a few nuts and lock washers and your set


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## darcy32171 (Nov 28, 2013)

Just found a 5/16ths Bottoming hole tap! It is all they have and NC thread. I`ll just make sure I snug the bolts up and use a "good" blue loc-tite and lock washers to help.


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## darcy32171 (Nov 28, 2013)

Just so happens: I get there and they did some digging and found me a 5/16ths 24 national fine! My chart says: Tap drill size 17/64`s, Not much room there when comparing the drill bit to the tap... My hand better be steady when drilling. I have the shakes at the best of times....god grant me 20 minutes without the shakes please.


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## TimY (Oct 27, 2013)

I'm with td5771. If you can't find studs make them.Cut the heads off some bolts,clean the holes and bolts with acetone or similar,use a Q-tip soaked with it to really clean out the stripped holes. Put a piece of tape on the flat area on the engine (keeps it flat and makes clean up easier) cut around existing holes in the engine on the tape. Now put a piece of tape on the good end of the bolt (the end you didn't cut) to the depth that has to stick out(again keeps the epoxy out of the threads you want to use and makes clean up easier) mix up JB weld or metal epoxy making SURE proportions are VERY correct this is the secret to a good epoxy mix . Coat the bolts and holes with the epoxy keeping the bolts as straight as poss. 
It would help if you don't have a heated place to do this warm up the engine first .


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## TimY (Oct 27, 2013)

P.S. before the epoxy fully sets wipe of any excess with a clean rag with acetone


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## darcy32171 (Nov 28, 2013)

The issue I have with using studs is: The bottom tabs have holes and the top are forks. The starter needs to be installed on an angle going under the shroud, then the forks go under the collared top bolts then it is angled towards the motor to install the lower bolts. 
There are really only two fixes if I use studs: 
1: cut the lower tabs so they are also fork style
2: remove the complete shroud (giving room so starter does not need to be angled), then install starter and replace the shroud.


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## nt40lanman (Dec 31, 2012)

Without eyeballing it myself, I still would have gone with a 1/4 helicoil kit, adding a bottoming tap to get threads to the bottom. You could still pull the cylinder cover off and drill all the way through into the crankcase to get enough depth, then use sealer on the bolts.


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## darcy32171 (Nov 28, 2013)

nt40lanman said:


> Without eyeballing it myself, I still would have gone with a 1/4 helicoil kit, adding a bottoming tap to get threads to the bottom. You could still pull the cylinder cover off and drill all the way through into the crankcase to get enough depth, then use sealer on the bolts.


Thanks, but I have two issues with that...
1: A heli coil kit up here where I`m from is $42 + 10% tax = $46.20
The bottom hole tap cost me $10.95 for a 5/16ths x 24 NF

2: Drilling straight through + adding sealant = fraggled nerves while running machine, hoping the sealant is actually doing its job.


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## darcy32171 (Nov 28, 2013)

Done! Drilled and re-tapped for 5/16ths 24 NF. Everything went pretty good and a nice day to be pullin wrenches outside. One opps that I caught before I did it was: I drilled and then I sprayed my tapered tap to start and then finish with the bottoming tap. Just as I was about to start making threads I double checked the tap and I had a 5/16ths 18 NC. it would not have been a huge mistake, I would have had to exchange the fine thread bottoming tap for a course one and buy new bolts. Oh well, it didn`t happen, I caught it! the bolts I got were 1.5" long, had to cut them down. I didn`t cut enough and had to use two washers under them...oh well thats fine.


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## TimY (Oct 27, 2013)

glad it worked what ever gets the job done!!!


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## HCBPH (Mar 8, 2011)

*Stripped bolt hole*

Had one - helicoiled it and worked out great for that one. Easy to do also, just insure you're correct on the depth to drill.


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## Spectrum (Jan 6, 2013)

I'm fond of these. You can order in all that you need.

Pete


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