oil pressure switch threads in case stripped need advice

[LCOX]

The threads in the engine case where the oil pressure swicth screws into on my type 4 engine are stripped badly and the switch won't tighten down at all.
-I bought a new oil switch and the info on the box it came in stated that the thread size of the switch are 10mmx1.0 pipe thread.
-I can't find this size in a heli coil kit here locally. Does any one know the correct size tap, drill, and insert size to repair this properly. Can a standard 1/4inch or 1/8 inch pipe thread tap be used. The hole appears to be too big to use a 1/8 pipe thread tap. As a last resort can it be glued in? Don't want to do this if possible. Any advice appreciated. Thanx L

[Busstom]

You could evaluate these options. It seems the missing element from these options is "pipe" thread (which in the US implies "tapered"). However, BSP (British Standard Pipe) is NOT tapered, which in my experience is useless for making a tight seal, but I do believe your oil pressure switch threads ARE tapered, so these items below may not be appropriate, but a quick search turned them up.

https://www.amazon.com/Thread-repair-helicoil-damaged-thread/dp/B01MCZHOX7

I know a hundred bucks is pricy, but... https://www.mechanicstoolsandbits.com/time-sert-1010-m10-x-1-0mm-metric-thread-repair-kit.html

Edit: Thinking outside of the box...you know, some guys run a remote line to this sender, so that the engine vibration isn't shaking the crap out of it. I'd guess one alternative solution is to tap the case with an oversize "pipe" thread, then reduce that somewhere along the remote line connection before it gets to the sender, if you were to go this route.

[raygreenwood]

[Wildthings]

This is a dangerous repair as even the smallest chip of metal is going to destroy the main bearings should it fall into the hole. I would fill the bottom of the hole with a thick grease and then use grease on the drill and on the tap. When done you need to carefully scoop out the grease being 100% sure that no metal is left down in the hole.

1/8 pipe and 10x1mm are very close to being the same diameter and tread pitch. People frequently use senders that are mismatched to the threads and mostly get away with it.

This might be a good place to use something like Loctite's thread repair compound. Have no experience with this product myself.

[aeromech]

You might try this to help keep crap out of your oil system.

You are going to need to cut new threads into the case. Off hand I don't know what size that would be though. Trying to glue something in place is just asking for trouble.
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[surfbus23]

What is "this"?

[Glenn]

[SGKent]

He's suggesting you find a way to keep filings out of your oil passages so they don't end up in your bearings. He is using compressed air. Some folks use a glob of grease, other folks take the engine apart and don't risk it at all. Some mechanics who do it for others gamble that the owner will never know that the bearing failure 5,000 miles later is due to the filings that ended up in the oil passage then the bearings when tapping that hole for new threads. I don't know what I would do if that stripped thread thing happened to me. It is not a happy full of joy moment. Probably I would look to see if the threads went deeper in the case and I could use a small extension and hose to a sender - otherwise I would be one of the folks who pulled the engine and split the case to fix it.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[surfbus23]

You mention a bearing failure but after some amount of time. Say you were to get a shaving down this thread. Would an oil change not be helpful in removing it?

[Glenn]

[Wildthings]

[Randy in Maine]

It is just a tricky fix. Do what it takes to keep the shavings out of the bearings/oil passages (air pressure in the oil filter and filling below the tap with grease and a couple of oil changes) and you should be OK. Then keep an eye on it. Drive it.