Stripped Gearbox Drain Hole

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baz said:
Use a spot facer and you will definitely have a flat surface
Click to expand...
The advantage of a countersinking bit is that the flat surface will be square with the bore - I'm not sure that's true for a spot-facer (if we're talking the same language)

Edit: my bad, what I meant was counterboring bit, which I think is the same thing as a spot-facer.
 
If you (or anyone else reading this) have a 3/8" BSF tap, why not try tapping a piece of scrap with that first, then see if you can run the M12 tap through without drilling. I reckon there would be a much better chance that the taper tap would stay perpendicular to the face.
 
cliffa said:
I reckon there would be a much better chance that the taper tap would stay perpendicular to the face.
Click to expand...


Yes, assuming the hole is perpendicular then the taper tap (used first as it should be) should follow the hole.
Stripped Gearbox Drain Hole
 
cliffa said:
If you (or anyone else reading this) have a 3/8" BSF tap, why not try tapping a piece of scrap with that first, then see if you can run the M12 tap through without drilling. I reckon there would be a much better chance that the taper tap would stay perpendicular to the face.
Click to expand...
Yep - you may be right, but I think there is a reason for recommended tapping drill sizes.
A single ( or more) trial in rolled aluminium plate will not, in my opinion, ensure success in the cast aluminium housing. I don't have any scrap casting for the trial.
Driving a tapered tap into a too small hole runs the risk of cracking the housing.
Or... I could be wrong!
Better to err towards the safe methinks.
 
All the necessary bits come with the timesert kit

www.accessnorton.com

Oil Drain Timesert Repair

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robs ss said:
The advantage of a countersinking bit is that the flat surface will be square with the bore - I'm not sure that's true for a spot-facer (if we're talking the same language)

Edit: my bad, what I meant was counterboring bit, which I think is the same thing as a spot-facer.
Click to expand...
I have only ever made my own from old drill bits or end mills
I leave the centre mandrel part of the cutter much longer
And dead size to the hole being counter bored
 
Would it make sense to install a threaded sleeve into the case that is threaded for an undersize drain plug which can be changed when the drain plug threads wear out?
 
Here is a link to various Timesert installation demos.

++ TIME-SERT Screw thread inserts. Threaded bushings for stripped threads repair threaded bushings inserts for stripped threads insert thread repair

stripped out threads, damaged threads, blown out sparkplugs, stripped thread, stripped out theads, helicoils, ford sparkplug repair, repair ford sparkplugs blew out with time-sert, thread repair problems, spark plug ford blown, blew out ford sparkplug, stripped theads, threads stripped out...
www.timesert.com

It is the right way to make the repair IF one is prepared to drop that kind of cash. If not I have used your plan before...and you are right about a squared up tap hole being key to a successful outcome.
Whenever I have to cut threads or drill/mill metals and need to control the shavings or "swarf" as it is sometimes called I rig up my shop vac and run it full tilt boogie right on top/next of the area I am drilling/tapping. Just be careful about it sucking up your inserts, taps, screws etc. It really does a great job of keeping the cuttings out of play.
 
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