Crankshaft Warped from Flywheel Removal

C

CMLT1000

Forum Newbie
New here and looking for repair advice.
Craftsman LT1000 (17.5hp B&S engine 31C707-0230-E1. I'm an idiot, did not research and pulled the flywheel with a harmonic balancer puller and side bolts were short so I removed the flywheel/crankshaft bolt and apparently pressed directly against the crankshaft end (with female threads). Seems I warped the end of the crankshaft such that I cannot get the bolt to start threading into the female threads in the end of the crankshaft. Everything looks absolutely fine, just can't get the bolt to start. Threads look perfect using a scope camera. Thinking maybe I just rolled the crankshaft end over a bit?
Looking for suggestions instead of tearing down and replacing crankshaft. Some ideas I've had:
1. Gently tap bolt in to try to push any "bulge" out until it can start to thread in
2. Drill out with a bit just smaller than the bolt to get rid of the bulge without going too far to mess up the threads
3. Drill out and tap to slightly larger and get new bolt. Would Grade 8 bolt be appropriate or non-hardened bolt? Doubt I could find a tapered/pointed bolt so would I just get a straight bolt 1/4" shorter?

Any suggestions on the above or other ideas much appreciated.
Thank you!
 
Just get a long tapered tap
We call them different names so it is the one with a lot of taper on the pointy end and almost not full threads
Aussies call them taper or first cut
The tapered end will pick up the thread a but deeper

If you want to spend a lot of money you can get a split restoring / reverse tap which expands like a dynabolt so you slip it in the hole then expand it out to engage the threads then wind it out to restore the damaged bit at the beginning.
When you arein the nut & bolt store buying that, get an allan headed cap bolt to put in the hole next time & a couple of longer grade 8's for you puller and put the lot in your special tools box.
 
Here in the states taps generally come in 3 types, Starting, plug and bottoming. Ypu want a starting tap. The taps you usually find at hardware stores are plug taps.
 
A tool like this is probably what Bert is suggesting.

Internal thread repair.JPG
The blue highlight numbers are not clickable links. Just a screen shop from my machine shop tool supplier.
 
Plus I feel it better to let some with experience in restoring these threads as helpful as those crankshafts are 280+ USD.
 
Not what I was thinking of but I do like it, gotta save some more toy pennies
This is what was thinking of

backtap.jpg

Had a 14 mm spark plug tool forever but needed 12 & 10mm for chainsaws & trimmers so ended up with a full set of them 4mm to 12mm as that was cheaper than just buying the 2
 
Get a spare bolt and grind a slight taper on the end of it, start it into the crank to dress the llead in threads.
 
bertsmobile1 said:
Not what I was thinking of but I do like it, gotta save some more toy pennies
This is what was thinking of

View attachment 52914

Had a 14 mm spark plug tool forever but needed 12 & 10mm for chainsaws & trimmers so ended up with a full set of them 4mm to 12mm as that was cheaper than just buying the 2
Click to expand...
You would you have the PN for kit you ordered so see if any of thread pitches is what I can use. Probably not but still like to look at them any ways.
 
Came off evil bay in the UK.
Looks like it was made in China because there are no brand names on them or the box they used to live in which fell apart sitting on the shelf.
Will go back through the records to see if the details are still there.
 
Thank you all for the suggestions.
The original bolt (not damaged) is tapered to a point and has no threads on the first 1/4" from the tip, and I can't get that in to get any type of grip. I think either I mangled the end of the crankshaft out of round or the tip of the puller press rod may have double-flared the CS end such that the outer edge rolled in and down so that the diameter of the hole is even smaller than the diameter of the threaded area of the hole. I don't know that I should, or even could, use a tap to both cut threads and widen or round the warped end of the CS. I was thinking of using an appropriate sized (hair smaller than the bolt) countersink drill bit to cut the opening wider and round. I would drill just a hair at a time and test with a spare bolt of the same size until I can just get the bolt to grip a bit. Once I have some type of grip on threads I would then try to repair the threads, probably with the restoring/reverse tap as Bert suggested.
Can a tap handle cutting threads and widening/rounding a hole, at the same time? Any better ideas on how to get the opening round and/or close to the correct size?
I appreciate all the feedback.
 
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