Z121S Lawn Mover bolt for Blade broke off in the Final Drive
The bolt - just purchased is a M12 x 1.25 x 30 I have not done many of these. I am not trying to drill out and re tap. I would like to use the correct tap and hopefully clean up the threads. What is the correct tap needed? is it the M12 x 1.25? What is the 30? it looks like pretty fine treads. Tom
StarTech
Lawn Royalty
I hate to ask this but just how dense are you? A M12-1.25 uses a M12-1.25 tap or die ( the screw itself would need a die and the hole it goes in takes a tap. Since this is a blind hole hole you need a bottoming tap to reach the bottom but you need a taper or plug tap to get started. Most stand length in this size nearly 40mm long and your screw is only 30mm long.
Two of these from my vendor is only $60 plus shipping.
Two of these from my vendor is only $60 plus shipping.
SeniorCitizen
Lawn Addict
In instances similar , a metric thread file covering 8 options is a handy tool .
use a M12-1.25 thread chaser if you haven't already got it done. Thread chaser doesn't cut threads, but it does a good job of cleaning up existing threads. I have used taps quite often in the past and on several occasions, they'll cut a new thread before it catches an existing thread and then the spindle is ruined. One could put a helicoil in them but no more than they cost, just as easy to replace the spindle shaft. The spindles are really sloppy tolerances on these mowers. On mine I have had to shim the bearings a little bit to put some "end play" in the shaft. Reason being, once you tighten up the nut, it pulls the bearings together too far, since the spindle housing was machined too shallow and the spacer too short. Just one of many things I have had to nitpick on them, BUT, it made a big difference as far as the bearings lasting more than 40-50 hours. I'm at over 300 on this set and no signs of getting loose or noisy (yet).
duke427
Forum Newbie
How to do to shim the bearings a little bit to put some "end play" in the shaft?
The right grade clean quality bolts with no boogered threads in either part ,tightened to the proper torque will solve your problem.I would look for a thread maintainer,not a tap,their is a major difference.The tap is for cutting new threads in a hole.The thread maintainer,moves and massages the existing thread without removing material.And I would check that blade for straightness and balance. Blades spinning this fast,need a certain amount of carefullness
You say it came out easy. You got lucky) Most likely you do not need to re-tap to clean the threads.
When looking for the correct tap though use the existing bolt as a gauge.
I would just get another bolt and use it as a gauge of the threads, turning it easy with a end wrench for feel.
Most likely the bolt was over torqued and overstressed the head popped off.
You need to check the others and make sure they have the correct bolt and use a torque wrench when tightening. (most are never torqued they just get impacted on and off.)
You should invest in a 1/2 inch torque wrench for such.
Fastenal is a good place to find your bolts. take the old one with you and one of the other ones as a reference show and tell.