Got a MaxPower shift knob and its at a 10mX1.25 thread pitch and was wondering if i could do a conversion to a 10mX1.50 thread pitch. any info would be great. Thanks!!

 

If you were really motivated, you could use a thread repair kit. You'd have to drill it out, tap it and install the thread insert. The thread repair kits aren't cheap, and I'm not sure what length insert you'd need.

http://www.grainger.com/Grainger/REC...pair-Kit-2G938

 

From the very little that I know about this brand from Google in the past 60 seconds, it looks like they usually come with several different threaded inserts to adapt to different cars? Therefore your shift knob should already have a M10x1.25 threaded insert installed, which you could remove and try to locate a M10x1.5 threaded insert with the appropriate outside thread. Grainger has a few of these as well; here is an example with an M10x1.5 internal thread and an M16x2 external thread: http://www.grainger.com/Grainger/EZ-...E34?Pid=search

If your shift knob doesn't already have a threaded insert, then the link posted above might be your best bet; but you will have to find someone to drill out the hole for you.

 

If there is a threaded insert that you can remove, that would be 100x better than using a thread repair kit.

If you're going with the thread repair kit, you'd also need the appropriately sized drill bit, a power drill, cutting fluid and a tap handle. I'd also highly recommend using a vice with v-blocks to hold the knob while you work, and of course, safety glasses.

 

With all of the awesome shift knobs available for our car that don;t require any modification to the car I'd say sell/trade what you have and get the right knob. Good luck either way!

 

Got it going, here it is mounted! All i had to do was re-tap it using a 10m x 1.50 tap to make it a coarser thread. worked like a charm!


shift knob

 

You ran a M10x1.5 tap through an already tapped M10x1.25 hole? Meh, whatever... if it is holding then I guess you are good to go. I wouldn't have done this with something that was holding my engine together, but I guess a shift knob is fairly non-critical.

This is what your threads look like now:



You can see that in a 25 mm section (~1 inch) you really only have about four "good" thread sections due to the overlap of the 1.5 versus the 1.25. Depending on the material of the knob, you may be able to pull really hard and strip those threads out. Just be careful and don't try to over-torque the knob when installing or it will strip.

 

Your criticism is mostly correct, but you also need to keep in mind that the two threads have different minor diameters. The M10x1.5 has deeper threads so a hole which was drilled out for the smaller M10x1.25's small threads used a larger tap drill so none of the threads will be full height. Maybe I'll try to find a picture later.

 

Yes, that is even more of a worse case for the new threads in the shift knob hole. The maximum minor diameter size of the internal threads is stated as 8.676 mm, but the hole was likely drilled with an 8.75 mm tap drill which is the standard size for M10x1.25 tapped holes. So he is missing a minimum of 74 microns of thread diameter on the inside of the shift knob that he would have had if it had been tapped for an M10x1.5 in the first place. However, his major diameter with the new M10x1.5 threads could potentially be a little larger than the old M10x1.25 threads, so this could even out regarding contact surface area on the threads.

Bottom line, it will probably hold with normal use, but don't twist that bitch down too tight!

 

HOLY CRAP!!!! clean your car!