Center section mounting problems: SOLVED

[Bill Elliott]

Today I got the center section in, huge milestone for me. I think it is good to post things I screw up so that others can learn or prevent from doing the same thing. This forum has been an invaluable resource. When I began to put the rear mounting bolts into the threaded holes of the center section the first one went in just fine. When I tried to start the second one it was more of a fight to get it lined up, in the process I managed to mess up the first couple threads. My first thought was uh oh gonna have to buy something because of my stupid mistake. Luckily the mounting holes for the back are threaded all the way thru, so I got a M14 2.0 tap and tapped thru the back to clean out the beginning threads on the other end. After the tap was all the way through a lot of debris came out. I don't know if the threads were gunked (spell check says this is not a word) up from the start or if it was a result of my screw up. Either way cleaned it out and was able to get the bolt in with little resistance. So if anyone sees this thread remember to use extreme caution starting the rear bolts, as I believe the center section is aluminum for the rear mounts making it easy to cross thread.

tap threads.jpg

[JohnK]

Cool - glad you got that worked out.

Just a quick comment about taps. Generally speaking, there are two types of taps. Thread cutting taps and thread chasers. The former are meant to cut threads in bare holes while the latter are meant to clean up existing threads. In a pinch a thread cutting tap can be used (carefully) to clean out an existing threaded hole but you run the risk of removing more of the thread, especially on a soft material like aluminum. I'm not saying that the gunk you found was a result of that, but just something to be aware of for those reading this down the road. Having a set of thread chasers on hand can be very helpful.

[Bill Elliott]

Cool - glad you got that worked out.

Just a quick comment about taps. Generally speaking, there are two types of taps. Thread cutting taps and thread chasers. The former are meant to cut threads in bare holes while the latter are meant to clean up existing threads. In a pinch a thread cutting tap can be used (carefully) to clean out an existing threaded hole but you run the risk of removing more of the thread, especially on a soft material like aluminum. I'm not saying that the gunk you found was a result of that, but just something to be aware of for those reading this down the road. Having a set of thread chasers on hand can be very helpful.

Thanks for that bit of info.

[CraigS]

I have seen a few threads where the mounts seemed to be a little too far apart, or maybe it was too close. Either way, some guys were able to get one bolt in (but not tighten it) and then use a ratchet strap to pull the diff a little sideways to get the second bolt lined up.

[Mike.Bray]

Cool - glad you got that worked out.

Just a quick comment about taps. Generally speaking, there are two types of taps. Thread cutting taps and thread chasers.

I would add two more flavors, standard thread cutting or general purpose taps and gun taps. Standard taps are usually 4 flutes and after rotating a few degrees need to be reversed to break the chips. Gun taps are usually 2-3 flutes and are designed to produce a continuous chip that is ejected in front of the tap. Gun taps do not have to be reversed, just tap as deep as you want. If you're tapping a through hole you will see the chips stringing out the hole. With blind holes the chips get pushed into the bottom and have to be dug out.

I only use gun taps, they're generally higher quality and less prone to breaking.