Re-tap vs. clean threads

[broncc]

Its best practice to chase any holes and bolts that don't snug up with fingers. Its so much nicer when you don't have to jam rusty bolts into gritty holes.

I use taps because I'm too cheap to buy the correct tools and accept the risk of increased thread clearance.

 

[Curious Hound]

I'm not sure I fully buy into the idea of a tap cutting new material away and making the threads sloppy. A tap is what cut those threads in the first place. So, I should just be cutting rust, dirt, grease and threadlocker out of the hole. I could be wrong and I'm not trying to argue. But it doesn't make sense to me unless you're careless and don't get the tap started right.

 

[alwaysFlOoReD]

I'm not sure I fully buy into the idea of a tap cutting new material away and making the threads sloppy. A tap is what cut those threads in the first place. So, I should just be cutting rust, dirt, grease and threadlocker out of the hole. I could be wrong and I'm not trying to argue. But it doesn't make sense to me unless you're careless and don't get the tap started right.

This is my thought too. But I do know that there is different clearances specced for different jobs. I have some die that can be squeezed shut or opened up to make a bolt tight or loose in a hole. I'm sure there are taps that are made to do the same. The run of the mill tap and die set is probably going to be in the middle of some spec, so could potentially remove metal. I take that chance....

 

[19Walt93]

My MINI required that I retap the threads when installing motor mounts. I thought it was a bit nuts, until I saw what came out of it (hardened loctite). That got me thinking about the Ranger and possibe rust issues/buildup on threads. So, if there's an option, what do you prefer? To be specific, this is for  any bolt hole, not just the motor mounts.

Don't use a tap, use a thread chaser so you don't over cut the threads and make the bolt more prone to pulling out. I have a Snap On kit I bought decades ago and I chase all the threads on blocks and other used components before I start to assemble them.

 

[pjtoledo]

I'm not sure I fully buy into the idea of a tap cutting new material away and making the threads sloppy. A tap is what cut those threads in the first place. So, I should just be cutting rust, dirt, grease and threadlocker out of the hole. I could be wrong and I'm not trying to argue. But it doesn't make sense to me unless you're careless and don't get the tap started right.

depends on the way original threads were created.
for instance, the front diff for 98+ has an aluminum housing and the cover bolts are thread forming. taps definitely open those up a bit.

especially if you cram a 5/16 tap into those 8mm holes

 

[85_Ranger4x4]

Its best practice to chase any holes and bolts that don't snug up with fingers. Its so much nicer when you don't have to jam rusty bolts into gritty holes.

I use taps because I'm too cheap to buy the correct tools and accept the risk of increased thread clearance.

My impact doesn't really seem to care though...

I'm not sure I fully buy into the idea of a tap cutting new material away and making the threads sloppy. A tap is what cut those threads in the first place. So, I should just be cutting rust, dirt, grease and threadlocker out of the hole. I could be wrong and I'm not trying to argue. But it doesn't make sense to me unless you're careless and don't get the tap started right.

Agreed

depends on the way original threads were created.
for instance, the front diff for 98+ has an aluminum housing and the cover bolts are thread forming. taps definitely open those up a bit.

Do you need to tap holes for self tapping bolts?

I have never even thought of doing that. They did it once they can do it again, if they don't like it they have nobody to blame but themselves.

 

[pjtoledo]

to clean the holes, yes.

I also ditch the thread forming and switch to regular bolts. which usually requires cutting the threads a bit deeper.

 

[Shran]

I'm not sure I fully buy into the idea of a tap cutting new material away and making the threads sloppy. A tap is what cut those threads in the first place. So, I should just be cutting rust, dirt, grease and threadlocker out of the hole. I could be wrong and I'm not trying to argue. But it doesn't make sense to me unless you're careless and don't get the tap started right.

New fastener into a new nut/threaded hole should be no problem - a tap into a brand new nut/threaded hole should remove no material assuming the bolt, nut, threaded hole, and tap are all in spec.

I have pulled bolts out of used nuts/holes that threaded in nice and snug and figured I should just chase the threads anyway only to find that the tap removes a little bit of metal. The bolt is then just a little loose. My theory is that when you tighten a bolt it distorts the threads to some degree depending on the material and how tight the bolt was. Chasing the threads with a tap doesn't return the threads to their original position...it makes them larger.

That's my opinion anyway, but I am no scientist.