Problems with subframe bolt

[mrscalex]

I'm clutching at straws asking but I will anyway.

When I put the replacement front subframe back on last night 3 of the bolts went in no problem. The 4th was stiff after 3 or 4 turns and then got stuck well before being fully home.

Now I'm always real careful about not crossing threads. If I can't do at least 3 or 4 turns by hand I stop. This bolt felt like it had gone into the thread fine.

I tried one of the other bolts that had gone in successfully and same thing. So it must be the thread not the bolt.

Is there anything that would cause this other than a cross thread? If somehow it is a cross thread then I guess all I can do is put a shorter bolt in and get the head welded to the subframe? But let's hope it doesn't come to that.

 

[Jack Ratt]

You could try and re tap the hole. Perhaps some "hardened" grease is stuck to the threads. If the thread on the bolt is good and free from any deformity it's unlikely that the thread in the hole is cross threaded I would think.

I'd try it again with a ratchet or spanner, but do it with light effort and a little lube.

 

[t-tony]

You can but tap & die sets cheaply enough. I would buy one and re tap the thread, if you're getting into cars it will come in handy for sure. Mine gets a lot of use.

Tony.

 

[mrscalex]

You can but tap & die sets cheaply enough. I would buy one and re tap the thread, if you're getting into cars it will come in handy for sure. Mine gets a lot of use.

Tony.

Thanks chaps. Really stupid question time @t-tony. I've never used a tap & die set before. Am I using it to clean out the existing size thread? Or am I deliberately tapping out a larger thread that will require a larger bolt.

I am going to give it a go with a bit grease only first though.

 

[Jack Ratt]

Use the tap to clean out the thread in the hole and the die to run down the thread on the bolt. Use the same size tap and die as the hole and bolt size.

 

[Daz3]

Thread is M12x1.5 if that helps I've probably got a spare tap I can post if you need one?

 

[t-tony]

Thanks chaps. Really stupid question time @t-tony. I've never used a tap & die set before. Am I using it to clean out the existing size thread? Or am I deliberately tapping out a larger thread that will require a larger bolt.

I am going to give it a go with a bit grease only first though.

Hi Rob, Garry ( Jack Ratt's) beat me to it. I've been replacing the clutch in a Renault Clio over the last two days and nearly everything was seized or rounded or both. So I've had to do a lot of thread cleaning and oiling but it makes rebuild so much easier in the long run. Another good addition to a workshop is a bench grinder with a wire wheel mounted on one end, invaluable kit in my eyes. Sorry mate, I keep spending your money.

Tony.

 

[mrscalex]

Thanks chaps. I'll pop down MM for the right tap but appreciate the offer of a loan.

It's a long hole/thread. Do I need an extra long tap?

 

[t-tony]

They come as standard length usually, but don't forget you will need something to turn it with.

Tony.

 

[mrscalex]

I've bought a set with both taper and plug taps. What's the difference?

 

[Jack Ratt]

A plug tap will usually get to the bottom, or near the bottom of a blind hole. A standard tap has a shallower taper. That's the only difference really

 

[t-tony]

You generally use a tapered tap to start a new thread in a blank hole. A plug tap has a more rounded end and is designed to make a thread right to the bottom of a "blind" hole. When cleaning a thread I would opt for the tapered thread and when using it turn it into the thread a couple of turns, then back one turn and continue like this until the thread is cleaned right through. Be VERY careful, especially in "blind" holes not to apply sideways movement as taps are made of high carbon steel and will break quite easily if you do. Being high carbon steel you can't drill the broken bits out. You will soon get the hang of it mate. Good luck!

Tony.

 

[Stevo7682]

Just be careful don't force it if you break the tap in the hole you'll be in trouble really difficult to remove.

 

[Stevo7682]

You generally use a tapered tap to start a new thread in a blank hole. A plug tap has a more rounded end and is designed to make a thread right to the bottom of a "blind" hole. When cleaning a thread I would opt for the tapered thread and when using it turn it into the thread a couple of turns, then back one turn and continue like this until the thread is cleaned right through. Be VERY careful, especially in "blind" holes not to apply sideways movement as taps are made of high carbon steel and will break quite easily if you do. Being high carbon steel you can't drill the broken bits out. You will soon get the hang of it mate. Good luck!

Tony.

You just beat me to that there tony

 

[Jack Ratt]

Just use plenty of lube just as you would with a tight fa...

If you have only withdrawn the bolt, the thread form can't really be damaged. It most likely just needs a tap running down it.

 

[mrscalex]

Thanks for the tips

 

[t-tony]

Welcome mate, if you need any info just ask!

Tony.