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Author Topic: Oh how I love garages  (Read 4379 times)

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Viral_Jim

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Oh how I love garages
« on: 27 May 2019, 16:18:59 »

 Oh how I love garages  ::)

Pulled the crankshaft pulley bolt only to discover that the previous belt change had been completed courtesy of some barely trained chimp...



So the T'can will have to wait until next weekend when I can get a replacement pulley bolt. I just hope I don't have to drill and tap the crank and go up a size. What do you chaps think, hoping in vain?

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ronnyd

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Re: Oh how I love garages
« Reply #1 on: 27 May 2019, 16:29:52 »

You might be able to clear that thread out if you can source a tap. Do you a friendly m/c shop?
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Re: Oh how I love garages
« Reply #2 on: 27 May 2019, 16:34:58 »

 Go to local fastner supply's take bolt, ask do you have one of these, guessing it's a m,14*1.25
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Viral_Jim

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Re: Oh how I love garages
« Reply #3 on: 27 May 2019, 17:43:54 »

Go to local fastner supply's take bolt, ask do you have one of these, guessing it's a m,14*1.25

Good idea, ive found a good-looking local place. Cheers :y

You might be able to clear that thread out if you can source a tap. Do you a friendly m/c shop?

Sadly not, not round here at least (not had chance to make a nuisance of myself yet!). Once I've got the bolt spec, I'll probably just order one from Amazon, given it will probably be a single-use item in my lifetime.  ;D

My main issue is I'm not sure how to determine thread pitch (will Google later) so I'll just goto the fastener place and ask them what they've sold me  ;D. Everything I've tapped before has been M5 / M6 size and threads are either "coarse" or "fine". But I suspect it's a bit more technical than that   ;D
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Nick W

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Re: Oh how I love garages
« Reply #4 on: 27 May 2019, 17:52:16 »

Go to local fastner supply's take bolt, ask do you have one of these, guessing it's a m,14*1.25

Good idea, ive found a good-looking local place. Cheers :y

You might be able to clear that thread out if you can source a tap. Do you a friendly m/c shop?

Sadly not, not round here at least (not had chance to make a nuisance of myself yet!). Once I've got the bolt spec, I'll probably just order one from Amazon, given it will probably be a single-use item in my lifetime.  ;D

My main issue is I'm not sure how to determine thread pitch (will Google later) so I'll just goto the fastener place and ask them what they've sold me  ;D . Everything I've tapped before has been M5 / M6 size and threads are either "coarse" or "fine". But I suspect it's a bit more technical than that   ;D




The easiest way is to use a thread pitch gauge, but if you had one you'd have done that already. It's worth buying one for other jobs, as they're cheap. Mine was about £5.


Next is to measure the distance between each thread crest using a caliper -  a cheap digital one will be plenty good enough and you might already have one. You'll be looking at a measurement of 1.25, 1.5 or maybe 1.75 mm.


If you have a decent steel rule you could use that, but it does require a good eye.


While you have the measuring kit out, check the diameter of the thread as well. This will enable you to acquire a correctly sized bolt.



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ronnyd

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Re: Oh how I love garages
« Reply #5 on: 27 May 2019, 18:27:25 »

Go to local fastner supply's take bolt, ask do you have one of these, guessing it's a m,14*1.25

Good idea, ive found a good-looking local place. Cheers :y

You might be able to clear that thread out if you can source a tap. Do you a friendly m/c shop?

Sadly not, not round here at least (not had chance to make a nuisance of myself yet!). Once I've got the bolt spec, I'll probably just order one from Amazon, given it will probably be a single-use item in my lifetime.  ;D

My main issue is I'm not sure how to determine thread pitch (will Google later) so I'll just goto the fastener place and ask them what they've sold me  ;D . Everything I've tapped before has been M5 / M6 size and threads are either "coarse" or "fine". But I suspect it's a bit more technical than that   ;D




The easiest way is to use a thread pitch gauge, but if you had one you'd have done that already. It's worth buying one for other jobs, as they're cheap. Mine was about £5.


Next is to measure the distance between each thread crest using a caliper -  a cheap digital one will be plenty good enough and you might already have one. You'll be looking at a measurement of 1.25, 1.5 or maybe 1.75 mm.


If you have a decent steel rule you could use that, but it does require a good eye.


While you have the measuring kit out, check the diameter of the thread as well. This will enable you to acquire a correctly sized bolt.




Exactly wot he said. :y
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Viral_Jim

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Re: Oh how I love garages
« Reply #6 on: 27 May 2019, 22:46:23 »


The easiest way is to use a thread pitch gauge, but if you had one you'd have done that already. It's worth buying one for other jobs, as they're cheap. Mine was about £5.


Next is to measure the distance between each thread crest using a caliper -  a cheap digital one will be plenty good enough and you might already have one. You'll be looking at a measurement of 1.25, 1.5 or maybe 1.75 mm.


If you have a decent steel rule you could use that, but it does require a good eye.


While you have the measuring kit out, check the diameter of the thread as well. This will enable you to acquire a correctly sized bolt.

Thanks for that explanation Nick, clear enough that even I can understand it ;). I've ordered thread pitch gauge and calipers as I own neither.  :-[

 Pretty confident as to which end of a spammer you hang on to, but when it comes to any kind of engineering knowledge, I'm done  ;D
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Nick W

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Re: Oh how I love garages
« Reply #7 on: 27 May 2019, 22:59:51 »

I didn't mention this because your problem bolt is metric, but you don't measure imperial pitches that way. Metric threads are defined by the distance between adjacent features, so you measure them directly. Imperial is defined as Threads Per Inch(TPI), so the reliable way to check without a gauge is to measure an inch and count the number of threads it spans.
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New POD

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Re: Oh how I love garages
« Reply #8 on: 28 May 2019, 22:13:25 »

You might investigate Thread inserts (Helicoils), which the aerospace world would fit as a matter of course.
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Viral_Jim

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Re: Oh how I love garages
« Reply #9 on: 28 May 2019, 22:53:58 »

You might investigate Thread inserts (Helicoils), which the aerospace world would fit as a matter of course.

I've heard of them, not sure how they work, will do some further research.

In any event, if I can't re-cut/clean the 18mm thread with a tap (coming tomorrow) I'll probably get a mobile mechanic to come and rectify. Mostly because I can't get a drill between the block and the AC radiator (not to mention the lack of an 18.5mm drill bit and an M20 tap).

So far I'm down £2.50 on a substitute pulley bolt, £20 on an M18 tap and tap wrench. I'd rather not snap a drill bit or a tap off in the crank. Call it quitting while I'm ahead.  ;D
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Andy B

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Re: Oh how I love garages
« Reply #10 on: 28 May 2019, 23:29:50 »

You might investigate Thread inserts (Helicoils), which the aerospace world would fit as a matter of course.

I've heard of them, not sure how they work, will do some further research.

In any event, if I can't re-cut/clean the 18mm thread with a tap (coming tomorrow) I'll probably get a mobile mechanic to come and rectify. Mostly because I can't get a drill between the block and the AC radiator (not to mention the lack of an 18.5mm drill bit and an M20 tap).

So far I'm down £2.50 on a substitute pulley bolt, £20 on an M18 tap and tap wrench. I'd rather not snap a drill bit or a tap off in the crank. Call it quitting while I'm ahead.  ;D

You don't need to go the full Helicoil route on a thread that's been damaged as little as this. Just clean it up with a tap & that will be enough. Just be careful with the tap ... you REALLY don't want to snap a hardened tap in the crank ... it'd be a tw4t & a half to remove.
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Sir Tigger KC

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Re: Oh how I love garages
« Reply #11 on: 28 May 2019, 23:44:23 »

Whack it back in with a smear of liquid metal. That'll be alright!  :y
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Re: Oh how I love garages
« Reply #12 on: 29 May 2019, 08:40:30 »

You don't need to go the full Helicoil route on a thread that's been damaged as little as this. Just clean it up with a tap & that will be enough. Just be careful with the tap ... you REALLY don't want to snap a hardened tap in the crank ... it'd be a tw4t & a half to remove.

Was about to say the same - snap a tap and you'll be spending several hours with a hammer and a punch trying to either drift it our or shatter it into pieces - or taking the crank out to have it spark eroded out of the hole..

But with that little damage (tbh the thread in the hole doesn't even look chewed in that picture) the tap should go in easily :y if it starts to bind, back it out a quarter turn to break any chips and then go in a bit further, rinse, repeat.
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henryd

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Re: Oh how I love garages
« Reply #13 on: 29 May 2019, 08:47:34 »

You might investigate Thread inserts (Helicoils), which the aerospace world would fit as a matter of course.

I've heard of them, not sure how they work, will do some further research.

In any event, if I can't re-cut/clean the 18mm thread with a tap (coming tomorrow) I'll probably get a mobile mechanic to come and rectify. Mostly because I can't get a drill between the block and the AC radiator (not to mention the lack of an 18.5mm drill bit and an M20 tap).

So far I'm down £2.50 on a substitute pulley bolt, £20 on an M18 tap and tap wrench. I'd rather not snap a drill bit or a tap off in the crank. Call it quitting while I'm ahead.  ;D

You don't need to go the full Helicoil route on a thread that's been damaged as little as this. Just clean it up with a tap & that will be enough. Just be careful with the tap ... you REALLY don't want to snap a hardened tap in the crank ... it'd be a tw4t & a half to remove.

Yes definitely care needed as the case hardening of the crank will be very difficult to tap although as already  said the hole threads look pretty good
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Viral_Jim

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Re: Oh how I love garages
« Reply #14 on: 29 May 2019, 10:17:46 »

Thanks chaps.

Duly noted re. busting the tap, as always I shall go gently and apply some suitable lubricant.  :y

However the job will have to wait until Sunday when I have some time to look at it properly.
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