Tapping extra-long holes

[h3rman]

Hey guys, not been on here in a while. I have a slight problem and was hoping you guys could help.

Basically, got my clutch changed and the spanner monkies at the garage put a bolt that's too long in the wrong hole when they re-fitted the gearbox. Now, the only reason I noticed was because there is an earth on this bolt, and because it was loose and had about 10mm movement the car would cut.

Anyway, I decided to fill the gap with some washers until I got the right bolt and found where the idiots had put the shorter bolt. Problem is, when I took it out, the threads in the side of the engine block are ruined, so you can't properly tighten it. It will nip up and start getting tight, then it slips back a thread and goes loose again, so I need to re-tap the hole and get a new bolt (last time those monkies touch it, I tell ya!!).

Anyway, my problem is that first of all, the hole is about 150mm deep and it's quite tight down there. I struggled to get a ratchet down there, and no way I would get a tap with 2 handles down there.

So 2 questions.....

First of all, where can I get extra long thread taps for an M14 bolt?

Second, does anywhere sell a ratchet attachment for thread taps, so I can do it with only 1 handle in a tight space?

I don't mind starting it with a normal tap holder to make it totally square, but I'll be there forever doing half a turn, loosening the handle, moving it, tightening it, doing another half turn, etc, etc.

Any help greatly appreciated! Or if there is an electric/air powered tap tool I could use that would be awsome!

 

[MarkMG]

don't know the answer to most of your questions but..
Could you not use a socket and ratchet on the tap, treat it as a bolt, just square?

 

[Delgado]

Failing that, could you not just make one with 2 bits of Flat bar/Plate, notch the correct size 'V' out of each end, tack them together to form a diamond/square of the correct size, then tack them to an old socket?

 

[^neo^]

Is it a blind hole or can you get to the other side of it?

 

[Ducati]

Hey guys, not been on here in a while. I have a slight problem and was hoping you guys could help.

Basically, got my clutch changed and the spanner monkies at the garage put a bolt that's too long in the wrong hole when they re-fitted the gearbox. Now, the only reason I noticed was because there is an earth on this bolt, and because it was loose and had about 10mm movement the car would cut.

Anyway, I decided to fill the gap with some washers until I got the right bolt and found where the idiots had put the shorter bolt. Problem is, when I took it out, the threads in the side of the engine block are ruined, so you can't properly tighten it. It will nip up and start getting tight, then it slips back a thread and goes loose again, so I need to re-tap the hole and get a new bolt (last time those monkies touch it, I tell ya!!).

Anyway, my problem is that first of all, the hole is about 150mm deep and it's quite tight down there. I struggled to get a ratchet down there, and no way I would get a tap with 2 handles down there.

So 2 questions.....

First of all, where can I get extra long thread taps for an M14 bolt?

Second, does anywhere sell a ratchet attachment for thread taps, so I can do it with only 1 handle in a tight space?

I don't mind starting it with a normal tap holder to make it totally square, but I'll be there forever doing half a turn, loosening the handle, moving it, tightening it, doing another half turn, etc, etc.

Any help greatly appreciated! Or if there is an electric/air powered tap tool I could use that would be awsome!

If the threads in the block are stripped all you are going to do by running a tap of the same size as the bolt down them is either partially clean up the damaged threads at best, or worst of all ruin what threads are left.

There are only two ways to correctly repair such damage, one is to drill and tap to to the next size of bolt, the other is a helicoil insert, both impossible due to the location as you describe it.

If, like most engine to bell housing arrangements, it's a bit over-engineered and there are plenty of other sound bolts holding the assembly together and that the bolt does not secure anything else you could try either one of the locktite products or such as chemical metal, bearing in mind that you won't be able to torque the bolt up to the correct spec.

If the threaded hole is not blind you could possibly pass a longer bolt of the correct size through with a nut on the end or pass the next size down bolt through with a nut on the back.

 

[Rich H]

As above just pop a 12 point socket over the tap and use the ratchet, done it loads of times when being lazy.

 

[Robotstar5]

I use a ratcheting tap wrench with a "T" bar handle that can be slid to one side.

 

[Hitch]

You can get sockets that are sized for taps....

J&L Industrial would be a good lookout for the tap.

Cant you move the earth to a different bolt that can be tightened properly?

 

[the snooper]

just sue the garage for the damage,
as mentioned above if the threads are already damaged a tap of the same size wont repair them it may need to be helicoiled or similar

 

[howardm]

Helicoil

 

[knoba]

Not being an expert, one final thought comes to mind;



If one studies the female aperture, and the dimensions from both bolts, one should be able to ascertain the exact dimensions & topography of the hole. If the available dimensions look promising; one can trim a new bolt to suit, with the optimal; wasted-shank length, thread length & bottom clearance (preferably from OEM stock ie. similar replacement part with correct thread pitch and diameter), one could make a bolt to replicate the dimensions of the hole with calculated clearances. Often manufacturers allow plenty of tolerances for hassle-free assemblies.

• Keep in mind that the strength of the replacement bolts will need to be matched in material, hardness, etc. (usually, but not always grades are relieved on the head eg. 8.8, 12.9, etc.) Best to choose a similar OEM candidate part if available...
• A clearance is needed between the bottom of the bolt & the bottom of the hole (suggest 1mm or >).
• The bolt will need to engage in the female threads, at least, the a distance of its own diameter (ie. M10 = a minimum of 10mm of intact thread).
• Make sure that the bolt is not bottoming-out on its own wasted shank (clearance).
• Torque the bolt to its correct value (easy to over-tighten by hand & place undue stress on the fixing).

Some good info on bolts here...

HTH

 

[Big Mick]

Put the earth strap on another bolt!!!!! Donj't worry about the damaged thread, as others have said, there's plenty of overkill in bellhousing attachments.

Cheers, Mick.

 

[knoba]

Big Mick
Put the earth strap on another bolt!!!!!

...yeah, do as you're told, h3rman!

Not knowing all the variables of the job, it's better to present OP with as many options as possible. That option has already been stated (it may over-stress the earth lead if placed in another location).

 

[^neo^]

If one studies the female aperture

Juvenile giggle on that

 

[h3rman]

Hey guys, sorry for not reply in sooner. Someone said it won't be possible to re-tap if the threads are damaged, they are not 100% destroyed, I mean I can start threading the bolt, and if I try and pull at it with my hand it won't just come out, it's properly threaded, but once you begin to torque up the bolt, it slips a thread and slackens up again, so just wanting to run a tap down it to make some fresh threads and get a new bolt to go with it.

Have done this on other bolts and it worked a treat. The hole is blind as is goes into the engine block itself. I know that 1 loose bolt will not make the bell housing fall off or anything, but I can be a bit fussy/perfectionist, and because I know it's not right I want to sort it.

Helicoil is out of the question unless I drop the gearbox or remove the engine, neither of which I plan on doing for 1 bolt. The earth is holding fine now, not cut out since I filled the gap with washers. There is no-where else I can re-locate it without extending the cable, and I would rather not go down that route.

Thanks for the advice on using a ratchet with a tap. Does anyone know where I can get an extra long tap for the hole? Something like 150mm (15cm) in length, size M14?

Cheers!

 

[scott0031]

Long series taps are available but doubt they will be that long. Try J and L industrial, cromwell tools, or tracy tools. Tracy tools might be worth a shout as they ca be very helpful to people needing to 'borrow' a tap for a small fee.


As mentioned i doubt a long series would be any where near the lengths you need. You can silver solder an extension on a tap or make an extension that goes over the end of the tap and hold in place with some baby grub screws on the square drive of the tap. Either way the extension bar would really needs to be made properly so it does not run out by vast amounts, this serves to reduce user error.


Your best shot at this in my opinion is hoping the blind hole is not tapped to full depth by the makers, often they are not in castings. The hard bit with re-tapping that hole totally blind is, with an extension that long you will tend to get lack of feel and ensuring you do not double cut the thread is the hard bit. So its a case of go very, easy lots of patience and finesse. If you do unfortunately manage to double cut it, you then have trouble.


If you do manage to re cut to the bottom of the hole, it goes without saying you will have to be very careful of the bolt length you use. You will have to make sure it is just short by a mm of the full threaded depth. Failing to do that could well crack the casing, pending how much material is round the tapped hole.


Try to remember though re cutting a damage thread will never make it a good thread. It will always be damaged and a lot weaker than original.




I wish you luck.


Kind regards,


Scott

 

[ford34/2]

blind hole

Good luck whatever you do,
but one thought does come to mind, be very very carefull of oil or lubricant in the hole after tapping, and especially too much on the bolt, the force of the bolt when it is screwed in and any surplus oil in the hole --when torking the bolt up the pressure of the oil will crack the casing,-- if as you say, its a blind hole.
sorry cant explain better.

Stan

 

[Pete.]

There are probably thousands of cars driving about with hard-to-reach bolts missing from the bell-housing. If it's not holding another part (like the starter motor) just move the earth strap to the next bolt along and leave that one out. It won't 'stress' the earth lead unless it's being pulled tight to fit it. Certainly won't affect how it works.

 

[Angusdog]

Does anyone know where I can get an extra long tap for the hole? Something like 150mm (15cm) in length, size M14?

Can you weld an extension on to a normal one? I did that for cleaning the threads in a Mini's rubber cone suspension before running the cone compressor as the threads get gunky. Weld a cheapy socket onto the end of your extension and you're in business. I like the cheap chinese stuff for this since you can manufacture one-off tools which are used infrequently.

 

[Rich H]

If you just want the bolt secured try an old trick, put a length of solder down the hole then wind the bolt in. It'll take up some of the wear on the threads and force the bolt to one side to engage the partially stripped threads. Can't be fully torqued up but will be solid enough.

Trying to tap a hole 150mm long is a non-starter IMHO, but if you insist you might find that a 3/8" extension bar will fit over the square end of the tap, wrap the square bit with insulation tape and then hammer them together. Then you can either use a 3/8" spanner on the other end or make use of cunning and find a way to fit a ratchet.