Caliper nipple

stranger12

those cheap helicoils , really?

I inserted a helicoil and could pull it out like as if it was very soft form of spring .
It doesn't look too safe

Gloomendoom

I used to work for a firm that made armoured vehicles from aluminium. Every threaded hole cut in the hull was helicoiled as a matter of course. Steel on steel thread contact is much more durable than steel on alloy. The insert also spreads the load giving a much higher load bearing capacity than screwing direct into alloy.

Gloomendoom

stranger12 wrote: »

those cheap helicoils , really?

I inserted a helicoil and could pull it out like as if it was very soft form of spring .
It doesn't look too safe

Screw a bolt into it and try and pull it out. Post back when you have.

Joe_Horner

stranger12 wrote: »

those cheap helicoils , really?

I inserted a helicoil and could pull it out like as if it was very soft form of spring .
It doesn't look too safe

Yes really, although on aircraft they're about 50 million times the price because they're certified for flight.

Once they're installed the insert is held in place between the body and the bolt / stud / bleed nipple and can't "unwind" like you've seen they can do when they're not fully assembled.

stranger12

I did that it seemed very strong but was still doubt full so I pulled out the helicoil which uncoiled it and it came off

The machine shop told me they are not proper fix and only temp solution.
On other hand if it is used in plane then above can't be true.

The helicoil seems cheap to believe it can hold the nipple in place under few hundred if not thousand PSI.

a shop is asking for £90 to fix that single hole which seems very dear and expensive .


I search for maching shops using the term fabricator or machine engineering shop on yell an didn't get many results.



When you helicoil, do you need to counter sink the top so the screw can thread into it ?

I bought an M12 bleed nipple which does not screw in but the helicoil does. there seems to be a problem with the thread guide on top which makes me think I need to counter sink it so the bolt can go in


I am trying to do all I can before I pay £90 to fix that hole. The caliper did cost me £80 only !!

I am not too concerned about paying £90 but want to try and fix it . If I felt like it is going to work then use it else pay the guy


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Gloomendoom

The problem you will have is that the hole you want to put the insert in is not a through hole. That is going to make tapping the thread for the insert difficult/impossible unless you have the correct plug tap for the job.

stranger12

Gloomendoom wrote: »

The problem you will have is that the hole you want to put the insert in is not a through hole. That is going to make tapping the thread for the insert difficult/impossible unless you have the correct plug tap for the job.

could you elaborate on what you mean by correct tools ?

I had to cut the top as it had extra two helicol threads. what would you do in situation that you have to use 1 and half helicoil insert.

but even after removing it and inserting the the m12 nipple, it bites and soon release which seems like a guide problem

Gloomendoom

You can get brake nipple repair kits with all the tools you need...

http://www.fraserbrowneng.co.uk/store/index.php?route=product/product&product_id=51

You might need to check clearances though. The repaired nipple may interfere with the wheel.

Joe_Horner

stranger12 wrote: »

The helicoil seems cheap to believe it can hold the nipple in place under few hundred if not thousand PSI.

A properly helicoiled thread will be stronger than a thread of the same size cut straight into the alloy body.

Besides which the pressure may be high but the actual forces involved are surprisingly low:

If we assume that the bleed passage in the caliper where the tip of the bleed nipple seals is 2mm (about 0.08 inches) diameter, then the area in square inches that the pressure is acting on is given by 3.1416 x (0.04^2). That's an area of about 0.005 square inches.

Under full-on emergency braking you might manage a pressure of 2000 psi in the system. But that 2000 PSI, acting on an area of 0.005 square inches, will only give a force of 10lbs (4.5Kg) trying to push the nipple out. That's just over the weight of 4 bags of sugar which you could practically hold in with duct tape!

takman

Joe_Horner wrote: »

Yes really, although on aircraft they're about 50 million times the price because they're certified for flight.

No they aren't they are pennies each and don't need any kind of extra flight certification compared to a consumer helicoil.