Кстати, я тут задавал вопрос о восстановлении сорванной резьбы и мне посоветовали набор Helicoil.
Там идут метчики и втулки. Как вариант можно применить к созданиб новых отверстий.
Цитата:
For anyone who doesn't know, a Helicoil is a stainless steel helix with a diamond shaped profile. Both the inner and outer vees are exactly the same as the vee in a thread (FWIW in metric that is sixty degrees and 57 in imperial.)
The hole is drilled out to what is essentially the outer diameter of the original thread. Then a special non standard thread is tapped into the hole. It has the pitch of the thread being replaced but the diameter of the Helicoil.
A special tool winds them into place. They are fitted with a very strong Loctite thread lock compound so they don't come out again.
So your aluminium part gets a very hard wearing stainless steel thread. It can be better than a new part. Indeed this kind of refinement is part of what makes high end engineering more expensive.
If I changed pedals a lot in expensive alloy cranks I would consider fitting them before the first use. However it must be remembered that the larger hole also slightly weakens the part. If there isn't plenty of metal around the outside then it might not be a good solution.
In a used part note that the Helicoil would be compromised if the hole was already worn any larger than the diameter of the pedal thread at any point. Stripped threads in working alloy parts can wear to an oval very quickly. The part might not have yet come out but parts of the hole will already be worn beyond the outer diameter of the thread so the Helicoil results can be quite variable.
I have had a Helicoil kit for a very common spark plug thread for many years and have used it a number of times, especially on small motors on water pumps. Doing them on an engine without removing the head is an art, especially avoiding the swarf and snap off that engages with the fitting tool from falling into the cylinder.
Fitting them on a crank would be a cinch because you have access to both sides of the part.
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ТУТ.