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Old 11-24-2009, 07:39 PM
cn90 cn90 is offline
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Location: Omaha NE
Join Date: Mar 2006
Posts: 14,352
Mein Auto: 1998 528i 5-sp 140K+

- I need to add this important addendum. If you deal with nuts and bolts and know the “science” behind it, stop reading. If you don’t, then you may want to Google how nuts and bolts work, and the bolt sizes (SAE vs Metric), Thread Pitch Spacing etc.

- For ex, if the bolt is M7 x 1.0, this means the diameter of the bolt is 7 mm and the distance between the threads is 1 mm.

To make it easy for you:

- If the hole is 6mm, then use M7 bolt (M7 = diameter of the bolt measured at the peaks of the threads)

- If you mess it up during the first time, then drill the hole to the next size which is 7 mm, then use M8 bolts. Be careful to put masking tape on the drill bit so you stop at 5 mm depth or so to prevent drilling right through.

- For most Tap and Die sets: the Tap has almost no effect during its first 3-4 mm. The very tip of the Tap is usually tapered a bit with almost no effect on making threads at all. So a Tap is basically useless here because the blind hole is very shallow (5 mm deep).

- Use some oil to help when making threads

- When making threads, make one (1) turn then back off to remove debris because you are threading with a bolt and not a tap.

- After the washer is in with RTV Gasket Material, use Toothpick to measure depth of the hole up to the washer. If you decide to use longer bolt such as 12 mm long then use 1-2 more washers. Whatever you do, the bolt should go into the hole for about 4 mm or so.

- You should have about 1.0-1.5 mm of RTV Gasket Material between the Washer and Housing. And best is to apply the washer and gently squeeze it down until you have about 1.0-1.5 mm of RTV Gasket Material, then let it sit for about 2-3h, then tighten with the bolt.

- Again, use 1/4” ratchet and when the bolt stops, just tug it with 2 fingers and that is it. No need for force here.
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