Hole size

[BASS]

Greetings All, I am currently replacing all my deck fittings. Most of them are 8mm bolts. All the old holes have been filled. What size do you think the new holes should be? I am using Abormast BR to bed everything down on. 8mm + tap them home or bigger and apply more sealant?

 

[MoodySabre]

I'd use a 8mm hole and tap them in. The sealant is to keep the water out and won't provide any structural strength. A bigger hole would just give the bolts room to move about and cause trouble.

Well, that's what I'd do.

 

[sailorman]

fit / tap thead dry then blow-away swarth apply sealant

 

[BASS]

Thanks for the promt replies, forgot to say I am drilling through F/glass and backing pads of 18mm ply.

 

[stephenh]

A trick I learned somewhere -

Drill your 8mm hole and then chamfer the edge of the hole with say, a 12 or 15mm bit; you then end up with a good ring of sealant where it is most effective and it will not get squeezed out ....

 

[oldsaltoz]

G'day Berni,

When you say you have filled the old holes, does this mean they were filled and re drilled before, or have you filled holes that had raw material at the inside edges? If they had raw material inside and you have filled them, you may need to re drill out to 14 mm-fill-and re drill to 8mm and use a mix of resin and Micro Fibres, not balloons or standard bog; this material will take the compression load between deck and inner liner if fitted, foam, balsa or composite core construction.

As for backing plates I would not recommend ply, too soft and prone to failure if overloaded or rot should it get wet. 5mm stainless or 8mm aluminium with well rounded corners and both top and bottom edges rounded bedded on micro fibres will last for many many years.

For the correct bolt sizes, be guided by the hole size in the fittings, putting a larger hole may even weaken the fitting.

I hope this helps.

Avagoodweekend......