Overdrill, fill, and tap

[David VanDenburgh]

I'm attempting to secure hardware to the deck for the leading edge of my dodger. I have overdrilled and filled the holes with epoxy twice now and both times I've tapped the holes for the 6-32 machine screws there's been hardly any bite to the epoxy; the screws strip it right out with only moderate pressure. I know this has been done routinely by some of you here. What am I missing?

Is it best to use straight epoxy or a mixture? If a mixture, what additive is recommended?

Thanks!

David

[Tim]

I always use epoxy thickened with cabosil. This makes a strong structural mix that ought to hold a screw thread when properly cured.

[David VanDenburgh]

Pardon my ignorance, but is it correct that West System's colloidal silica is the same as cabosil?

David

[David]

I use West System high density 404 filler and let it cure for about a week to gain full hardness before taping the holes. They are impossible to strip out when done correctly. Are you using the right size bit and tap?

David

[David VanDenburgh]

I use West System high density 404 filler and let it cure for about a week to gain full hardness before taping the holes. They are impossible to strip out when done correctly. Are you using the right size bit and tap?

David

If a whole week is required to gain full hardness, then that might be the source of my problem. I only let the epoxy cure for a couple of days - approx. 48 hours. I did park an oil-filled electric heater under the part (the sea hood) on low heat to facilitate curing, though. I'll try it again and allow more time.

By the way, yes, I'm using the right size bit and tap.

Thanks for the response.

David

[Tim]

Pardon my ignorance, but is it correct that West System's colloidal silica is the same as cabosil?

David

Yes. Cabosil=colloidal silica. It's also variably known as aerosil or fumed silica. All the same thing.