Screws vs. threaded inserts

[brendellajet]

For those of you that wrench/maintain your own boats, has anyone ever used a threaded insert in fiberglass or plywood? Typically I would through bolt, but in places where I have no choice I'm considering using a threaded insert (stainless) rather than just using a stainless screw, especially if it's for a service item that may be removed from time to time. Any opinions?

 

[rrrr]

I would use a pronged tee nut in plywood if there is access to the back of it.

A nutsert or rivet nut, as they're called, won't work. The fiberglass or plywood substrate is too soft for the insert to set.

 

[lbhsbz]

For those of you that wrench/maintain your own boats, has anyone ever used a threaded insert in fiberglass or plywood? Typically I would through bolt, but in places where I have no choice I'm considering using a threaded insert (stainless) rather than just using a stainless screw, especially if it's for a service item that may be removed from time to time. Any opinions?

A subject that touches my heart...

I fucking hate using a wrench on the backside of things, but I also hate sheet metal/wood screws. Since I have a lathe, I'll typically make my own TEE-nuts to fit the situation and epoxy them in place.

Depends what you're putting them into...check out McMaster Carr...they have a bunch of threaded inserts. If they don't have anything that will work for your situation...draw a quick napkin sketch of what you need and post it up. I'm bored most nights after the wife and kid go to bed, I'll make 'em for you.

 

[brendellajet]

A subject that touches my heart...

I fucking hate using a wrench on the backside of things, but I also hate sheet metal/wood screws. Since I have a lathe, I'll typically make my own TEE-nuts to fit the situation and epoxy them in place.

Depends what you're putting them into...check out McMaster Carr...they have a bunch of threaded inserts. If they don't have anything that will work for your situation...draw a quick napkin sketch of what you need and post it up. I'm bored most nights after the wife and kid go to bed, I'll make 'em for you.

These would go into solid glass or glass over ply. Pretty sure McMaster has what I need, just wanted to see what the consensus was.

Thanks for the offer, I spend a couple hours on the lathe at work each week.

 

[brendellajet]

I would use a pronged tee nut in plywood if there is access to the back of it.

A nutsert or rivet nut, as they're called, won't work. The fiberglass or plywood substrate is too soft for the insert to set.

Thanks, if I could use a T-nut I would. Back side is not accessible.

 

[Carlson-jet]

These would go into solid glass or glass over ply. Pretty sure McMaster has what I need, just wanted to see what the consensus was.

Thanks for the offer, I spend a couple hours on the lathe at work each week.

Go stainless and use dielectric grease.

If you want true corrosion resistance, Nothing beats titanium. "-)

 

[lbhsbz]

These would go into solid glass or glass over ply. Pretty sure McMaster has what I need, just wanted to see what the consensus was.

Thanks for the offer, I spend a couple hours on the lathe at work each week.

Depending on what you’re holding in place, loc-tite makes a thread restoration compound...2 tubes with a release agent. I would go this route before I used threaded inserts for low load fasteners.

 

[Spudsbud]

I would use a pronged tee nut in plywood if there is access to the back of it.

A nutsert or rivet nut, as they're called, won't work. The fiberglass or plywood substrate is too soft for the insert to set.

+1

 

[Racey]

You can just tap the glass, it's pretty f'n strong. If you want to really have a strong hold put a heli-coil in with loctite 680.

Wood/Sheetmetal screws should NEVER be used in glass. A machine screw is far superior.

 

[Rajobigguy]

https://www.mcmaster.com/stainless-steel-rivet-nuts
Works great in fiberglass, especially if you use a little epoxy on them before install.

 

[SFOcean]

I have used these in 3/4" plywood deck in my Avanti (from stringers to outboard chine in engine compartment).
Worked quite well, very strong compared to big stainless steel wood screws. The machine screw's ability to be removed multiple times without any strength degredation was my primary reason for the use of the inserts.