Heavy fixing with large head, only 30mm deep.

[xLnT]

Hello,
I am going to attach a 50kg item to 28mm thick wood (don't want it to go through). I was planning to use 4 pieces of 6x30 big dog screws, but they don't seem to be manufactured in shorter than 40mm.
I don't want to use a coach screw, is there a suitable screw with a large head to use?

Or should I just use the thickest 30mm long screw I can find and use a washer?

 

[jonaserik]

28 mm timber is I believe only available up to 145 mm, and there's not much to fasten just screw/bolt in that doesn't go through. What is the width of the 28? And where is it attached, is it spaced paneling or what?

 

[xLnT]

28 mm lumber, I think, only comes up to 145 mm and it's not much to attach just screws/bolts into without going through. What width is the 28? And where is it attached, is it sparse paneling or what?

It's several 28x120 (decking) mounted above each other as a fence. I'm thinking that 4-6 screws on an area of 50x30cm should handle the attachment without going through.

 

[jonaserik]

There are several 28x120 (decking) mounted above each other as a fence.
I think 4-6 screws on an area of 50x30cm should handle the attachment without going through.

So it's a few double 28s, 2 X 28 is 54 mm, then it might work if screws/bolts go through all. You should pre-drill with about 2mm smaller holes than the core of the screw/bolt to prevent the wood from cracking, which normally happens when driving them directly in. Spit on them first before driving them in, a bit of lube doesn't hurt.

 

[xLnT]

So there are some double 28s, 2 X 28 are 54 mm, then it might work if screws/bolts go through all. You should pre-drill with about a 2mm smaller hole than the core of the screw/bolt, so the wood won't crack, which normally happens when driving them straight in. Spit on them first before driving them in; a little lubrication doesn't hurt.

No, not double, single on top of each other on edge.

 

[jonaserik]

No, not double, single stacked vertically.

Vertically, then you're out of luck. You can't get a good grip between them in a proper way; it's not homogeneous wood you're attaching to. You'll have to rethink how to assemble it. Perhaps by attaching a board 28 X ? 120, or as wide as you need, underneath them and screw in with many screws, then attach your items from below right in the joint. But you must hit the upper ones at least in the middle. You must pre-drill so the wood doesn't crack. It's also good to drill a few extra holes in the bracket for more screws.

 

[xLnT]

On edge, then you're screwed. You can't get a proper grip between them; it's not homogeneous timber you're attaching to. You'll have to rethink how to assemble it. Maybe by placing a board 28 X ? 120, or as wide as you need, underneath them and screwing with many screws, then attach your items from underneath in the middle of the joint. But you must hit the upper ones at least in the middle. You must pre-drill to avoid the wood splitting. Preferably, drill some extra holes in the bracket for more screws,

I have trouble understanding what you mean; I'm not sure you understand me. I have 2pcs 95x95 posts vertically down into the ground (cc1200). Then I have screwed several 28x120 boards from below and upwards. Do you mean that it wouldn't be possible to attach something weighing 50Kg to this construction without through-mounting and 4-6 attachment points?

 

[Johan Gunverth]

You might be able to use stainless rampamuff and any bolt for this? If you install the rampamuffs correctly, they will definitely hold much more than 50 kg.

 

[jonaserik]

I'm having trouble understanding what you mean, not sure you understand me.
I have two 95x95 posts vertically down into the ground (cc1200). Then I've screwed several 28x120 boards from the bottom up.
Do you mean it wouldn't be possible to attach something weighing 50Kg to this structure without through-bolting and 4-6 attachment points?

OK, a little misunderstanding on my part then. I was thinking more like it was on the ceiling. If it's posts, the pull will be straight down, then it can hold well as you think. The shear force will load downward and it would take a lot for it not to hold. What's important then is that there is no bending at the attachment point, but that the pressure runs in line with the post from top to bottom.

 

[xLnT]

Ended up using stainless wood screws (hex head) 6x30mm with an 18mm washer, so I'll have to pre-drill a bit and then secure it. It should hold.

 

[RoAd]

You might be able to use stainless steel rampamuff and any bolt for this? If you install the rampamuffs correctly, they will definitely hold much more than 50 kg.

This!

 

[xLnT]

Why do you consider rampamuff a better alternative than above?
A rampamuff is more suitable for entirely different purposes, such as very hard types of wood, or when you need to screw in/out the screw very frequently.

 

[RoAd]

Why do you think a rampamuff is a better option than above?
A rampamuff is more suited for entirely different purposes, such as very hard types of wood, or when you need to screw in/out the screw very often.

In your case, they provide a good ratio of diameter vs length. The increased diameter allows it to "bite" better into the wood. A model intended for M12 can be driven to the depth you have. They hold firmly. I've used them in everything from Cumaro to Furu.

Your solution will of course also hold.

 

[Johan Gunverth]

Why do you think rampamuff is a better option than the above?
A rampamuff is better suited for completely different purposes, such as very hard woods, or when you need to screw in/out the screw very often.

It was one of the suggestions for you when you couldn't find suitable fastening. Rampamuff is used in many places where parts are only joined in an assembly. Even just once, for example, in some furniture. The thing with rampamuff is that it has two different pitches so that the inner has lower friction when tightening and the outer (usually) stays in place. You might need to glue the outer thread, especially with stainless steel sleeves.

Now you solved it when you found another fastening, so the “problem” is out of the way for this time.