Stop these carriage bolts from spinning when I tighten nuts

[DaveC426913]

TL;DR

Clearly I am installing them wrong. I thought they would bind on the wood. They just spin.

I need to bolt 2x6's down to the lip in my new pool. The pool lip is metal, about 4" wide and has holes for bolts to go through.

I have 2 1/2" long 3/8ths carriage bolts and nylon lock nuts (because that's all they had!)

Picture this, but 2 1/2" long:

I drilled 1/2" holes through the lumber (because the next smaller size would have been 3/8" and I was pretty sure the 3/8" bolts would bind in the wet wood). I also drilled very shallow (1/8") countersinks so the carriage bolt heads will sit flush.

Problem:
When I try to wrench the lock nuts on, they provide enough grab that the carriage bolts just spin.

Questions:

1. Will switching out the nylock nuts for regular nuts sufficiently mitigate the problem?
2. Should I get some of these a] in addition?, b] instead?
   
   
3. Should I have drilled 3/8" holes instead of 1/2" holes? (I tried jamming some wood shims into the hole to bind the bolt but that failed completely.)
4. Is any of this going to survive being 3" from a swimming pool? Do they come in stainless steel?

 

[Baluncore]

1. The oversize hole means the square shank does not grip sufficiently for Nylock. Use normal nuts. Put super-glue under the bolt head when you assemble it.

2. Not needed if you use normal nuts.

3. The bolts are designed for use in holes of their shank diameter, with normal nuts.

4. Yes, it comes in stainless steel, type 316 for marine applications.
If you have a chlorine environment, you must use 316, and must protect wood with a marine paint.

 

[DaveE]

Don't oversize the through hole. You may have to seat the bolt with a hammer. Also don't countersink, use a counterbore if desired. The square section of the shaft must be able to dig into the wood at the top of the hole.

 

[DaveC426913]

3. The bolts are designed for use in holes of their shank diameter, with normal nuts.

I only drilled out one board. It would not be too late to replace it with a new board and drill 3/8" holes, if that's for the best.

4. Yes, it comes in stainless steel, type 316 for marine applications.
If you have a chlorine environment, you must use 316,

I will do that. Not sure if I can get those at a regular hardware store. Maybe I should visit a marine chandlery.

and must protect wood with a marine paint.

Hm. Are pool decks usually painted? I did not think they were.

I built a (cedar) deck all around my above-ground pool. Ner paitned or stained it. Lasted 20-25 years before start to disintegrate.

I'm using pressure-treated wood this time (or plan to). I just found out that you can't paint PT unless it's had its treatment washed/sanded off. Maybe I should switch to cedar before I get too far.

 

[DaveE]

I just found out that you can't paint PT unless it's had its treatment washed/sanded off.

I think you can paint it with a high quality primer if it's dry and clean. However, when I get PT wood, it's always still quite wet.

 

[DaveC426913]

I think you can paint it with a high quality primer if it's dry and clean. However, when I get PT wood, it's always still quite wet.

Yeah. They said a couple of months.

 

[hutchphd]

Is pressure treated recommended for pool decks? I guess the newer stuff is more benign. How about the plastic resin decking systems?

 

[Baluncore]

These days, coach bolt threads are not cut, they are rolled, so the thread outer diameter is greater than the shank, and smooth. I prefer to drill undersize, to fit the shank, then grease and hammer the thread through the hole in the timber. The metal thread is not damaged, and the wood fibres will spring back against the shank.

Always consider lubricating nails and screws before use. Spraying a little WD40 into a box of fasteners, makes it easier to do the assembly.

 

[Rive]

TL;DR Summary: Clearly I am installing them wrong. I thought they would bind on the wood. They just spin.

I have 2 1/2" long 3/8ths carriage bolts

Yep. As far as I know these bolts are more about locking metal parts (with square holes) to wood.
It may work for some hard woods but I would not hold my breath for that. Never worked properly for me (I'm mostly working with soft wood).

Should I get some of these a] in addition?

Yep, this may work. Alternatively, you may look up 'fanged bolt'.

 

[DaveC426913]

Is pressure treated recommended for pool decks? I guess the newer stuff is more benign.

This is as I understand it. I believe they're stopped using arsenic. But I do not have a reliable infomation source.

How about the plastic resin decking systems?

Perhaps.

 

[jrmichler]

Not sure if I can get those at a regular hardware store. Maybe I should visit a marine chandlery.

McMaster-Carr has everything, including 316SS carriage bolts: https://www.mcmaster.com/products/b...6-stainless-steel-square-neck-carriage-bolts/. Price $10.51 USD per pack of 5.

I have ordered from them several times, with good experience every time. From their web site:
We offer standard next day delivery to most businesses in Canada. In addition, our standard delivery covers all duties and tariffs.
We also deliver to businesses across Europe, Asia, Africa, Mexico, Central America, South America, the Caribbean, and Oceania. Our partner carriers like DHL can usually deliver in 2-4 days. We are also happy to use your preferred shipping provider.

This is "the" source for most any small mechanical thingy you ever heard of, and a good place to find stuff that you did not know existed. It's a standard resource for mechanical engineers and tinkerers.

 

[DaveC426913]

McMaster-Carr has everything, including 316SS carriage bolts: https://www.mcmaster.com/products/b...6-stainless-steel-square-neck-carriage-bolts/. Price $10.51 USD per pack of 5.

Thanks. This is the kind of thing I am leary of ordering online because I don't really know what I'm going to get if I can't see it and touch it.

For example, if I simply want to order some standard carriage bolts, why is it asking me to pick ... whatever that dropdown is.

What am I getting? "Models"? Wait, can I buy 2-dimensional carriage bolts?? Do they come in an envelope instead of a box? Can I assume shipping weight is "zero"?

I know those are CAD formats. What I don't know is why I am picking them while in the midst of ordering the real thing.

I thought for a minute that it was going to 3-D print my parts for me, and I got to choose what file format the print file would be.

OK, I see. A CAD diagram is a way of checking the product's physical specs that's better than a photo.

Wild ride, this.

 

[jrmichler]

The local hardware store only has 1/4" stainless carriage bolts up to 4" long, and I needed some 4.5" long. I ordered them from McMaster-Carr last night (Saturday), and got an email with tracking number this morning that they were shipped with expected delivery Tuesday.

Designers working with SolidWorks software really like McMaster-Carr. Click on that Download button, and the exact part is loaded directly into the assembly.