3/4" Plywood / Drywall Screws Question

[Anonymous]

Thanks for the tips. Big Boy, thanks for the pics. Yes, the length of the shelf has a lot to do with the amount it sags (in fact, the sag is porpotional to the length cubed, as well as inversely porpotional to the thickness of the shelf cubed - which is why the reinforcement beams make such a big difference). This is why I made my shelves short, with a pretty beefy reinforcement beam.

Your shelves are holding some serious weight.

In any case, after spending a day in the garage, I can say my career of screwing wood screws into the ends of plywood has come to a close. Even with very large pilot holes (larger than I really wanted to use), I still split the wood, I'd say 1 in 5 or 6 times. That's way too much. These are industrial looking shelves, and the way I made them all the splits are hidden and not carrying load, but I know they're there!

I may experiment with driving some drywall screws into the ends of plywood just to see how those work - experimentation for future module construction.

I really like the idea of using 4x8 stock for everything - little material waste when choosing between 1 x 2, 1 x 4, 1 x 6, or a flat sheet - very cool. But, I'm also now convinced 3/4" thick plywood is way too thick for a module top for my tastes.

I may re-visit the lumber section of the local Lowe's to see how their 1x material is looking.

Something quite interesting to me is David Barrow complained about the straightness of 1x lumber, but used 2x2's for legs. I don't know about everyone else, but for me, finding a straight 2 x 2 is like finding a needle in a haystack.

Something interesting in terms of vibration of a structure: To have a very stable structure, Ideally you have a lot of mass at the base, and less and less mass towards the top of the structure. (you've never seen anyone knock over a pyramid, have you?).

This leads me to want beefy legs and a lightweight table top for my modules.

[jrbernier]

Drywall screws work fine with standard 1x4 lumber. Plywood is tougher stuff - I have made standard 1x4's from 3/4" plywood - Ripped by the local Home Depot. I need to 'pre drill' pilot holes in this stuff! The cost is cheaper than buying standard lumber, even with the current 'high' cost of plywood. I had a couple of sheets ripped up into 1x4 and 1x2's for .25/cut.

Jim

[dknelson]

Drywall screws have worked OK for me in my David Barrow influenced "domino" segments. Of course that method uses so many of them that perhaps the load bearing problem alluded to above does not really enter in, as no one screw carries a particularly heavy load. Nor have I had one rust at all.
In terms of screwing into the edge of plywood, I think it would not work with 3/4" plywood but I have done it with 5/8" plywood and it worked OK without pilot holes BUT it was 50 year old plywood that was salvaged from a house's floor boards and from a laundry chute. It was quickly evident that this was a quality of plywood which is hard if not impossible to obtain at the lumber yard any more. For one thing it is dead flat!
I was using the plywood to make a bench following a Jim Hediger idea -- making the legs from two 4" strips of ripped plywood made into an L shape for corners. It worked well and is very strong but I am not using it for the layout.
Dave Nelson

[Big_Boy_4005]

You are welcome for the tips, that's what the forum's for.

I too hate it when shelves sag. My library sits on shelves that I bought from a local furniture store.



Originally the shelves had their front support attached with some kind of heat activated glue. Under the weight of the magazines that glue failed. I ultimately reglued and nailed those pieces, and have never had a problem since (10 years).



Shelf length is a big factor in how much reinforcement you will need. My shelves are 3 feet long. An oak 1x2 was used on the shelf fronts. It is both decorative and structural.

As far as the dado idea goes, it can be done with multiple passes of a standard blade. There are specialty dado blade sets that can do the job in one pass, but the router may be the best tool for the job. It too can do it in a single pass, but if you change bits, you can do a wide variety of different operations.

There is a system of particle board based shelves, that most home improvement stores carry. The actual shelves would need some reinforcement, but the side pieces are totally adjustable with the predrilled holes and pegs.




Thanks for the compliment on the benchwork. It is a little rougher in person, but it gets the job done, and it holds my 325 pounds in those locations where I need to climb on it.

[Anonymous]

You have gotten me thinking about the screw/glue combo. I may just screw them together. Then my shelves are "semi-adjustable". Since they're sort of "industrial grade" shelves, I don't mind unsightly screwheads too much if it will allow me to adjust the shelves at a later time.

[Anonymous]

Big Boy,

Thanks for the tips.

I should have mentioned the shelves are going in the closet.

Every book shelf I've ever bought has sagged, and frankly, I'm fed up with it. So I'm going for some home-grown rediculously strong bookshelves that will hold binders, old textbooks, you name it.

Thanks for the Dado cut tips. I may have to pick up the tooling for that (I'm guessing a blade of some sort?) for future projects where I'm trying to make things look nice.

Nice looking benchwork there!!!

[Big_Boy_4005]

CARRfan, once you start using glue, you are partially replacing the need for fasteners. A screw is actually sort of a clamp. Nails, especially the longer pneumatic fini***ype are often sufficient to hold the pieces in place while the glue dries.

For the book shelves, if you don't want adjustable shelves, you might want to consider dadoing the sides to accept the shelf ends. Then a little glue and some finish nails will give you a very strong and good looking result. A dado can be cut with a table saw, radial arm saw, or a router.

I do a fair amount of wood working too. I don't mind working around some of the irregularities in dimensional lumber. I'm not to the point of replacing it with ripped plywood, because I plan to cover all of it with some other material.







I'm not so worried about the module contruction, that method should be fine. The bigger issue is the load requirement of the shelves.

[Anonymous]

Big Boy 4004, I understand the concerns about screwing into the ends of plywood. I feel comfortable giving it a try with pre-drilled holes. Didn't get to start the project last night, but it's going to happen today.

David Barrow recommended this in his MR modular layout series for putting modules together. He said it's hard to find straight dimensional lumber (I've had the same issue) and recommends ripping 1x4's out of 3/4" thick plywood.

The difference is he nails & glues them together, whereas I'll be pre-drilling, screwing and glueing.

The guy is an architect and is way into layout construction, so I figure his methods are probably pretty good.

I'll let everyone know how it goes.

[nedthomas]

Drywall screws being all thread make is difficult to pull two boards together. If the lumber is hard enough the thread in the top board prevents the screw from turning after the head seats. Screws called cabinet screws have threads only half way but in most applications still require a pilot hole. I have only been able to find them in 1 5/8" length. To long to screw two 3/4' boards together.

[CP5415]

I haven't had a problem with using drywall screws either.
I would not use MDF on a railroad but I have used it on shelving in a pantry I built in my kitchen. To prevent sagging, it is supported fully on 3 sides as well as about 6" on either side in the front.
As with building practices mentioned above, I pre-drilled each hole to prevent some nasty words being said.

Gordon

[Big_Boy_4005]

QUOTE: Originally posted by Mark300

Well....it's never a good idea to use drywall screws in any cabinet/carpentry making endeavor much less installing them into plywood ends.

Drywall screws are non-load bearing, unfinished and prone to rusting in any environment except in drywall.

Use deck screws or galvanized since they are structural and drill pilot holes in end conditons like plywood edges. Keyless chucks on drills make this easy.

Instead of plywood, consider using 3/4" MDF or similar composite if you must apply fasteners into the ends.

HTH

Happy Railroading,

Mark

I don't agree with much of what in being said in the above quote. I have been using drywall screws exclusively on my layout with zero trouble. Galvinized is totally unnecessary.

MDF is junk for model railroads, and worse for bookshelves. It will sag something awful.

As far as putting screws into the edge of any kind of sheet goods, bad practice. Take a piece of dimensional lumber, and use it as a cleat. When I need to create a butt joint between two pieces of plywood, I take a scrap piece of plywood, and screw and glue it under the joint.

In the case of the book shelves, the top and bottom would be stronger if cleats were used to make the connection. For intermediate shelves, why not use adjustable pegs?

For the modules, use simple frame construction with dimensional lumber, then just screw the plywood tops on.

[Anonymous]

I should have mentioned I'm using wood screws with pilot holes, not drywall screws.

Thanks for the tips guys!

[Texas Zepher]

QUOTE: Originally posted by Mark300
Well....it's never a good idea to use drywall screws in any cabinet/carpentry making endeavor much less installing them into plywood ends.

[#ditto]
I once bought a supposedly "fine" furnature bed & canopy set. When I got it home it had fast tapered dry wall screws for assembling. The pieces didn't fit right. I tried to take it back and they claimed I was assembling it wrong. I showed them on their floor model how nothing really lined up right (silly of me not to notice, but in the big show room it is easy not to see an upright is really 100% vertical). Bottom line is I added to my worldly wisdom that day, "If it (anything other than drywall) uses drywall screws it is cheap and junky".

[Anonymous]

Bought my lumber. Using 3/4" plywood.

2 drills in hand - one for drilling, one for screwing, no changing bits!

And I'm off to practice benchwork (disguised as making bookshelves).

Actually, I really need the bookshelves, but I'm planning on transferring my techniques directly to making modules in the near future.

One rule of home improvement is you must pick up a new cool power tool with every project. In this case, picked up a skillsaw to complement the table saw, as well as a square and some cool clamps.

Lovin life in the railroad construction room (uh, I mean garage).

[selector]

Strongly agree. Pilot holes are the way the pros would do it....cuz it saves headaches, re-cutting, waste, swearing in front of kids, etc. Pilot holes will cost you a grand total of 2 minutes and 30 seconds for the entire book case. So......?

[Mark300]

Well....it's never a good idea to use drywall screws in any cabinet/carpentry making endeavor much less installing them into plywood ends.

Drywall screws are non-load bearing, unfinished and prone to rusting in any environment except in drywall.

Use deck screws or galvanized since they are structural and drill pilot holes in end conditons like plywood edges. Keyless chucks on drills make this easy.

Instead of plywood, consider using 3/4" MDF or similar composite if you must apply fasteners into the ends.

HTH

Happy Railroading,

Mark

[Anonymous]

CARRfan,

Been ther done that. Tried the quick and lazy route, screwing plywood ends without pilot holes and it split the piece that was being screwed from the end real bad. So now I always take the extra few minutes to make the pilot holes. It's worth the hassle for the more solid construction.

Trevor[:)]

[Anonymous]

David Barrow nails his "dominoes" together. Is there less chace of delamination of the plywood with nails?

I really like the idea of using one stock material (3/4" plywood) for the entire module (or in this weekend's need: bookshelf) construction.

How about wood screws but using pilot holes? Still sloppy practice?

Here's what I have in mind: 100% 3/4" plywood:

This will require screwing from the shelves vertically down into the horizontal cross braces. Figured it would be ok with drywall screws.j

As you can see, none of the screws would be load-bearing. The loads are taken up by the horizontal beams.

Should I make the crossbraces out of oak or pine 1x material instead, or could I get away with pilot holes and wood screws in plywood?

[ARTHILL]

Good Advice. They make a special screw for this with a special drill bit, but the costs are prohibitive and only work fair. Dado is the way to hide the joint, blind dado the best. Cleat is easiest. The other issue with book shelves is sag. Plywood without a spine will sag after about 18". The spine can double as a front decoration that hides the plywood and covers the dado. That us what I tend to use. There is no need to get into these issues railroading.

[Blind Bruce]

Cacole is quite correct. Edge fastening is not recommended at all if weight, such as bookshelves, is concerned. A cleats of 1X2 fastened to the sides of the bookcase will support the shelves nicely with no fear of delaminating the plywood. You should glue the cleats as well. The preferred alternitive is a dado cut using a router or table saw.
BB

[cacole]

If you mean into the edge of the plywood, not without a pilot hole. The screw will pu***he plywood layers apart without a pilot hole, and the screws will not hold very securely.

[Anonymous]

Is it a good idea to screw into the ends of 3/4" plywood with drywall screws without drilling pilot holes?

If I need to drill pilot holes, I don't want to use drywall screws.

Using this info to build some bookshelves - but will use the same technique to build some modules soon.