Author Topic: Which Screws Won't Cause Bleed through on Wood Filler For Bookcase  (Read 11088 times)

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Offline MarkF

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #25 on: September 07, 2023, 02:40:50 am »
No screws.

Dado slots and wood glue.
I've built many bookcases and tables.  They are basically made of 3/4" boards (some with plywood tops in my workshop).
It's all joinery and glue.  The glue holds it together.  Not the screws.

I have 4 bookcases and 3 tables that are over 20 years old without any issues.  I used a few brads and clamps to hold them together while the glue dries.  The one table has a heavy band-saw sitting on it and none of the joints have come apart in all these years.

You should not be relying on screws or nails to hold your woodwork together.
 
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Offline jpanhalt

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #26 on: September 07, 2023, 10:19:49 am »
I agree on the dado (or cleat).  A quick search revealed some opinions (stackexchange):

https://woodworking.stackexchange.com/questions/10995/nails-plus-glue-into-endgrain-vs-screws-plus-glue-vs-dado-for-shelf
https://woodworking.stackexchange.com/questions/7898/endgrain-screw-withdrawal-force

Pocket screws in the shelf bottoms might be an option that would not require any filler.  A small dado (1/4" deep or less), glue, and pocket screws for fixturing should be quite strong.  I suspect a shallow dado with your end-grain screws would allow easier alignment than simply using end-grain screws in a butt joint.  Dados are made on a presumably square machine, while end-grain screwing would depend on proper drilling of a pilot hole and carefully driving the screw perpendicular or robust clamping.

I have used poplar mostly for patterns and not for finished pieces.  (One exception was the bottom rail on a garage door that was 2" thick.)  Does 3/4"  poplar cup as badly as softer woods?  If cupping is anticipated, dados or cleats would provide better resistance.
 

Online David Hess

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #27 on: September 09, 2023, 02:14:10 am »
No screws.

...

It's all joinery and glue.  The glue holds it together.  Not the screws.

...

You should not be relying on screws or nails to hold your woodwork together.

Good glued joints are stronger than the wood.

I recently repaired an old hardwood desk which was coming apart after rough handling during a move.  The only structural nail joints were in sheer, but it had that old dark brown glue (hide glue?) for the rest and it had completely failed.  I replaced the nails with GRK finishing screws and clamped the whole thing together with Tightbond after cleaning the joints with water and sandpaper.
 

Offline CatalinaWOW

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #28 on: September 09, 2023, 03:21:47 am »
I'll pile on for dado joints with glue, with screws just to hold things together while it dries.  The screws aren't absolutely necessary, but they are far cheaper than buying enough clamps to do the job, and make the project ready for the next assembly step immediately.

I have never had a problem with screws staining the wood in an indoor environment, but it is quite common in outdoor environments. If you live in a highly humid location and the environment for the shelves is not conditioned it is conceivable that the screws will do some staining.  Brass generally doesn't, same with stainless steel.  The coated construction screws are resistant to staining, but given enough moisture and minor dings to the coating during transportation and installation they aren't absolutely stainproof.  Dry wall screws are among the worst for staining, and I have even seen stains from the moisture in paint on rare occasions.

The old hide glues do fail after enough time, moisture and rough handling.  I think the modern glues hold up better, but don't really have any experience with 50 or more year old joints with the new glues which is about as young as any hide glue joint is going to be.  I do have experience with them up to 40 years and if not used in wet locations they do fine.  But I suspect 50 years will satisfy your needs.  Some of the new glues are rated for outdoor use, but can report that they don't hold up to extreme wet environments.
 

Offline T3sl4co1l

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #29 on: September 09, 2023, 04:35:41 am »
Good glued joints are stronger than the wood.

I recently repaired an old hardwood desk which was coming apart after rough handling during a move.  The only structural nail joints were in sheer, but it had that old dark brown glue (hide glue?) for the rest and it had completely failed.  I replaced the nails with GRK finishing screws and clamped the whole thing together with Tightbond after cleaning the joints with water and sandpaper.

Mattias Wendel recently (well, maybe it's closer to last year by now; or previous years for that matter!?) did a whole bunch of measurements on various styles of joints (butt, lap, tenon, box, pinned, screwed, etc.), including several glues, and found comparable results.  Mind, not all the joints failed at the wood rather than the glue -- most did fail at the glue, and this was relatively soft material (white pine) I think?? (or maybe it was including maple as well, I forget; look up the videos, they're great!*), but it's close enough that you don't really mind.

Or if you don't mind utterly overkilling it, there's always epoxy. :^)

*I can think of, basically just a few complaints with methodology/analysis, IIRC; which leaves quite a lot of useful results and conclusions.

Tim
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Offline bostonmanTopic starter

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #30 on: September 12, 2023, 02:22:14 am »
I meant to ask, did anyone understand the stress analysis I posted in Reply #12?

Someone did that for me a while back. It shows how the wood will bend based on varying the location of the threaded rods. Unfortunately the mechanical engineer performed the analysis for me, but then he left and I left.

I understand the visual, but I don't grasp which location is the "ideal" distance between rods.
 

Offline T3sl4co1l

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #31 on: September 12, 2023, 03:11:19 am »
You mean this? https://www.eevblog.com/forum/mechanical-engineering/which-screws-are-safe-for-building-a-bookcase/?action=dlattach;attach=1866340

Well, the displacement decreases as separation decreases, but I don't see what loading is. Or, is it just the arrows? What about weight on the ends, or in front / behind the mounts?

The poles will tilt/twist a bit too, and it's not clear if those were modeled as rigid points, or material with some flex itself.  For sure they will not hold the support points level.

Flex is easy enough to understand from moments.  The further away a force is applied from a support point, the greater its torque against the support.  For a given load anywhere on a uniform beam with two support points, the ideal positions are 1/4 and 3/4 since any point is at most 1/4 the beam length away from a support.

Exact values change whether the mounts are rigid, when higher dimensions are included (i.e. the shelf is a sheet moreso than a beam), etc., but that's a quick starter.

Tim
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Offline CatalinaWOW

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #32 on: September 12, 2023, 05:20:17 am »
You mean this? https://www.eevblog.com/forum/mechanical-engineering/which-screws-are-safe-for-building-a-bookcase/?action=dlattach;attach=1866340

Well, the displacement decreases as separation decreases, but I don't see what loading is. Or, is it just the arrows? What about weight on the ends, or in front / behind the mounts?

The poles will tilt/twist a bit too, and it's not clear if those were modeled as rigid points, or material with some flex itself.  For sure they will not hold the support points level.

Flex is easy enough to understand from moments.  The further away a force is applied from a support point, the greater its torque against the support.  For a given load anywhere on a uniform beam with two support points, the ideal positions are 1/4 and 3/4 since any point is at most 1/4 the beam length away from a support.

Exact values change whether the mounts are rigid, when higher dimensions are included (i.e. the shelf is a sheet moreso than a beam), etc., but that's a quick starter.

Tim

I know you know this Tim, but to clarify for others, the 1/4 and 3/4 positions are ideal for a uniformly loaded beam.  And it isn't a bad approximation for a bookshelf since books are somewhat uniform in weight.  But if you have ten copies of the CRC Handbook of Chemistry and Physics, it would be worthwhile to spread them out along the shelf.

The usual practical approach to all this is to make the shelf much stiffer and stronger than is absolutely necessary per the structural analysis.  That way the accuracy of the assumptions about loading, joints and material properties of the shelf are not critical.  It also allows you to put the support rods where the house structure demands and even adjust them for practical reasons.  For example it is convenient to have the rods at the end of the shelves where they can double as bookends, and where they don't interrupt putting books on the shelf.  Not ideal structurally, but these shelves aren't being launched into space so a little extra beef isn't the end of the world.

If you look at the equations for beam deflection it is immediately obvious why adding a lip on the shelf is such a powerful way to improve shelf performance.  Even greater results come from putting a back (even of something really weak like pressboard) across the back of the shelves.  It has the added benefit of keeping books from being pushed off the back.  May not satisfy the aesthetic goals, but that is where the engineer and artist in your soul have to do battle to come up with a final solution.  A compromise that some find appealing is a tensioning cable under the shelf, combined with a riser similar to the bridge on a stringed instrument.
 

Offline bostonmanTopic starter

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #33 on: September 12, 2023, 03:50:21 pm »
Without a vertical beam of some sort down the middle of all the shelves, I'd assume nothing is going to keep the shelves from bending.

The analysis the guy did (I believe) is based on a load, and believe he was using 500lbs as a "safe" assumption (not including wood weight).

The analysis is helpful, but I didn't see which rod spacing was ideal. All the analysis showed was deflection at different points for rod distancing.

Without looking, from what I remember, I have approximately 240lbs of books (some are thick text books like physics, calculus, etc... and others are much smaller). The weight of the Poplar wood I haven't done yet, but it will be 1-1/16" thick wood, 48" wide shelves, slightly under 12" spacing between shelves, 11-1/4" depth, six shelves (including the one across the top that will be against the ceiling), and the two sides.

I'm over estimating at the moment, and saying the weight of wood for each shelf is 50lbs (totaling 300lbs), and each side is 100lbs, so wood weight total is 500lbs. Add that to my current books and that's 740lbs.

He did a calculation for me and I think 5/16" stainless steel threaded rod (one on each side) would hold triple that after even after using 50% reliability number from the maximum 70,000psi load that the rod specification has.

My personal preference is to go with 3/8" (or even maybe 7/16") rod, and, from what I can estimate on the load stress analysis, place the rods 12" from the sides for the best deflection reduction. The sides have a dado, so the shelves won't tilt forward to back, and shelf bending is just the nature of anything horizontal.

 

Offline T3sl4co1l

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #34 on: September 13, 2023, 05:13:17 am »
Without a vertical beam of some sort down the middle of all the shelves, I'd assume nothing is going to keep the shelves from bending.

Well it will ALWAYS bend -- as it must.  You can only reduce the bending arbitrarily; well, not even arbitrarily, really, because even if you make it out of carbide, or diamond, I mean, you can't go up from there, once it's solid material of the highest modulus, that's all you can do, no matter the price.

But needless to say, in practical terms, using stiffer materials (steel > aluminum > wood > plastic) and stiffer designs (solid plate of given thickness vs. ribbed/trussed beams of given height vs. plate of much less height) gets deflection down to reasonable values (say, imperceptible deflection; <0.1% would be alright).


The ratios of stiffness dictate how much load is shared between shelf and pole, and also of course load distribution and shelf shape.  I get the feeling, steel rod isn't quite stiff enough to break at any achievable strain rate versus that kind of load, with panels that thick, but thicker obviously will hold more.  Yeah, 5/16 or 3/8 feels about right.

Note that it needs to transfer that load /somewhere/; if you have a big fat beam across the top, that'll do something.  Otherwise it's just chaining shelves together (I guess??) which doesn't mean anything if all are evenly loaded.  And the value proposition is then, saving on shelf thickness, trading it for that beam instead.  If you're just doing shelves and nothing else, the rod only does something when some shelves aren't loaded.

Or if it's at an angle to transfer load to the sides, that would be something, but not very convenient for actually using the shelves obviously. :P

Tim
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Offline MarkF

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #35 on: September 13, 2023, 05:36:36 am »
The bookcases I've made are out of 1"x12" pine boards and a width between 30" to 36".
There is also a 1/4" plywood back which is glued to the sides and each shelf.
Also, the shelves are spaced approx 14" in height.

If the shelves are movable, you will of course need a wood strip (1.5" to 2" wide) glued to the front and back edges of each to keep them from bending.



I have not had any problems with the shelves sagging/bending.  I don't see any need for metal rods.
I also have some half height bookcases (made the same way that are 4 ft wide).  Each shelf is completely filled with magazines.  There are no bending problems but I would not recommend making 4 ft wide bookcases.
« Last Edit: September 13, 2023, 05:45:48 am by MarkF »
 

Offline bostonmanTopic starter

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #36 on: September 13, 2023, 12:09:11 pm »
The rods (as mentioned) are to suspend the bookcase.

I plan to place a beam across my attic joists and suspend the bookcase with the threaded rod.

Per my original post, I believe stainless screws are the best option to avoid bleeding through the wood filler. I looked into pegs to cover the screw holes on the side of the bookcase, but the grain and color doesn't match the stuff I have. Some of the Poplar I have has dark grains and some light green I believe. In any case, I think the original post can be considered closed because going with deck screws may cause the chemicals to bleed whereas stainless steel screws are the best option.

As for threaded rod displacement, does the 12" from that analysis document look correct? I'm uncertain what the document is telling me except how the shelves bend based on rod positioning, but looked liked 12" from the sides was the best choice.
 

Offline PlainName

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #37 on: September 13, 2023, 01:08:49 pm »
Quote
The rods (as mentioned) are to suspend the bookcase.

I plan to place a beam across my attic joists and suspend the bookcase with the threaded rod.

Ah! That's a very different thing to what everyone is imagining. Could be quite cool :)

In that case I would go for the horizontal strip for strengthening. It would usually go underneath at the back,  but in your case I think it would be dual-purpose to have it on the top side - it will stop (or vastly reduce) the shelves bending and also prevent the books falling off the back. Use the support rods as bookends.
 

Offline bostonmanTopic starter

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #38 on: September 13, 2023, 02:47:48 pm »
Well, in my defense, this thread deviated quite a bit.

I'll admit, I didn't make the subject line read quite clearly as my question intended. It was meant to start off as questioning materials and chemicals of screw heads and whether using Deckmate (i.e. the yellow screws) would bleed through wood fill.

As with any project and engineers, many provided great feedback and alternatives. I further deviated by asking about rod positioning based on the analysis I attached.

Before I drill holes in the shelves (plans are to do so this weekend), I want to understand the best location. So far I think the 12" from the analysis is the best, but I'm somewhat guessing on the deflection based on looking at the physical bending photos of each different location.

As for screws, as I've mentioned, I think stainless steel (the screws to hold the shelves in the dados onto the sides of the bookcase, not the vertical threaded rod going through each shelf - although that will be stainless steel too) are my best choice to avoid bleeding.

Just to elaborate, the three things I'm confirming: stainless steel screws for the bookcase sides are my best choice, 5/16" stainless steel threaded rod (one on each side) will be an adequate diameter to hold (over estimating) 1200lbs total weight including wood (although I may actually go with 3/8" threaded rod or possibly 7/16"), and is 12" from each side the best deflection point to drill holes for the threaded rode?
 

Online Ian.M

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #39 on: September 13, 2023, 03:30:25 pm »
Stainless threaded parts are extremely high risk for galling.  There's no way I would risk running multiple stainless nuts an average of half the length of a couple of yards of stainless allthread.  It only takes ONE seized nut while getting them into rough position to wreck the rod so badly you'll have to cut it up to remove it, and start over.

You've got three alternatives here - bronze nuts wont gall on a stainless thread, or turn the thread off the rod in a lathe, except for 1" below each shelf position, and use plenty of copper antiseize to reduce the risk of galling when spinning the nuts over each 1" threaded section.  Of course  that has its own problems around woodwork - cleanup wont be fun!  The third alternative is *NOT* to use stainless.  Galling of bright zinc plated steel nuts and allthread is minimal if kept lubricated during assembly. However, you've then got to keep it dry or you will have a high risk of rust staining.
« Last Edit: September 13, 2023, 03:51:30 pm by Ian.M »
 

Offline jpanhalt

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #40 on: September 13, 2023, 03:39:55 pm »
How do you plan to attach the threaded rod to the cable? 

Amazon has stainless lifting eyebolts with female threads (attached).  Those in the picture are 8mm and 10mm.  I suspect SAE threads in the 3/8" size will be easier to find than smaller ones.  I suggest swagged loops for the cable, but I have seen some that clamp the cable.  Metric threaded rod from Zoro is reasonably priced.  I just got some about a month ago.

EDIT: Stainless is probably not needed.  Black iron is pretty popular for home interior use.
« Last Edit: September 13, 2023, 03:42:39 pm by jpanhalt »
 

Offline T3sl4co1l

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #41 on: September 13, 2023, 04:44:42 pm »
Ahh, rafters, that explains that.

Yeah, you might want to use galvanized rod instead of stainless; or galvanized nuts on it, perhaps.  The risk of that bleeding is less than the almost-certain bleeding of liberally-smeared anti-seize...

Note that you can always put in more rods, and probably should, unless you have some other means of controlling sway and twist.  Just two rods hanging down, say, even a few feet, sounds like a wobbly mess, especially when loaded.

Oh also, so the total load is carried on the rods, that explains that, and I would much prefer thicker rod in that case, maybe even a few 1/2" rods.

Mind that rafters don't carry much torsion, which will be front-to-back sway.  Maybe that's what the cables are for; I seem to have skimmed over their mention.  Diagonal bracing to nearby rafters would be more effective (variably cables go slack then twang, slightly better to avoid the nonlinearity), and that can be just ordinary angle iron or whatever.

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Offline bostonmanTopic starter

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #42 on: September 13, 2023, 05:56:42 pm »
No cables, not sure how that got brought up.

The beam across the attic joists will be laid across about four or five joists. These joists rest directly on the load bearing wall, so the weight is transferred to the basement columns.

I considered front to back and side-to-side sway, but will screw the bottom of the case into the wall. Not much force is needed, so two screws (one on each side) will be more than enough (I can always put more screws if needed).

This way the 2x4's in the wall will not have any load on them, they'll just hold the bookcase from swaying. All the vertical weight will be on the rod.

Attached are two rough drawings to (hopefully) clear any confusion.
 

Offline T3sl4co1l

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #43 on: September 13, 2023, 06:08:54 pm »
Ah, that solves twist too.  Probably make the wall anchor screws in slots so they don't try to bear weight, that should do it?

Tim
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Online wraper

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #44 on: September 13, 2023, 06:13:20 pm »
The only screws I have are the yellow Deckmate
Yellow screws are a better type of zinc plated. Basically the best corrosion resistant screws after stainless steel.
 

Online themadhippy

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #45 on: September 13, 2023, 06:14:57 pm »
instead of a beam have you considered  unistrut and  zebadees
 

Offline bostonmanTopic starter

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #46 on: September 13, 2023, 06:30:22 pm »
Quote
Probably make the wall anchor screws in slots so they don't try to bear weight, that should do it?

Exactly. If any expansion or sagging takes place, the screws in the wall will be safe.

Quote
instead of a beam have you considered  unistrut and  zebadees

I planned to use unistrut instead. It's a small detail, I posted the pictures JUST for a visual on what I'm talking about. Also, what is Zebadees?

Unfortunately I think this thread has gone off the deep end as I should have just asked whether Deckmate yellow screws will bleed through wood fill. Maybe I shoudln't have mentioned the bookcase portion of the project. :)
 

Online themadhippy

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #47 on: September 13, 2023, 07:05:47 pm »
Quote
Also, what is Zebadees?
What we call the spring nuts,after a popular 70's cartoon character

 

Offline djsb

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #48 on: September 13, 2023, 07:10:16 pm »
Are there any references that cover the traditional construction of bookcases and shelving for use in the home? The only thing that I've ever made is a pair of transmission line loudspeakers using 18mm thick MDF. I did a bit of in secondary school, but that was a LONG time ago. Thanks.
David
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Online Gyro

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Re: Which Screws Are Safe For Building a Bookcase
« Reply #49 on: September 13, 2023, 07:15:00 pm »
Quote
Also, what is Zebadees?
What we call the spring nuts,after a popular 70's cartoon character

Yay, The Magic Roundabout, bring back Dylan!  :D  (not forgetting Florence and Dougal obviously)
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https://en.wikipedia.org/wiki/The_Magic_Roundabout
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