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Strength of 1 1/2 inch Red Oak Dowel Rod

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Forum topic by Sanding2day posted 04-14-2015 11:40 AM 3094 views 0 times favorited 18 replies Add to Favorites Watch
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Sanding2day

1001 posts in 1307 days


04-14-2015 11:40 AM

Topic tags/keywords: dowel strength oak dowel bar foot rest dowel joinery

My first project was that of my “shop bar” and it has long bothered me that I did not have a foot rest. It was my intent to purchase the typical brass bar but have not had the finances which I desired to devote to this and have made due to this point with a stack of my excess 2 by 4s under an old shower curtain rod…

I have recently finished a section of fencing and have an excess of 4 by 4s and a 3’ section of Red Oak Dowel and thought I would improve upon this Wont take much

My intent is to stain one up with the same Mahogany ish color as the bar, stain the dowel with Golden Oak, drill 2 inches into the base 4 by 4 and through the soon to be foot rest glued and wedged with Walnut in 3 places on the front and 2 place on one side.

Although I am confident this would provide adequate strength for a simple foot rest it is my desire to ensure that a 500 lb man could jump up and down on it and not be likely break the dowels.

I have searched for a testing of dowel strength when used in similar applications and have not found any results and am curious if anyone knows of a test location or simply has experience with use and can assure me that this method will provide more then adequate strength or although fairly committed let me know if this is a poor plan. Will post a picture once completed likely next weekend. Thanks,

Click for details

-- Dan


18 replies so far

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PaulHWood

335 posts in 1713 days


#1 posted 04-14-2015 12:28 PM

What is the dowel diameter and what is the span, wood is very weak in horizontal shear.

see the diameter in the title now, what is span between supports?

-- -Paul, South Carolina Structural Engineer by trade, Crappy Woodworker by choice

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BroncoBrian

435 posts in 1419 days


#2 posted 04-14-2015 12:50 PM

I used a lesser wood on a ladder for our playground. 36” wide with ropes tied at each end. The ladder has been through 2 winters in CO and they are fine. I know a square would be a little stronger than a rounded rod. I just used hard maple for a mobile base to hold a 400 +lb jointer and that also worked (1.5” x 1.5” x 24”).

I am thinking you will be fine. Make don’t glue it. Just use a pocket screw from below. Then you can swap it out when you need to or if I was way off!

-- Bigfoot tries to take pictures of me

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PaulHWood

335 posts in 1713 days


#3 posted 04-14-2015 12:57 PM

While Oak is harder, it is not stronger in beam use then say southern yellow pine.

Square is almost twice as strong and stiff as round.

I think it will be fine for your use as long as it is supported every few feet and you have your 500 pound friends refrain from jumping on it.

-- -Paul, South Carolina Structural Engineer by trade, Crappy Woodworker by choice

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Sanding2day

1001 posts in 1307 days


#4 posted 04-14-2015 01:54 PM

Thank you for the feedback…. Will have 0 span Paul, intent is simply to have additional 3 1/2 to rest feet. Total expanse at base of bar is 79 in and made first cut at 82 1/2 for 45 deg around corner.

Bronco I had not intended to glue to bar and was considering pocket hole screws from underneath, believe that is a good plan to ensure a tight fit…

Paul… Surprised that twice as strong is accurate and really southern pine stronger then oak? Either way materials are here and what Im using, not sure but imagine the 4 by 4 is pine of some type. No 500 lb friends and no jumping but do want it capable of taking it!

-- Dan

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Sanding2day

1001 posts in 1307 days


#5 posted 04-14-2015 01:59 PM

Cuts done, time for drinking, sanding, and staining…. Will Attempt drilling calculations and mounting this weekend, been up since 0600 yesterday and back to work tonight through tomorrow so nearing sleepy time!

-- Dan

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Sanding2day

1001 posts in 1307 days


#6 posted 04-14-2015 02:03 PM

Did post that on 2nd viewing I caught your strength vs hard distinction Paul… Just didn’t go through on my phone… Good point, thanks….

-- Dan

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Sanding2day

1001 posts in 1307 days


#7 posted 04-14-2015 02:24 PM

Apparently posed incorrectly regardless. Just measured to ensure appropriate drill bit was ready and it is a 1 1/4 dowel…

-- Dan

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PaulHWood

335 posts in 1713 days


#8 posted 04-14-2015 02:47 PM

Ok, thought 4×4 would be used as bracket like typical foot rest and the dowel would span between.

Generally there is no load on a footrest unless there are kids hanging on it.

Moment of Inertia (stiffness measure) for round bar is 3.14xD^4/64 or .049 D to the fourth
Square stock is d^4/12 or .083 D to the fourth so roughly 70% stiffer

-- -Paul, South Carolina Structural Engineer by trade, Crappy Woodworker by choice

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firefighterontheside

13448 posts in 1317 days


#9 posted 04-14-2015 02:51 PM

I’m not sure I understand Dan. How will it have zero span? I’m thinking you can not go more than 16” without support or that 500lb friend of yours will be making firewood.

-- Bill M. "People change, walnut doesn't" by Gene.

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bigblockyeti

3666 posts in 1181 days


#10 posted 04-14-2015 03:30 PM

Pine is not as strong as oak. Statics, Strength of Materials, Machine Design, and the list goes on, all of these classes will confirm that.

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Sanding2day

1001 posts in 1307 days


#11 posted 04-14-2015 05:06 PM

Heading for a few hour nap but allow me to to attempt to clarify intent. The 4 by 4 will be the foot rest and the dowels set about 20 inch (not determined) apart but 3 over 79 inch will b err the joinery along with two/three pocket hole screws from underneath.

The 4 by 4 will run parallel the bottom rung and the dowels will be sraight through and wedged/2 inch into rung.

Thinking in addition ro 3 on long and 2 on short sides and pocket holes I will use 2 1/4 inch dowels to hold sides together…

Sure if that didn’t clear it up the pic this weeken. I hope will…

-- Dan

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firefighterontheside

13448 posts in 1317 days


#12 posted 04-14-2015 05:18 PM

So the dowel will be in short pieces. Then I would say they will be strong enough and the joinery will likely be the weakest point.

-- Bill M. "People change, walnut doesn't" by Gene.

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PaulHWood

335 posts in 1713 days


#13 posted 04-14-2015 05:19 PM

Latest edition of the National Design Specification for Wood, table 4A and 4B

Red Oak no 2 Fb=800psi, White Oak no 2 Fb= 850psi

SYP no 2 Fb=1100psi which is actually down from a few years ago it was 1500psi

harder and stronger are two different things.

I have had all of the below classes


Pine is not as strong as oak. Statics, Strength of Materials, Machine Design, and the list goes on, all of these classes will confirm that.

- bigblockyeti


-- -Paul, South Carolina Structural Engineer by trade, Crappy Woodworker by choice

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OSU55

1056 posts in 1450 days


#14 posted 04-14-2015 08:35 PM

In tension perpendicular to the grain, white oak = 800, red oak = 800, longleaf and loblolly pine = 470; In compression perpendicular to the grain, white oak = 1070, red oak = 1010, longleaf and loblolly pine = 960. It very much depends on the specific loading of the strucural member in question.

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TheGreatJon

295 posts in 694 days


#15 posted 04-14-2015 08:42 PM



Pine is not as strong as oak. Statics, Strength of Materials, Machine Design, and the list goes on, all of these classes will confirm that.

- bigblockyeti

For most materials strength will typically decrease with hardness. Also, did you really talk about materials properties of wood in your engineering classes? I think we may have talked about it for a few minutes in Materials, but I’m pretty sure all the professor said was (imagine a giant of an old man with a walrus mustache and a southern accent) “properties of wood in general will vary widely depending on grain structure.”

-- This is not the signature line you are looking for.

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