Time stops for a pile of century-old wood

 

 

Wanting to know what size blade cut these markings, I did some research. Then a bit of math using a formula. The straight line is called the chord and the other, the rise.

[(rise-squared x 4) + chord-squared] ÷ (8 x rise) = radius

I used millimeters for accuracy; chord = 140mm, rise = 4mm; 19600/32 = 612.5 x 2 = 1225mm = 48”

 

The whole story:

 

This pile of wood looked interesting. It had remained curbside for a few days. Eventually I stopped. With a little more forethought I wood have taken the pile. But only grabbed the drawer bottoms. And they sat in my basement until Mid-Covid ... I found images of the boards on my blog from August 2018.
 

 

 

In the rough, and a few projects. The fourth board chosen had these blade markings. After online sleuthing this morning, I find the phrase kerf marks and kerfs (term confirm please).

 

 

 

 

 

 

 

 

 

The slat shelf is my favorite; I use it every day as a pillow shelf. Radiator closed (it usually is off), linens and blankets put on hooks, pillows on the pillow shelf, window opened, door closed, the whole compartment aired out daily.

 

 

 

Hope you enjoyed the tour!  - jim

Good save and great use of the material.  Too bad you couldn't/didn't salvage the whole pile

 

Kerf & kerf marks - IMHO, the kerf is the gap left when the saw blade cuts through the board.  In my mind a gap doesn't leave marks, the saw blade did.

***Notice when I typed the word "kerf" that it became underlined?  Supposed to take you to a TPW dictionary for the word - but it doesn't seem to do that, or maybe I don't know how to access it... hey @John Morris, what's the key here?  May just be semantics, but I've never heard or used the term kerf marks.

 

Getting to your formula, I'm sure our resident "math guy" @kmealy  could join in here with some commentary.  My first question is whether the speed the log was carried by the blade, or with a bandsaw the speed of the carrier by the log would make any difference?  Or blade speed, or tooth size...

 

**Edit, kerf was underlined when I typed it, but the underline went away once I posted.  Obviously I need a course in the TPW dictionary

Edited February 7, 20224 yr by Cal

19 minutes ago, Cal said:

Too bad you couldn't/didn't salvage the whole pile

Yes. I get nauseous recounting my ignorance that summer of 2018. Clear aged 5/4 sugar pine, likely. A few blocks away, '00 or so, I found a table outside a church covered with contact paper. Its top was 5/4" x 22" sugar pine.  

 

These bottoms were 1/2" stock, hand-planed on three sides to fit a slot on the drawer sides and back, tacked on the front. Back before closets, before folks own twelve coats and enough clothes for a family of fifteen, when masonry structural walls interrupted modern flow, nooks would have been filled with whatever method was favored by the carpenters. These were built-in-place to size drawers. I've seen them before but never realized their architectural significance. 

I've salvaged some old wood and was never sorry I did.  Takes some work and can be hard on blades but I have never been disappointed with it.  I like what you have done with your nice find.

Absolutely Beautiful!

Good reuse of otherwise landfill.

 

Thank you! One plank left but no table saw for now (time to hand-rip?). The previous project, a shelf with vertical board beneath for belt / shirt hooks, is in the basement joist bay awaiting the authentic period hooks.  [I've gotten to the point finished items are underfoot]. Can you believe a plumber buddy SCRAPPED the perfect nickel-plated brass hooks removed from a series of c.1925 apartments undergoing renovation?

 

Otherwise down to scraps; it's brittle so this little project will take all week. Then back to heart pine. 

10 hours ago, Cal said:

 

Getting to your formula, I'm sure our resident "math guy" @kmealy  could join in here with some commentary. y

 

Easier for me to derive the formula that find it.  See the diagram, chord is 2a, rise is b, unknown radius is r

Using the Pythagorean theorem

a^2 + (r-b)^2 = r^2

simplifying this to solve for unknown r,

a^2 +r^2 - 2rb + b^2 = r^2

a^2 + b^2 = 2rb

(a^2 + b^2) / 2b = r

 

Which, if my mental math is working is the same as your result, but a little simpler because I took the cord length / 2 as my known.

 

If you have a compass and straightedge, you can find the center of the arc, and thus the radius without any arithmetic.

 

There is this one down in West Liberty, OH...

Note the size of the saw blade...and..this was the SMALLER of the 2 in the shed..

28 minutes ago, steven newman said:

Note the size of the saw blade...and..this was the SMALLER of the 2 in the shed..

3 hours ago, kmealy said:

(a^2 + b^2) / 2b = r

Hey! It works!

4916/8 = 615mm = a little more than a 24” radius 

 

 

Now, that's a conundrum!

5 minutes ago, Gene Howe said:

Now, that's a conundrum!

 

I always called them comics

Always thought most of these sawmill blades were similar size, but irregardless bigger than I want to get close to. 

This comic reminds me of a problem.  I took the GRE (Graduate Record Exam), sort of the ACT or SAT for grad school and took the 2 general sections, then the math advanced section.  I got a chuckle out of the two women in front of me in the morning line who said something like "Ok, now the area of a circle is pi R squared, right?"  and I'm thinking, "Well, what am I supposed to do with the verbal half of the general exam, memorize the dictionary?"   Anyway, the general 2 parts were OK.  Then I got to the advanced math part.  To make matters worse, it was the weekend before term finals, so I had a lot of studying to review 4 years of math notes plus my current classes before the exam.  I decided that if I didn't know a question in a section (usually 15-20 questions at a time), I'd skip it and answer the ones I knew, then come back.  There were several sections where I just skipped them all and frustrated, started over to try to solve some of them.   It was the hardest exam I ever had and thought I'd just blew my chances to get into grad school.  One of the questions was like this record, it was a tape spool with a certain diameter, rotating at a rpm certain speed, with a film thickness of so much.  How fast was the film coming off?  I did my best on it and later that evening, it occurred to me that I could figure out the answer, but I had gotten it wrong.  I got my results in a few weeks, and lo and behold, I had gotten a 91 percentile on the math part.  I guess it was really tough for everyone.

15 minutes ago, Gerald said:

bigger than I want

Nine feet, according to one resource:

 

After 1813 or 1822 saw mills use large circular saws, up to 3 meters (9 ft) in diameter.