The Forestry Forum is sponsored in part by:

iDRY Vacuum Kilns


Forestry Forum
Sponsored by:


TimberKing Sawmills



Toll Free 1-800-582-0470

LogRite Tools



Norwood Industries Inc.




Your source for Portable Sawmills, Edgers, Resaws, Sharpeners, Setters, Bandsaw Blades and Sawmill Parts

EZ Boardwalk Sawmills. More Saw For Less Money!

STIHLDealers.com sponsored by Northeast STIHL


Woodland Sawmills

Peterson Swingmills

 KASCO SharpTech WoodMaxx Blades

Turbosawmill

Sawmill Exchange

Michigan Firewood, your BRUTE FORCE Authorized Dealer

FARMA


Baker Products

ECHO-Bearcat

iDRY Wood Lumber Vacuum Drying for everyon

Nyle Kiln Dry Systems




Author Topic: Timber grading  (Read 1031 times)

0 Members and 1 Guest are viewing this topic.

Offline ljohnsaw

  • Senior Member x2
  • *****
  • Posts: 3849
  • Age: 60
  • Location: Northern California
  • Gender: Male
  • Happily retired... Working harder than ever!
    • Share Post
Timber grading
« on: January 17, 2013, 01:43:23 AM »
I need to understand the codes on the beam calculator.  When I look at the list of species to choose from, I see codes after the names: SS, B+S, and P+T.  I think SS is surfaced 2 sides, right?  What do the other two mean?  I understand the #1 and #2 (how many/where knots are located, bark areas, etc).  When you are using your own trees, what do you usually get out of pines, #1 for beams since you are pulling them from the center?

Thanks
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/32" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

Offline Jim_Rogers

  • Board Moderator
  • *****
  • Posts: 7367
  • Age: 67
  • Location: Georgetown, MA
  • Gender: Male
  • Keep your chisels sharp.
    • Share Post
    • jrsawmill.com
Re: Timber grading
« Reply #1 on: January 17, 2013, 09:25:47 AM »
SS does not mean surfaced two sides that's S2S

SS means structural select.

B+S means Beams and stringers.

P+T means posts and timbers.

The difference between B+S, and P+T is two inches.

What I mean is if a timber is an 8x8 it's in the P+T category. If a timber is 8x10 it's also in the P+T category. But as soon as the second dimension goes to more than 2" then it is assumed that the timber will be used as a beam (example an 8x11). So it's in the B+S category.

Beams mean the timber is horizontal. There is no such thing as a vertical beam.
Stringers as you all know are the pieces of lumber that hold up stair treads. And they must be strong or the stairs will fail. Rafters are also in the "stringer" family.

Timbers that are in the P+T category have lower grade rules due to the fact that most of them could be used as Posts. And wood is strong in compression. Knots in compression don't fail, usually.

But, knots in beam can be a problem if they are big. When we look at pieces of wood to be used as beams we always look for "crown" the sweep in the piece from end to end. And we put the crown up so that gravity, and the load on the beam will push it down, towards being straight. If it was crowned down and then the load is applied the bow would be even more. This would make a very un-even, un-level floor system.

Also, when we are inspecting beams that are fairly straight, no crown, we look at the size and location of the knots. And roll the beam over so that the knots are near the top surface of the beam. Knots are strong in compression. But weak in tension. The lower side of the beam would be in tension. The upper side would be in compression.
Some where in between these two "zones" of the beam is the area known as the "neutral axis" where there is neither compression or tension. It would be best if the joints/mortises could be cut in the neutral axis area. As these would not effect the strength of the piece.

I hope that helps you to understand which values to use when you select your values in the calculators.

Jim Rogers

If not keep asking questions.
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Offline WindyAcres

  • Full Member
  • **
  • Posts: 71
  • Location: Tatamagouche, Nova Scotia
  • Gender: Male
  • Forester
    • Share Post
Re: Timber grading
« Reply #2 on: January 18, 2013, 07:29:23 PM »
Quote
Also, when we are inspecting beams that are fairly straight, no crown, we look at the size and location of the knots. And roll the beam over so that the knots are near the top surface of the beam. Knots are strong in compression. But weak in tension.
Cool, I did not think about that, good point, thx.

Just use common sense, get nice trees for your beams + overbuild, then you dont have to worry about things..  :)
2011 Woodmizer Lt40 Hyd G28, Stihl Chainsaws, Tractor with Farmi Winch, Woodturning Lathe,....

Offline canopy

  • Full Member x2
  • ***
  • Posts: 203
  • Location: Thailand
  • Gender: Male
    • Share Post
Re: Timber grading
« Reply #3 on: January 18, 2013, 08:05:05 PM »
No matter how much overbuild I think it is still good practice to be in the habit of carefully inspecting each member individually, optimizing knots, crown, and other attributes to allow each to perform at its absolute best.

Offline Jim_Rogers

  • Board Moderator
  • *****
  • Posts: 7367
  • Age: 67
  • Location: Georgetown, MA
  • Gender: Male
  • Keep your chisels sharp.
    • Share Post
    • jrsawmill.com
Re: Timber grading
« Reply #4 on: January 19, 2013, 08:36:40 AM »
No matter how much overbuild I think it is still good practice to be in the habit of carefully inspecting each member individually, optimizing knots, crown, and other attributes to allow each to perform at its absolute best.

Well said.....
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension


Share via delicious Share via digg Share via facebook Share via linkedin Share via pinterest Share via reddit Share via stumble Share via tumblr Share via twitter

xx
Timber grading?

Started by scgargoyle on Timber Framing/Log construction

12 Replies
3484 Views
Last post January 04, 2008, 05:43:03 PM
by Don P
xx
Timber Grading

Started by Scott G on Sawmills and Milling

10 Replies
2481 Views
Last post January 23, 2007, 04:46:14 PM
by Don P
xx
Grading timber in MA

Started by ex-Engineer Wannabe on Timber Framing/Log construction

12 Replies
2526 Views
Last post October 21, 2005, 07:03:36 PM
by ex-Engineer Wannabe
xx
Timber Grading course by TFG

Started by rjwoelk on Timber Framing/Log construction

8 Replies
445 Views
Last post August 30, 2019, 06:49:38 PM
by Don P
 


Powered by EzPortal