I received an email from a poster who thought I might actually still remember how to use the octogon scale. It got me thinking, maybe someone in here actually does. Here’s my reply to the question, but I don’t know if I’m giving out good information. I thought it might be interesting to find out if anyone actually knows how to use that scale (on the framing square), or if anyone actually uses it at all for anything?
You’re taxing my brain a bit when you ask about the octogon scale. I know we were taught how to use it in Carpentry school but we really didn’t have any useful applications for it. If memory serves me correctly we did do some field application but I cant remember what it was.
Consequently, because the information wasn’t implanted in my brain, I can only give you a guess.
The octogon scale is used in conjunction with dividers. Dividers are tools that have two points and can be spread. They are kinda like a compass used in drawing. Anyways, you set the two divider points on the octogon scale and then do something with them. I just can’t remember what it is you do! You might experiment a little and figure it out.
I think the one useful application that they showed in the book was turning a square piece of stock into an octogonal spindle. The book showed the dividers being used to pinpoint the exact corners of the octogon.
I’m kinda getting a flashback. I think you create a circle with the desired diameter. Then you set your dividers up with the octogon scale. Then you walk the dividers around the circle, which gives you a perfect octogon.
Anyone know the real answer?
blue
Replies
Egads! Now I can't recall, or recall only in pieces. I know I've seen the dividers/compass method for laying out an octagon graphically. But, danged if I can remember that, or the nifty on-the-square method either . . .
Marty'd likely send us a Milk of Amnesia (or similar CRS) "cure" . . .
Drawing a circle and walking the compass around the circumference will give you a hexagon. You can alway lay out an octagon with a compass and straightedge by beginning with a square.
I can't recall how to use the tables on a framing square ... I'll have to check that out tonite.
Joe Bartok
Edited 11/4/2005 4:56 pm ET by JoeBartok
Octagon - draw a line, draw a circle with the center on the line. Draw a perpendicular line through the center point, bisect the 90º quarters. Connect the now eight lines intersecting the circle.
How the square might help I don't know, but somewhere I have a little book that knows. I don't know where the book is, so no help from Joe H.
Find the center of say a 12" square both ways, then set dividers to six marks on the octagon scale, mark each side of your center marks, and connect those diagonally. hope I explained well enough.
blue... i'll pull out my 1916 edition of "The Steel Square" by Fred T. Hodgson..
a great 50 cent investment at a yard sale..
hmmm , lesseee now...
"Octagon, "Eight-square scale, -- This scale is along the middle of the face of the tongue, and is used for laying off lines to cut an "eight square" or octabon stick of timber from a square.
[then it shows a diagram A, B, C,D, are the four faces ]
Suppose the figures A,B,C,D, Fig. 9, is the butt of a square stick of timber 6x6 inches.
Through the center draw the lines AB and CD parallel with the sides and at right angles to each other.
Withe the dividers take as many spaces (6) from the scale as there are inches in the width of the stick, and lay off this space on either side of the point A as Aa and Ab; lay off in the same way the space from thepoint B as Bd and Be; also Cf and Cg and Db and De. Then draw the lines ab,ed, ef, and gh. Cut off the solid angle E, also F, G, and H; there is left an octagon, of "eightsquare" stick. This is nearly exact."
that's it..... now of course , you all know what the usual purpose of this octagon stick is , right ?.... for 5 dog bones...... first to answerMike Smith Rhode Island : Design / Build / Repair / Restore
ships mast. Spheramid Enterprises Architectural Woodworks
"I don't think it's funny no more" Nick Lowe.
no.. but good guess....Mike Smith Rhode Island : Design / Build / Repair / Restore
second thought would be a hub of some sort..cuz stop signs weren't invented yet..LOL Spheramid Enterprises Architectural Woodworks
"I don't think it's funny no more" Nick Lowe.
that's a WAG... see joe's responseMike Smith Rhode Island : Design / Build / Repair / Restore
to make an octogon shaped spar, lay your framing square blade diagonally across one side of the timber from heel to blade end mark 7" and 17" and bring these to the butt end of the timber and repeat on all three remaning sides connect the points on the butt end and you have an octogon. This is called the spar makers rule and works great. As to the table on the square Draw a square as big as you want up to what the table will handle. say 12" for this case bisect the square in half both ways as in a x and y axis set a pair of devivers to the first notch and the 12 th notch .Then place one side of the deviders in the center of each side and swing to either side of each side center . then connect these side marks and you have an octogon. is that clear or confusing? There is also half the hypotnuse method.
A 6x6 Timber would measure 5.5" so that would give you 2.278175" or 2-1/4" for all eight sides of the octagon.A 4x4 tiumber would measure 3.5" do that would give you 1.449747" or 1-7/16" just under 1-1/2" for all eight sides of the octagon which would be used for an Octagon post for a ridge to set your 8 rafters into.Joe Carola
Edited 11/4/2005 6:29 pm ET by Framer
joe.. you win the dog bones..
most common use.. the center block for an octagon roof structure..... like firinstance... a gazeboMike Smith Rhode Island : Design / Build / Repair / Restore
I was robbed! I SAID A HUB..what else do call that? Spheramid Enterprises Architectural Woodworks
"I don't think it's funny no more" Nick Lowe.
Ruff..............Ruff.......Joe Carola
This was brought up a while back. I drew a picture of the scale on the framing square.
http://forums.taunton.com/tp-breaktime/messages?msg=36653.15
Start with a square piece of stock. Put one point of the dividers on a corner and the other on the center of the square. Lock the dividers. Now put one point on a corner and turn the dividers 90 degrees and make a mark on the edge of the piece in two directions. do this at each corner and you will end up with 8 marks that , when connected, will give you perfect octagon.
That is the beauty of the dividers; no math required!
ay yi Yiii ! do it like I do .. the Easy Way.http://junior.apk.net/~jbarta/octagon_layout/
That was fun. Now how about laying out a regular pentagon.
No CHEATING with calculators ... use a compass and straightedge only.
Joe Bartok
Edited 11/5/2005 3:22 pm ET by JoeBartok
no fair. you are a math genius
So are you..ya just don't know it. Spheramid Enterprises Architectural Woodworks
"I don't think it's funny no more" Nick Lowe.
I think it is a Joe thing. Bartok,Wood,Carola
Yeppers..ruck me funnin..I was robbed, rail roaded and lambasted all becasuse of a venacular misinterpretation..I hate it for me.
Eddy wanted them bones, now I gotsta go shopping..(G) Spheramid Enterprises Architectural Woodworks
"I don't think it's funny no more" Nick Lowe.
Really?
I won't play for fun...what is the coffer?
If you ever understood chess, and it's failings, we are on for a match.
Consider that as a challenge..
I'll give you one coordinate to help you..picture the grid as NESW. Having 8 east and 8 north Where do you start the idiomography?
Pick it and run with it.
I anxiously await this. Spheramid Enterprises Architectural Woodworks
"I don't think it's funny no more" Nick Lowe.
> Now how about laying out a regular pentagon....
Use the black diamonds on the measuring tape. Start with a circle having a circumference of 8 ft, wrap the tape around it, and the points of the pentagon are on the black diamonds. Build your gazebo this way, and it'll probably look OK under the light of the full moon.... ;-)
-- J.S.
Thanks John, I'll check that out.
Tomorrow I'll have access to a scanner and will post a sketch of one of the many possible geometric solutions. Beginning with a semi-circle we can lay out a Golden Rectangle with compass and straightedge only. Once we have the rectangle we can find the 36°-72°-108° needed for a pentagon.
Joe Bartok
Edited 11/7/2005 3:24 pm ET by JoeBartok
Still can't scan my drawing but I Googled this link to geometric methods of determining the Golden Ratio.
Joe Bartok