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Author Topic: scribe rule framing  (Read 6089 times)

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Offline Tony_T

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scribe rule framing
« on: February 02, 2005, 11:54:00 AM »
Hi everyone I’m a newbie to the forum and framing.

I hope to build a barn using timbers from ash trees harvested on my land.  I have some experience cutting lumber as I’ve harvested timber and worked at a sawmill to get myself through college.  I presently have a small mill capable of cutting small stock (< 16 ft timbers/lumber).  Thus for some of the larger pieces I may have to hew some of the timbers.  In addition some timbers from my mill will at times be slightly out of square and/or have some taper.  To deal with the irregularities of both the sawn and hewn lumber I plan on milling the smaller pieces slightly oversize and frame using the scribe rule method that brings me to my current questions of square vs. scribe rule.  I have been learning bits and pieces of the secrets of the scribe rule from a master framer who has been kind enough to answer my questions no matter how simple or naive they may be.  He simply wants to pass the knowledge on to others and his eyes light up when he begins to speak about old barns and doing things in the “old way”: Richard Babcock.  I hope to help him in one of his restorations both disassembling and re-erecting using traditional techniques, before I start on a project of my own

I’ve searched a bit and there is some excellent books (i.e. Ted Benson ) and web-based information on square rule framing (e.g. Jim Rogers work).  Jim was kind enough to invite me to attend one of his workshops some time ago but other commitments (e.g. teaching) have prevented me from doing so. I have not found much step-by-step information on the scribe rule method.  Things I have seen mentioned is that; 1) mating surfaces on tie beam are “housed” in square rule but not in scribe rule, 2) that scribe rule framing does not lend itself to making "interchangeable" pieces, for instance identical posts for several similar bents, 3) for the scribe rule elaborate means such as having the timber laid out over a template on a level floor below are needed to lay out accurate joinery using scribe rule.

I have seen the “true beam” within a beam mentioned for the square rule method of framing using “housed joints”.  What I mean is not fully housed joints, such as the housed dovetail used in summer beams or the housed mortise and tennon used for bearing tie beams. But an accurate surface that is square and paralell to the true beam itself to which the tie beam is joined.  From what I have learned so far this was common to the scribe rule as well as the square rule so I am perplexed as to why this is used as a criteria for a “square rule” framed structure. That is which method the structure was originally framed with.

As far as interchangeable pieces Richard totally disagrees that reliable pieces cannot be fabricated using the scribe rule.  Trial assembly of the bents is done on the ground but is this not true for square rule framed structures also?

I have also watched the layout of a timber starting with a log, the timber being a gunstock post typical of “English/Scotish frames”.  It was done on the ground with the log supported by two short logs and held in place with log dogs.  This was done without elaborate templates using simple tools (axe , compass, chalk line, saw,  chisels and plumb bob) so I am again perplexed as to why templates on a level surface are needed to lay out the joinery.

Please realize I am a newbie.  I don’t want to ruffle anyone’s feathers or step on any toes, I just desire to explore what others have leaned and/or experienced about scribe rule framing.

Thanks in advance for your comments, advice, and insight.

Best regards,  Tony


Offline JoeyLowe

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Re: scribe rule framing
« Reply #1 on: February 02, 2005, 02:55:16 PM »
Tony:

Welcome to the forum!  I'm going to be watching this topic closely since this subject geniunely interests me.  You are very fortunate to have a mentor such as Richard Babcock.  I imagine that man has probably forgotton more about timber framing than most of us will ever learn.  ;D

I understand completely the dilemma of out-of-square beams and/or those with a slight taper.  If I'm not mistaken, the Guild did offer a scribe rule seminar through some of their affiliates.  They have also offered some mini classes at their annual conferences too.   Some of the old Guild journals have excellent articles on scribe rule joinery too.  Nonetheless, and hour listening to Mr. Babcock may teach you all you need to know!

Good luck and welcome again!
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Joey Lowe

"Working towards perfection has to be a part of anything one does.  You've got to put yourself into it." ... Sam Maloof (chairmaker)

Offline ARKANSAWYER

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Re: scribe rule framing
« Reply #2 on: February 02, 2005, 10:09:52 PM »
  Ok let me try this.

  There are 4 rules that I know of in timber framing.
 
1.  Mapping,  It is alot like scribe rule but you do the lay out in your head mostly and cut around defects and irregular places to make a tight joint.  It is hard to do and when you start fitting you have to fudge a bit.

2.  Scribe rule,  this is where you lay your timbers out on each other and use a square and plumb bob to transfer lines between the pieces.   When you lay out your timbers you must put the best face out and up and level them so the transfered lines come out right.  Since the timbers are in place and the lines are scribe from piece to piece there is not need to "house" the joint.  But that timber will only fit in that spot.   When the piece is real irregular we pop a chalk line on two faces 90 degree from each other and use them for our "face".

3.  Square rule, just means with in every timber is a perfect timber that is a bit smaller.  So if you have a 8x8 timber then we assume there is a 7 1/2x 7 1/2 inside and we take the outside/up face as the square face and cut from there.  This is why the joints are "housed" most of the time.  If it is a tapered timber then from the small end we take out perfect timber from and cut the whole timber as is it was the small size from end to end.  This is easier to draw on blue prints and once noted all timbers can be cut and for the most part interchange.

4. Mill Rule,  These are 4 sided (most of the time dried) timbers that are machined to a size.  They are often run through large machines that does the joinery.  This is the way most timber frame packages come and are CAD done.

  If you mill your timbers then you will use the square rule and should be able to cut all your bents and the pieces interchange and fit if the joints are done the same and with care.  You should always test fit your joints on the ground before rasing.  Once it is in the air is not the time to find it does not go together.
  I would not use ash in a barn frame.  Bugs love it and it seems to rot easily.
ARKANSAWYER
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Offline Tony_T

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Re: scribe rule framing
« Reply #3 on: February 03, 2005, 02:31:39 PM »
Hi Joey and Arky,

Joey, nice work on your current project.

Arky, I read your posts all the time on the woodweb.  I have learned a lot about milling/wood there from your posts. 

I realize ash is not the best wood to use in regards to rot and bugs but its what I've got to work with. It is strong and hews real easy. I've got many ash that are straight and clear for ca. 40 ft. Little or no oak on the property and only a small amount of beach, lots of maple but that will be  a struggle to do jionery on and/or hew.  I figure if I can keep it dry the rot and bug problems will be minimal.  If there is any sign of the double DanG PPBs (powderpost beetles) I'll kiln things before setting up the frame.  Will try to find some locust for the sills.

Concerning the scribe rule, from what I've seen so far all the layout is done using a compass and chalk lines.  Starting with the log (slightly longer than the desired timber) propped up off the ground on two short pieces and held in place using log dogs.  Two flat surfaces are hewn on the top of each end.  Inside each surface a circle is inscribed with the compass, the diameter of the circle being the width of the rough surface of the beam.  A chalk line is then snapped from the edge of each circle to give two paralell lines running the lenght of the log, these lines are then used to hew both sides of the timber.  With two sides finished the log is turned 90 degrees and the process repeated, A plumb bob can be used to check that the second round of hewing is square to the first.  To mark a line to square off the ends a line is snapped between the centers of each circle running the lenght of the timber.  The compass (using the same setting as the original circles) is placed on the intersection of the centerline and the circle and  arcs are struck to the left and the right.  The points where the arc intersects the original circle to the left and right of the centerline when joined make a perfect right angle to the centerline of the timber, joining these points to the intersection of the centerline /circle gives an equilateral triangle.  If the process is repeated for the remaining point that the original circle intersects the centerline the two triangles give "the star of David".  Joining the two points of each triangle of the star nearest the edge of the beam gives a line perfectly paralell to the centerline of the beam, just inside the hewn surface.  This can be used to accurately locate a "housing " to join a tie beam (e.g. this is your true beam within a beam). 

I've seen how to locate the positions of the braces and square a tie beam to a post using the compass but need to lean more before I can describe how a mortise and tennon are laid out using the compass.

I hope the above is clear I don't have a good way post drawings but will give it a try........




Offline Greg

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Re: scribe rule framing
« Reply #4 on: February 11, 2005, 05:35:35 PM »
Hi everyone I’m a newbie to the forum and framing.

...

As far as interchangeable pieces Richard totally disagrees that reliable pieces cannot be fabricated using the scribe rule.  Trial assembly of the bents is done on the ground but is this not true for square rule framed structures also?

Thanks in advance for your comments, advice, and insight.

Best regards,  Tony


Tony,

From my understanding, when using square rule - if done properly, trial assembly should not be required.

Thats the whole point, to do all the joinery generically so you don't have to mate up individual piece to each other.

Then on raising day it all fits together on site perfectly, the first time, with no problems. Gulp :D

Greg

Offline Jim_Rogers

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Re: scribe rule framing
« Reply #5 on: February 12, 2005, 06:11:32 PM »
From my understanding, when using square rule - if done properly, trial assembly should not be required.

Thats the whole point, to do all the joinery generically so you don't have to mate up individual piece to each other.

Then on raising day it all fits together on site perfectly, the first time, with no problems. Gulp :D

Greg

In a perfect world, and with perfect cutting of all joints. This could be true. But these don't always happen perfectly.
That's why I wrote the Standard Procedures for Timber Framing (click this title for shortcut) story which includes a section about "trail fit up procedures".

It's one thing to be putting a shed with a few friends by hand. If a joint doesn't fit right you can easily trim it to fit.
But when doing a large barn or house frame with a crew and a crane, you don't want to have anyone standing around with their hands in your pockets while your trim a tenon......
Proper planning prevents poor performance......

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Offline ARKANSAWYER

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Re: scribe rule framing
« Reply #6 on: February 14, 2005, 09:00:27 PM »
  First rule of nail bending taught to me by GrandPa was "Measure twice and cut once".  After that it was make sure it fits the way you want it to.  I always fit every thing together before raising and mark and tag each piece so I know where they belong.  Like Jim said you do not want every one standing around while to trim this and that while the clock is running and coin is spending.
ARKANSAWYER
ARKANSAWYER


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