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Author Topic: Reference faces vs. centerlines  (Read 2486 times)

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Offline pizza

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Reference faces vs. centerlines
« on: April 12, 2019, 08:25:47 AM »
Hi. I'm getting ready to build a small timber frame style shed for firewood storage. I'm a woodworker but new to timber framing. Although I have taken classes in TF but they were many many many years ago. So I'm considering myself a beginner. My shed is only 87" by 99" and I'm using 4" x 4" (actual size) white oak timbers. This is a fun foray into TF for me and I can't wait to get started.

However, I'm torn on whether I should use the reference face method or striking centerlines on the timbers. My timbers are to arrive on Tuesday this week so at this point I don't know how wavy, bowed, twisted, crooked or square they are. Although I was assured by my sawyer that they should be "pretty good", we'll see. 

I'm generally following Will Beemer's book "Learn to Timber Frame" and he is using the reference face technique laying out the joinery. 

I'm a bit nervous about not making a mistake as I have only a few extra timbers for "just in case".

There is a good video on Youtube  by a TF guy up in Idaho (I think) building a TF shop and he pretty well narrates and describes what he is doing and, most importantly why, as he lays out and cuts the joinery on the beam. His channel is called "Fouch Family Off Grid" and the video has the words "Chain Mortiser Demo" in the title if you want to search for it. He uses the centerlines technique basically. I've watched it at least 3 times. Their videos are great.

What if, say, my 4" x 4"x 8 ft posts have got boughs (bows? not sure how to spell it) in them, say as much as half inch? I've read that some will plane the boughed side flat and basically establish the two reference faces, which seems like alot of work compared to just striking a centerline. BUT if you just strike a centerline and don't fix the bough, that face won't be flat for the eventual siding that will be applied.

Now granted, my structure is just a fire wood shed and I'm siding it with rough planks with large gaps for good air flow, and the flatness of the post won't matter but still what if this wasn't a little shed but say a house?

Not to mention if that post had not only a bough in it but was slightly out of square or twisted slightly, then what? 

Any thoughts or advice would be greatly appreciated. I think I'm coming down with "analysis paralysis". :)

Thanks all!




Offline Heartwood

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Re: Reference faces vs. centerlines
« Reply #1 on: April 12, 2019, 08:42:46 AM »
Hi pizza,

The snapped chalk line doesn't need to be centered. If you want the timbers to be close to flush to the outside (reference) face you would measure in  a set distance from that face at the joint at each end and snap the line there that might represent one face of most mortises all along that timber, and establishing a line you could square off from. This line might be 1.5 off the reference face, or in your case 1"-1.25" since your joinery will be narrower.

If the timber is twisted then you would need lines on two or maybe all four faces, laid out using two framing squares set parallel to each other at each end joint and measuring down a set distance from the square. Or plane the timber square and parallel at the end joints and snap lines from there. See page 55 of "Learn to Timber Frame".

1/2" bow or twist on an interior timber may not matter, but on an outside face with siding where it did matter I would plane some of it off (recognizing that the timber may bow back the other way somewhat once the stress is released), or reject that timber.

Best wishes for a successful project!

Offline D L Bahler

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Re: Reference faces vs. centerlines
« Reply #2 on: April 12, 2019, 10:07:43 AM »
I always have used snap lines. Of course I also learned from a different tradition, so take it for what it's worth to you. 

My opinion, though, is that I just don't trust a reference face.

I tend to snap lines on all 4 sides. My theory is that I can use an imaginary timber of perfect dimensions the most efficiently by using 4 reference lines. In my mind these lines reference to the theoretical perfect timber, and not the actual imperfect timber in front of me. SO I have immediate access to perfection on every face, it just gets a little complicated to actually utilize properly.

As an aside, European carpenters sort of combine both ideas. What I have learned is to take timbers that have seasoned for a year or 2, that way they've shown you how much and in what way they are going to move, and plane those down to perfect dimensions. But still don't trust the faces, because wood is not to be trusted. (Note, and sorry if this adds an unnecessary level of confusion, with 4 reference lines, you can actually accomplish full scribe without having to ever lay timbers on top of each other. You can just use the reference lines to determine any joints deviation from the ideal, and adjust the adjoining member accordingly. I learned this from a Swiss master carpenter, and it astounded me that it actually works. The downside is there is a lot of math and numbers to keep track of, which introduces a risk of error that doesn't exist in true scribe or square rule) 

Offline timberframe

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Re: Reference faces vs. centerlines
« Reply #3 on: April 13, 2019, 12:19:27 PM »
I always have used snap lines. Of course I also learned from a different tradition, so take it for what it's worth to you.

My opinion, though, is that I just don't trust a reference face.

I tend to snap lines on all 4 sides. My theory is that I can use an imaginary timber of perfect dimensions the most efficiently by using 4 reference lines. In my mind these lines reference to the theoretical perfect timber, and not the actual imperfect timber in front of me. SO I have immediate access to perfection on every face, it just gets a little complicated to actually utilize properly.

As an aside, European carpenters sort of combine both ideas. What I have learned is to take timbers that have seasoned for a year or 2, that way they've shown you how much and in what way they are going to move, and plane those down to perfect dimensions. But still don't trust the faces, because wood is not to be trusted. (Note, and sorry if this adds an unnecessary level of confusion, with 4 reference lines, you can actually accomplish full scribe without having to ever lay timbers on top of each other. You can just use the reference lines to determine any joints deviation from the ideal, and adjust the adjoining member accordingly. I learned this from a Swiss master carpenter, and it astounded me that it actually works. The downside is there is a lot of math and numbers to keep track of, which introduces a risk of error that doesn't exist in true scribe or square rule)
This is what I usually do too.  The timbers I use are milled well  but life usually means they don't get used right away and by the time they're on the horses in front of me, no faces are good enough to lay a square against.  A perfectly straight chalk line is reliable though.  

Offline pizza

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Re: Reference faces vs. centerlines
« Reply #4 on: June 13, 2019, 04:55:20 PM »
Ok. When lines are made on the face of the cut ends what reference do you use to make the two horizontal lines equal distance from the floor (if you have a floor to reference from?). You can't just strike a horizontal line 90 degrees from the vertical plumb line and then do the same at the other end  and know those tow horizontal lines are coplanar on a level plane can you? 

Offline Jim_Rogers

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Re: Reference faces vs. centerlines
« Reply #5 on: June 13, 2019, 05:03:30 PM »
For level horizontal lines use a level and put them the same distance from the floor. Hopefully your saw horse are the same height.
Jim Rogers
Like this, only with a timber not a log:


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

Offline Heartwood

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Re: Reference faces vs. centerlines
« Reply #6 on: June 14, 2019, 06:51:26 AM »
When you establish the level and plumb lines on the end they don't need to be level with the floor (what if your floor's not level?); you can be on unlevel ground and the ends at different heights. Instead, you should sighting down the timber so that a line snapped from end to end from those level and square marks will fall where you want the planes to run through the log. If scribing, then, when you actually do the setup you would level those lines up on the sides longitudinally.
Level and plumb lines on the two ends by definition are coplaner, even if not parallel or perpendicular to the surface beneath. The earth is round, after all!

Offline Mad Professor

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Re: Reference faces vs. centerlines
« Reply #7 on: June 17, 2019, 03:16:09 PM »
Hi pizza,

The snapped chalk line doesn't need to be centered. If you want the timbers to be close to flush to the outside (reference) face you would measure in  a set distance from that face at the joint at each end and snap the line there that might represent one face of most mortises all along that timber, and establishing a line you could square off from. This line might be 1.5 off the reference face, or in your case 1"-1.25" since your joinery will be narrower.

If the timber is twisted then you would need lines on two or maybe all four faces, laid out using two framing squares set parallel to each other at each end joint and measuring down a set distance from the square. Or plane the timber square and parallel at the end joints and snap lines from there. See page 55 of "Learn to Timber Frame".

1/2" bow or twist on an interior timber may not matter, but on an outside face with siding where it did matter I would plane some of it off (recognizing that the timber may bow back the other way somewhat once the stress is released), or reject that timber.

Best wishes for a successful project!
I learned to do something similar from Dick Babcock.  But it was all scribe using dividers/compasses. Works on bowed, twisted, or curved wood
You set a circle for your timber width, it's a reference circle, save it.   The edge of each circle just touches what you want for a reference face. 
Snap a chalk from the center of the circles on the ends (centerline).  Drop a plumbob on the end of centerline to transfer the center to the opposite face. 
You can flip the cant and do more layout
Scribe two more circles from each original circle center, at chalk line, 1 radius distant towards ends on chalk line, these will allow you to square the ends.  To do this you trace an X on the scribed circles , to where adjacent circles intersect.  Connect two intersects and you have a perfect 90o.  See pic #1 for shouldered M +T, they look like X marks.  You sacrifice 1 circle radius on each end of timber to square it
For mortises and tenons, scribe another smaller reference circle.  This circle can also be used to measure a housing, use 1/2 of the smaller circle from a reference/chalkline edge.  See shoulder, bottom right has 1/4 of circle left.
I hope this makes sense?
I did this my first TF project a wood rack.  No tapes, measures , squares, just a divider, chalk, and plumbob.
You can layout other angles and braces/pockets just using a divider too.  Perfect 45 and 60 degrees


 

 

 

Offline timberframe

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Re: Reference faces vs. centerlines
« Reply #8 on: July 03, 2019, 10:41:53 AM »
How are you making put with this Pizza?  I'd be interested to see how you're getting on.

B

Offline TimFromNB

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Re: Reference faces vs. centerlines
« Reply #9 on: July 10, 2019, 01:10:17 PM »
Pizza, I know the feeling. I am working on my first frame and started with square rule, but as time moves on and timbers dry and move, I am forced (at least so I think) to use levels and snap lines (I believe called snap line square rule). I've reached out to Will a few times and he's been a lot of help.

Too often, I find myself sinking into analysis paralysis, especially where this is my first frame and am not sure what tolerance is really acceptable. 

What I struggle with when using the level/snap line method is using a level to check all my housing faces and when boring with the mortiser. I find it much more repeatable and easier to be able to check them with a combo square off the reference face, but that's not the case when your timbers are twisted. I guess the fact my first level was not accurate explains some of that :D. Any tricks that can be shared?

Hopefully when I come to put it together, I will see that some of this was over analyzing and that in most cases, square rule was sufficient.

Offline pizza

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Re: Reference faces vs. centerlines
« Reply #10 on: July 22, 2019, 11:09:52 AM »
Hi. I'm not doing that well with my project. I had to return all of the timbers I received due to them being bowed twisted and crooked. So much so that I was not confident I could do the Square rule method -the snap line method is something I don't yet feel comfortable with. Although I've been reading up on it and TRYING to find some one showing a detailed video of that method on-line. I have not found anyone clearly showing it yet though. Although the Great Plains Craftsman (Youtube, great channel BTW) has the best one yet.

Does anyone know of a good timber supplier in Southeast PA that I can call to get 4" x 4" white oak green timber? PLEASE let me know.

So, back to making those level and plumb lines at both ends of the timber...I get that. However many have said that once you mark those at each end then those horiz lines should be on the same plane. Yest they're on the same plane BUT that plane could be tilted. 

Because, say, you've made those plumb and level lines at each end BUT one of the horiz level lines is higher than the other (in this case I don't have a level floor to mark them from). Now I go and connect those two horiz lines to each other by striking chalk lines on the long sides of the timber. That struck line is now canted at an angle making the two cut ends of the timber NOT perpendicular or square to that line.

aaaaaaH, now I see,  this means I can square those two ends to that long chalked line on the side of the beam using a square aligned with that long chalked line. See my illustration.  

Offline timberframe

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Re: Reference faces vs. centerlines
« Reply #11 on: July 22, 2019, 01:13:33 PM »

" I have not found anyone clearly showing it yet though. Although the Great Plains Craftsman (Youtube, great channel BTW) has the best one yet."

I'm actually in the editing phase of a video on this right now, though I'm not sure if it would be called line rule or snap line square rule, or what....  It's kind of a melding of a few things....  I can send you a sneak preview of the video in a few days if you send me your email to dovetailtimber at g mail dot calm.

You can give me a critique before I publish to the rest of the world!

B

Offline Tristimulus

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Re: Reference faces vs. centerlines
« Reply #12 on: July 28, 2019, 11:31:06 PM »
Hi. I'm not doing that well with my project. I had to return all of the timbers I received due to them being bowed twisted and crooked. So much so that I was not confident I could do the Square rule method -the snap line method is something I don't yet feel comfortable with.
James Mitchell in the book: "Master's guide to Timber Framing" described center line method for building timber frames.

Offline Heartwood

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Re: Reference faces vs. centerlines
« Reply #13 on: July 29, 2019, 08:39:11 AM »
You reach a point when there are so many variables in a bunch of timbertwist, bow and out-of-squarenessthat scribing is much more efficient than snap-line square rule. If carpenters rejected such timber historically in Europe nothing would have ever been built; many there and in North America use scribe rule regardless of how true the timber is. It requires more handling of timber and often (but not always) a layout floor, and produces the best results if one knows how to do it accurately.
There are a series of articles on scribing in the Timber Framers Guild journal Timber Framing (you can review the index on their website), including "Snap-Line Scribe" by Glenn Dodge.
I also recommend Rupert Newman's book "Oak Frame Buildings".

Offline Heartwood

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Re: Snap line scribe
« Reply #14 on: July 29, 2019, 05:53:53 PM »
There will be a snap line scribe workshop at the Timber Framers Guild Conference in New Hampshire this coming weekend.
Timber Framers Guild - Enriching Community Through Craft.

Offline timberframe

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Re: Reference faces vs. centerlines
« Reply #15 on: July 30, 2019, 11:15:17 AM »
You reach a point when there are so many variables in a bunch of timbertwist, bow and out-of-squarenessthat scribing is much more efficient than snap-line square rule. If carpenters rejected such timber historically in Europe nothing would have ever been built; many there and in North America use scribe rule regardless of how true the timber is. It requires more handling of timber and often (but not always) a layout floor, and produces the best results if one knows how to do it accurately.
There are a series of articles on scribing in the Timber Framers Guild journal Timber Framing (you can review the index on their website), including "Snap-Line Scribe" by Glenn Dodge.
I also recommend Rupert Newman's book "Oak Frame Buildings".
In researching all this, I found the terminology to be a bit of a nightmare.  There's line rule, centre-line rule, scribe rule, snap-line scribe rule, plumb line scribe rule etc.  Some people use line rule as a general overarching term to refer to anything that employs snapped lines, where others accept it as centre lined approach only as developed in Asian countries.  Some people think that if you're using snapped lines in square rule, that it shouldn't really be called square rule anymore but a version of line rule....unless you think that term is reserved for only one thing as above!  :) That's all before we get into more esoteric things like French lofting methods etc.  I've found contrasting definitions from well known, apparently authoritative sources too which makes it a bit of a nightmare for newer folks getting started.  I'm still new enough to all this that I can remember the frustration from my initial research.

Offline Heartwood

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Re: Reference faces vs. centerlines
« Reply #16 on: July 31, 2019, 08:54:29 AM »
I only know of two "rule" measuring systems: Square Rule and Scribe Rule; other terms like "mapping" or "mill rule" aren't really systems with procedures to follow. In terms of lines, you can use snap lines with either square or scribe rule, or not; snap lines are a tool that are part of the larger system. If you're laying out a perfect timber within from a snap line, centered (see James Mitchell's "virtual rule") or not centered, that's snap line square rule (as opposed to layout from a face/edge). If you're using a plumb bob, that's another tool, and is either part of the scribe rule system (aligning to a floor drawing, perhaps, or just a plumb reference between two or more timbers - plumb line scribe) or using it to establish your snap lines on twisted timbers in square rule (can also be done with levels). In snap-line scribe rule, you would snap lines on the timber and reference these with offsets to your floor drawing, rather than plumbing down from an edge or face.
Never heard of "line rule" although some may use it; I think you're still going to be ending up using some version of scribe or square rule, referencing to those lines.

That's my perspective, anyway. Carpentry is full of arcane terms from different traditions. The joy of it is to get experience in as many different techniques as possible to find the one you like or that is needed in a particular situation.

Offline timberframe

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Re: Reference faces vs. centerlines
« Reply #17 on: July 31, 2019, 12:55:52 PM »
I only know of two "rule" measuring systems: Square Rule and Scribe Rule; other terms like "mapping" or "mill rule" aren't really systems with procedures to follow. In terms of lines, you can use snap lines with either square or scribe rule, or not; snap lines are a tool that are part of the larger system. If you're laying out a perfect timber within from a snap line, centered (see James Mitchell's "virtual rule") or not centered, that's snap line square rule (as opposed to layout from a face/edge). If you're using a plumb bob, that's another tool, and is either part of the scribe rule system (aligning to a floor drawing, perhaps, or just a plumb reference between two or more timbers - plumb line scribe) or using it to establish your snap lines on twisted timbers in square rule (can also be done with levels). In snap-line scribe rule, you would snap lines on the timber and reference these with offsets to your floor drawing, rather than plumbing down from an edge or face.
Never heard of "line rule" although some may use it; I think you're still going to be ending up using some version of scribe or square rule, referencing to those lines.

That's my perspective, anyway. Carpentry is full of arcane terms from different traditions. The joy of it is to get experience in as many different techniques as possible to find the one you like or that is needed in a particular situation.
It's a wild world that's for sure.  I got so confused that I had to teach myself how to deal with imperfect timbers without scribing.  I borrowed from a few resources, but didn't have Mitchell's book at the time.  Interestingly, I ended up with a system that is very similar to what he describes in the second part of his book " Master's Guide to Timber Framing"!  I thought that was pretty cool.  I don't always centre my lines like he does, but it depends.  
B

Offline pizza

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Re: Reference faces vs. centerlines
« Reply #18 on: October 24, 2019, 08:33:09 AM »
Hey guys, finally getting back to this. Although I'm still at a frustrating loss for finding someone to supply me with decent timbers around here in southeast PA. I'm tempted to go back to the original sawmill who gave me those twisted and bowed timbers (that I returned) and explain that I maybe more confident to deal with them but I doubt if even they would want to take a second chance with me. I know they wouldn't take them back again a second time if they are really bad. Jeez what a predicament I made. I'm tempted to change plans and use 3.5" x 3.5" pressure treated wood from Home Depot but don;t want to really do that with that green slime on them and on my tools.

Just wanted to say thanks so very much for your input and insight on methods to layout joinery. I'm going to try and get a copy of the books mentioned.

pizza 


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