Dealing with “out of square” timbers

[Jim_Rogers]

Dealing with "out of square" timbers by Jim Rogers May 29, 2010

While I sit here sharpening bandsaw blades for my sawmill, I thought I'd write about how to deal with "out of square" timbers. And laying out joinery on them.

To begin we need to look at a drawing, I have created.
As shown here:



First; this is an end view of an 8x8 post, let's say from the bottom looking towards the top.
And the joint we're going to layout is a through mortise for a girt that will connected one bent to another, in an eave wall, not necessarily a corner post, but it could be. Also, we need to remember that all through mortises are laid out from both sides and that the holes bored by the boring machine are done half way in from each side, so the exact location of the mortise on both sides of the timber are very important.

Next, on the top of the drawing of the post we have the reference face/side, on the left hand side we have the adjacent face/side and these are shown on the surface of the timber with two triangles drawing with pencil, lumber crayon, or white chalk, whatever the framer uses.
In order to show them in this drawing I have turned them up so that we can see them.
They are pointing to the reference edge. This is the edge that the measurements will be "pulled" from, basically the zero end of the tape or framing square.
The other two faces of the timber are known as the "opposite reference" and the "opposite adjacent".

Now as this timber is an 8x8 and the rule is that a tenon or mortise is 1/4 of the thickness of the timber the tenon and mortise will be 2" wide/thick. And the layout will be 2" off the reference edge.

And in order to be correct and straight this mortise must pass through the timber perpendicular to the reference face.

The timber is not a square but a parallelogram with two sets of parallel faces. A common shape of timbers coming off the mill when things don't go 100% correct.

This is shown by the dashed line, and the out of shape timber is out by 1/4" in 8", shown by the gap at the end of the tongue of the framing square, which is in position to layout the mortise on the reference face.

If we use the surface of the timber to layout the mortise on the reference face, all is well as the corner is the reference edge and we can pull 2" over and 2" thick/wide mortise as shown at the top of the drawing.

However if we use the surface of the adjacent face as the point where we "pull" the two dimensions, the mortise will be out of line with the true plane, as shown by the red lines.

To be in the correct position, and in a parallel plane to the eave wall, the mortise location on the opposite reference face of the timber needs to be located by measuring over from the framing square the 2" and 4" as shown by the green lines.

If the timber is consistently out of square then you could "pull" the dimension and just make it 1 3/4" from the adjacent face. But to be sure you should rely on your steel layout tools for locating your mortises and tenons in the correct plane.

It is important to understand where to "pull" your dimension from in order to make your joinery straight and true, and perpendicular to the surface you need it to be from.

If you have any questions about this please ask so that I can help you understand how to deal with out of square timbers.

[Jim_Rogers]

Of course if the timber is out of square the other way, that is with the 1/4" gap at the reference edge you'll have to adjust your dimensions again to get the mortise in the correct location.

[Dave Shepard]

Thanks for the post Jim. I was trying to think of how to respond in the other out of square thread, but it's very difficult without a drawing.

[Jim_Rogers]

Yes, Dave, it is very hard to describe without using a drawing to show what you are talking about....

Understanding the names of the locations on the timber is as important as understanding how to lay it out.

Jim Rogers

[Raphael]

This is my one example... I wish I'd drawn a horizontal line at the bottom of the timber to show how far out that is.

[Jasperfield]

Jim,

That is a really good example AND a great explanation.

Is this one of the topics included in your new book? And, when might we be able to buy a copy?

[Brad_bb]

Jim, If I may, in your example, the "opposite reference face" was parallel to the "reference face".  If it was not, what would YOU do to assure that you bore from the opposite reference parallel to the reference face? How to assure your boring machine were squared up?

Are you really writing a book?  Or is someone just teasing?

[Raphael]

  If you take the single face timber in my picture and rotate it 90° to the right and stick a boring machine on top, the line will tell you how much to shim the machine.  It's base should be parallel to the line not the timber, or alternately the bit should be plumb to the line.

 In a case where you have a good face on the bottom of the timber and you're boring into a wonky face you can lay the square's leg against the bottom of the timber and shim until the bit is parallel to the body of the square.  You can also measure (at two or more points) from the machine to a straight edge laid against an adjacent reference face to verify it's shimmed correctly.

This is one area where an old boring machine can beat the chain mortiser, especially when you've got a 2" mortise and a 1.5" chain.

[Jim_Rogers]

As Raphael has mentioned that would be the method used to try your best to make your through mortise and boring machine holes correctly, that is shim the base of your machine until the bit is true to the position you want.

Or you flatten your timber with a hand plane so that the machine sits correctly.

Just teasing......

[Brad_bb]

I was just curious how others would do it.  With shims/wedges, you're have to move them with the machine as you reposition for your next hole.  It would probably be more of a pain with a Boss because of it's small frame front end.  A machine with a wood base would probably be easier.  If this were a common issue, screw adjustable feet could be placed on the base.

[Raphael]

I do prefer the wooden base on my Millers Falls for that very reason.
Strips of thin plywood and veneer running down the timber work out really well, you can often clamp or pin them in place allowing you to move the machine up and down the mortice without disturbing them.

It really shouldn't be a common issue, if it is you might consider changing you timber supplier, species or milling technique.

[routestep]

Brad I shim up my boring machine or my chain mortiser also.

But, if time is not an issue get a T auger bit or two or three. As long as my beam is level (use Rafael's line on the end)I can use a T auger and not register on the face that I am boring into. It is slow but with a spotter I can go straight in to the wood.

[frwinks]

great thread Jim, too many printed/online articles and books assume working with perfectly milled sticks all the time.  What if people choose to work with live edge, crooked, waney, hewed, out of square, twisted funky stock? 
Here are some pics to help visualize the process of snap line square-rule   

plumb the timber in the center (will take out twist evenly on both ends)





plumb the ends mapping only the lines you need  (no sense of snapping too many lines or measuring off the center line)







I use the plumb lines on each end to establish the level lines on the other two faces if needed, and again only snap the lines I need ie. instead of a center line, I snap 4" off the edge for 2" M/T layout which becomes inside line of the M/T. 

Hope this saves a few timbers from the burn pile ;D

[Mad Professor]

If you can find a hewer, learn from him.  They start with "round out of square beams". Plenty of square houses/barns that they built.

Get a plumb bob, level, and compass/divider. Learn how to layout with the divider, you don't need a square or tape.

[Mad Professor]

great thread Jim, too many printed/online articles and books assume working with perfectly milled sticks all the time.  What if people choose to work with live edge, crooked, waney, hewed, out of square, twisted funky stock? 
Here are some pics to help visualize the process of snap line square-rule   

plumb the timber in the center (will take out twist evenly on both ends)





plumb the ends mapping only the lines you need  (no sense of snapping too many lines or measuring off the center line)







I use the plumb lines on each end to establish the level lines on the other two faces if needed, and again only snap the lines I need ie. instead of a center line, I snap 4" off the edge for 2" M/T layout which becomes inside line of the M/T. 

Hope this saves a few timbers from the burn pile ;D

Nice pictures!!  You can take a step back and go to "scribe" techniques.  Use a divider and a set circle to mark your beams  "true inner beam".

With the plum line on the end of your beam, the circle can also be used to mark the margins of the inner true beam, on the end of the beam.

The plum, at the end, can also be transfered to the "bottom" of the beam, another line is snapped, and you have a dead center on the opposite side.  Use your circle on the snapped line to lay out your joinery. If the beam is twisted /bent then another snapped line on each side gives you a starting point , and where to layout housings.....

[routestep]

I don't use a plumb bob that much in laying out timber joints, instead I use framing squares, combination square and spirit level.

But looking at frwirks' pictures I can see the utility of a plumb bob, using only gravity there is nothing that can bend or get out knocked out of square. But the spirit level becomes important I guess and having a good end cut.

frwirk - How did you set up your cut lines for the initial end cut?

[Raphael]

frwirk - How did you set up your cut lines for the initial end cut?

I'd start with a datum line down the 'reference' face of the leveled timber then square and plumb off of that to create a working end cut.

[Mad Professor]

I don't use a plumb bob that much in laying out timber joints, instead I use framing squares, combination square and spirit level.

But looking at frwirks' pictures I can see the utility of a plumb bob, using only gravity there is nothing that can bend or get out knocked out of square. But the spirit level becomes important I guess and having a good end cut.

frwirk - How did you set up your cut lines for the initial end cut?

Yes, a circle (or two) ( looks like a future 6 X 8"), on the end.  The same circles used on the "true beam".

Set your compass/divider settings on a beam for a reference you can come back to, SCRIBED INTO THE BEAMS WOOD.  Standardize all your beams/posts/ tenons/mortises to those dimensions.  Come back to those to get your settings again as needed. 

You do not need a square or a tape.....

[frwinks]

hi Mad P (may I call you Mad P ;D)  My ultimate TF goal is to go full scribe.  I've messed around with it on my current frame, not enough IMO, but due to space and timelines involved I had no choice.  I enjoy working with with unique sticks, scribing will allow me to get even more creative ;D ;D

initial cut? The rough cut I just eye ball, once the lines are snapped, everything else is laid out off the lines 

[Stumpkin]

Get a plumb bob, level, and compass/divider. Learn how to layout with the divider, you don't need a square or tape.

If you have a plumb bob what do you need a level for?

You will need a chalk line too.
A straight edge is very handy for connecting points laid out with the dividers.
My straight edge is bent 24" from one end at exactly 90 deg. very handy!

Learn how to layout with the divider! 
Then you will know how much time a square and a tape can save you.

Then you will want a laser. ;D

[Brad_bb]

A Stumpkin sighting!  Been awhile...

[Stumpkin]

When dealing with out of square timber it is sometimes useful to have a third hand to hold your square "out of square".





When laying out with the dividers it is difficult to set the center point of an arc on the edge of a timber. The problem is solved by a short piece of angle.



Drill and file the end like this. The dimple should be directly in line with the inside face of the angle.



Tom

[Stumpkin]

Checking a recycled timber for twist using multiple framing squares.



Line of sight works well for long timbers and when the wind is blowing too hard for plumb bobs and string lines.  Tom

[Raphael]

I really like that third hand for the square...  Did you fabricate that yourself or have it made?

[frwinks]

thanks for sharing the pics, great to see home made tools and all the different methods used by others