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Question on Square Rule

Started by mmhailey, October 01, 2010, 11:56:45 AM

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mmhailey

Well I started cutting timbers yesterday for my 16X24 Kingpost.





When I surveyed the 6 Posts, I was really surprised at their uniformity.  The smallest was an exact 8X8 and the largest was a 8 3/8". I did tell the sawyer to make sure and not undercut the dimensions, but after 1 year stickered I thought they might have shrunk a bit more. I haven't actually put a tape to the rest of the pile of 8X8's ie; rafters, girts, tie beams, but I'll bet they are pretty close  to the ones I have measured. Now for the question.

I did take a workshop a couple of years ago, and have done a couple of small projects since then, but they were all Mill Rule. I thought I would do this one using square rule. I thought I had it down, but now that I am ready to cut mortises , I am not so sure.  ::)  Here is a pic of what I have a question on?

This is Post one, and you are looking at West Side which is the best edge side.





I drew the model with full size timbers, and it turns out they all appear to be slightly oversize anywhere from an 1/8 to 3/8"

:-\ Do I get out the planer, and plane them all to 8" and call it Mill rule, or do I slip to 8" or even 7 1/2" and try Square rule?  If I do go to 7 1/2" do I have to change the positions of the top most edge of any of the mortises?

What would you do??? :-\

I have 2 more Post top Tenons to cut this morning, and also square off the bottoms, and cut the notches for the Rim Joists, so probably will not be ready to lay out mortises on the posts till later this weekend.

Give a man a fish, feed him for a day. Teach a man to fish, and turn him into a liar.

Jim_Rogers

Quote from: mmhailey on October 01, 2010, 11:56:45 AM

This is Post one, and you are looking at West Side which is the best edge side.





I drew the model with full size timbers, and it turns out they all appear to be slightly oversize anywhere from an 1/8 to 3/8"

:-\ Do I get out the planer, and plane them all to 8" and call it Mill rule, or do I slip to 8" or even 7 1/2" and try Square rule?

The reason you use square rule is so that you don't have to "get the planer out" and to make joints that come out right in timbers that are 1/8" to 3/8" oversized or undersized.

mm: if you want to begin with a mortise then layout the through mortise on the post, first. That is on the inside towards the tie beam, and also on the outside where the mortise will come through. We layout all mortises on both sides and drill in half way from both sides. Chisel the mortise out and make it the correct size and location, first. Then cut the timber to create the housing, reducing the timber width/thickness at the joint to your "perfect inner timber;" the 7 1/2" one inside.

The other things I see, based on your sketch model, is that you have the triangle on the wrong surface of the post. The side of the bent that goes towards the gable end of a building is the reference face. The side of the post, which is the outside of the building, and will be covered with siding is the adjacent face. The edge where these two surfaces meet is the arris where you pull all your dimensions from in order to make your measurements all come out right.

Second, thing I see, based on your sketch model, is that you have your brace in the wrong spot. It should move 1/2" to the right towards the post. The leg of the right triangle that makes up the brace layout starts at the shoulder of the tie beam at the housing, not at the surface of the post.

You may need to read my brace layout story again.

I hope that helps you to understand square rule.

And keep asking questions and trying the layout first before you cut anything.

Jim Rogers

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

Jim_Rogers

Here is the way I see it, or would do it:



This drawing shows the correct locations of the triangles for understanding and marking your reference face, adjacent face and the arris between the two.

Also it shows the two legs of the right triangle and the hypotenuse line on the brace.

The two legs of the right triangle have to be the same length (2'6" or 30") for the brace to be at a 45° angle.

Hope that helps.

Jim Rogers

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

Jim_Rogers

When you layout a tie beam mortise you want it too look like this before you start any cutting:



and the outside or adjacent face would look like this:



To begin to do this layout, what I would do is mark the two faces of my timber with the two triangles near the joint, and I usually mark these triangles on both ends of my timber as well. So that wherever I am standing, and looking at my timber, I can easily see the triangles.

The next thing I would do is locate my mortise/housing measurement on the arris.
This is shown on the drawings above as little black pencil tick marks on the edge of the timber. Not really big marks, but just enough so that you can see them, easily. And I would do them on both surfaces so that I can use them on both.

Once these marks are made, and they have to be at the correct spot so that the top of the tie beam is the correct elevation above the floor system, whatever that may be, we can basically put the tape measure away as we won't need it again. The rest of the layout can be done with a "Big Al" layout template or a framing square.

I'll assume you don't have a "big Al" so I'll describe how to do it with a framing square.

Now with your framing square against the adjacent face so that the tongue of the square is truly at 90° to the arris, place it like this, in line with the tick mark on the arris:



On the top scale of the framing square tongue, you measure over to the point where your housing will start which is 7 1/2" from the arris. So adding that to the 2" body of the square it should be 9 1/2" and you put your pencil down there and draw a line out to the edge of the timber. Whatever thickness the timber is doesn't matter just draw the line out towards the center of the building away from the arris.

Then move your framing square up and to the same at the other tick mark.

Next you flip your framing square over and a place it like this:



And now you can connect the first and second line you drew with a vertical line, to complete the layout on this side of this timber.

To insure that the framing square is in the right location and true to the arris the line (shown here as a black line, at the red arrow) should be in line with the arris on both the top and bottom of the tongue of the square.

More coming....



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

Jim_Rogers

Now you move to the inside of your timber or the correct name of this face is "opposite adjacent"....

And put your framing square on it like this:



Draw a line completely across the timber to the other edge, and then move the framing square up to the top of the housing and draw the top line. Keep the framing square tight to the reference face and you'll have a line that is 90° to the reference face.

After you have these two lines and with your layout being 2" off the layout face and then the mortise being two inches wide you can just lay your framing square on the surface and keep the back edge flush with the reference face and draw the first vertical line between the two housing lines:



Then slide the framing square over keeping the back side in line with the line you just made and watching the tongue line as well draw the second line:



This completes the four lines needed on this face of the timber.

The next thing you have to do is to do the outline of the housing on the face of the timber that is opposite the reference face.

You'd do that the same way you did the first outline of the housing but on the other side.

You must use the adjacent face to keep your framing square true and just draw the line, in line with the housing starting at the 7 1/2" offset point and out to the edge of the timber at both the top and bottom.

And then connect those two little lines with the vertical line, and those three lines are the only lines on that face of the timber.

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

Jim_Rogers

To finish off the housing on the opposite reference face you need to place your framing square like this:



And create the two little lines first. The move your framing square to create the 7 1/2" long vertical housing line connecting these two little lines as was done on the other side. This will complete the three lines needed on this side of the timber.

The last thing to do is to do the through mortise outline on the adjacent face.

To begin we only draw the lines that are cut lines as solid lines. And what I mean by that, and we see this very often when beginners start laying out joints, is that they usually draw a line all the way around or across a timber:

Like this:



A solid line is a cut line.

If you need to draw a line across a timber, for the purpose of locating some other point on another side, make it a dotted line, and never a solid line.

Someone else may think this is a cut line and cut your timber on that line, and make it worthless......

So you place your framing square like this:



And you only draw the line from 2" over to 4". Then move your framing square up to the top tick mark and again draw a line from 2" over to 4".

After you line up your framing square on the edge of the timber and draw a vertical line connecting the first end of these two lines. Then slide over 2" and use this first vertical line as a line up line and draw the second vertical line.

This complete the outline of the through mortise, on the adjacent face.

And the tie beam mortise with housing is laid out on all four sides of the post in the correct location and no extra lines.

End of today's lesson.....

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

mmhailey

Wow Jim... Now go rest your fingers!! That was great.

The sketchup pic is not very clear with small pixels, but it is a Gable end post. So my reference side is toward the gable end I believe.

The pic also shows that the girt was downsized to 7" from 8" just before it enters the post. This was from the original plans, and I suppose what the designer liked for a look, not a Square rule cut.  Here is another pic without the confusing dimensions. Post and Girt are 8X8 and brace is 4X6. Hopefully you can see the 1/2" housing for the brace, and the 1" housing for the girt.






I guess this is what confuses me so much... ( Not that it would take a lot) ... ???  In my mind the 1" cut as the girt enters the post should have no effect on the brace. The plane of the post and bottom of the girt ( prior to the cut back) are at 90 degrees. I cut both post and girt back to 7 1/2" at the brace housings, and everything works right? One housing on the post might be 5/8" deep or another might be 7/8 for whatever it takes to get down to the true 7 1/2" timber. Am I totally screwed up on this??







Give a man a fish, feed him for a day. Teach a man to fish, and turn him into a liar.

witterbound

I think you're on the right track.  I think what Jim saw in your first drawings was that you were pulling the 2'6 and 2'7 measurements from the 1" reduction on the girt.  As you have pointed out in your latest posting, you're really pulling the measurement using 7 1/2 inch reductions in both the post and girt.  So, you're triangle is really going to have girt and post legs of 2'6.5 inches, right?

Jim_Rogers

There are three points used to layout a right triangle and brace. Where the two end points of the hypotenuse are, is very important to laying out the brace right. The point where the 90° right angle is, does not matter that much. As it is just a point created to measure from but you have to understand where it is so that the measurements come out right.

And you can have a measurement line 2' 6 1/2" if you want. However it creates a odd length hypotenuse and a 30" brace layout makes a very nice 42.42" brace layout. 42.42 is 42 and 7/16's inches roughly.

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

mmhailey

Jim.... Thanks again for your help.  Your discussion of how to layout from the arris on a post was great. Whenever you write your book, make sure and save that part as a chapter.....

My intention all along was to have a 2'6" ( 30") brace layout. The 1" cut back from this original set of plans added so much confusion I have just decided to layout with the standard cut back to the true timber. Actually I measured my girts last night, and some are pushing 8 7/16 so cutting back to the 7 1/2" will show up pretty dramatically anyway.

Here is a sketchup I did, hopefully to help me layout the housings today.





The Hypotenuse is hard to see where it is coming from, but it's starting point is inside the housing, not at the outer edge. I have a couple of hours of finishing off the bottoms of the posts this morning, then I'll need to redo my story pole, with the new dimensions. I'll check at lunch time too see if anybody made any further comments.



Give a man a fish, feed him for a day. Teach a man to fish, and turn him into a liar.

Jim_Rogers

mm:
Was there a question in your last post?

It looks right to me.....

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

mmhailey

Jim,

No question I suppose. If you agree that the layout for the brace pockets look good, I'm happy too  8)

Cutting the mortises, and housings for the 6 posts should keep me busy for a week or so, then my next item will be Girts which shouldn't take that long.

I will have more questions on this thread I am sure. I haven't got my head around Square rule when it comes to laying out my Kingposts. 

Thanks again for everyone's help.  I am taking pictures and promise to post some.

As they say " More to follow"



Give a man a fish, feed him for a day. Teach a man to fish, and turn him into a liar.

swampfox

Hey MM,

Jim sure does make quality posts around here!

One other thing you might want to look at is the nosings of your braces.  I would not want the bottom of the brace to terminate inside a housing (for instance on your bigger sticks).  You could take the biggest timber and find the correct nosing for that and duplicate or you could make a different brace for some larger sticks that are not common.

As far as the kingpost, my suggestion would be to snap a centerline and work off of that for your housings.  In short you are establishing the reference edge as a center of your post.

Good Luck

Jim_Rogers

If the brace is laid out right there shouldn't be a point on the end of the brace.

It should look like this:

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

swampfox

I was speaking of the nosing being all the way in the housing.




This one is over emphasized, but if you have standard square rule braces with equal nosings and along comes an 8 1/2 timber you could find your standard bracing looking something like above.  I would just make a different brace because it looks not right to me.

mmhailey

I had read that you might want to increase the 3/8" line a bit for larger brace Stock. I haven't taken the tin off the pile of purlins, and brace stock yet, so I don't really know what my dimensions will be. If they are too big, I'll just run them through my portable Planer.

Got all my post top tenons done and have started on the girt mortises.



Give a man a fish, feed him for a day. Teach a man to fish, and turn him into a liar.

Jim_Rogers

swampfox:
I do understand your point, but your dimensions appear to be off a bit.

When you are laying out a brace for a 1/2" reduced timber joint you use a 3/8" layout line on the brace which is the hypotenuse of the right triangle.

Like this:



This insures that the "nosing" is 1/2" and it should match the depth of the housing......

However if the timber is way oversized as you have shown then yes, it won't look right.

If this was the case then to make the brace "look right" you would move your 3/8" layout line to be a further away from the actual face of the timber.

Like this:



But this would have to be done on both ends in order for the brace to remain at a 45°

The brace layout line is located on the brace in direct proportion to the depth of the housing. The deeper the housing the further the brace layout line is away from the actual arris of the brace stock.

I hope this helps all to understand brace layout.

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

mmhailey

Another question.

Which side of the tie beam do you reduce to 7 1/2"?  Top or bottom?





I am guessing the bottom, but I am not sure it matters?

Give a man a fish, feed him for a day. Teach a man to fish, and turn him into a liar.

Jim_Rogers

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

mmhailey

I made the changes to my Sketchup model, to depict the cut back to the 7 1/2 perfect timber.





Thanks for the info.  :)
Give a man a fish, feed him for a day. Teach a man to fish, and turn him into a liar.

canopy

I am guessing the bottom, but I am not sure it matters?

It matters a lot. In square rule the top would be the reference surface to keep the beam level and at the correct height which is necessary to keep margins from stacking up and becoming a tower of babel. The critical thinking about square rule is you don't just cut 1/2" off the bottom of the tie beam to achieve that height. You must measure from the *top* of the tie beam down 7.5" and cut off whatever is left which only on a perfect timber would be 1/2", but real world will be a little more or less.

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