Cutting angles for checked in gate

[Tiger]

I'm thinking of putting a gate on a couple of set back fence posts. These posts are set back at about 45 degrees to the rest of the fence. I have seen one property near by that also has this arrangment. It looks like they have notched the rails to fit around the posts. How do you accurately work out the cut out angle on the rails so that you get a good fit on the posts?

[Tiger]

Upon reading this post I realised it perhaps wasn't as clear as it could be. I have a fence line at the front of the property. The property slopes down away from the house. I'm thinking of attaching a gate to some posts which are set back from the main fence at approx 40 degrees. These posts are about 700 mm away (perpendicular) from what would be the fence line. The set back posts are also on higher ground as the property slopes upward from the fence line. My question is how do you work out the compound angles of the rails that would attach from the fence posts to the set back gate posts. You would have 2 angles to worry about as the set back posts are on higher ground. I had a go with some scrap 70 x 35 and didn't get far. Hope this makes sense.

[joe greiner]

Makes a lot more sense now. As I understand it, the posts are more or less square, and you wish to place the sloping rails so that a V-notch at each end straddles a corner of the post. The angles can be calculated, but a graphical layout to scale (or full size if feasible) would be simpler.

Establish horizontal work points as the corners to be straddled. Distance 'x' is measured parallel to the fence; distance 'y' is measured perpendicular (your approximate value of 700). Call the diagonal measure between work points 'L1.' Now draw another triangle with 'L1' as the horizontal measure, and a vertical measure 'z' for the vertical offset. The hypotenuse of this triangle is the true length along the top surface of the rail between work points.

Now it gets complicated. In a production environment, angles from the second triangle could be used to make a sled fixture, and angles from the first triangle could be used for table saw angle settings. But you only have one or two (or three?) rails for each side of the gate, and you'd likely waste a lot of timber to mistakes in setting up. And note that the two sides may have slightly different geometries. So marking the timber for each cut with a hand saw may be more expeditious.

It would take several pages to explain the layout in words, so I've made a sketch to illustrate the process. Measurements 'x', 'y', 'z', 'L1', and 'L2' are as described above. 'W' and 'T' are the rail dimensions. Lines which appear to be parallel are parallel, and lines which appear to be perpendicular are perpendicular. The two rotated squares at the lower part of the sketch are the fence and gate posts. The entire drawing need not be made full size; having secured the true length 'L2' and the angles, only the end details need to be drawn full size and transferred to the timber.

Maybe this will help. A real carpenter may be able to provide some more insight.

Joe

[Tiger]

Thanks, Joe. You have pretty well summed up the problem.I tried using a test piece but couldn't get close enough to be really satisfied with my result. I can't imagine a carpenter spending too much time on just four small rails. I thought about using geometry and trigonometry but even that wouldn't give you the precision that you need to make a nice flush fitting job. I like your idea of setting out on paper and will give it a try but like you said a fully fledged carpenter would have some system in place for dealing with these situations.

[journeyman Mick]

Well I guess I'm fully fledged . I'd set all the posts in their holes then mark where the rails are to run. I'd run string lines where the rails are to meet at each post. If they are to be have a V notch in the end to meet the posts at an angle then you'll need to run the stringline on the top centreline of the rails. Measure along the stringlines for the rail lengths and use a bevel to work out all your angles. There's probably a more elegant, mathematical way of working it, but this is how I'd do it.

Mick

[joe greiner]

There's probably a more elegant, mathematical way of working it ...
Mick

Maybe, maybe not. Sounds pretty direct to me. With two different bevels (top and sides), a ship carpenters bevel would be handy. May late Dad had one of these:

http://www.goantiques.com/detail,luf...ers,91846.html

in his collection. Several years ago, I discussed it with a Lufkin rep for identification. The consensus was that the different blade lengths facilitate remembering which was which on the way from the ship to the bench.

Joe

[journeyman Mick]

I've seen pics of those double ended bevel but never seen one for sale, otherwise I'd probably own one or two. When I was doing boat fit outs I'd usually have three or four bevels with me, and seeing they're all different it was easy enough to keep the angles sorted. I'd usually mark the end of the timber I was cutting (usually a scrap for trial fitting anyway) with exaggerated approximations of the required angles. The angles were usually quite different so this worked well to keep them sorted also.

Mick

[Tiger]

<TABLE id=HB_Mail_Container height="100%" cellSpacing=0 cellPadding=0 width="100%" border=0 UNSELECTABLE="on"><TBODY><TR height="100%" UNSELECTABLE="on" width="100%"><TD id=HB_Focus_Element vAlign=top width="100%" background="" height=250 UNSELECTABLE="off">Thanks for that Mick, stringlines are the way to go. Good to hear from you again. I know you've had a terrible loss recently but the thread was closed before I could send condolences. I hope that things are a little up for you now.


Joe, nice tool but not sure that would help me much as the posts are a metre away and the rail slopes upwards so you'd need a bevel that could swivel in 2 different planes.
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[joe greiner]

Joe, nice tool but not sure that would help me much as the posts are a metre away and the rail slopes upwards so you'd need a bevel that could swivel in 2 different planes.

Not exactly, Tiger. You use one bevel to mark the top and bottom, and the other one to mark the sides, transferring around the cross section of the rail. I've met some folks who made their own ship carpenter's bevels, but two separate bevels with a dab of paint on one of them if they're identical would work just as well.

Joe