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Up Topic Welding Industry / Welding Fundamentals / Center to Center layouts
- - By aevald (*****) Date 11-07-2006 22:11
Hello everyone, I just thought of this one the other day. It's probably one of the most basic of things that most fabricators learn at the beginning of their careers, so it could also be overlooked fairly easily too. Whenever an item requires a series of parts to be laid out on a specific spacing such as the rails for handrails or rungs on a ladder or other similar such items, it is usually simpler and more accurate to make these layouts using a running dimension and also lining up the parts, edge to line.
     An example: a simple ladder made out of 1-1/2" tube steel. Let's say the ladder is 5'-8" tall and the rungs are 1'-6" wide, the first rung will probably be located on a 1'-0" center above the ground line and then each additional rung will be 1'-0" away from the other one until you reach the 5'-0" mark, thus requiring 5 rungs for this ladder. To begin the layout you will generally find the center point 1'-0" away from the end of the ladder side rail, once this point has been located you can either go 3/4" less than this dimension or 3/4" more than this dimension and draw a line across the material, this is the edge that you would line up the edge of the rung with. If I drew my line at 11-1/4" I would put an X on the side of the line that would be greater than this dimension and that is the side that I would locate the rung on. If I put my line at 12-3/4" I would put an X on the side of the line that is less than this dimension and that is the side that I would locate the rung on. After I had located the first mark at either the 11-1/4" or the 12-3/4" point I would use this mark to layout the rest of the lines for the additional rungs. I would put my tape's 1'-0" mark on the first line and then at the 2'-0", 3'-0", 4'-0", and 5'-0" points I would put the other marks on the ladder side rail. Once I had completed this process I would take the other ladder side rail and put it side by side with the rail that I had just marked and transfer the marks across the one rail to the other one. I could then proceed to line up the rungs with the marks on the two side rails, pull them into place with some furniture clamps or similar holding devices and then take a diagonal measurement from corner to corner from both sides of the ladder, shifting it until these dimensions were the same and proceed to tack it together. Once I had tacked it, I would most likely use a piece of scrap material tacked diagonally across the two rails to hold them in position while I welded it out.
     When you did the layout for the side rails you would NOT want to make your measurements with a 1'-0" rule measuring from one layout point to the next, as you could accumulate a lot of error this way. Hope this made sense and that someone might be able to use this process to help them out. Regards, aevald
Parent - - By Sourdough (****) Date 11-12-2006 04:01
I know this may be redundant, but autocad or any similar software can save you a bunch of time, unless of course you are in the field at the time. At that time I get on my laptop. Within 30 seconds I have a layout that I can print out and have a foreman/toolpusher approve. This is coming from a highschool drop out! I love my job. . .

Thought you guys got rid of me, didn't you??
Parent - By webbcity (***) Date 11-12-2006 04:21
sourdough , you did good . i wish i would have learned more about computers but know what i must do - thats to get my son trained so he can do that . if i live long enough  i'll try to make one more road trip and see you and others on this forum . stay in touch  willie 
Parent - By aevald (*****) Date 11-12-2006 08:11 Edited 11-12-2006 16:28
Hey there Sourdough, the main reason for this post was to give some of the less experienced folks out there a heads-up on some basic layout techniques. I would certainly agree that autocad and other drafting tools and programs can save a fellow a ton of grief and time when it comes to layouts.
     I have seen folks do layouts for ladders(and other things) using the blade on their tri-square and moving from one mark to the next, doing one side and then the other, and then wondering why it looked all out of kilter when they got done. CUMMULATIVE ERROR, it'll get you every time. One of the points of my post was to stress selecting a ground zero point (so to speak) and then to make sure that everything that is done on a particular part or project relates to that point and by doing so will save a lot of problems in the end. 
     Another thing to note (this would apply to what you said about using autocad), many times when I have fabricated stairs for various applications I have run into some notations on prints that can be somewhat frustrating. Have you ever seen a notation on a print that looks something like this: ( 11 spaces @ 1'-0 3/4" + = 11'-8 7/8" ) ? If you multiply the 1'-0 3/4" by 11 it doesn't equal 11'-8 7/8", so to do this correctly and have it work out as it should, you need to take the 11' - 8 7/8" and divide it by 11, using the product from this you would first take this answer and round it to the nearest 1/16", then go back to the answer in it's long form and multiply it by 2, then round it again, multiply it by 3, round it again and proceed to do this until your final answer was the 11'- 8 7/8". Some might argue that you don't need this sort of accuracy, I would say that a craftsman will strive to be as accurate as possible at all times and in the long run attention to detail will save you a lot of grief and problems. Have a good one everyone, Regards, aevald
Up Topic Welding Industry / Welding Fundamentals / Center to Center layouts

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