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View Full Version : Anybody have any tips on cutting a 45 on large pipe

kyleb0789
04-17-2012, 01:29 AM
I have to cut a 45 on some large pipe. I think it's 26" not for sure just know it has been used and ain't perfect round. I have 20 of them to do they are just going to be drop pipes for a ditch so don't have to be perfect. I don't have a pipe wrap or anything to use so was wondering what's the best way to get them as close as possible without one any help would be greatly appreciated. Thanks

mrmikey
04-17-2012, 03:50 AM
A couple of if's,
If you have access to a crane and if they're not too long. Pick them up from one end and hang them at a 45° to the floor and use that as a surface table marking around the circumference.....Mike

kyleb0789
04-17-2012, 04:04 AM
They are going to be out in the field will have a excavator though. But I have to cut a 45 on the culvert pipe and one on the riser so it will come up to form a 90

WookieWelding
04-17-2012, 07:05 AM
get yourself a pipe wrap and punch it out then cut its not like there expensive

ExpatWelder
04-17-2012, 08:56 AM
You don't have to have a pipe wrap, you can use a belt, some cardboard, some drywall tape, just about anything you have lying around. Drywall tape works great because once you get the circumferance, you can double and fold the tape over and over then put it back around the pipe and the creases where you folded it indicate where to mark for the layout.--Matt

fdcmiami
04-17-2012, 10:34 AM
i was going to post a description of how to layout a 90 degree el. two 45 degree sections. graphically and mathematically. then figured if you had to come here and ask what to do and you don't know for certain the exact diameter of the pipe and so on, then why bother.

my first suggestion would be find the diameter of the pipe. if you can't measure across the opening for the diameter then wrap a tape around the pipe and divide by Pi (its a function on most calculators)

if they are all the same call someone and have them print you out a pattern; or patterns if they are different. that was the best suggestion so far. if you attempt to do anything else you are going to have a big mess on your hands. fitting pipe gores together that have been laid out by someone that hasn't done it before is generally a nightmarish experience

go to a sheet metal shop, preferably industrial ventilation, find a guy with gray hair and see if he'll layout the pattern for you. lol

good luck.

kyleb0789
04-17-2012, 10:13 PM
I haven't Been out to see the pipe yet the guy just called me and told me he had some used pipe he needed elbows put on. But I would appreciate if u could post more info on how to mathematically figure it and info on how to use the cardboard and tape plz thanks for the replies

ExpatWelder
04-18-2012, 04:53 AM

fdcmiami
04-18-2012, 07:44 AM
They are going to be out in the field will have a excavator though. But I have to cut a 45 on the culvert pipe and one on the riser so it will come up to form a 90

this is a pretty simple problem (if you've done it a hundred times lol) the 90 is done with one cut. if done correctly the piece that drops can be turned 180 degrees and will mate with the throat of the other piece. this is why it is important to get your cut close, if you don't you will be in need of a wirefeeder and a lot of wire. a LOT of wire if you are doing 20 pipes. also, although you say it's not important you have to admit it will look better if your pipe finishes plumb.

the flat pattern is the most simple of patterns except for one thing, if you are going to lay it out manually and use a steel square to connect your lines, that line pattern is not something that is easily done, it comes with the experience of having done it a few times.

my first suggestion would be to call this outfit. it looks like they are close to you.

http://www.claytonfab.com/

find out about having a piece cut. 26 ga sheet metal would be good and fairly sturdy in the field. or you could use the flat pattern to lay out some paper templates and throw them away after you make your marks.

it's a good idea to leave a center punch mark at the 180 degree point of the dropped piece to match up to zero on the throat; this alignment will save you some grief on the fitup.

now, a 26 in pipe pattern is going to be kind of big, the elevation of the opposite side, at 180 degrees will be app 26 inches. tan 45 = 1 26 x 1 = 26. for simplicity, i am aware the pipe od will be a little greater.

so if you allow for a four inch throat you will end up having a piece that is 30 inches wide at one point. the advantage to having the pattern like this, if it will fit, is that you now have a straight edge on one end to true up the pattern. do this by finding center point of your pipe at the top; 0 degrees. we would sometimes, because we had the facilities, add an extra 6 inches to the cut length at the throat and put in a standing seam witth a couple of holes to slide a bolt through to pull the pattern tight. field conditions usually determine if this is necessary.

if this wrapper turns out to be to big for conditions then you can still trimp it to form the cut profile, it just gets a little trickier from there.

there is also another sheet metal shop in the area, duncan sheet metal, some of these old farm support shops have some decent layout guys in them, they fabricated a lot of the round work you see, or used to see, coming out of grain silos, lumber yards, fabric co's etc.

good luck.

fdcmiami
04-18-2012, 06:09 PM
the flat pattern is the most simple of patterns except for one thing, if you are going to lay it out manually and use a steel square to connect your lines, that line pattern is not something that is easily done, it comes with the experience of having done it a few times.

this should have read; the 90 degree el is one of the easiest patterns to layout. consisting of two 45's. it is also one of the more uncommon; how many right angle directional changes do you see in pipe. i am talking hard rights, no radius.

the steel square, it was early, should have read steel rule. we would use a 72 inch spring steel rule (they could literally be rolled up) to connect the points laid out on the pattern.
again, this is not for beginners.

if i were to get this job today i might do the layout myself or i might just pick up the phone and have the pattern done for me. in your case however i would strongly urge you to have a pro do the layout for you or you'll be working on those pipes come christmas. not to mention the extra welding rod, grinding discs and oxy'/acetylene you will need to make them work.