i have a difficult question to put into words in a title !!!

Brace the 6" pipe outside not inside with 4" pipe.

I fully understand what you are saying...

Get some thin card roll it into a 4" tube by wraping it around the pipe and taping it.

Remove tube from the pipe then cut it with scisors until you eventually get the right profile.

Place the card tube back over the pipe and mark it!

Then play with your favourite angle grinder!

BTW, that's called using CAD !

(cardboard aided design)...

I am about to rcv my CADD degree. I think I overpaid.

Who says you need a $$$$$ computer drafting system, when you can buy sissors and cardboard!

Or get a 4" hole cutter and cut a hole in the 6" pipe! Insert the 4" tube and weld it! maybe easier!

Or get a 4" hole cutter and cut a hole in the 6" pipe! Insert the 4" tube and weld it! maybe easier!

Actually, you want to use a 6 inch hole saw on the 4" pipe, at whatever angle they will meet. This assumes that you don't wish to weaken the 6" pipe at the join. See The Old Joint Jigger (Google "joint jigger" - I'd provide the link but the server cuts me off when I try) for the method. Their tool is too small, but a good-sized drill press or a milling machine should be able to handle what you need; it will just take more time to set up. You can even have non-intersecting centerlines (oblique) and this method will work fine. Use the angle grinder to bevel edges as joint preparation.

They always are on display at AirVenture (Oshkosh, WI EAA fly-in: on now) and are widely used in building tubular fuselage structures.

what you really need is a pipe marking tool, buy beg or borrow one and the desired angles will be a cinch. Curve O Mark is a good one. Anyone who works with pipe much will have one and maybe you can borrow it or get them to mark it out for you , won't take em a minute. jack

There are tools that pipe fitters use to roll in 45's. They are wraparounds and pipe fitters' handbook.

I do not think that you need to roll in a four inch fortyfve to a six inch pipe because....depending on the method of shoreline anchoring it would not necessarily be required to roll in the four inch for welding. If you plan on a concrete anchor then you may consider an alternative, easier method of placing the four inch pipe.

Fix the six inch pipe. Place the concrete shoreline base with a four inch by 3/4" plate imbedded vertically for the final weld to the four inch pipe. After measuring and cutting the four inch roll in then crush the ends closed. The ends can be crushed over four inch plate as above and welded to the pipe. Cut the plate to forty fives and weld to the six inch vertical and the four by 3/4 plate base.

y

The four inch can be cut to fortyfives or nineties on both ends. The four inch pipe with plate welded in place could be clamped to the base plate, welded to the six inch pipe, and cut and welded to the base plate for final tiein.

You need a pipe fitters blue book which has tables with measurements to guide one through the different sized lay outs. You can try Pipefitter.com-Fishmouth Computer Calculated Pipe Template Measures that deals with most all known laterals, saddles, miters etc.one might run across. But if you are only doing a few of the same size then the cardboard method works as good as any in my opinion.

pipewelder

Hey ... as 'Pipewelder', we all defer to you ...

(Do I get a gold star ?...Or one of Hendrik's GOOZ cards?)

You'll get the patent for the Cardboard-Aided Design software I suppossed...

Good one there!!

what about the hole in the six inch? will cardboard work for it too?

That wasn't my idea...

But... Don't be silly a cardboard hole just isn't strong enough...

Even the holes on our golf course need to be stronger than that...for the rare occaision when something falls into them...

We now get them from China, but you have to be carefull when handling them as they smash if you drop one onto a hard surface.

There again, I think everyone may have missed the point. The angle is arbitrary. The pipe would have to be cut with a 3" radius cutter, assuming of course that the diameter of the 6" pipe is actually 6". I am not sure about the actual diameter of a 6" pipe as the nominal size is usually not the actual size. However, a pair of calipers would remedy that problem. The other thing I am thinking (dangerous) is that if you are welding the pipes together that you may only need to roughly fit the pipes together by hand grinding and allowing the weld to fill the gaps. This would be trial and error of course but under some circumstances this may be your only option (such as not having a milling machine or 3" radius cutter available).

And what point did I miss back at trick 1 eh?

You did not reveal that the angle at which the 4" pipe is welded to the 6" pipe is not terribly important. He may choose any angle that suits his fancy.

Yes exactly, you muppet!

My method allows him to do whatever he likes at any angle he chooses!!!

I demand my gold star else I shall throw my toy mouse out of my basket!

Oooh sorry I see you are not a muppet but a Dr Suess character!

Oh nevermind. I yield to one who must get the last meow.

How about using a trammel! ie, a small block of wood that you follow round the 4"pipe marking it off as you go! then get your angle grinder and.........

If you get a pipe fitters blue book you simply look up a 4" on 6" lateral for what ever angle, divide the branch pipe into 8 equal sections, layout the measurments from the table and connect the dots with a stiff bendable straight edge( broken band saw blade) Clean your torch tip and cut the sucker. After you get the saddle(branch) cut use it or make a template from it to layout the hole in the header pc. all this should not take over 15 to 20 minutes. The cutting is the easy part the layout takes a little more time. There is another way that templates can be made on a drafting table but although they are really accurate I don't think that degree of accurcy is needed here. I have made hundreds of cuts like these on fences where i use a 4" post and 2" pipe rails. It is alot easier in this case to cut the hole in the header a little larger and just stick the square cut branch into the hole so no saddle cut is nessasary. This works better because it eleminates the saddle cut altogether.

pipewelder

Why don't you crush the four inch and forget the cardboard and fitters handbook?

Cardboard does not work well. The expense of a wraparound and fitters handbook may be prohibitive. Besides it appears we are dealing with cardboard hole mentality and that ain't smart... to have to deal with it, that is.

Sometimes Fitters use a simple method to do this job. Square cut the 4 " pipe end. Keep it perpendicular on the circumference of 6" pipe. take a 10 gauge stub of wire about 3"-4" long. Keep this piece of stub length-wise at different points on the circumference of the 4" pipe, letting one end touch the circumference of the 6" pipe. Mark the corresponding points at the other end on the 4" pipe which will give points of the profile to be cut. Usually fabricators follow this method at the site when they do not have pipe fitter's tables.

We are not using this pipe for transmission or storage so why hassle a newbie with a four inch to six inch rollin fit? One question is how is the four inch to be anchored at shoreline or is it to be driven into earth?

This is called the trammel method! I've used it many times for all sorts of things including carpet cutting, wooden joints, skirting boards, kitchen worktops, etc, etc! Never fails me!

The idea of cutting a paper template and wrapping it around the smaller tube to mark the cutting line works well. A few years ago we bought an operation that did this type joint routinely. They were using a "cut and try" method of making the templates, and one of the guys had a pretty good eye for that method. I applied a little trigonometry to the problem for a better fit, and developed an Excel spread sheet to calculate the points of the require curve. From another reply it sounds like the result probably duplicate tables found in some Pipe Fitters manuals.

I didn't see any way to attach a file to this reply, but would be happy to e-mail the Excel file to you or post it someplace for general use.

Be sure to include calculations that include wall thickness differences.