Fitting Tubes at Home for Welding

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About: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying posting things I have learned and done since I got my first ...

Intro: Fitting Tubes at Home for Welding

You have a project that requires you to weld tubing together at a right angle, but you do not have any commercially made equipment for cutting a nice concave in the end of a tube where it joins another tube. This Instructable will show you how to do a good job in your home workshop.

I do not like welding EMT (conduit). I am using it here solely for the sake of illustration. What this Instructable demonstrates would work well with black pipe.

Step 1: My Setup

I am using a metal cut-off wheel mounted on a radial arm saw. The metal tube rests on a small accessory table I made.

Step 2: Make a Table

I made an accessory table from scraps of plywood. It is about 4 inches high. The surface is about 6 x 17 inches. I use it for a variety of things, including holding work while I use a drill chuck on the right end of the arbor for special drilling operations. The table has a flat surface on its bottom so I can clamp it to the saw table.

Any horizontal arbor would work if you do not have a radial arm saw. But, there will be some things about this process that will rely more on your eye and less on the guidance provided by the table.

Step 3: Raise or Lower the Saw Arm

Raise or lower the saw arm so the center of the shaft is at the same level as the center of the tube. When you grind a profile in the top of the tube, the same profile will be produced in the bottom of the tube. That is the key to coping the tube end for the tube to which it will join by welding.

Step 4: Use Masking Tape

I use masking tape to mark something I want to cut or grind. It makes something very easy to see, despite the bright sparks and (normally) dark metal against a dark stone. Wrap a little masking tape around the end of one tube.

Step 5: The End Goal

The end goal will be to cut a profile in the end of one tube so it very closely fits the contour of the other tube's side.

Step 6: Mark the Profile

Use a marker pen to outline the desired profile on the masking tape. Do not worry if you cannot accurately draw the whole profile.

Step 7: Start Grinding

Start grinding. You are guiding the process by your hand and eye while the tube rests on the accessory table. Go slowly. Try not to roll the tube, but to keep pointing up the same part of the tube that was upmost at the start of the grinding process.

Step 8: Check Your Work

Stop frequently to check your work, especially as you are nearer to completion of the task. Here you can see quite a gap. More grinding is needed on the two shoulders. Go slowly and check often.

Step 9: Finished

Here you see the two tubes fitted together ready for welding or brazing. The fit is almost as good as a machine designed for this job might do. Obviously, this is not for the demands of production, but it works well for an occasional project at home. Any small gaps can easily be filled by the welding or brazing process.

With some care, you could use this process to cope tubes that will meet at angles other than 90 degrees. Some extra planning would need to go into your setup.

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    37 Discussions

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    TiggerLube

    4 years ago on Introduction

    I have used white vinegar on galvanized metal to make paint stick more efficiently, but never used it to prep for welding. I just open the shop doors and turn on a fan.

    I like the idea of doing the double miter cuts as away to make the pipe fit better.

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    RamboBrite

    5 years ago on Introduction

    When it comes to welding EMT conduit, your best solution is to avoid welding it at all costs. However, if you do any projects with welding it, either have a fan handy to get the fumes away from you, or sand down the galvanized coating to bare metal out to about 2"-3" away from where you're working. There will still be smoke coming from the interior coating, so you'll still want plenty of ventilation. Also, invest in a respirator. They're cheap.

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    moisture

    9 years ago on Introduction

    Great tip, thanks. You mention welding conduit: can you give some tips on how to do this without poisoning yourself? If you have the time, an instructable on the subject would be fantastic.

    6 replies
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    dodgedartgtmoisture

    Reply 8 years ago on Introduction

    A coworker at a previous job was a journeyman welder. I remeber him discussing a a job he did on-site in a factory using all galvanized materials for the structures they were making.
    I do not recall him mentioning about grinding off the zinc coating. i DO recall him mentioning that the welding fumes from galvanized were a huge problem. They made every effort to avoid the fumes (masks, etc...) but also he said to drink a lot of milk to absorb and counteract the effects from breathing the fumes.
    Mike Bynum

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    weldordodgedartgt

    Reply 6 years ago on Introduction

    Milk SHOULD NOT be used as an antidote for zinc poisoning. This is a dangerous old wives tale! There is nothing in milk that counteracts the effects of the zinc in your system.
    Zinc poisoning occurs in two ways -ACUTE from large amounts in a very short period of time and Cummunlative from exposure to relatively low doses over a long period of time.
    ALWAYS USE A RESPIRATOR AND ADEQUATE VENTILATION WHEN WELDING ZINK COATED PRODUCTS.

    Also remember that grinding the zing off of the out side of pipe/tubing does not remove the zinc from thet insider of the work piece. For flat work you also have to clean both sides as well.

    Weld safe or die!

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    nedfunnellmoisture

    Reply 9 years ago on Introduction

    Grind off the zinc coating up to an inch beyond the weld and still ventilate well. While welds can be deposited through galvanized coatings, it is not a good idea from a weld integrity standpoint.

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    gamnopartsnedfunnell

    Reply 8 years ago on Introduction

    I've done plenty of welding on galvanized material, & we never ground it out, but it does stink & is bad for you, but if you know you're going to be welding it & drink some milk beforehand, it will prevent you from getting sick.  Don't ask me how it works, but it definitely prevented me from tossing my breakfast on more than one occasion. Of course, I do NOT condone, or recommend it. ;)

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    Phil Bmoisture

    Reply 9 years ago on Introduction

    I am only a home hobby welder with no real training. I know the zinc coating on galvanized metals creates problems with the weld as well as making unhealthful fumes. The few times I have done it, I have tried for as much ventilation as possible. It is also a good idea to grind off the coating in the area where you will be welding. It still seemed to be difficult to make the arc behave.

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    2 stroke

    8 years ago on Introduction

    when i weld conduit with my stick welder it smokes a lot and crates a heck of a lot of smoke i wear a swiming snorkel withe the tube away from what i am welding so i dont breathe i extended the tube with some waster drain hose that i bought new why does it smoke a lot

    4 replies
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    sillywilly2 stroke

    Reply 6 years ago on Introduction

    That's the galvanized coating burning away! This smoke is very toxic and should be avoided at all costs. I usually set up a fan to blow smoke and fumes away from where I am working but the snorkel idea is good also. The best and most convenient way to weld it is to have an exhaust fan hood over your welding area in addition to small fan blowing fumes away, towards the hood. I like using EMT for jobs that do not require too much strength. It will burn through when using a buzz box. I prefer brazing it since I have a gas welding setup I've owned most of my adult life. Works good although the acetylene sure has gotten expensive over the years!

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    2 stroke sillywilly

    Reply 6 years ago on Introduction

    nah welding it with a buzz boz is easy just tack it insted of running a bead and use 1/16 welding rod and put the welder as low as it can go gas welding is good too but i suck at it i was doing it in metalshop. it seems to be a very slow and boring process. not to mention it warps the steel like crazy stick,and wire for life lol

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    djohnson42

    7 years ago on Introduction

    Let's not make this difficult! I've used this method for up to 2" dia. carbon steel pipe (schedule 40 and thinner): Insert the pipe you want to "miter" into a vise in either the horizontal or vertical position. Use a "torpedo" level to make sure it is positioned correctly. Heat the end to be mitered with an oxy-acetylene torch until it is almost white-hot. Position the side of a short cool length of the size pipe you want to match to the miter at 90 degrees against the heated end and strike the cool pipe with a 6 lbs. mall. I use a torpedo level to be sure I'm holding the cool pipe at the correct angle. If the angle you want is not 90 degrees, use a magnetic angle finder to position the cool pipe before striking. With a little practice, you'll make a perfect fit every time, and it only takes a minute or so. If you need an angle less than eighty degrees, or so, the cool pipe may slip when struck with the mall. In that case, get as sharp an angle as you can, tack the cool pipe to the hot pipe on the side that doesn't need to be coped more, re-heat the part of the hot pipe that needs more cope -- and strike that part of the cool pipe until you get your correct angle on the hot pipe. This method is frequently used for modifying pipe handrail in the field.

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    Phil Bdjohnson42

    Reply 7 years ago on Introduction

    I commend you on a very interesting way to make coped joints on metal tubes. But, there is one problem. Many of us do not have an oxy-acetylene torch, including myself. I was trying for a workable, if imperfect, way someone with a basic arc welder and a simple grinding wheel could do a reasonable job at making a coped joint for welding.

    I see you are a quite new member of Instructables. One thing you will learn is that many of us do not have a welder. I am very thankful that I finally do. I try to be cautious about publishing things that require a welder. When I can I suggest ways someone without a welder can complete the project I am describing. Even when I do a project that requires welding, I try to remember many who might read about it will not feel left out. Perhaps you might do an Instructable on your way of making coped joints for metal tubes.

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    purplewg

    8 years ago on Introduction

    You can remove the galvanize by soaking the ends to be welded in Muratic acid. The same stuff they add to pool water. Just use good ventilation outside. Let it soak for about 30 minutes and rinse with water. I use it full strength. I do this on EMT and Galvanized pipe.

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    Some good ideas. Could you also drill the pipe with a bit close to the diameter of the pipe