Another newbie question....

I am making a stand for my new mini-mill - imagine a rectanglular shape
made of 1 inch steel tubing welded together. Problem is, I cant seem to
stop the damm thing from distorting - I can get it square by
measurement, but it distorts in the horizontal plane. I tack welded
each corner, that went ok, but when I finished the seams, it was
twisted. Is there an order of welding I should be doing, do I belt it
flat with a 10lb hammer - what? I am using a stick welder - dont have a
MIG so I am aware its the heat "pulling" it out of true. There must be
a way of overcoming this......any suggestions?

Andrew VK3BFA.

Andrew VK3BFA wrote:

I tack welded each corner, that went ok, but when I finished the seams, it
was twisted.

The first step was OK, the second wrong. :-)

After tack welding one side, flip it over and tack the other side.
Without experience, let it cool down (If you know what you do, you don't
have to let cool down). Check flatness. Now start welding where you
would like to shorten (or where the angle is below 90 deg.). Always
check angles and flatness and correct with the next weld.

A bit confusing, but there is only one thing to remember:
If you weld a seam the point where you started to weld will shink less
then the point where you end welding. Say you have a 90° joint and start
at the inner point, the 90° will come out more. If you start from the
outward, it will be less than 90°. If you start at the middle and weld
inwards/outwards you will have very little shinkage.
If you got the feeling, you can put the parts together _out_ of angle
and when you have finished it will be dead 90°.
It is more complicated if you butt weld two flats:
If you lay the flats down and weld, you will end with: both ends
pointing upwards and slight V lengthwise.

Only practice will get good results. It also helps to clamp (but it
won't stop distortion). Don't think that MIG/MAG will solve the problem.

But with a OA-torch you can pull everything straight. :-)


Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO - YADRO - Eigenbau-Digitalanzeige

Andrew VK3BFA wrote:

Another newbie question....

I am making a stand for my new mini-mill - imagine a rectanglular shape
made of 1 inch steel tubing welded together. Problem is, I cant seem to
stop the damm thing from distorting - I can get it square by
measurement, but it distorts in the horizontal plane. I tack welded
each corner, that went ok, but when I finished the seams, it was
twisted. Is there an order of welding I should be doing, do I belt it
flat with a 10lb hammer - what? I am using a stick welder - dont have a
MIG so I am aware its the heat "pulling" it out of true. There must be
a way of overcoming this......any suggestions?

Andrew VK3BFA.


I don't understand what's happening to you, but I have had good luck first
welding a square frame by clamping all pieces rigidly to a stiff table and then
welding solidly and letting cool, and only then unclamping. Once that is done
and square, then I stand up the "legs" and clamp them at the bottom, then I take
extra stock and also clamp them rigidly at the top so they can't move, then,
using careful welding techniques designed to balance the distorting forces, weld
them up and let cool, then unclamp. If you have to, then use a hydraulic jack to
do gentle straightening.

GWE

All welds will pull toward the weld area. It has to do with the weld
area being both hot and plastic. The hot weld will expand outward since
rest of the material remains relatively cold. As the weld area cools and
shrinks, it pulls the base material in that direction. Stick versus Mig
makes no difference.

Several choices:
-clamp the whole thing down, do the welds, let it cool, unclamp
-set it up crooked, weld, hope it pulls into place.
-Do short welds on opposing sides/ends
-Weld it up, crank it into place with hammer and clamps
Most projects will use some combiation

For 1" square tube frames I solidly tack weld (3/8" tacks) the whole
frame. Then I use a woodworker's pipe clamp (use 3/4" pipe if you have
them to square the thing up. Diagonal across the sides in normal as well
as one going through the center. If the frame is twisted, use the pipe
clamps as levers to twist it straight.

Weld 1 side of 1 joint (1" of weld), next weld on the opposite side and
opposite end of the frame. Check squareness every half dozen welds, use
the pipe clamps to keep things where they should be. Plan on running the
clamps a bit past where it 'should' be to allow for spring back.

cheers.


Andrew VK3BFA wrote:
Another newbie question....

I am making a stand for my new mini-mill - imagine a rectanglular shape
made of 1 inch steel tubing welded together. Problem is, I cant seem to
stop the damm thing from distorting - I can get it square by
measurement, but it distorts in the horizontal plane. I tack welded
each corner, that went ok, but when I finished the seams, it was
twisted. Is there an order of welding I should be doing, do I belt it
flat with a 10lb hammer - what? I am using a stick welder - dont have a
MIG so I am aware its the heat "pulling" it out of true. There must be
a way of overcoming this......any suggestions?

Andrew VK3BFA.

Agreed on the 3/4" pipe clamps. It helps to clamp down to a spacer so
that constant spacing is maintained. Plan on clamping the whole thing
at once, not just one end.

Nick Müller wrote:
Andrew VK3BFA wrote:

I tack welded each corner, that went ok, but when I finished the seams,it
was twisted.

The first step was OK, the second wrong. :-)

After tack welding one side, flip it over and tack the other side.
Without experience, let it cool down (If you know what you do, you don't
have to let cool down). Check flatness. Now start welding where you
would like to shorten (or where the angle is below 90 deg.). Always
check angles and flatness and correct with the next weld.

A bit confusing, but there is only one thing to remember:
If you weld a seam the point where you started to weld will shink less
then the point where you end welding. Say you have a 90° joint and start
at the inner point, the 90° will come out more. If you start from the
outward, it will be less than 90°. If you start at the middle and weld
inwards/outwards you will have very little shinkage.
If you got the feeling, you can put the parts together _out_ of angle
and when you have finished it will be dead 90°.
It is more complicated if you butt weld two flats:
If you lay the flats down and weld, you will end with: both ends
pointing upwards and slight V lengthwise.

Only practice will get good results. It also helps to clamp (but it
won't stop distortion). Don't think that MIG/MAG will solve the problem.

But with a OA-torch you can pull everything straight. :-)


Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO - YADRO - Eigenbau-Digitalanzeige

Thank you to all who replied - some of it I have to think about - BUT
- will make up a jig I can clamp the work to to keep it rigid while I
weld it. Alas, at this stage my welds look like they were put on with a
butter knife - I count it a GOOD day when I dont blow holes and have to
fill. But it will get better, - practice, practice, practice... this
metal work business keeps on generating the need for more
tools/accessories as I go along.....

BTW - a few people I have spoken to over the years report this
phenomena - some days, you just start welding and it goes like a dream
- other days, its so awfully bad and horrible you have to walk away in
disgust!. Is this some arcane knowledge, a spell I need to recite, or
just the way it is?
Andrew VK3BFA.

"if a machine breaks down, its no good going and using another one.
They all belong to the same union..."
Anon.

On 1 Feb 2006 03:49:47 -0800, with neither quill nor qualm, "Andrew
VK3BFA" quickly quoth:

BTW - a few people I have spoken to over the years report this
phenomena - some days, you just start welding and it goes like a dream
- other days, its so awfully bad and horrible you have to walk away in
disgust!. Is this some arcane knowledge, a spell I need to recite, or
just the way it is?

If you find that spell, please forward it on to me. I'm relearning how
to weld and have forgotten it entirely some days. g

It's also time for me to make a welding table and weld some extra
parts onto my spare 4-wheeled hand truck for a welding cart.


-
Press HERE to arm. (Release to detonate.)
-----------
http://diversify.com Website Application Programming

Look over in sci.engr.joining.welding for more stuff related to
welding.

Randy Zimmerman used to have a web site devoted to distortion from
welding.

Hmmm. No one seems to have mentioned that you need to space your parts
so they are not right up against each other. Try taking two pieces of
metal and putting them in contact with each other and weld them. The
weld is on one side and when it shrinks it pulls the pieces on the one
side. This distorts them. Now space them apart about the same as the
thickness of the metal. Now when you weld them, the molton metal is
between the pieces, and when it shrinks it pull more equally on both
sides. Not no distortion, but much less.


Dan

On 31 Jan 2006 04:35:02 -0800, "Andrew VK3BFA"
wrote:

Another newbie question....

I am making a stand for my new mini-mill - imagine a rectanglular shape
made of 1 inch steel tubing welded together. Problem is, I cant seem to
stop the damm thing from distorting - I can get it square by
measurement, but it distorts in the horizontal plane. I tack welded
each corner, that went ok, but when I finished the seams, it was
twisted. Is there an order of welding I should be doing, do I belt it
flat with a 10lb hammer - what? I am using a stick welder - dont have a
MIG so I am aware its the heat "pulling" it out of true. There must be
a way of overcoming this......any suggestions?

Andrew VK3BFA.

Careful planning of the order of welds minimizes distortion. Careful
planning also includes having hydraulics, some chain and a utility
pole available!