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Grahame Collins
4th Nov 2007, 11:08 AM
Good morning everyone

Given the forum is a bit quiet I thought it pertinent that I might post some comment about grinding after the weld is laid down.

Grinding is carried out in a lot of cases as a cosmetic repair cos we don' want the world to see the bird $hit we have just deposited. In TAFE even in the Xray cert classes it was still a common thing to see seemingly experienced operators grind away most of what they had just welded.
Why ? Either lack of experience or lack of control of the arc welding process they were using.

My mission today is to help and inform welders in the efficient and intelligent use of the angle grinder.

How deep is the penetration into the metal? Based upon the hundreds of mechanical fillet break tests I have performed on welders certification welds I am able to tell you that the best of them never penetrated more than 2mm into the plate. This is using 3.25mm diameter rods at 140 amps AC.
Using that as a bench mark I estimate that most home set ups won't make even half of that- I won't go oo far into it but will say arc length and electrode types make up quite a lot of that difference.

Yes folks there will be differences but I am working on what I think may be the average small home machine set up out there OK!

Imagine we are running a bead to butt weld two equal thickness plates together,say 6mm . Our small home machine ,say a 10 amp GMC can run a bead of 2.5 diameter rod at 110 amps down the line of the joint. Above the plate surface it deposits metal maybe a millimeter in height. Below the plate surface if there is 0.7 of a millimeter we have done well.

The weld has a few holes ,slag inclusions and undercuts .It is not pretty.Reaching for the angle grinder,we grind the surface metal off. All that remains is .7mm thickness of weld.

Is this strong enough for your particular weld application?

As an alternate if flush finish is really necessary, the edges of the joint can be beveled and the weld bead deposited into the valley,then flushed off. An added benefit is that distortion is nearly eliminated as the weld is closer to the center line of the joint which reduces the" pivot" of the potential bend.

Check out the diagram below

have a Super Sunday
PS Sorry moderators - Should have put it in the welding sections- Old habits etc ,etc.

Grahame

BobL
4th Nov 2007, 11:48 AM
Good post Graeme.

Like anyone, the stuff I find trickiest is the thin stuff, like 1.6 mm SHS tubing. What's the real penetration with this stuff likely to be? When I look inside the tube at a weld sometimes it looks like like the weld bead has penetrated right through - other times you can't see anything except the heat scorch. This is also often the stuff one needs to have flush eg sliding one piece inside another.


. . . . . .Imagine we are running a bead to butt weld two equal thickness plates together,say 6mm . Our small home machine ,say a 10 amp GMC can run a bead of 2.5 diameter rod at 110 amps down the line of the joint. Above the plate surface it deposits metal maybe a millimeter in height. Below the plate surface if there is 0.7 of a millimeter we have done well.


It's not an excuse for poor welding but in your example whether 0.7 mm is enough can depend on if a weld can be run on the other side of the joint and how much flex or force the joint needs to support. If I can get a solid bead down on one side I tend to be a bit more agressive with the grinder on the other.

Cheers

scooter
4th Nov 2007, 11:52 AM
Thanks, Grahame, I like reading these threads, always adds to the knowledge base. :)

Now, converting that knowdedge to practice... :hmmm:

Grahame Collins
4th Nov 2007, 12:25 PM
Hi Bob and Scooter

Real penetration (for 1.6mm box ) is likely to be anywhere between what I said around .7mm and burn through. Thats because of a heap of variables starting out with the metal volume,amps setting,arc length, electrode type and travel speed.Another factorI suspect compounds the problem (but am unable to prove) is that the initial arc strike that I believe jolts the arc voltage up increasing the heat factor and burn through on that 1st strike..

The Box section especially the light wall stuff is a PITA because of the wall thickness. The absolute small VOLUME of metal cannot absorb and dissipate the heat of the weld quickly enough.

The smaller the dimension of the box, the bigger the problem.ie low volume,less heat dissipation. By sleeving the box section you have increased the volume of metal and help conduct away that excess heat which will burn through.

I think I can help a bit more here.If we work smarter not harder ,we could improve the heat conduction by heat sinking with pieces of copper sheet say 1mm thick.

You might find some copper( to flatten out) from a bit of fairly big bore offcut copper pipe. The box section could be laid out on the copper sheet and also you could make right angle brackets which could be clamped on to support the joint in assembly and further wick away the heat.

If you didn't want to pi$$ around with bits of copper just dunk the work in a bucket of water intermittently.

I have had good results with it before and am confident it should work for others. to me welding problems like that are just pure physics.

Cheers Grahame

Grahame Collins
4th Nov 2007, 12:59 PM
Guys ,
I have just had another brain phart and remembered this.

Welding a tee piece of thinwall hollow section can be a big pain.

Burn aways at the cut edge can be drastically reduced by coming from a low angle and away from the cut edge.

The rolled edge makes for a natural valley but the cut surface will burn away if directly arced on. 3/4 of the arc on the solid and the rest overlaps the cut side.

Are also factors


Short arc,
Lowest amps possible
Quickest usable travel speed

See the pic

Grahame

BobL
4th Nov 2007, 01:30 PM
Thanks for the excellent tips graeme, am about to do some SHS in the next few days so I will try your suggestions.

With the copper sheet idea, how badly does it mark/melt the copper especially if one does end up blowing a hole in the steel? I have some square cross section 3mm brass angle that I could use but don't particularly want to damage it in the process.

Cheers
Bob

Grahame Collins
4th Nov 2007, 01:53 PM
Bob,
if heat is indirect probably no more than needing a buff up.

If direct heat there will be some marks.Brass reacts a little different to copper because of the zinc content which will vaporise as soon as anything over about 600 degrees is imposed upon it. save your goodies and just dip in water -often.

Grahame

BobL
4th Nov 2007, 03:49 PM
I realise this is not going to be as good or as quick as a water dunk but I have taken to using a water squirter/spray for small stuff if I don't want to take the whatever I'm welding out of the vice, or it's part of a larger frame etc that is too difficult to dip into a tub of water. I usually keep squirting till it stops steaming and instantly evaporating and there is a film of water on it for at least a few seconds. The fact that it does not take a large volume of water demonstrates the large heat capacity of water.

Cheers

BobL
4th Nov 2007, 08:49 PM
OK - took Graemes advice on SHS and here is the evidence.

I'm basically welding a T piece from two bits of 20 mm x 1.6 mm SHS.

This is about normal for me (bear in mind I have a condition called "essential tremor" which is just another term for shakey hands, and the more I concentrate the worse it gets). I call this my standard "turkey poo" welding, reasonable strength but not very pretty. Look at the ground off weld underneath - also not good.
http://www.woodworkforums.ubeaut.com.au/attachment.php?attachmentid=59423&stc=1&d=1194168039


Here is a second go. A bit better except for the pinhole. The gobby bit on the LHS is from another run.
http://www.woodworkforums.ubeaut.com.au/attachment.php?attachmentid=59424&stc=1&d=1194168039


Here's one that I think worked out pretty well.
http://www.woodworkforums.ubeaut.com.au/attachment.php?attachmentid=59425&stc=1&d=1194168039

Here I'm welding a small 20 x 60 mm rectangle of 6 mm thick steel onto the flat side of a 20 mm x 1.6 mm SHS.
http://www.woodworkforums.ubeaut.com.au/attachment.php?attachmentid=59426&stc=1&d=1194168039

Here's a bit better one of the same thing(I think I may need to move the rod a bit faster).
http://www.woodworkforums.ubeaut.com.au/attachment.php?attachmentid=59427&stc=1&d=1194168039

Getting there, slowly. . . . .
Comments, suggestions ? ?

Thanks Graeme.

martrix
4th Nov 2007, 09:04 PM
nice pics Bob. Your right about the first one looking like turkey poop.:q:D

The last one looks the goods, probably because it was thicker steel. Your using an Arc right? How many amps?

DJ’s Timber
4th Nov 2007, 09:08 PM
Not bad Bob :2tsup:, I reckon your amps may be a tad too high though.

BobL
4th Nov 2007, 09:48 PM
nice pics Bob. Your right about the first one looking like turkey poop.:q:D

The last one looks the goods, probably because it was thicker steel. Your using an Arc right? How many amps?

Thanks guys,
This is all done using my $99 home welder - I could take the job to work, or around to BILs, and use a MIG, but for a simple job like this I find the cheapie does OK.

On the 1.6mm SHS I'm using 2 mm rods with the current set at 65A. On the thicker steel I'm using 2.5 mm rods with 85A. If I set the current lower than these settings I find it very hard to strike an arc. It could be my rods, they are more than a year old and they are not stored in airtight containers (just folded pastic bags). I also wouldn't trust the current indicator on my welder it looks like its been bent and restraightened.

What I'm making is a conventional outboard blade clamp for my small mill. I'll post more on this on the small milling forum.

Cheers

Grahame Collins
4th Nov 2007, 11:01 PM
Hi BobL

Nice camera work!

Your travel speed is pretty close, Bob, but amps may be a touch high or arc length a bit long or rod angle to sharp. All 3 cause undercutting See the little undercuts on the rear side of the last pic? Its not a major fault unless its own a high strength job like a boiler shell OK!

Some welding rods don't like welding over their own slag.
A small chisel or something small and sharp driven into the slag holes to clean it out,(and rip it up it with a stiff wire brush ) will yield better results when you put another pass over it.

Grahame

Note the shape of the ripple pattern.Its about the right travel speed if it is crescent shaped -as Bobs are.

martrix
4th Nov 2007, 11:07 PM
If I get my new MIG setup tomorrow, I will throw up some pics for your assessment too Grahame. I will be trying to turn a new leaf with my welding.......minimal use of the angle grinder.:wink:

BobL
5th Nov 2007, 12:01 AM
Thanks for all the tips Grahame - very helpful.

I can certainy see my arc length is not always steady mainly because my hands shake - its worse with a new (long) rod so I have taken to cutting rods in half with pliers. I also find I can maintain a slightly steadier arc if I move the rod in little circles or small side to side swings.

I used to be quite good at this before the shakey hand problem but am finding it hard getting back to my former skill level.

Fossil
5th Nov 2007, 09:22 AM
I have a samll oven in my workshop. I picked it up from a council cleanup a couple of years agao. It comes in very handy for all sorts of jobs. If I am having a welding day, I throw the rods in the oven for the day while I am working. Just over 100 deg is all I find I need. Really dry sticks will make your life easier.

BobL
5th Nov 2007, 09:36 AM
I have a samll oven in my workshop. I picked it up from a council cleanup a couple of years agao. It comes in very handy for all sorts of jobs. If I am having a welding day, I throw the rods in the oven for the day while I am working. Just over 100 deg is all I find I need. Really dry sticks will make your life easier.

Thanks for the tip fossil.

Grahame Collins
5th Nov 2007, 07:06 PM
I will be trying to turn a new leaf with my welding.......minimal use of the angle grinder.:wink:

If more would use the angle grinder, a lot more before than after welding, we could reduce all this $eagull $hit <Grin>

If you are a bit shaky like - drop your gloved left hand fisted - down to the bench- but with index finger pointing and drop the near the end (notice I said near -not at the end) the electrode over it to steady the electrode up. Fossil is dead right about the rods in the oven.100 degrees C is spot on.Rods will pick moisture up if stored in open packets. I will be happy to look at your mig runs Matrix

I have another post coming on overwelding and distortion and complete with MS paint illustration. In the welding section too,before I get into strife with the mods.

She who must is home ,so its time for a cuppa
see you lot later
Grahame

scooter
5th Nov 2007, 09:25 PM
If you are a bit shaky like - drop your gloved left hand fisted - down to the bench- but with index finger pointing and drop the near the end (notice I said near -not at the end) the electrode over it to steady the electrode up.

Great tip! I shake like I've got the DTs, amplified when I use a new rod (I usually cut them in half for this reason) so this tip is a good 'un for me. I had thought I'd get a belt if I touched the electrode. :-

BobL
5th Nov 2007, 10:23 PM
Crikey Scoot, you're only 38 mate I got 15 years on you, mind you come to think of it mine started about your age. Apparently every one has these nerve twitches but they are usual random in most people so they cancel each other out. About 2.5% of folks have something called sympathetic twitching where a lot of the twitches happen in synch, magnifying the effect.

I've been starting off welding two handed and when I get going I move to one hand but Gra's idea sounds good - must go and try it. The problem with two handed is sometimes you need to hold something awkard in place - can't have too many clamps and one of my faves is this edge one (http://www.carbatec.com.au/store/index.php?main_page=index&cPath=60_7960_7981).

Burnsy
5th Nov 2007, 10:43 PM
The use of copper sheeting is a trick used by car restorers to weld up pin hole rust spots in car repairs. If you hold a sheet of copper on the back of the hole you can weld it up then take the copper away.

Question about sticking the rods in the oven. I only use my welder every few months so my rods sit around (in plastic container) for a fair while and some have been around for a few years. If I put the whole lot in the oven would this rejuvinate them back to like new or do I need to use them straight out of the oven? I can see SWMBO asking what the hell am I doing already:D

ds2006
5th Nov 2007, 11:05 PM
Thanks for the tips everyone - have some rust holes to patch up soon, so will be looking out for some copper. I use a mig for almost all my welding but also have an arc welder that I am teaching myself to use. Just need to find the time to practice.

Best thing I ever did was buy an auto darkening helmet. The quality of my welds improved as I could use two hands to hold the gun or even one to hold the job whilst I spot. I think not having to start in the dark was the main reason. Nothing worse than lining the tip up and then dropping the mask to find you start your weld 5mm (or more) away form the joint!

Magnetic angle clamps are another investment that make me wonder what I did without them.

BobL
7th Nov 2007, 12:46 AM
Ok I dropped my amps as recommended, using brand new 2mm rods and things have just gotten worse. :(

I'm now @ 55A (as shown on the welder scale) mainly because I'm now working on 1.2mm SHS - boy is this tricky stuff with just a stick machine.

Firstly its taking 6 - 10 attempts to strike an arc and then the poo factor has gone up significantly. They all now look like my first run or worse!

On a more positive note I haven't made anywhere near the number of holes as I have in the past using Grahames tip of keeping the rod oriented towards the thicker side. Excellent tip.

I think I might try 60A? I was using 65A on the 1.6 mm SHS.

Cheers

Wood Butcher
7th Nov 2007, 07:58 AM
The trick with thinner metals is speed. You need to have enough amsp to make sure that you get the penetration but you can't go to slow because you will burn holes. I have this problem with students regularly. They always go too slow on the thin stuff and burn holes, and strangely enough the go too fast on the thicker welds??? Go figure that one out!?!

wheelinround
7th Nov 2007, 08:44 AM
Hi BobL

One thing I noticed in the photo's is NO clean up of the area to be welded removing paint etc makes for a cleaner start to the weld easier to get that first spark/arc.

One trick I was taught with hard to start rods is knock off a bit of the end of the rod Flux and its bonding agent. I either used a pair of pliers and just griped and turned a tiny fraction of the tip or run/drag/bounced the rod off some steel at the tip this gives metal to metal contact.

For shakey hands starting at intersections etc I place the side of the rod down past the weld joint and draw back slowly after dropping the helmet.

Being comfortable when practicing helps if your sitting down and the job is a stretch then your uncomfortable. If your stooping over its uncomfortable. Wait till your doing overhead welding lying down twisted and in a small space with just enough room to move.

The shudders n shakes I had when I first started welding was hammered out of me and I do mean hammered, the TAFE teacher & fellow I was working under would walk up behind those they were teaching and slam a hammer down while they were welding.:oo: talk about needing a change :doh:. After about 1/2 doz of these situations you got to be able to put it out of your mind and calm yourself so much so some of us wouldn't even hear the lunch hooter to intent on listening to that wonderfull sound of weld being deposited and the hum of the machine.


Ok I dropped my amps as recommended, using brand new 2mm rods and things have just gotten worse. :(

I'm now @ 55A (as shown on the welder scale) mainly because I'm now working on 1.2mm SHS - boy is this tricky stuff with just a stick machine.

Firstly its taking 6 - 10 attempts to strike an arc and then the poo factor has gone up significantly. They all now look like my first run or worse!

On a more positive note I haven't made anywhere near the number of holes as I have in the past using Grahames tip of keeping the rod oriented towards the thicker side. Excellent tip.

I think I might try 60A? I was using 65A on the 1.6 mm SHS.

Cheers


BobL You changed rods being newer they would not have absorbed moister and begun to crumble the flux ( I guess the other rods were old)
Are they similar rods type flux coating etc.
I am guessing they are, look at the tips of the rod and you'll see what I was saying above that resin and flux cover the tip and trying to weld through paint and oil on steel is not good.

wheelinround
7th Nov 2007, 08:54 AM
The trick with thinner metals is speed. You need to have enough amsp to make sure that you get the penetration but you can't go to slow because you will burn holes. I have this problem with students regularly. They always go too slow on the thin stuff and burn holes, and strangely enough the go too fast on the thicker welds??? Go figure that one out!?!

I went through that at TAFE WB when learning as did most of the class its an easy one to answer.
Larger rods and higher amps push the rod ( you have learned to be master of the rod not let it master you) you tense up or over relax.

To explain this the teacher showed how by resting the grip on his open palm and the higher amp rod would push it along danced off the metal due to the force of arc and ams. While the lighter amps and lighter rod just burnt holes. He taught us to change from one rod to the other changing amps on both and back again to get the feel and weight difference.

Grahame Collins
7th Nov 2007, 05:56 PM
OK guys i hear ya!
The problem
You have dropped the amps to suit the smaller diameter rod and the rotten basket won't arc properly.
.The solution
A bit of scrap plate adjacent (up to 100mm away) to the welding area that you can strike on -draw and arc - get the electrode warmed up so to speak - and then jump across to the to be welded area
and arc will run _( if amps are not too low).No pharting about now-while the rod end is still red hot -jump over-no trouble at all with your auto darkening shield.

No chunks of bird poo to make the bead look crap and no nasty words to shock the neighbors.

It will work - its all about technique.
trust me
Grahame

thesupervisor
7th Nov 2007, 06:05 PM
if you have a inverter type machine revers the leads so you have + earth - electrode
this will make all the heat go into the earth so you will be able to run more amps they use this for full penertraltion on low hyg rods on pipe work, well thats what i was taught it will also leave the bead more raised so be prepared for more grinding

BobL
7th Nov 2007, 06:14 PM
OK guys i hear ya!
The problem
You have dropped the amps to suit the smaller diameter rod and the rotten basket won't arc properly.
.The solution
A bit of scrap plate adjacent (up to 100mm away) to the welding area that you can strike on -draw and arc - get the electrode warmed up so to speak - and then jump across to the [I]to be welded area
.......


Excellent! - and "slightly " I didn't think of that!

Dean
8th Nov 2007, 10:40 AM
I used to be quite good at this before the shakey hand problem but am finding it hard getting back to my former skill level.

Too much chainsaw milling Bob :p

BobL
8th Nov 2007, 10:42 PM
Too much chainsaw milling Bob :p

Could be, that and too much coffee (one of my other distractions is being a barista judge)

Actually I've had the sympathetic tremor condition for as long as I can remember and it has been a PITA especially when it comes time to do fine work at work or in the shed.

As far a chainsaw milling goes, within two hours of continuous milling with the big (111 cc) chainsaw my left thumb and tip of my pointing finger were starting to go numb (from holding onto the trigger) and the numbness lasted for many days but my right (welding) hand was fine. Then I converted the trigger to an outboard lever throttle (beaut.com.au/showpost.php?p=582234&postcount=60) and no fuzzy finger or hand feeling at all. Recently I bought a pair of these (http://www.otbproducts.com.au/safety_products/anti_vibration_glove_full.htm) gloves. They are pretty exxy but they are extremely good for vibration although I can see them being a bit hot for summer.

Dean
9th Nov 2007, 12:45 PM
Could be, that and too much coffee (one of my other distractions is being a barista judge)

Actually I've had the sympathetic tremor condition for as long as I can remember and it has been a PITA especially when it comes time to do fine work at work or in the shed.

As far a chainsaw milling goes, within two hours of continuous milling with the big (111 cc) chainsaw my left thumb and tip of my pointing finger were starting to go numb (from holding onto the trigger) and the numbness lasted for many days but my right (welding) hand was fine. Then I converted the trigger to an outboard lever throttle (beaut.com.au/showpost.php?p=582234&postcount=60) and no fuzzy finger or hand feeling at all. Recently I bought a pair of these (http://www.otbproducts.com.au/safety_products/anti_vibration_glove_full.htm) gloves. They are pretty exxy but they are extremely good for vibration although I can see them being a bit hot for summer.
Thanks for links :)
Yeah those numb fingers could be a problem. I was doing a bit of milling yesterday and the fingers were feeling it after 5 or 6 passes :)

But not to hijack this thread... Great tips Graeme. I sometimes burn through the thinner stuff with my arc welder, particularly when butt welding the cut end of RHS (where it is thinnest). Your tip to angle the rod toward the thicker material will be undertaken on my next attempt :)
Thansk again.