Welding Tips and Tricks

I am new to tig welding and have been doing my research but have a question I hope someone can clear up. What is a general guideline to use to choose what size gas cup and flow rate. Also if you use a smaller cup do you lower your flow rate because of the smaller oriffice or turn it up? I have only been practicing with mild steel right now and am using a #6 cup with about 16-17cfh and it's mainly 1/8 in steel. Also would it be possible to use a small cup for versatiltiy, and with a gas lens for good cover, on most jobs? I am only a hobby welder so no x ray testing or anything like that but I do plan to go to lincoln tig school when I get the time. Also the machine is a dynasty 200dx. Thanks

Another question, helium/argon mix is only for aluminum or can it be used on steel?

I'm using a #6 cup at 7 litres a minute on 2mm and 2.5mm MS and haven't thought about changing, as this is working well.
7L per min = 14.837Cf per hour

I have also had great success with a #6 and the use of a gas lens. I run my flow at 10-15. If you drop in cup size you will have to reduce your flow even more. I'd say keep it about 7-10. I once was using a #4 cup and didn't reduce my flow (although I was using more gas probably 25-35) I was getting terrible coverage. and kept turning the flow up and things were getting progressively worse. Then I remembered my welding instructor mentioning something about this that too much flow out of these smaller cups will actually cause turbulence and actually pull the air to your weld zone. So as a rule for me I keep the gas flow down with these smaller cups. Adam

thanks for the responses, I ordered a gas lens set since I neeeded cups anyway so I think it was a good idea. Also what about the helium/argon mix, it sounds like it's only for aluminum but haven't heard an answer yet. Thanks

I wouldn't bother with the Helium mix if it's only for ms, but yes for Aluminium where you need the extra heat.

I'm looking into a gas lense for my Miller #17 TIG torch. What gas lense set up would you all recommend for TIG welding on 1/16" (.063) 308L stainless? I've been using a 1/16" tungstun (red) sticking out about 3/8" from a #7 cup with about 8-10 CFH flowing, 120 amps set on DCEN and it seems fair but not great. The worst problem is my torch blowing metal away at the beginning and end (edges)...............!%$#@! I then strated working from the middle of the joints and that helps on start but still blows away the edge at the ends even with my letting up on the pedal some.

Thanks for any recommendations.

Bob

You can use helium/argon mixture on mild steel or stainless. Its just not very cost effective. Brian

Hey Bob, I may be wrong but the picture you posted there doesn't look like 1/16" S.S. If it is though 120 amps on 1/16" S.S. is very hot. And 120 amps with a 1/16" tungsten is also pretty hot. I would just cut the heat back about 50 amps or so. Brian

It might be useful to think about what is a good speed of shielding gas flowing out of the cup. If we knew that a gas speed out of a cup were a good speed setting, then it would likely hold true for any cup size. We could then easily determine what cfm is needed to develop a given shielding gas speed out of the cup, for any cup size.

For example, a couple people here said that 10-15 cfm worked well through a #6 cup. The middle of that range 12.5 cfm, which through a #6 cup (.110 square inches) give about 3 mph, or about the speed of someone walking.

Then if we knew that 3 mph were then a good shielding gas speed, we could easily calculate how to get it with any cup size:
#7 cup: 17 cfh (.150" sq) = 3 mph
#6 cup 12.5 cfh (.110" sq) = 3 mph
#5 cup: 10.5 cfh (.077" sq) = 3 mph
#4 cup: 5.5 cfh (.049" sq) = 3 mph

I found some quite detailed info on gas cup and argon flow rate selection in CK Worldwide's TIG welding specification document (a sort of "how to" TIG weld guide): http://www.ckworldwide.com/technical_specs.pdf

There is a chart (bottom of page 4) showing recommended Argon Flow and Cup Size for various tungsten diameters, metal type (Ferrous and Aluminum) and body type (Gas lens and Standard).

Example:
for welding aluminum with a gas lens and a 3/32" tungsten, use a 6-8 cup, and 10-15 CFH Argon.

Hi!
I found this topic searching for cup size guidelines. Is seen lots Jody''s vids and read a lot here but is there some guide for choosing cup size other than a small one for tight spots?
Thank for all the help!
Nelson

jakeru wrote:It might be useful to think about what is a good speed of shielding gas flowing out of the cup. If we knew that a gas speed out of a cup were a good speed setting, then it would likely hold true for any cup size. We could then easily determine what cfm is needed to develop a given shielding gas speed out of the cup, for any cup size.

For example, a couple people here said that 10-15 cfm worked well through a #6 cup. The middle of that range 12.5 cfm, which through a #6 cup (.110 square inches) give about 3 mph, or about the speed of someone walking.

Then if we knew that 3 mph were then a good shielding gas speed, we could easily calculate how to get it with any cup size:
#7 cup: 17 cfh (.150" sq) = 3 mph
#6 cup 12.5 cfh (.110" sq) = 3 mph
#5 cup: 10.5 cfh (.077" sq) = 3 mph
#4 cup: 5.5 cfh (.049" sq) = 3 mph

That is essentially what you are already doing when you adjust the mass flow rate anyways. In essence you are ajusting the speed of the gas flow as time goes by. The advantage of using the cubic-foot-per-hour units is that it provides a gauge of sorts to know how much welding time you can get from a cylinder of gas. Not only that, speed readings also need to be adjusted, as you just simply cannot take the "middle ground" to work for everything (the very reason that CFH numbers have a range in the first place). Also the numbers arbitrarily work out nicer (see below)

The speed values you eventually come up with will inevitable be a range in order to take into account variables. For a #6 cup, as an example, you will find the optimum gas speed to be from 1.98-3.72 MPH, roughly, depending on factors like collet body type, tungsten stick out, and joint geometry, just to name a few. As you can see the numbers are "clumsier" to work with, compared with the integer units of CFH.

If you know enough math, you can still easily develop the non-linear function that can spit out the CFH number for a given cup size to match your data table. It will be quadratic in nature, as you can see from the fact that a #4 cup needs about 5.5 CFH, but a #7 which is not even twice the diameter, but already needs 3x the mass flow rate.

Ok, I've read the posts in this topic. From this and the info links it seems like for a given size tungsten, there is one size cup I should use. The gas flow shold be set to produce about 3 mph flow through it.

I had a welder who teaches it at my shop today. He saw my welder from across the room and said the cup is too big. He couldn't know what size tungsten from where he was. I had a 10 with gas lens I was doing tests with previously. What gives?

BTW he never heard of Jody. I guess experts don't watch instructional videos? Nice enough guy. I'm just trying to get the straight dope on this.

Gas flow rate is relative to cup size. Cup size is relative to gas coverage area needed. Tungsten size is relative to amps. Tungsten size has nothing to do with cup size.