Mig gun and connector information needed

I have two Lincoln R3S welders each with LN7 feeders. One of the welders is a 250 amp and the other is a 350 amp machine. I have one gun, a Tweco number 4. I plan to put this on the larger of the two welders and then get a 250 amp gun for the smaller one. These machines may be old dinasours but they were cheap. The only down side I see is that they take up significant floor space.

When I look at a Tweco catalog I find about 5 different models with no clear explanation of why one would select one over the other. I see a series for spray arc using mixed gases. Does one really need a different gun for CO2 vrs C25 or other mixes? Is there anything really differnt about these guns or is it just marketing? Do you have any recommendations or advice in making a selection.

I also see the guns are rated at either 60 or 80% duty cycle. This adequate for my purposes but seems kind of strange to put 60% guns on 100% machines.

The next question is connector style. Obviously the Miller ends don't fit the Lincoln feeders but what do the Tweco connectors fit? The catalogs say an adapter may be required but I can not find said adapters in the catalogs. Do they exist? The reason I ask is that I am cheap and will try to find a used gun at a low price but want to make sure that I end up with something I can use.

My next and last question should probably be in another thread but since I am on a roll here goes.
Most my use of wirefeed welding has been with inner shield so I have question regarding using gas. What is recommended in the way of purging air from the gun or is it even requried and if so how often if use is intermittent?

Thanks,
Bill

Nothing wrong with the R3S's. Only one small circuit board in it to fine control voltage and the LN7's are a good feeder. Now the LN7 does not have a gas valve standard. Does yours have an adapter with the gas valve attached? A lot of the time the will be set up to take the tweco connection. If there is no gas valve you will have to add one. It uses a 120v valve.

The base LN7 will run the basic innershield gun without gas and you can buy guns with the same lincoln fitting as the innershield gun but with a hose barb for the gas connection. Tweco sells the adapters I can get the part number from work.

Dont worry about duty cycle. You will never hit it.

The tweco connection is used on almost all of the new Lincoln welder, also hobart used to use it as well as a couple of others.

First time you hook the gas you will purge the line for about 30 seconds. After that dont worry. Use 75/25 and you will never go back to innershield. Dual shield is also nice but really expensive. Over $120 for a spool. Standard 70S6 will be fine.

Thanks macona,

Both LN7s have the gas valve installed and both have the same adapter. I just do not know if it is a tweco connection or a Lincoln connection. The one gun I have does match up to both adapters. I was looking on line at the Tweco mig catalogs but I could not find any pictures or drawings that were detailed enough for me to see the difference. I could probably get this info from a dealer but I really don't like to mine them for information when the probability of them selling me the solution is very small. A new gun sells for more than I paid for the larger unit with the feeder included.

And I have to agree one can not hit high duty cycles in a shop environment without automatic type welding equipment and if it was a concern one should just use a larger gun.

Currently both feeders have .035 rollers and figured I would probably buy the .045 kit for the larger unit. Also might consider getting a smaller kit for sheet metal work. However it seems like a real pain to change wire size. In fact that is how I ended up with the second setup. I thought I would keep my eyes open for a second feeder and along came a complete unit for what I was prepared to pay for a feeder. Then the seller started asking me if I was interested in several other items. I did have some interest in some of them and when I asked him how much he just started loading my truck. He gave me 30 gallons of grease and about 18 partial spools of wire. And then he got called to a meeting before he had a chance to give away the rest of the shop (bad timing on my part).

Bill
It looks like you are on the right track for "economical" - read CHEAP - MIG welding.
TWECO makes guns and adapters for nearly any welder. A welding supply with an experienced salesperson is your best source of info - even if you're not buying it new.

Different gases/different guns? - The only reason to change gases is to match your welding material. Different guns aren't needed.

DUTY CYCLE - You have answered that one.

Don't give up the INNERSHIELD just yet - it's the only way to MIG outdoors or in a breeze!

YES, changing rollers and wire sizes is a PIA. That's the reasoning for having multiple machines.

I've got a gob of steel as big as a baseball on my welding table from triggering my gun before I start a weld to make I don't have air bubbles in it.

Sound like they have the tweco adapters on them. The old stlye Lincoln innershield connections are about an inch in dia. If the gun fits then you are good to go.

Hi Bill., the term adapter is misleadiing. You can buy a Tweco , Lincoln ( tweco style front end ) , Bernard, Tregaskiss, Miller guns etc with a Lincoln style power pin . You dont take a gun of a different power pin ( lets say Tweco #4 ) and put it in an adapter to go to Lincoln

For example, you can buy a Lincoln Tweco Style gun and put a Lincoln, Miller, Hobart etc power pin on the end ( they unscrew out of the gun )

the exception to this is Bernard quick connect and Euro style / Fast Mate style quick connects need an adapter

Just choose your rear connection style ( most popular is Tweco #4, Miller , Lincoln ) to be "Lincoln" .

If you are set on "Tweco style" consumables, you can go Tweco Brand or Lincoln Brand guns .

BTW There is no difference with the Tweco Spraymaster series. Any MIG gun can be used for spray. The difference for this series is as follows

- a a general rule, a MIG guns "rating" is at 60% with a 100%CO2 . For example, a 400 amp guns rating is with a 100% CO2 gas

- To spray, you require approx 85% inert so you do not benefit from the cooling effect of the CO2 as much

- as a result, a 400 amp gun becomes approx a 300 amp gun on a spray gas

Twecos Spraymasters are rated knowing it will be used with a mix blend

Again, any MIG gun can be used for spray. Only difference is the nozzles for spray recess the contact tip

Spraymasters are different in the tips. They use a more massive tip and gas diffuser to handle the heat of sprayarc. Also the tip is inset further into the nozzle for a longer stickout for spray wheras guns set up for short arc often have the tip flush to the end of the nozzle. The spraymasters usually come with a screw on non-adjustable nozzle.

And you can spray no problem even with 75/25 at higher currents.