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View Full Version : Finally found an oxy/acet rig



DICKEYBIRD
06-19-2010, 10:19 AM
I've been searching Craigslist for 2 yrs now and finally got a deal on one of the little HVAC rigs. Yes, they're small but really all I'll need and can afford.

The cheapo Chinese rigs are $275 - $325 new with empty bottles and all the used ones I've found were $200 - $250 with almost empty tanks. I found a Uniweld set (USA made) in good condition with full bottles for $135 and snapped it up for my Father's day gift to myself. At least SWMBO did go pick it up for me.:)

It was cheap due to missing tips. It has a good Model 71 handle but no welding or cutting tips. It has a sturdy metal tote (scuffed up but SOLID) and the hoses & reg's are in excellent shape. Should make an excellent addition to the shop.

Question: I found a source for the tips for $21.00 each + shipping but am waffling on what 2 sizes to get. A #2 is a must (IMO) for the average small stuff I think I'll be doing (welding thinwall steel tubing, silver-brazing, hardening drill rod tooling, etc) but am at a loss for the 2nd one. I'm guessing a #4 would be a good compromise for the odd large brazing or bending job I come across in my little shop. What say ya'll?

Herm Williams
06-19-2010, 11:22 AM
First I would go for a # 1 tip. also get a propane cutting tip if you are going to do any cutting. I like ans use propane for brazing and cutting, because it is easyer (for me at least) to control heat. The acy regulator will fit the propane tank. I have not tried to weld with propane but other than welding propane works as well and costs about 80% less to use.
re

Black_Moons
06-19-2010, 12:38 PM
If your using those tiny (12" tall) actylene bottles, you basicly shot yourself in the foot in terms of tip sizes.

Actylene can only be drawn out of the bottle at a slow rate (im sure someone will quickly post the exact rate..) because its diffused into actone and has to bubble out, Draw too much off too quickly, and you'll start drawing actone through your regulator and torch.

Propane of course, has no such problem.. However, you basicly can NOT weld with propane, its not hot enough and IIRC contaminates metal with hydrogen.

You can cut, braze and preheat with propane, and its general much cheaper to use then actylene (less risk too, and MUCH less explosive if there is a leak or inadventant venting) And is MUCH MUCH easyer to get a propane bottle refilled.
(That said, cutting is done with much more oxygen then fuel, the fuel is only to preheat)

To convert to propane I believe you use diffrent tips but the same torch, I could be wrong.. I think you can use actylene tips with propane but lighting and keeping it lit is harder.

Never heard that an actylene reg fit on a propane bottle. Theres lots of perpose made propane regulators out there for welding though.

DICKEYBIRD
06-19-2010, 01:29 PM
Ahh, OK so there's a limited amount of flow from the little tank; that makes sense.

The maintenance dude at work has the exact same size Uniweld HVAC rig and it came with a #2 tip and a small cutting torch so one would assume the little tank will flow enough gas to feed a #4 or 5 tip??

I don't plan to do much cutting if any at all so won't be investing in the additional equipment to switch to propane.

metalmagpie
06-19-2010, 01:59 PM
If your tank holds e.g. 21 cubic feet of acetylene (I don't know anything about the tiny portable tanks) you can only draw 3 cubic feet per hour. That's the rule: 1/7 of the tank capacity (in cubic feet) per hour.

You left out a whole lot of critical information. Who made the torch? Was it Harris, Victor, Smith or Airco? If it wasn't one of those, I suggest you just start looking for a torch setup and don't bother investing in tooling up an off-brand torch.

Once you determine the maker and model of your torch handle, then it's time to go online and find a tip chart. These show information on what size tip for welding what size metal, also gas flow rates required. Once you have that information, then look at the required flow rates, look at your tank capacity divided by 7 (if you don't know that number take it to a local welding supply and ask) and see what tip sizes you can use. Then you know what tips you can use. Don't make any assumptions like you were getting ready to.

Oxyweld single stage regulators can work OK but they can also be junk. I suffered with a set of those back in the '80s until I got a better set, then a better one .. now I have WAY too much oxyacetylene gear.

Anyone want a perfect, brand-new-rebuilt set of Airco 2-stage regulators? Victor VTS450/460 perfect 2-stage regulators? Airco or Victor small, medium or large torch handles, probably with torch attachment and selection of tips? Like I said, *way* too much stuff. Problem is, I like the stuff too much, sigh.

metalmagpie

reggie_obe
06-19-2010, 04:40 PM
You may have erred on the small side. http://uniweld.com/catalog/torches_handles_attachments/oxyacetylene_oxyfuel_torch_handles/tube_mix.htm According to the chart, welding capacity is 1/4". Have you ever tried gas welding steel sheet with filler rod? Cutting capacity, depending on the attachment is either 2" or 6". Very little Acetylene is consumed by a cutting torch, that's why the process is often referred to as "burning". My gas torch is primarily used for cutting and heating. I haven't tried brazing yet. For welding I have my MIG, much easier to lay down a solid bead.

DICKEYBIRD
06-19-2010, 05:02 PM
You may have erred on the small side.Are you referring to the low heating capacity of the model 71 torch handle and its attachments? Yes, I knew it was very small but I have an AC-DC stick welder for heavier stuff. The little HVAC set is for small, light hobby work and the physical size fits my shop well. The little light handle fits my hand well too.

I can drag the big Harris rig home from the auto dealer where I work if I need big heat.:D

Black_Moons
06-19-2010, 05:18 PM
You may have erred on the small side. http://uniweld.com/catalog/torches_handles_attachments/oxyacetylene_oxyfuel_torch_handles/tube_mix.htm According to the chart, welding capacity is 1/4". Have you ever tried gas welding steel sheet with filler rod? Cutting capacity, depending on the attachment is either 2" or 6". Very little Acetylene is consumed by a cutting torch, that's why the process is often referred to as "burning". My gas torch is primarily used for cutting and heating. I haven't tried brazing yet. For welding I have my MIG, much easier to lay down a solid bead.

Note: thats the capacity of his torch HANDLE alone, Actual welding and cutting capacity may be MUCH lower due to the limited flow allowable by the small actylene tank.

http://www.metalartspress.com/PDFs/common_cylinder_sizes.pdf
shows the common sizes. the 'MC' type tank is the one you get in the tiny portable kits, all of 10 cubic foot. applying the 1/7 rule thats 1.4cuft/hour flow rate.
You'll have to do some searching to find the flow rates of the verious tips..

chipmaker4130
06-19-2010, 06:57 PM
Aside from cylinder flow rate, the biggest problem with the small 'MC' and similar size bottles is the price of a re-fill. The 145 cu. ft. and up acetylene bottles are MUCH more cost effective. You'll 'buy' a larger set several times over by sticking with the small rig.

RussZHC
06-19-2010, 09:03 PM
welding thinwall steel tubing, silver-brazing, hardening drill rod tooling, etc)

I don't have any experience relative to what most on this site do BUT I have done a bit of work with thin wall tubing.

It will depend a bit of the exact type of steel. I can only speak to bicycle "type" steel tubing and that has many subtle variations from basic 4130 to very precise and in some cases proprietary mixes of other alloys.

It will depend a lot on the definition of "thin wall" and if you are welding using steel rod or brazing using bronze/brass or rods with mixes of silver and less likely, nickel (possible but "less likely" as it is not really a stocking item and can be very expensive).

# 4 or # 5 would be good for bending quite thick flats but I have used "0" or even "00" on occasion the most often ("00" mostly for the little braze on fittings, you barely have to get the metal warm the spots are so small)...depending on rod and how much build up you want, you may find that # 2 is too large.
May sound odd but I have always found trying to source a # 1 tip difficult and to me, if I could find them regularly that would be the one I would prefer.

oldbikerdude37
06-19-2010, 11:06 PM
Propane kicks butt, just ask an scrap guy.

For shop work I like a Victor, you can cut unbelievably thick stuff. you do have to turn things up where its not so safe like 12 PSI acetylene and 100 psi oxygen but it will blow away steel 10 inches thick.