Oxy-Acetelene Plate Cutting - How to with hand torch [lots of pics]

[dominick]

 If you ever need to cut some steel plate into an irregular shape and all you have is an oxy-acetelene hand torch, below are a few photos and a "how to" on a method that works fine for me.  The plate shown is 1" thick but this method works for any thickness plate.  What is most important with making a clean cut is having a cutting tip that is in good or new condition.  For this project I purchased a new No.2 tip.  It is also important to follow the recomendations for proper tip size for the material you are cutting and proper oxygen and acetelene pressure.

1.  You first need to cut a template from thin aluminum or sheetmetal  [approx .050 thick] of whatever you are planning to make.  If it is to be the precise size then allow for the approximately 1/3 the tip diameter and make the template that amount smaller around the edge.

2. Now that you have the template made, lay at least three 3/8" nuts on the steel plate you are cutting to space the template above the plate. Use C-clamp vice-grips right above the nuts to clamp in place.




3.   Begin your cut slow and steady keeping the torch perfectly vertical in all directions and following the side of the torch tip against the edge of the template as a guide.


4. If you are cutting a matching pair of plates, once the pieces are cut, grind the flat surfaces clean and clamp the plates together at a 90 degree angle and tack weld together.




5.  I use a 7" industrial rated disc grinder and grind away checking the edge frequently for squareness.



6. You can build up the low spots with a wire feed welder which will cut down on grind time.




7.  Follow the grinding procedure with a sanding disc for a smooth finish.

8.  After you are satified with the finish, drill whatever matching holes through both pieces, then grind loose the tack welds and sand smooth the inside edge and surface of the plates.


9.  Now you are ready for assembly.  Good luck!

[accuratemike]

Dom, I built a CNC O/A torch machine for just such occasions. It is small, as machines usually go, 30"x30" capacity. But it fits in my garage/shop. Here is a project I used it for: http://www.accuratepower.com/Rest/ , look at the edges. Almost NO grinding.I have cut from 1/8" to 1" with it. It would go heavier (I have the tips), 1/8" is about as thin as you can go.  I have been looking at your work and wondering how you go about it. Enjoy, MIKE

http://www.accuratepower.com/Torch/

[Cat Whisperer]

DOM -

Great sequence of pix and instructions!

Smoke and flame?

 

[dominick]

Dom, I built a CNC O/A torch machine for just such occasions. It is small, as machines usually go, 30"x30" capacity. But it fits in my garage/shop. Here is a project I used it for: http://www.accuratepower.com/Rest/ , look at the edges. Almost NO grinding.I have cut from 1/8" to 1" with it. It would go heavier (I have the tips), 1/8" is about as thin as you can go.  I have been looking at your work and wondering how you go about it. Enjoy, MIKE

http://www.accuratepower.com/Torch/

Thanks for the info Mike.  Very impressive set-up.  My post is to show how the home shop metal fabricator can cut duplicate plates with the minimum of equipment.   Thanks for the compliment Tim. 

[dominick]

Here's the completed mortar.

[Terry C.]

Nice!

Looks hefty, how much does it weigh?

[EL Caz 66]

Nice! What size bore does this beast have?

[dominick]

 It weighs 325 lbs. and the bore is 2.625" [soda can size]  1-1/4" diameter powder chamber.  The barrel weighs 190 lbs. and the carriage is 135 lbs.  Dom

[Rickk]

Dom, have you ever tried Oxy-Propane instead of Oxy-Acetylene?

I haven't tried cutting anything as thick as 1" wiith my setup (at least not yet), but for 1/4 inch and such it has worked just like Acetylene except that it is way cheaper and cleaner.

When I went to the welding supply store to ask about converting to Propane the guy behind the counter took me into the welding shop they run. They had about a dozen gas setups in there, and none had acetylene on them. They were all fueled by propane. They sell acetylene, but don't use it themselves... kind of ironic.

Unlike acetlylene, a 20# gas grill propane tank seems to last forever. The welding shop was set up to cut thicker metal, so they were using 80# tanks on all there setups to prevent the tanks from freezing up when drawing a high volume of gas.

All I had to do to convert is to get different cutting and welding tips. I already had a gas bottle connection adapter as propane tanks have the same fitting as "plumbers tank" acetlyene tanks have on them.

I don't miss the black soot all over my face when the fuel is running too lean one bit 

Rick

[Double D]

In an earlier life I was a for a short time a sawmill dismantler.  We used oxy-propane. Not only was it cheaper but faster. Never failed when we went into some sawmill the Millwrights would come by and snicker about the junk equipment we used especially the oxy-propane cutting equipment.  The boss kept us in beer challenging those guys to a cutting contest...nobody could touch him.

This was before my cannon making days, but boy I sure wish I had some of the 10 and 12 inch shafting we cut up from some of the sawmill equipment set up to handle the old growth logs.  They don't make equipment like any more.

[SHOOTALL]

I have used both and had the opportunity to convert a bridge building fab shop to oxy-natural gas , We were restricted to acy. in alot of places for safty . Cost and aval. were always the thing . As far as fast a good burner could use either and a poor one nither ! Most of my burning was in the pipefitting business and have to say the oxy-acy. cut a smoother finish . Most likely due to lower pressures giving operator better control , we do not care to grind any more than we had to .
Also an ACY torch uses a smaller tip size for the same heat of a larger propane torch .

[dominick]

Rick, I never tried it but I was told that it is not as precise and neat cutting as oxy-ace.  Maybe that's not the case and if so I would be willing to try it.  I usually have slag free cut on 1/2" and thinner plates but the 1" thick stuff combined with my 30+ year old junk regulators [I have to guess at the pressure]  makes for a less that perfect cut.  Can I use an acetylene regulator with the propane set-up? 

[dominick]

SHOOTALL, That's what I heard.  I didn't read your post before I responded to Ricks.  

[Rickk]

All my cuts look like poo anyway, so I can't comment on the smoothness of the cuts.

The regulator is the same. You just need an adapter if you don't already have one to fit a propane tank. It is the same fitting as an Acetylene "Plumbers tank" so most welding supply shops should have the adapter.

You will need different tips for both cutting and welding though, as the fuel/oxidizer ratios are way different. If you don't get propane tips it will blow out every time you try to bring the flame up to working flame size.

One of the really nice parts about it is the cost of the tank. Propane tanks are way cheaper. I am just using a regular 20# BBQ grill tank for mine. I havn't had to fill the tank since I converted a few years ago... Propane seems to last forever.

You can get a single cutting tip in whatever size you most commonly use and swipe the tank off your BBQ grill just to try it.

[Cat Whisperer]

Rick, I never tried it but I was told that it is not as precise and neat cutting as oxy-ace.  Maybe that's not the case and if so ...

If I'm not mistaken, it's the flow of oxy that combines with the iron to produce the exothermic reaction for cutting.  Hence, the differences between the two fuels are only of how much and fast they do the initial heating.  The difference in cutting would be a function of the design and quality/cleanness of the cutting tips.  In some applications I've seen kerosene and oxy used.  (Cutting granite - several feet thick.)

[Rickk]

here is a good discussion of propane verses acetylene.
http://www.cousesteel.com/AndysPlace/PropaneAcetylene.html

Apparently it isn't too great for welding, but great for cutting. I have used it for cutting quite a bit, and brazing as well, but have never tried it for welding as MIG is way easier.

[SHOOTALL]

cutting is rapid oxyidation IE . rust !