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brazing/welding dilemma Answered

I'm building a cnc machine and I just bought a whole bunch of steel vat a surplus store. I need to braze or weld them together, but I can't braze since the objects too big for my propane tank, it disipates tthe heat to fast. I can't afford an arc welder. What should I do? I don't want to use nuts and bolts because that adds wiggle to the machine and I lose all of my accuracy.

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im staring the mini 3 axis milling machine as seen on here im making the manual version first then maybe adding the stepper motors and all the drivers and software but that way hi-tech for me at the mo so will be making a uprated secone version of the first with all motors and measuring tools. would love to see your CNC when complete.

well, I've never weld before, I don't think I can drill through the eighth inch angle iron, and I don't have access to old microwaves. what's jb weld?

hmmm... that might do it, is there a different cheap fuel than propane that gets hotter?

(A) Propylene gets within fifty to one-hundred-fifty degrees of MAPP's rating (depending on the expert being quoted), and only costs about sixty percent more than propane in refillable cylinders; this is not true for disposables.
NOTE: Your torch needs to be rated for Propylene or MAPP; otherwise, its tip may just melt if it's an air/fuel type.

(B) Many zinc based aluminum filler alloys are quite strong enough to hold steel assemblies together; they don't need much heat to work, and some will bond well to steel. Gentle hint: A clean part surface and proper flux are the keys to success here, rather than so called miracle products (unless you just feel a need to spend sixty dollars a pound for some).

totally going off my own design, this cnc machine will be able to mill a 1.5 foot by 1.5 foot by 1 foot tall material. Just to give a taste of the powerfullness, these motors are rated a 297oz/in. Hooking that up to my threads, it could mill a 60 or 70 pound object, or even more with super good accuracy. I'm using picstep, and the degrees could be as small as .1125 of a degree.

MAPP gas by it self burns hotter than propane but not hot enough for true Brazing.
MAPP gas used with an O2 bottle rig would allow you to braze thin steel with brass or silver rod. But the torch kits can be expensive.
Arc welding thin steel can be tricky without lots of practice. Flux-cored welding wire welders work better but you still have slag.
The best and easiest way for beginners to weld thin steel is with a MIG welder. MIG will also weld Cast type metals
.
MIG welding uses Argon as an inert gas to shield the puddle from contamination. No flux/ slag clean up required.

Use 'Argon only' bottles for Aluminumn, Stainless-Steel, or mild steel.
C25 (25% CO2/75%Argon) bottles will work for Mild Steel.

Big ARC Welders give the deepest heat penetration and are best for the thicker, stronger welds.

Do not confuse a {flux-cored Welder which uses flux-cored welding wire, eliminating any need for gas and regulators that normal MIG welders require} with MIG welding. They are similar to buzzbox arc-welding with small gauge rod but easier.

I am a 'Jack of all trades, Master of FEW.
For a CNC setup, you do NOT want any flex between the tooling and work material, even on PCBs.
There are too many factors to consider when welding to make a "One size fits all" answer.
{Equipment, SKILL LEVEL !!, type/thickness of metal, kind of joint, HOW CLEAN THE JOINT IS, Type/Size of filler material, External stresses - Environment on the joint when in use.}

My grandfather would Braze everything, My neighbor was a Stick Welder for a Steel Mill, A place where I worked, we had MIG and Tig welders. I learned quite a bit {General Welding} but never had the hours of practice that these others had, but with enough work ( maybe taking a class), most anyone can weld. Since you are asking these questions, I believe you are a beginner. More homework is required. When learning to weld, YOU WILL MAKE MISTAKES ! Try to find someone with different Welding Equipment and try the various methods.

The one general welding online reference I like is:
http://64.78.42.182/sweethaven/BldgConst/Welding/
Published by SweetHaven Publishing Services
Based upon a text provided by the U.S. Navy
Maybe because I spent 20 years in the US Navy.

Other ref:
Welding Journal - January 2008
Copyright 2008 American Welding Society | All Rights Reserved
"Tips for Better Weld Finishing "
http://www.aws.org/wj/2008/01/wj200801/wj0108-26.pdf

For a short description of Welding Procedures:
http://www.weldingengineer.com/

For a Quick description of Welding Alloys per Procedure:
http://www.harrisproductsgroup.com/consumables/

For more Welding links than you ever wanted:
http://www.khake.com/page89.html
I find that not all links are up to date

DIY MIG Welding
http://www.mig-welding.co.uk/

I'm going for big and accuracy, this thing will be able to mill tiny circuit boards, and mill big pieces of wood, maybe even aluminum.

I'm 13, but I'll be turning 14 in february, cnc machines actually seem easier to build than you think. Just doing about a day's worth of research, I found that the PicStep design was the easiest, best controller to build, browse mouser for a couple of days for all of the parts, made all of the circuit boards, and after about 10 hours of work I made all of the electronics. All a cnc machine is 3 stepper motors, a couple of really long screws and threads, a couple of ball bearings, and a router, it's really simple!

using 3 PicStep's, with a 4-axis break out board, google PicStep I've so far built almost 3, I just have to get a couple more of the lmd's

__$80 at harbor freight__

Is putting the parts in an oven an option? If they'll fit - crank the temperature up and let the steel get nice and hot... That should give you more time to braze ;)

Vibration will probably loosen them fairly quickly, but if Thread-Lok is used, it will be ok for a longer period of time.

. Would bolting things together and then soldering work? The bolts would provide strength and the solder would help eliminate wiggle. Just a guess; never tried it.