PDA

View Full Version : building up a shaft with spray weld powder



davidh
07-26-2010, 04:36 PM
has anyone done this on their lathe, at home ?

i have a very corroded rack gear from a old mr2 toyota and its really bad where the plastic bushing keeps it centered on the housing. the gears are fine i bought a new bushing (interesting part, almost like something over engineered from a mercedeed or such).

i was given a Welco Powder Spray gizzmo with directions and metalic powder a few years back and have never tried it. . . they say you can easily build up .060 afte you clean and prepare the mother metal.

i have real asbestous sheeting to cover my lathe and i think i should try it but am apprehensive.. ..

200 degree mother material, fire up the torch after mounting it in the tool holder somehow, turn the lathe to about 200 rpm and let it spray fire and powder from about an inch away from the mother shaft.

of course the shaft needs to be turned down prior and threaded to hold this stuff on, and machined to size after but i have seen the final product on some hydraulic rams and it has lasted for many years of use. . .but i didn't apply that stuff.

are there any words of encouragment out there. or discouragment ?

Evan
07-26-2010, 04:50 PM
This sounds like a good excuse to build a jig with some steel on steel sleeve bearings at each end and a "three jaw chuck" made of a piece of pipe with bolts threaded at 120 degrees that bear on the work inserted in the pipe.

In fact, it would be remarkably similar to my picket twister with a low rpm motor.

http://metalshopborealis.ca/pics2/pickettwister1.jpg

Dr Stan
07-26-2010, 04:58 PM
35+ years ago when I was stationed on the repair ship USS Samuel Gompers AD-37 we had two different set-ups for spray welding.

One was a "hot" spray in which there was a coating of a nickel alloy applied to the worn part. We had several different alloys available including one that came quite close to the hardness of stellite. This was a very good process which we used to build up pump shafts from .025"/side to .060/.070" a side, reface steam valves used in 1200 PSI systems and lots of other applications.

The 2nd one we called a "cold" process which sounds like the one you have. It required a 90 degree included threaded surface and was akin to a braze. We tended to only use it for bronze and brass applications as there had been problems with the coating peeling off.

So you need to consider this was 35 years ago and I would like to think the process has improved. It could also be we just leaned toward the process we liked and knew how to use well. We may not have been prepping the parts correctly.

BTW, as a "rule of thumb" we would nickel plate anything up to .025" per side and spray weld those items that needed more than .025"/side build up.

oldbikerdude37
07-26-2010, 05:08 PM
Iv done flame spray. its an involved process but not too bad.

first you spray the tool and part with break cleaner that does not stay. use the tool to cut many v grooves in the part like a thread but not a thread. like stab a treading tool in .030" every .030" to make a large surface area.

get the part hot like 600f then hit it with a bond coat, hook up the spray coat and build it up.

let spin and dont mess with it, cut from center out on both sides in .005" passes or less. dont let cold air hit it or it will faLL OFF.

it might be fine for a pump shaft thats stone hard but otherwise just weld the thing up and cut it down.

I dont know how much you have paid for flame spray but the price is high, I would never pay for that crap and I can do it. I can machine the whole part new cheaper .that powder is expensive.

noah katz
07-26-2010, 05:13 PM
It's just for a low speed bushing, right?

Rather than risk warping/softening the rack w/heat, why not turn it down a little and use a reduced I.D. sleeve?

becksmachine
07-26-2010, 10:24 PM
The powder spray process is not nearly as dirty as the wire feed style, but if your shop looks anything like Evans, you probably won't like the way your shop/lathe looks when you are done.

The process is very dirty, and the resulting dust is very abrasive. But the finished results are very good if done correctly.

Machining the sprayed area can be challenging, I would used a brazed shank tool ground with a very small or no nose radius. Your results may vary, but many times the sprayed metal sticks to itself very well, not so good to the underlying parent metal.
Any excess tool pressure tends to crack the "shell" and the sprayed metal will fall off to the accompaniment of an imitation of a drunken sailor.

Go ahead, ask me how I know this. ;)

Oldbikerdude has the process described fairly well, I can tell he likes doing it as much as I do. :D

Dave

Black_Moons
07-26-2010, 10:31 PM
Whats wrong with rigging up bearing block to support the shaft (wood screwed down to clamp 2 bearings to a scrap peice of plywood?) and doing it.. in your welding area. Have a friend turn the shaft for ya. Or buy a 12v DC gearmotor for power windows ($15 at surplus stores) and hook it up to the end. just tackweld the 5/16" hex shaft it needs to the end of your existing shaft. Or hell, Tape it on.
(Small variable bench supply = variable RPMs)

You could also use a mig welder insted of the spray process... Spraying metal sounds awfuly messy. With proper preheating and cooling, mig should'nt warp the shaft too much.

DFMiller
07-26-2010, 10:39 PM
Where the heck is Sir John theses days? This seems like the perfect post for his knowledge. Last I heard he was going to scrap a POS Bridgy. Has his Karma caught up to him?
Dave

Dr Stan
07-26-2010, 11:25 PM
How 'bout a pic of this shaft? Would it be easier to just make a new one?

bborr01
07-27-2010, 12:11 AM
I have been thinking of starting a thread about spray welding, but it looks like I won't need to.

I recently bought a spray welder and all the powders and cleaners for a price where I didn't feel like I could turn it down.

Still haven't tried it, but this thread has me wanting to put a piece of scrap to the test just to try it out.

Brian

oldbikerdude37
07-27-2010, 12:36 AM
Seems to me the flame spray powder was like $180 a pound 15 years ago.

if you have money flying out yer rear end then use flame spray always.
It is the best stuff for seal surfaces but remember that you spray 3 OZ that 2.99 OZ ends up in the chip pan so bring yer wallet.

a seal surface on a 5/8" shaft and spraying and machining it cost $150, that same job was $300 across town.
nobody wants to do it unless you throw money at them, and I dont want to suck the fumes of that crap, its evil.

oldbikerdude37
07-27-2010, 12:42 AM
I have been thinking of starting a thread about spray welding, but it looks like I won't need to.

I recently bought a spray welder and all the powders and cleaners for a price where I didn't feel like I could turn it down.

Still haven't tried it, but this thread has me wanting to put a piece of scrap to the test just to try it out.

Brian


go for it if you are cold it will machine like concrete, if its too hot it will be like foil or hard surface rod. ,, do it right and it will be hard and machine like glass and be so smooth its amazing.

macona
07-27-2010, 01:15 AM
Building up a shaft by spray welding is black magic. Those who can do it well without warping the crud out of parts get good money to do it. If you value the part take it to someone who knows how to do it.

oldbikerdude37
07-27-2010, 01:27 AM
Building up a shaft by spray welding is black magic. Those who can do it well without warping the crud out of parts get good money to do it. If you value the part take it to someone who knows how to do it.

Its very cold so warping is not an issue and not magic, its just expensive is all and getting a good bond is the whole trick.

you spray the tool and part with brake cleaner and sure as hell dont use any cutting oil. :p

davidh
07-27-2010, 04:34 PM
well your comments encouraged me to NOT try this spraying on a expensive shaft.

so i cut off the threaded end of the inner tie rod and screwedit in the endofthe rack so as to make a center for one end so i could hold it between the three jaw and a live center and whittled off .035 +/- a couple and next i will attempt to make a bushing similar to the one i bought but .035 smaller id of course.

the harder way would have been to just cut off the rusty half of the rack, bore and thread a hole in the end and make a new part with a matching bored and threaded hole and just loctite it together using a good stud. the area where the teeth are is still usable.

i may do that yet. . . depends if i can get a bushing made that i can affix inside the bore of the housing. the orig. bushing is made with three little round mountains that snap into holes inthe housing before that rack is pushed thru it. when the rack is in place the spring action is no longer possible so it stays in place.

i will attempt to tap the nylon in the same three spots the holes are in the housing and screw three very short screws into it.

then another thought was to make the bushing out of aluminum. . . .. it would easily accept a little tapped hole and using loctite on the tiny screws, it would surely stay where it belonged.

our friendly toyota dealer wants a tad over $900 for this assembly. i think not. . . .

i better take some pictures.

decisions decisions ! ! !

gopher
07-27-2010, 09:39 PM
Had a rotatec sprayer.Results were very good.To spray a shaft u turned down the worn part to clean the metal.Then u cut threads in the area to be sprayed(nothing special just use a threading tool & cut threads fine about .020 to .030 deep.Light torch heat shaft checking with temp stick 300 degree(use the stick beside where u are going to spray,not on area to be sprayed)when sick starts melting start spraying.Check the shaft every so often with a 550degree temp stick if stick melts u need to stop spraying & let the shaft cool a little.After part cools turn shaft down.Used to spray several times a week,never had any problems

lazlo
07-27-2010, 10:08 PM
I have been thinking of starting a thread about spray welding, but it looks like I won't need to.

Likewise -- I've been wondering if it's feasible to do thermal spray in a home shop with surplus Ebay gear, but based on the comments here, it sounds like a PITA.

So how does buildup with thermal spray compare with just welding it up like John does? I gather it's colder and much less likely to warp, but doesn't build up nearly as much thickness?

bborr01
07-28-2010, 12:20 AM
Last week I had a shaft that the seal had worn a groove into.

I thought about trying out the spray welder on it but found out that the price for a new one was over $1500 if I messed it up.

So I tig welded it with stainless rod, turned it down and polished it. Turned out great. I welded the shaft a little at a time, alternating sides so it wouldn't warp. It didn't.

Got the guys machine up and running in no time.

Brian

ADGO_Racing
07-28-2010, 12:43 AM
When we were just a job shop we Spray Welded for one particular customer. It wasn't profitable for us, as about 30% of the time we had to do it over, and sometimes over and over, for it to work. You could do EVERYTHING EXACTLY the way it is supposed to be done, and still flake off. We returned the equipment and either stick or tig welded shafts, and sleeved bores (Also welded some of them too). There is a bit of a trick to welding a shaft, but if done properly, it works well, and doesn't warp enough to be a problem. We routinely welded shafts from about 3/4 inch on up. Smaller ones we just made new.

The other problem was the mess it creates. I was never a fan of using a torch on my machines, and spraying that crap around just confirmed my feelings about the practice.

I think even the "successful" spray welders, have a fair number of do overs. You just don't see it, because most times you just drop it off, and pick it up tomorrow or the next day or later...

macona
07-28-2010, 02:26 AM
Its very cold so warping is not an issue and not magic, its just expensive is all and getting a good bond is the whole trick.

you spray the tool and part with brake cleaner and sure as hell dont use any cutting oil. :p


Not very cold and warping is a huge issue. The heat builds up as the layers build up.

JoeLee
07-28-2010, 07:08 AM
has anyone done this on their lathe, at home ?


are there any words of encouragment out there. or discouragment ?

I wouldn't do it on my lathe !!!!!!! I would rig a set of centers to turn the part on and do it outside. I Have two different spray weld setups, one is I think Roto Tec, and several different powders. The powders are not cheap.

JL.......................

Evan
07-28-2010, 09:49 AM
you spray the tool and part with brake cleaner and sure as hell dont use any cutting oil

DO NOT USE fluorinated/chlorinated brake cleaner!!!! One good sniff of the fumes from the slightest trace left on a part being heated or welded can cause permanent lung damage.