Oxygen heating

[Richard gadsby]

hello I wonder if you could help me.
I need to get some oxygen to use on a propane oxygen torch setup. The question is how much/ what size bottle to get for heating up and removing 21 rusted on screws. I guess I want to know how long a bottle lasts roughly for this sort of thing.
The reason I'm confused is the bottles seem quite tall and thick yet only hold 10 litres?
Please help .
Many thanks in advance Richard Gadsby
Ps if it's the wrong place for this I'm sorry and could a moderator please move it!

 

[the snooper]

the bottle will be 10 litres but it wont be 10 litres of oxy the gas is compressed

 

[Richard gadsby]

Ok thanks for that so the other part being how much do I need for heating up 21 machine screws (get red hot) so I can remove them?
Many thanks Richard

 

[the snooper]

I wouldn't think a great deal, what are they in ?

 

[Richard gadsby]

Hi thanks again, they are holding bottom blades on a triple gang cylinder mower, have got new blades and cylinders but need to get these screws out to replace the blades.
They have been on this machine for the last 10 years sat in a barn for the last 5 and just won't budge so the plan is to heat them up red hot so they expand and then shrink again so that they will undo!
They don't need to survive process as I've got nice shiny new ones!
I just need them out so the machine is ready for the grass in 3weeks or so.
Thanks for replying Richard
Would 5 litres or 10 be best any idea?

 

[the snooper]

you really need to heat up the part the screws fit into, so that will get bigger freeing the screws off, I would imagine a small bottle would be fine for that amount

 

[Richard gadsby]

Oh ok that may be the way to go so If I get a big bottle there will be plenty in it I don't want it running out near the end! Many thanks again Richard

 

[the snooper]

good luck with it

 

[Richard gadsby]

Thanks will post back after and let you know!!

 

[slim_boy_fat]

When I used to do that very job as a greenkeeper, I used to soak with penetrating oil, leave for a day or two with 'top-up's in the interim, then attack them with a lump hammer and an impact driver - never failed yet.

The so-called 'workshop' I operated from had neither power or heat, so needs must.........

 

[Dee J]

Of course there is the old technique of welding (arc or mig) a nut on the top of each screw - gives something to get a grip on, and heats up the screw as an added benefit.

 

[Paul99]

When I used to do that very job as a greenkeeper, I used to soak with penetrating oil, leave for a day or two with 'top-up's in the interim, then attack them with a lump hammer and an impact driver - never failed yet.

The so-called 'workshop' I operated from had neither power or heat, so needs must.........

I was going to post almost the exact same experience / solution. The grounds maintenance company I worked for used to farm nearly all mechanical work - especially this type of job to local garages until I started doing a few bits that quickly became a lot more bits when they realised how much money they were saving. I mostly preferred it to the actual grass cutting TBH but it was always a struggle with very limited tools they had back then. Now though their a huge outfit with several full time mechanics repairing kit for others too. I often think back and realise leaving for a pretty worthless 3 year uni course was a mistake - the parents are only just accepting that I was right about that all them years ago...

 

[blenkie1]

Cutting grass in 3 weeks time? Blimey which country are you cutting it in?

 

[Richard gadsby]

Already started cutting! Did my first 5 of the year last week (I'm a gardener) in lincoln uk. I was still cutting first week of December it's been very mild here this winter. The grass is ready for cutting now but they don't pay for any before last week in March ( this may change though as I have a meeting on Monday with them)
Just been in Nottingham today and my dad has done his already!

 

[Bill Edwards]

Different suppliers may fill bottles to higher fill pressures, meaning that some 10l bottles will actually hold more gas than others.

For the amount of work you have I would buy the cheapest 5 or 10l cylinder you can as it should do your job several times over, it won't need much gas.
It is possible to work out what the gas consumption will be - there is data available for the different nozzles that are available, and you can work out how many hours a bottle will last.
But your job sounds too small to be worth worrying about.

Presumably you'll be getting the outfit (gas, regulators, flashback arrestors which are essential, hoses and a torch) and keeping them for future jobs?
If so I'd be looking at gas suppliers who don't require you to rent the cylinders as these are suited to higher volume users.
Suitable suppliers could be http://www.hobbyweld.co.uk/products/oxygen/ or http://barnet-welding.co.uk/Oxygen?zenid=8ulgoikdnithg062mkar6jghp2


As a useful thing to know, I find that one of the most successful ways to free off rusted parts is to heat them until they are red then pour cold water over them to cool them as quickly as possible. The quick cooling seems to be the most effective method of freeing the rust bond.

 

[Gareth J]

Yea, as above, don't worry about heating the surrounding metal, it will take loads longer (and more gas). Blast the bolts and get them as hot as possible then cool them quickly. The different rates of thermal expansion move the components. You might be able to achieve the same effect just by welding onto the bolt heads - keep building up the weld until you can safely weld a nut on top. Use the nut to work free with plenty of penetrating fluid. no gas required...

 

[Richard gadsby]

Thanks for all your replies I'm a bit cautious about the rapid cooling as I think it's cast iron? I don't want to crack it.
As far as the kit goes yes I will be getting a starter kit of hoses regulators torch etc as I think it will be a useful addition to my tool set!
Thanks again for your replies

 

[Bill Edwards]

Touch the metal with an angle grinder. If the sparks are a red color (cast iron) then think very carefully about using any heat, never mind cooling with water.

 

[Richard gadsby]

In that case i think it's steel as I have cut 2 bolts off it already and I nicked it a couple of times and the Sparks weren't red in colour. That's a good tip

 

[Paul99]

Bedknives are definitely steel and surprisingly soft at that too - I guess their designed to wear quicker than the spools as their much cheaper and easier to replace. If you're not worried about destroying the CSK screws then I'd definitely go down the route of welding nuts onto them - it'll be quicker and easier than grinding the head off and winding out the stub.