Recommend Cutting Fluid for Both Steel and Aluminium.

[actonblue]

Can anyone recommend a brand of cutting fluid that will do for both steel and aluminum .
I have to chase some bottom bracket threads.

Cheers.

Colin.

[inc]

If by chase you mean running a tap down an existing thread on a few bottom brackets any lubricant will do.

[YahudaMoon]

Olive oil, veg oil, multi purpose oil, you could even use white spirit, turps or washing up liquid as these are all oil based. I use white spirit for sharpening my wood chisels in work as it's readily available. They will all help cut steel. If your cutting a thread then I would pick an thicker oil like a vegetable  oil over something like WD40 or white spirit.
In the old days lol, engineering firms used whale fat because it was easily watered down. Maybe they still do ?

[actonblue]

These are interesting replies because I had been under the impression that you had to have special fluids which stop the metal overheating and help protect the cutting tool.
Come to think of it Park's cutting fluid is based on soy.

The bottom bracket threads I am working on may require a little cutting as the cups are not going in too well.

[Zoidburg]

Use a carpenters pencil.

No swarf stuck in the thread by the fluid when done.

[actonblue]

Carpenters pencil? Just rub it on the cutting tool?

[hubner]

Maybe a special fluid is needed in a factory, but I would've thought a light oil will be fine for chasing a BB by hand.

[Tewdric]

I use Park cutting fluid but I'm sure good quality  chain lube would be fine for slow speed cutting.

[teethgrinder]

In the old days lol, engineering firms used whale fat because it was easily watered down. Maybe they still do ?

I'm no engineer, but I've worked on drills, mills, lathes and saws. We generally use cutting paste for tapping threads and coolant for most other things.

I wouldn't bother buying cutting paste especially for one job, but if you're going to do quite a bit of it, then it's pretty cheap to buy and a small pot will last for years, even decades for domestic use.

As said, pretty much any lubricant will do. Grease, oil, even plain old water. I'd go grease.

Use a carpenters pencil.

No swarf stuck in the thread by the fluid when done.

That's a new one on me. Is it poor man's cutting paste?

I suppose toothpaste or bicabinate of soda might help a bit, they're very fine abrasives.

[Zoidburg]

It's graphite.

Dry lube.

[Valiant]

I use 3in1 on the odd occasion I need to do so.

[CommuteTooFar]

Trefolex might be suitable.

Small quantity can be bought here

Chronos Ltd Threading Accessories

[actonblue]

Thanks for the advice I quite like the idea of olive the healthier non toxic alternative.

[Steve Kish]

I use Screwfix stuff.  Very good for thread chasing (steel) and drilling (steel, ali and ti) but TBH, I've never used it for cutting.

[rafletcher]

These are interesting replies because I had been under the impression that you had to have special fluids which stop the metal overheating and help protect the cutting tool.
Come to think of it Park's cutting fluid is based on soy.

The bottom bracket threads I am working on may require a little cutting as the cups are not going in too well.

The speed at which you will work will not need any special cutting fluid.

[Steve Kish]

I made my own bottom bracket chasing tool by stripping an old Shimano bracket and slotting the cups - worked well on my powder coated frame where the numpty coater hadn't cleaned the threads after blasting and baked the residual blasting agent in there!

[jsabine]

The instructions for Park cutting tools (at least headset and bottom bracket chasing/facing kit) are full of dire warnings about how only their special cutting fluid will do, and use of anything else will result in DESTRUCTION AND FIERY DEATH (or at any rate premature blunting of the tools).

Given this is only for occasional use, am I OK to keep on doing as I always have, and just use a few good squirts of GT85 or similar, or should I actually spend four quid and buy a can of cutting fluid spray from Screwfix?

(Obviously if I need to, I'll buy the Park stuff, but I'm just trying to calibrate how much I should discount their marketing spin.)
</thread necromancy>

[Chris N]

For occasional low speed cutting jobs like that almost anything will do just fine.  Chain oil or similar that sticks to the cutter/workpiece would be good.

[Brucey]

the obvious functions of a cutting lubricant are that it

a) cools the cutting edges (which can see high temperatures locally even in hand use)
b) helps to prevent swarf sticking and for it to be carried away
c) helps the parts of the cutting tool that rub and not cut to slide easily.

A lot of different products will suffice for these purposes.

However there are other ingredients in specialist  tapping and cutting lubricants which are designed to help prevent tool wear. These are like EP additives (as found in good quality gear oils) but with knobs on. It isn't an accident that EP-type gear oils and tapping/cutting lubricants smell terrible; both contain weird compounds that are not found in other lubricants.  Unlike EP additives in other lubricants, such matters as long term corrosion are not of much concern in tapping lubricants; it only has to work brilliantly for five minutes and then the job is done; this means that the EP additives can be plentiful and different to others; for example this means that it is so heavily chlorinated that if left in situ it might promote corrosion in the long term but this is not a problem, provided it is cleaned off.

Thus traditional Rocol tapping lubricant (eg RTD) is quite unlike other lubricants that you might find in the workshop. If you want taps and dies to last as long as possible then you should use the best specialist  lubricant of this sort that you can find.

If you have nothing else then an EP gear oil is the least  unacceptable substitute in many cases.

cheers

[Jakob W]

Interesting to hear that hand taps and dies can see high temperatures - does using a cutting lubricant make much difference here? On a machine tool the jet of cutting fluid obviously makes a difference, but I'm surprised to hear that it makes much difference over a normal grease in hand use.

[jsabine]

Thus traditional Rocol tapping lubricant (eg RTD) is quite unlike other lubricants that you might find in the workshop. If you want taps and dies to last as long as possible then you should use the best specialist  lubricant of this sort that you can find.

So on the basis that I:
  i) use the cutting tools so little that any old crap will probably sustain them for as long as I need to use them, but
  ii) am not completely lacking in mechanical sympathy,

should I
  a) continue to use whatever comes to hand,
  b) spend £4 on whatever Screwfix offers,
  c) spend a tenner at Chain Reaction on half a pint of Park CF-2,
  d) spend £20 at Amazon for 500g of Rocol RTD paste, or
  e) choose something else entirely?

I would, frankly, rather spend twenty quid on social lubricant rather than on cutting fluid, but given that a tub that size will almost certainly outlast me - as I say, I don't use the tools very often - I'm sure I could stretch to it.

(I suppose this question really comes down to, is RTD paste close enough to being the 'best specialist lubricant' for the job, or is something else, maybe either CF-2 or one of Rocol's liquids, a better call?)

[Brucey]

RTD is available in liquid, paste, or spray form. It is fiercely expensive.  I use liquid, because it has a fighting chance of getting to where it needs to go; i.e. right where the cutting edge is cutting/shearing the metal.  As I mentioned before if I didn't have any I'd probably use gear oil, in a pinch, instead.

Given that BB taps can be resharpened, and are often damaged by being chipped (which is not much dependant on lube, normally) I'd worry a bit less about using the exact right thing.

BTW you can often tell if the lubrication during tapping is a bit too, er, 'sparing' if you start to see tiny wisps of smoke emerging from the cut; this is the high local temperatures exceeding the flash point of the lubricant. 

cheers

[rogerzilla]

If just paint is in the threads, you don't really need any.  Just reverse the tap intermittently to clear it.  For metal damage/resizing of threads I have some cutting oil but any oil is better than nothing.  I once cut half an inch of new thread onto a chromed steel M6 bolt.  That was hard work.