Cutting Oil Recommendations

[actonblue]

I have to chase the threads on a bottom bracket(steel frame) and I need to know what cutting oil to use?
I have heard from friends who work in various engineering related jobs that I could use any lubricant one even said if need be olive oil.
I want to protect the threading tool so should I follow friends advice or go for the proper stuff.

Cheers.

Colin.

 

[gbb]

Your friends are right...you can use almost anything, especially as you're (i assume) cleaning, chasing existing threads.

Normally cutting fluid performs two functions, lubricates to allow easier cutting...and heat dissapation.
Cutting by hand isn't really going to generate much heat so that only leaves some lubrication to ease things along a bit.

 

[sdr gb]

Any lubricant should be fine. It is used to keep the tool cool so it produces a cleaner thread. Never tried tapping anything out using olive oil though.

ETA: gbb beat me to it.

 

[actonblue]

I think my friend may have been stretching the point with the olive oil but he did say if needs must.
So I wont damage the tap if I do not use the recommended cutting oil?

Thanks.

Colin.

 

[gbb]

I think my friend may have been stretching the point with the olive oil but he did say if needs must.
So I wont damage the tap if I do not use the recommended cutting oil?

Thanks.

Colin.

Taps although incredibly strong are brittle but i really can't see that re-tapping an existing thread should damage it.
If a tap breaks, it breaks on the shank 99.9% of the time (i know, ive tapped hundreds of threads). I'd imagine the shank on a tap big enough to do BB threads must be more than thick enough not to break.

The conditions in which a tap breaks are usually any threads under 6mm and its usually because the pilot hole is too small or the tap goes in askew and of course the shank on a small tap is small so more likely to snap.
Anything bigger than 8mm usually only breaks when you're using a drill with the tap to gain more speed or force. Cutting by hand carefully, making sure it goes in straight should be easy peasy.

If you do go ahead yourself, watch the very first few threads. If it starts to go wrong there, it'll just get worse and worse. If it does, come back out and start again. Offer the tap in by hand at first , see if it starts cleanly. Straight and true and slowly.

 

[rusty bearing]

The shank on our taps are @18mm or 3/4" in old money. Bear in mind you need a right and left hand tap so don't get them confused.....

 

[Rohloff_Brompton_Rider]

the best lube is water, thats why machining (turning, milling etc) use water soluble gloops. but seeing as your just tidying up some damage / dirty / worn threads, any oil whatsoever will do, as you'll hardly generate any heat. the 'proper' cutting gloop, that i use to use on pipe threading machines is called Rocol (iirc). tbh, i'd just run it dry, no point in risking getting any mineral / vegetable oil in the frame, if this runs back into the new bb, it could theoretically eat the seals.

 

[actonblue]

It's a new Surly frame and they recommend cleaning up the BB threads before building up the bike.
I will clean up whatever lubricant I use before inserting the bottom bracket.
St Sheldon Brown(patron saint of bike mechanics) recommends engine oil or kerosene.

Thanks for advice I will keep you posted after I do the job.

Cheers.

Colin.

 

[gwhite]

I've built up two Surly frames now and you should have little trouble with the BB as really you are only "chasing" the threads rather than cutting threads. Surly also face the BB shell which is very handy if you're fitting outboard bearings.

 

[actonblue]

Cheers gwhite Surly say you have to face the BB. Did you put framesaver or similar stuff in the tubes? They also recommend that.

 

[slowmotion]

I use Rocol. It's good stuff.

http://www.lawson-his.co.uk/scripts/details.php?cat=Metal Cutting Lubricants&product=1790

 

[the_mikey]

For the purposes of lubricating the tool to chase the thread of a BB then an a light smearing of some grease or oil will do. It helps if it's something that can be easily cleaned out while removing any swarf, most of it, if any, will come out with the tap tool.


Typically cutting oil is used when using a tap in a pillar drill for example, the oil helps dissipate heat and lubricate the tool, bearing in mind the tools job is to cut a thread into metal. You're only using it to ensure the existing thread is clear of paint, dust, swarf and imperfections.

 

[Saddle bum]

Tallow or Lard. You are not cutting much if you are just chasing out the threads.