Why does saliva produce a better looking finish than oil when machining steel?

[romartin]

I have known this trick since I was a lad using my fathers lathe but I don't know why it works. Is there a product which produces a similar result?

 

[ronkh]

:fan:
??

 

[90LX_Notch]

Wow. This has to be the strangest first post ever. Should be interesting to say the least.

 

[lazylathe]

Odd indeed!!

Although a quick google reveals that thisis recommended by a poster on lathes.co.uk!
When drilling some oils are too viscous when using very small drills.
Says to apply a small drop of saliva which is just right for the job.

I am thinking too much bacteria etc....

Andrew

 

[Blogwitch]

It's an old trick I use occasionally if I am putting in a small centre, but I have never tried it for drilling deeper holes.

It is quicker and easier than reaching for the cutting oil bottle, and where I used to work, all the old hands used the same trick for centre drilling.


John

 

[n4zou]

Another thing saliva does better than anything else is preventing your dive mask from fogging up. That was the first thing I learned in US Navy Diving Class. Spit in your mask and smear it all around with your fingers. The only positive aspect of this was never worrying about someone stealing your mask.

 

[b.lindsey]

Well that's a new one to me and one i won't be teaching my machine shop students as long as other more ...shall we say commercial...alternatives are available.

Romartin, welcome to the site. Perhaps you can post a short introduction in the welcome section about yourself....that always helps.

Regards,
Bill

 

[TroyO]

LOL... saliva, blood.... everything I make seems to get one or the other (Or both) on it.... LOL.

If it makes you feel better I usually scrub stuff off with dish soap and water before assembly.

 

[steamer]

Odd indeed!!

Although a quick google reveals that thisis recommended by a poster on lathes.co.uk!
When drilling some oils are too viscous when using very small drills.
Says to apply a small drop of saliva which is just right for the job.

I am thinking too much bacteria etc....

Andrew

Even if it does work...there's no way in hell anything in my SHOP let alone lathe is going to get my spit on it....My shop is not that hygenic.

And Yes Romartin...please do post in the welcome section when you get a chance....

Dave

 

[romartin]

Thank you all for your comments. Believe it or not, my question was serious - it DOES work (and I still don't know why). For small enough steel objects I always lubricate the final cut using my finger on which I have carefully perched a blob of saliva. When the cut is over, I carefully dry the part and then wipe it with an oily rag. I learned this process in the early 1950s probably from advice in an issue of "The Model Engineer". Thank you Andrew for your google research; without that comfort I would now start to develop a complex. I promise not to conduct experiments using other body fluids.
I have just done a post in the welcome section.
Ian

 

[modelman1838]

I know it is usual to machine brass dry without cutting lubricant, but usually when drilling and threading it does make an awfull squeak. I then apply a bit of saliva on with my finger,it may not help the cutting but at least it stops the squeaking.
Hugh

 

[Tin Falcon]

maybe some water soluble oil diluted with water to recommended ratio. hmm new one to as well.
Tin

 

[BAH101]

I will make the assumption that you should never use your tongue as an applicator ;D

 

[Siddly]

I thought I knew most old school engineering dodges thanks to my mentor, an incredibly foul mouthed and disreputable ( but heart of gold ) machinist who learnt his trade in the 1960's

He never told me about that one though, and it seems right up his street as well

 

[Blogwitch]

I thought I knew most old school engineering dodges thanks to my mentor, an incredibly foul mouthed and disreputable ( but heart of gold ) machinist who learnt his trade in the 1960's

This is the problem with modern day machinists, they want everything 'just so' and if it can't be bought, they don't want to know about it.

Get hold of some old freebie download books from the turn of the century, especially manufacturers lathe operating manuals, and it will open your eyes as what you can do with your lathe.

The people who ran machine tools in those days had to come up with all sorts of tricks and fixes to do things that we laugh about nowadays, because we can just go out and buy 'stuff' to do these jobs, those chaps couldn't. Just like starters today, they can't afford to get it all at once, so a lot of these old tricks should be shown, just so that they can start to use their machines to the full.
This main post might sound unhygienic, but I can tell you, there are most probably worse things hanging about in the far reaches of peoples shops, unless of course you are one of those people who prefer to clean up every last scrap of swarf, and even polish the floors, rather than machining.

When I started to show my machining on here, many moons ago, people were amazed at some of the things I got up to by means of getting the job done, but they weren't my ideas, just ones that I had picked up during my travels and by reading old books.

There is very little new any more, just old ideas brought up to date.

Maybe one day, someone will release a new wonder lube called 'lesser spotted tapeworm spit', and the chap will make a million.


John

 

[steamer]

Hi Bogs,

I don't think any of the comments were derogatory Bogs,,,But I have to say most here hadn't heard of that one before......

Dave

 

[Siddly]

This is the problem with modern day machinists, they want everything 'just so' and if it can't be bought, they don't want to know about it.

I think you are being a teeny bit unfair Mr Bogs. I constantly see amateur machinists on the net doing some really clever and resourceful stuff.

One thing that does worry and puzzle me is the lack of emphasis on benchwork, todays solution to every task seems to involve a machine when sometimes a file could do the same job quicker ( considering the set up time on the machine and assuming proficiency with a file )

A couple of years ago a friend of mine showed me the curriculum for an introductory engineering course he was considering taking. While 30% of it consisted of what I can best describe as compulsory political correctness the module on benchwork was actually optional !

It's a hobby horse of mine, benchwork. Probably because I once hated it, but then grew to like it. Nothing like the zeal of the converted

 

[Blogwitch]

Dave,

Heard of which one?

Siddly,

I wasn't aiming specifically at newcomers, a lot are very talented, but the people who seem to think that everything to do a job can be bought.

You only have to look at the questions, and not just on this site either, usually, how do I do this and what tool can I buy that will do it for me.

Tools do help, but a lot of times, bits and bobs in your workshop can be utilised without going to the nearest tool store or webshop.

I can hardly use my machines any more, but it isn't a case of buying new tools that will get the job done, but what I can remember about how to do jobs without any special ones. In fact there are now some bits in my shop that I don't think I can use any more, like my four jaw chuck, but I never liked four jaw work anyway, so it isn't much of a loss, I will just use my faceplate or mill a lot more.

I also fully agree with you about the benchwork. If it can be marked out, it can usually be made with a hacksaw, files and a drill. But the problem with that is muscle power, and it takes too long, people just want to push a button and have the machines do everything for them.

They haven't really found the secret of why a lot of us do model engineering the 'old' way.

I will just add, I am not against semi automation, power feeds etc, I have had to do it with almost all my machines, otherwise I would have to give up machining completely, as I am basically working with one hand now, but I still get onto the bench to the best of my ability, and rough it out now and again, to me that is pure therapy and enjoyment.
That is just a small part of the above 'secret'.


John

 

[steamer]

Saliva John...

 

[Siddly]

John - I should take a moment to thank you for the plans and write up on that steam engine. I downloaded those a month or two ago from somewhere or other ( I'm assuming you are the same Bogstandard )

While my level of interest in steam engines is roughly zero ( which is why I can't even remember what kind of steam engine it was, they are all greek to me ) the machining tips had me either nodding my head in approval or more usually exclaiming 'wish I'd thought of that'

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