What is "cutting oil" really?

[AJMD429]

Getting ready to tap my Puma stainless for a Williams receiver sight, and everything I read admonishes me that I must use lots of 'cutting oil' when I tap hard stainless steel.

The hardware store didn't have any. The auto parts store didn't have any.

I have on hand the usual stuff: WD-40, Hoppes#9, tractor gear oil, 5-30 motor oil, 10-40 motor oil, automatic transmission fluid, and 'Liquid Wrench' - but alas - no "cutting oil"

My neighbor has a cutting horse but if I can't find any REAL 'cutting oil' is there something just as good?

[Rimfire McNutjob]

I'd go with the ATF in a pinch myself. The "lots" is for the cooling effect it has so that the tool doesn't lose it's temper. You're using a center drill right?

[bunklocoempire]

Getting ready to tap my Puma stainless for a Williams receiver sight, and everything I read admonishes me that I must use lots of 'cutting oil' when I tap hard stainless steel.

The hardware store didn't have any. The auto parts store didn't have any.

I have on hand the usual stuff: WD-40, Hoppes#9, tractor gear oil, 5-30 motor oil, 10-40 motor oil, automatic transmission fluid, and 'Liquid Wrench' - but alas - no "cutting oil"

My neighbor has a cutting horse but if I can't find any REAL 'cutting oil' is there something just as good?

I've used various handy oils for various metals (never specifically on purty guns ) -mostly drilling and some tapping, I have not tapped stainless but have drilled it.

I prefer gear oil for large holes or motor oil for smaller holes. I always try to drill/tap as sloooooow and w/steady pressure as possible. I also paint my Jeeps with spray cans and brushes.


Bunkloco

[mescalero1]

It does act as a coolant in a limited capacity when hand tapping.
It also acts to help flush away chips, the trick is to go slow and clean out often.
It's main objective is to act as a lubricant

[deerwhacker444]

the trick is to go slow and clean out often.

+1

I can't empahsize enough how important that is in stainless..!

Stainless,....yuk....

[Mike Hunter]

Go back to you hardware store and buy a little bottle of pipe threading oil, or dark cutting oil, its highly sulperized and stinks to high heaven.

Running a tap in SS, go very slow and clear the chips often, stainless can be some hard stuff, normal HSS taps really don’t like SS.

[Nath]

Olive oil works too

Nath

[stretch]

I've used Marvel Mystery oil to good effect with taps. I like something a little bit heavier for
drilling, but for hand tapping the thin oil is fine, and I think flushes the chips better. Choose
your poison and take your chances...........

[marlinman93]

Tapmatic is designed particularly for tapping holes, and will work better than cutting oil too. Use it on the bit to drill the hole also. I use Kroil in a pinch, but Tapmatic is better for that job.

[cjm135]

Use a starting tap (pointed). When you start the tap make sure it is not cocked or tilted, try to be straight as possible. Once it starts cutting make a 1/4 to 1/2 turn and back up to break the chip (a 1/4 turn) and proceed with every 1/4 to 1/2 turn of cutting and a 1/4 turn reverse to break the chip. Take your time. Cutting oil provides a good lubricant and will reduce/remove the heat of the cutting action. Check with your local Grainger or tooling supply house. You can buy it in a can much like the 3 in 1 oil tins. Word of caution, don't over power the tap. You don't want to break it while cutting the threads.

Get a good tap handle.

[AJMD429]

Lots of helpful advice. I got a decent tap handle, and it has a 'guide' so you can chuck it in the same press you drilled the hole with (you actually chuck the guide, not the tap!), so it seems like it shouldn't be too hard to keep the threads square to the receiver.

I'll try to remember to take a few pics.

[Chuck 100 yd]

I have Tap Magic oil to use on the very hard ones but use the dark pipe threading oil most of the time. Look in the plumbing section of the hardware store for it.
I drill and tap in the milling machine and use the chuck loosly over the tap as a guide with the tap clamped in a two piece tap handle griped very close to the bottom of the shank.
Also use gunsmith quality carbon steel taps not Hi-speed steel taps. If you do snap one off a couple taps with a punch on the broken tap will shatter it and it can be picked out with little or no damage to the gun.
Dont rush it and do it when you are alone and not bothered by kids and such. Have fun!

[brucew44guns]

There are many different blends of cutting oils for all sorts of metals, and speeds of drilling and tapping and threading. Seems to me that a job like you have, very low speed with not much heat at all, and since you don't actually have a commercial cutting fluid, just some light oil like atf or 5w/30 would do ok. And importantly to back up frequently to clean out cut material---and you have it made.

[piller]

I have used Smith's honing oil as a cutting tool coolant when there was nothing else available. It worked better than the cutting tool coolant that Northern Natural/Enron provided us with. There was lots of good advice in the posts before mine. No matter how many times it is said, don't rush it can't be said enough. Hardened Stainless is not forgiving of errors. Now just for fun, who can tell me if that steel would be face centered cubic or not?

[Tycer]

Do not use a mineral oil when tapping aluminum. Use Olive or veggie oil. Mineral oil will gall aluminum.

[jhrosier]

I've tapped many thousands of holes in stainless in past years.
What you need for stainless is a good high pressure type lube to keep the tap from binding in the hole.
For hand tapping there are two automotive products that should work well.
The first, and one that I would use, is STP oil treatment.
I haven't bought any in a long time and don't know if it is still available.
I would imagine that the copper colored anti-sieze compound would work in a pinch, for hand tapping.

Jack

[m.wun]

rapid tap makes a paste for taping and drilling and it makes alot less of a mess,doesnt run all over..

[DavidF]

They have it at Home depot in the plumbing section next to the black pipe.

[mescalero1]

Depends, what series stainless is it?

[Rustolium]

Cutting oil is used to lubricate, cool, and flush chips away. I would use Tap Magic, if you can find it. Otherwise almost any light oil would work. Beeswax is also a good lube for aluminum. Good luck with your project!

[Chuck 100 yd]

Milk makes a good cutting fluid/lube for a Aluminum,Copper Brass and the like. Try it,you will like it!!

[Rusty]

I just happened to remember something I read years ago in one of the Foxfire books. Foxfire #5 I think it is has the section in it on flintlock rifle making. They have writings in it from Hacker Martin, a well known rifle maker from Virginia. IIRC he talks about using hog lard for a lubricant when he was working a rifling machine thru a bore. I know it's not stainless steel but ya never know what might work best.

[David Grubb]

This site has the Tap Magic for stainless steel. I have purchased from these folks and they are good and quick. The product number you need is 8705T63.
http://www.mcmaster.com