Cutting fluid: tips to save your taps

November 2, 2018 11:17 am

We all know it, dealing with a broken tap can be a pain.

Although there are several ways to deal with it, drilling out a broken tap out is generally time-consuming, challenging and requires a lot of extra work.

How to prevent this from happening? Two magic words: CUTTING FLUID.

Cutting fluid is a (cutting tool) life saver in operations like tapping, reaming and drilling.

Drilling in particular calls for lubrication at the drill’s tip and flushing to eject chips from the hole. Without fluids, chips can bind in the hole, and average roughness of the machined surface can be twice as high as what is possible with a wet operation. Lubricating the point of contact between the drill’s margin and the hole’s wall can also reduce the torque required from the machine.

Although some alloys, like aluminum, are typically more forgiving due to the relatively low cutting temperature, it is generally better to use cutting fluid in any occasion.


What type of cutting fluid?

There’s definitely a great variety of lubricants out there that can be used. Some of them are more suitable for soft alloys, while some others are designed to perform on harder materials, like Titanium or Inconel.

Here are some of the best options available in the market and the material they are most suitable for.



Tap Magic Cutting Fluid


The classic. Probably one of the most used cutting fluids in the trade. Although the regular version is expected to work well on any type of material, we recommend using the Tap Magic Aluminum on aluminum parts to avoid stains.

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3-IN-ONE Multi-Purpose Oil

Another pretty solid cutting fluid, and it’s been around since the 1800s. Works just as well as a lot of other fancier and more expensive fluids in the market.

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Not exactly the cutting fluid that any machinist would imagine, but it’s cheap, and can be used in multiple occasions. Rub some of it on your tap and be sure that it won’t break.

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BruteLube Cutting Tool Wax

Another effective multi-purpose wax. This cutting fluid – or cutting wax – works pretty well on harder materials like stainless steel or exotic alloys.

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BOELUBE Machining Lubricant

Like the wax mentioned above, this cutting fluid works great on harder materials. A minimum quantity applied to any tool will keep any tool cool and make it last longer.

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Probably the best cutting fluid to operate on Titanium. Just apply a little bit of this magic fluid in the hole and this will prevent your tap from breaking.

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Castrol Variocut Tapping Fluid

If you are going to tap a hole, this is what you want to use, Extends tool life and nearly eliminates broken taps. Works particularly well on stainless steel and copper.

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  • Howard says:

    What ever happened to original Tap Magic
    The fluid before “Imporved ” Tap Magic was introduced

  • Penny Sake says:

    What about Relton Rapid Tap for metal or Relton A-9 for aluminum? I have had great success with these. Also Viper Venom with it high sulphur content for heavy duty use.

  • Robbie says:

    You didn’t mention “Spray-Tap” cutting Fluid great stuff.

  • 32yrs says:

    Moly-dee may work well in copper but I would make sure you clean out the hole really well just after you’re finished. I have found it will stain if you don’t clean it out well.

  • Bluey says:

    I’ve always used plain animal fat when tapping steel — Sheep fat is the best

  • Gfwhell says:

    Im 83 in my youh I used tallow, beef tallow from the butcher


  • Morganman says:

    Great advice and supportive product information. Another good product particularly for tapping is ‘Temaxol’ a yellow past which loses viscosity as the temperature rises and then it runs into the gaps between tap / die. Works with drilling too.

  • Doggie says:

    I can remember the original “tap magic” The one that had the cloronated “tricloromethane in it was the absolute best. They have yet to even come close to the cutting ability of ANY other brand / type. It was outlawed in the mid nineties because of it’s cloronated solvent base. I still have / use some of that tap juice, as I knew it was being outlawed and I purchased a small stock of it. When you mix it with 80% dark cutting oil and 20% “tap magic” you wind up with something that cannot be beat. It greatly extends the life of taps, reamers, and high speed steel, lathe form cutting tools. Like I said, nothing comes even close to the ability that this combination does. I think that this cutting fluid is still available because it was the thing for cutting exotic metals, like what is used in the aircraft industry. And at last count it cost about $40 a pint can. When I purchased my stock the price was about $30 per gallon. I think that I’ll try to find some of this stuff, just to see if it is still available.

  • GodsChildUPC says:

    I’ve used Tap Magic on almost everything. It’s like my best friend in the shop, and I’ve used Anchorlube on stainless steel process piping in which it gives off a funky smell. Good to know about 3-in-1 didn’t know that could be used as cutting oil.

  • Tony says:

    Mixture of carecut and surrclean works best on drilling or reaming aluminium

  • Tom Coe says:

    I have found that a mixture of approximately 50% kerosene and 50% “lard oil” works extremely well for both taping and machining in most metals, doesn’t cost a lot, is readily available and is not corrosive nor staining to the metals, tools and/or machinery. It also cleans up easily and well and doesn’t, seem to have adverse effects on most people’s skin or allergies.

  • Wingnut says:

    WD40 is an excellent tap / drill fluid on aluminium. I’ve also used Milk of Magnesium on 304SS.

  • Sherm says:

    Four years ago I bought a bottle of NAPA Cutting Oil. It has never failed to do a good job.

  • dougspair says:

    I’ve had very good success with both Anchorlube and Moly-D…..they are expensive, but you only need a tiny amount. they are both great for just about any Stainless steel work.

  • Tonyoldschool says:

    In a pinch, I’ve used automatic transmission (ATF), worked great!

  • Jimbo says:

    I’ve always used an old bottle Cool Tool for tapping steel. Smelly stuff. Upon reading all the positive comments about Castrol Moly-Dee, I wanted to try it. However, I don’t want to take a requisition to the boss, because bringing any new lubricant or chemical into the building means we have to file MSDS sheets and keep the records forever. One would think with a name like Moly Dee, it probably has molybdenum disulfide powder (a common high pressure lubricant) in it. But I could not find Moly listed on the MSDS. I happened to have some of the very fine powder on hand. I mixed it with a small quantity of Cool Tool. NOT HELPFUL. Jammed up the tap real good.

    Anyone have a bottle of Castrol Moly Dee? What are the listed ingredients?

  • Jim says:

    I used “Cool Tool ” in the past before they took out the chlorinated solvents . I was in limbo trying other cutting oils with no great luck. I had this job 100pcs of 316 stainless steel with a 1/4 NPT hole in the center . I knew it was going to be a “PITA”.
    So I decided to try every cutting oil I could find and find out which one worked best . I was using a Bridgeport mill to power tap them at sub 60 RPM . I used a new tin coated tap . I flooded each time with the different oils , some were better than most.
    The best one still was not perfect., still had a little tearing , I didn’t want to use a lot of taps . So I looked around the shop for something to try. I saw I had a bottle of Dura-Lube there. I tapped 2 holes with it , The quality of the cut , looked like CNC milled threads . Wow to start with. I thinned out the Duralube with kerosene to be able to pump it with centrifugal pump.

    90 some tapped holes later , threads were perfect and tap looked new . Plus the price is 1/2 or less than the others .
    I have been using Duralube for @10 years and nothing else . Been at this for almost 50 years


  • Bruce says:

    I have tried them all. The one I have found the best, exceptional even with a dull bit, tap, or cutting tool. It is Mistic Metal Mover!

  • bbae says:

    Lard or bacon grease works very well and the bacon grease is free at my house and it smells good.

  • DOC_SLS says:

    MolyDee is the best high pressure lube for mild, medium carbon, and high carbon steel alloys. It works good on many stainless steels, however Mystic is best on some stainless alloys.

    You can use almost anything else on aluminum.

    Don’t use MolyDee on copper. It works great, however it stains copper.

    Straight cutting oil is always a good one to use on most applications.

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