Air micro die grinder review

1/8" - 3mm collet chuck

air micro die grinder

An air powered micro grinder is one item that you should have in your workshop - also referred to as a high speed or pencil die grinder.

I have a compressed air supply in the workshop for dusting off work and pumping up tyres, but had never bothered to go very far down the air tool path.

Many of these tools are aggressive, noisy things that can be a bit brutal on some jobs.

A needle de-scaler for removing welding slag was the full extent of my air powered tool inventory.

However, investigation revealed that these small air powered die grinders are something else again.

Try a claimed 65 thousand RPM rotational speed for a start, with 90 PSI air pressure driving the unit.  Those are seriously powerful performance statistics.

65K micro die grinder

Given that identical looking units claim speeds of from 54K to 70K RPM, the truth is pretty academic and probably difficult to measure anyway.  Whatever the actual speed, these things really motor.

The air powered unit is very impressive and made me re-think my long standing view of Dremel tools as being toys - not so.

It's a lot cheaper and more powerful than a Dremel and the electric clones that compete against it. 

You also can't burn out the electric motor, as it doesn't have one.

You do of course need an air compressor to drive it, with a filtered air supply.  This means it's not as portable as a regular Dremel.

But for workshop use it's ideal.

So I perused the internet and eventually purchased a basic unit from an internet store in Hong Kong for the princely sum of $29 AUS delivered.

This was the cheapest I could find.

size of air micro die grinder

Here it is in action.

It looks exactly like the ones sold by regular brand name suppliers.

Prices vary wildly for identical units.  I paid $15 for mine (plus $14 postage) from a seller on Ebay.  You should be able to easily get one for less than $40.

It's quite common for retailers to ask $60 - 160 for the identical unit.

Don't get ripped off.  Shop around.

Sherline sell the same unit and various mounts which enable it to be used as a mini toolpost grinder, or as a milling attachment for their micro lathes.

Basic air grinders like these are medium/light duty units and have two ball races supporting the main shaft.  

Many of the grossly inflated priced units claim to be industrial or "professional" grade (whatever that means).  However, only the 4 bearing models are industrial grade, and they look totally different to the universal alloy bodied type sold by most stores.

Like all air tools, they require a drop of oil each time you use them - for long life.

Mine appears to be identical to the Neiko and the Sealey SA673.   In fact all of the alloy bodied units look exactly the same, and probably are.

Sealey have an online parts diagram which shows how the unit is constructed. 

I sourced two sets of tungsten carbide burrs at about $30 AUS each (delivered), and one of those 100 piece multi tool kits that are intended for a Dremel, but fit these units just fine.

The carbide burrs are seen below - 6 mm tips on the left and 3 mm on the right.

3 mm tungsten carbide burrs

The smaller burrs on the right are easier to control, but the big burrs really chew through soft metal and are better for larger jobs.  The little grinder drives both sizes equally well.

You can also use diamond coated burrs.  These are extremely durable and can grind through the hardest of metals, weld, case hardening, tungsten, carbide, glass, ceramic, or porcelain.

Long lasting and cheap to buy.  Excellent.

Two sets are shown below.

diamond coated burrs

The top set are 4 mm diameter cylinders, the same size as used to sharpen small chainsaws. 

The mixed set has many useful profiles.

They come in a number of grit densities with the 120 grit being the most readily available and best for all round use.  I'm pretty sure mine are all the 120 grit.

Diamond burrs will eat stainless steel and anything else hard that you care to throw at them.

Stuff that a file would simply bounce off is no problem.

Carbide is better for softer materials, as diamond may clog.

Below is an assortment of regularly used burrs and abrasives stored in the grinder case.

pencil grinder accessories

What you get

The kit came in the blue plastic case seen above, and included a well finished anodized alloy bodied die grinder with a fitted 3mm collet, and attached inlet and exhaust air hoses.

You also get two small collet wrenches, another smaller 3/32" - 2.35mm sized collet, in line oiler, oil bottle (with oil) and a large Nitto style air connector.

No tool bits or accessories are included in this kit.

I fitted a different brass connector to the air hose to accomodate my older style fittings.

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South Australia