Air Die Grinder: Straight or 90°, 1/4in or 6mm, Which Burr?

Your burr slips in the collet, the grinder can’t reach the job, or air hisses through but the spindle won’t turn. Choose the body for the access you need, match the collet exactly to the burr shank, pick a burr cut that suits the metal and keep the motor oiled.

The Air Die Grinders range at PartsForMachines has 107 products from Chicago Pneumatic, Sealey, PCL, Sykes Pickavant, Draper and Mueller. They include straight, 90° angle, long-reach and micro grinders, some sold as kits with carbide bits or grinding points.

Straight, 90° or Pencil: Which Air Die Grinder Do I Need?

A straight grinder covers general grinding, deburring and porting; choose a 90° angle head where a straight tool can’t reach, and a pencil grinder for fine detail. A 90° angle die grinder such as the SA674 is 160mm long.

Pencil grinders take 3mm (1/8in) shanks and spin much faster: the 6151959104 weighs 0.2 kg and runs at 60,000 rpm. Straight grinders run from light ones, such as the 375 W 6151600090 at 0.38 kg, to 900 W-plus models of 1 kg or more. Pick a light one for one-handed detail and a heavy one for long spells of heavy grinding.

1/4in or 6mm Collet: Why Won’t My Burr Fit or Stay Tight?

Because 1/4in and 6mm are different sizes: a 1/4in collet is 6.35mm, so a 6mm shank sits undersize in it and a 1/4in shank won’t enter a 6mm collet. Don’t mix metric shanks with inch collets; fit the collet that matches the shank.

A grinder titled 1/4in (6mm) may have either collet: the 6151600040 has a 1/4in (6.35mm) collet, the 6151600360 a 6mm one. Check the collet size in the specification before you order burrs. For mixed shanks, the GSA671 straight die grinder accepts 3mm and 6mm collets.

Single or Double Cut: Which Burr Suits Steel, Stainless or Aluminium?

For steel, stainless and cast iron, a double cut burr is the usual choice; for aluminium, brass and copper, use one made for non-ferrous metals.

Cut names vary between makers: one sells its non-ferrous burr as single cut, another as aluminium cut. Check which metals a burr is made for. For fine work, the 902140SP micro die grinder and carbide bit set has bits in five shapes on 3mm shanks.

Air Gets Through but It Won’t Spin: What’s Wrong With My Die Grinder?

A likely cause is stuck vanes in the air motor, so the air slips past them instead of turning the rotor. Water or dirt in the air can leave rust or a sticky residue that holds them.

Disconnect the air, put a few drops of air tool oil into the inlet and try again. Then oil it as its handbook specifies and keep water out of the air. If it still won’t turn, the vanes or bearings may be worn or damaged. If it slows as soon as it cuts, check that your compressor keeps up.

What Should I Check Before I Buy?

• the body: straight, 90° angle, long-reach or pencil
• the collet size, 3mm, 6mm or 1/4in, against your burr shanks
• the free speed, and that every burr or point is rated at or above it
• the air use at load against your compressor’s output, and the inlet thread
• the controls: safety lever, speed regulator, spindle lock and exhaust direction

Browse the Air Die Grinders range, or contact the PartsForMachines team by WhatsApp, telephone or email with the job, your burr shank size and your compressor’s air output.

Product options, delivery options and returns terms are shown on each product page. A 30-day return policy applies to eligible items.

Frequently Asked Questions

Will a small compressor run an air die grinder?

Only if it delivers at least the grinder’s air use at working pressure; otherwise the grinder slows as the pressure falls. The 6151600090, a small 375 W grinder, uses 7.1 l/s (about 15 cfm) at load: compare that with your compressor’s delivered air.

How far should the burr shank go into the collet?

As far as it will go, with at least 10mm gripped by the collet. Pushing the shank fully home keeps the overhang short, and a longer overhang lowers the speed at which the burr or point can safely run.

Can I use 3mm (1/8in) burrs?

Yes, with a 3mm collet. Pencil and micro grinders here take 3mm shanks: the SA673 micro die grinder runs at 58,000 rpm and comes with ten grinding points, air tool oil and an in-line oiler.

When is a long-reach die grinder worth it?

When the work sits deep in a casting, bore or recess a standard grinder can’t reach. The SA656 260mm long-reach die grinder has an extended shank, while the 6151602150 and 6151602160 are 603mm and 853mm long.

Which speed should I run a burr at, and does a speed regulator help?

Use the burr maker’s speed range, running harder steels slower than softer ones. A speed control, such as the variable speed lever on the 65130, lets one grinder cover both.

Can a drill do a die grinder’s job?

Only if it runs fast enough. Burr speed charts run into tens of thousands of rpm, such as 14,000 to 24,000 rpm for a coated 3/8in double cut burr on unhardened steel; the grinders here run at 12,000 to 60,000 rpm. Check your drill’s speed.

Is it worth repairing a die grinder, or is it disposable?

Repair can be worth it. Vanes and bearings are replaceable parts on many air grinders, so a tired motor need not mean a new tool. Some motor work is for an authorised service agent, so get a quote and weigh it against a new grinder.

Does the exhaust direction matter?

Yes, for comfort and a clear view of the work. Most grinders here exhaust to the rear, and some, such as the SA654, have an outlet that turns through 360° to send the air away from you.

What does CNOMO mean on a die grinder?

It marks a version built to CNOMO, a French automotive industry standard. A CNOMO version may take a 6mm collet rather than 1/4in, so check the collet size in the specification before you order burrs.