In Brief.

Die grinders, both the electric & air powered varieties, are widely used within the metal-working & engineering industries. They are excellent for tidying up & smoothing welded joints, removing burrs & flattening sharp edges. They are also commonly used in the engine rebuilding industry & are a necessary tool in all tuning & performance workshops.

Grinding attachments commonly fitted to die grinders include: rotary burrs, grinding stones, flap wheels & wire brushes. 

We can not stress enough the importance of purchasing grinding attachments that are specifically rated for these high speed machines. If you try & use an attachment not specifically designed for die grinder use, there is a very real chance of it shattering due to the excessive speeds that make die grinders so effective.

Generally speaking, a high speed power drill would not usually operate at a speed higher than 4,000 rpm. Die grinders operate at speeds at least six times as fast! The maximum operating speeds of the grinders reviewed ranged between 25,000 & 31,000 rpm.

In some cases, similar looking drill or grinding attachments are manufactured at much lower speed ratings & are only designed to be fitted in a power drill. If an incorrect attachment such as those designed for a drill only was fitted to a die grinder it will, as underscored previously, shatter & send dangerous fragments everywhere. This could cause serious injury to the operator & anyone else that happened to be in the path of these tiny missiles!

What We Did.

For the purpose of our reviews, the die grinding tests were performed on a solid aluminium part - a 4 port inlet manifold from a petrol engine.

If you were a motor sport enthusiast for instance, you might well consider increasing the size of the inlet ports on a manifold which allows engine gases to flow more freely thus increasing the performance of your engine.

We selected a long tapered shaped rotary burr (see photo) to grind a small amount of aluminium from the rim of each inlet. As amateurs in the motor sports arena, we probably did not grind to the same extent that would be the case in a professional tuning workshop.

What We Found.

With each test, our operator applied downward pressure on the tool for a reasonably aggressive rate of material removal. He then used less pressure to produce a finer, smoother finish.

There did not appear to be a great deal of difference regarding the performance of these machines.  They all seemed to perform this particular grinding task equally well.

The price of the reviewed machines ranged from $119 – $468. The Bosch GG27 LC & the Protool SGP 30-8E head the field as the more expensive die grinders. However, in return, they offer a higher maximum speed, variable speed control, the option to purchase a 3mm or 8mm collet chuck, &, the option to purchase a work bench mounting accessory.

* Please heed the following safety advice whilst operating these machines, &, always refer to the safety manual for your particular make of die grinder.

Safety.

• Check that the speed marked on the grinding attachment is greater than the maximum speed of the machine.
• Ensure that the dimensions of the grinding attachment are compatible with the machine.
• Do not operate these machines in an environment where the danger of an explosion exists.
• Sparks are generated when grinding metal. Ensure that no combustible material is located within reach of flying sparks.
• Observe the direction of rotation. Always hold the machine so that grinding dust or sparks are directed away from the body.
• Position the power cord away from the work area.
• Check that the work piece is properly supported.
• Ensure that the grinding attachment is firmly tightened before use. Run the tool in a safe position & at no load for a short period of time. Stop immediately if excessive vibration or defects are detected.
• Always use eye & ear protection. Other protective equipment such as dust mask, gloves, helmet & apron should also be worn.