Ingersoll Rand Straight or Inline Die Grinders - IR die grinders are offered in 0.4 HP (G1 Series), 1.0 HP (M Series), and 1.35 HP (G3 Series). Choose the horse power based on the job at and hand and remember that more is not always better. With more horsepower comes more weight and if you are using the tool in a production environment all day long, you don't want a heavier tool than the job requires. In contrast, if you need to take down big welds or remove lots of stock, a bigger tool with a bigger carbide burr will be required.
Ingersoll Rand Pencil Grinders - Pencil grinders are designed to be used in intricate de-burring applications. They spin at high RPM's and can be found in machine shops, turbine blade manufacturing facilities, and in mold shops. Artists even use them for carving wood and plaster. Pencil grinders, (also known as precision grinders) come quipped with an 1/8" collet, so detailed material removal and contouring is the name of the game. Use them with small diameter carbide burrs and make sure the tool selected can handle the high RPM output of the grinder.
Ingersoll Rand Type I Wheel Grinders - IR hasn't changed their straight grinders for decades because quite frankly they are awesome as is. These grinders are super robust, American made, and engineered to take off material fast. These tools terminate in either a 3/8"-24 or 5/8"-11 spindle which are designed for use with grinding wheels ranging from 3" up to 6" in diameter. Use these high horsepower grinders in horizontal fashion for removing gatings in a foundry or working large I.D. parts in a fab shop.
Ingersoll Rand Plug and Cone Wheel Grinders - Similar to the Type I wheel tools above , but without the guard, these USA made grinders are designed for similar applications that require more contouring, and perhaps where a bulky wheel guard won't fit. Use these tool with your favorite cone or cylindrical stone type abrasives that has a female thread for screwing on the spindle of the tool. Another heavy foundry or steel fabricator favorite.