Which of the following should be checked before/when turning on milling machines?

• A. Tool clearance
• B. Color of the machine
• C. Viscosity of coolant
• D. Their weight

Answer: (A)

Before turning on a milling machine, the most important check is that the cutting tool has proper clearance. This means confirming the tool is securely mounted, and that its length and diameter won’t collide with the workpiece, clamps, fixtures, or the vise as the tool moves through its programmed path. Verifying clearance helps prevent immediate crashes, tool breakage, and damage to the part or machine. In practice, you’ll confirm the tool’s correct length and diameter, ensure the correct tool is loaded, and review the toolpath or run a dry run to make sure nothing will intersect the setup. The other options don’t affect startup safety in a direct way: color is cosmetic, coolant viscosity matters during cutting but isn’t a startup check, and the machine’s weight isn’t relevant to a safe initial startup.