4. How do we cut left handed threads on a lathe?.
Left hand threads are designed with an LH at the end of the thread designation. Left hand threads are used in application where the nut may loosen because of the rotation of the motor or spindle. The procedure for cutting left hand threads is the same as that used for cutting right hand threads with two notable differences: the compound must be set at 29° to the left of the operator, and the lead screw direction is reversed so that the threading pass is made from the left to the right. Left hand threads typically require a recess at the thread start location. When grinding the left hand threading tool, the side cutting edge angle on the left hand thread cutting tool is opposite of the right hand thread cutting tool.
5. Explain the difference between High speed steel versus Carbide versus Indexable carbide tooling for machining? Explain advantages and disadvantages.
The two materials from which most cutting tools are made are carbide and high speed steel (HSS). While there are a vast number of classifications and metallurgical variations within each material, the most common grades used for rotary cutting tools such as engraving cutters are C-2 micrograin carbide and M2 HSS.
High Speed Steel Versus Carbide.
Carbide will certainly last longer under most conditions. HSS is also vastly preferable to carbide in high heat situations. For deep mortising cuts, a HSS bit will outcast a carbide every time. Excessive heat breaks down the bonding agent that holds the carbide particles together, causing the particles at the cutting edge to fly off, blunting the edge.
Carbide Versus Indexable:.
Carbide drills have a diameters ground to very tight tolerances, the hole must be precise without addition finishing operations. Indexable tools, have a greater diameter tolerances due to the tolerance of the basic body as well as the tolerance of the insert used. For this reason, Indexable drills are normally considered roughing tools.
