80° Carbide Insert
While carbide inserts may have a higher upfront cost, they offer excellent value by providing four usable cutting edges per insert and significantly reducing time spent on tool sharpening.
Carbide cutters excel at machining difficult materials such as cold-rolled steel, stainless steel, and bronze, delivering consistent performance and long tool life. They are also compatible with aluminum, brass, and leaded steels—though for these softer materials, a finely honed high-speed steel tool may still yield the best surface finish.
This is the 10-pack of replacement carbide inserts for the following tool holders:
- 80° Carbide Tool Holders
- 80° RH 3/8″ Boring Bar
- 80° LH 3/8″ Boring Bar
- 80° RH 3/8″ Boring Bar w/2 Flats
- 80° LH 3/8″ Boring Bar w/2 Flats
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INSCRIBED CIRCLE | 0.250″ (6.35 MM) |
CUTTING EDGE LENGTH | 0.254″ (6.45 MM) |
INSERT THICKNESS | 0.094″ (2.38 MM) |
CLEARANCE ANGLE MAJOR | 11° |
INCLUDED ANGLE | 80° |
ISO INSERT DESIGNATION | CPMT 21.51 |
CORNER RADIUS | 0.016″ (0.4 MM) |
MINIMUM FEED PER REVOLUTION | 0.002″ (0.05 MM) |
MAXIMUM FEED PER REVOLUTION | 0.006″ (0.16 MM) |
DEPTH OF CUT MINIMUM | 0.004″ (0.1 MM) |
MAX DEPTH OF CUT | 0.059″ (1.5 MM) |
Related products


1/4″ HSS Tool Blank Set
Lathe tools—also known as tool bits—are the cutting tools used for turning, facing, and other operations on a lathe. The most commonly used are high-speed steel (HSS) tools, which are suitable for machining a wide range of materials including wood, plastic, aluminum, brass, and steel. HSS tools maintain their hardness at temperatures up to 1000°F (588°C), making proper depth of cut, cutting speed, and feed rate essential for optimal performance.
One of the key advantages of HSS tools is how easily they can be resharpened using a standard aluminum oxide grinding wheel. Once sharpened, they retain a keen cutting edge through extended use.
Each Sherline lathe comes with a pre-sharpened 1/4" HSS cutting tool. Pre-ground tool sets—featuring right-hand, left-hand, and boring tools—are also available. However, for long-term savings and flexibility, learning to grind your own tools from blanks is recommended. Custom-shaped tools can be saved for repeat jobs or re-ground for new applications.


55° RH and LH Tool Holders w/Carbide Inserts
These tool holders are available individually in right-hand or left-hand configurations, or as a matched pair. Each holder includes a 55° carbide insert, a hold-down screw, and a Torx® key for installation. Designed with a 3/8" square shank, they fit standard 3/8" tool posts, and the insert tip is precisely 0.375" from the base of the holder—an industry-standard dimension.
The 5° offset angle of the cutting tip provides added versatility for certain operations. For example, when the holder is squared with the crosslide, it allows you to turn an outside diameter (O.D.) up to a shoulder and then finish the shoulder by backing the tool out—while maintaining proper tool clearance.
Constructed from case-hardened steel with a durable black oxide finish, these holders are built for long-lasting performance.
Although carbide insert tools are more costly than high-speed steel (HSS) tools, they offer an advantage: when the cutting edge becomes dull or chipped, you can simply rotate the insert 180° to use the second edge—essentially giving you two tools in one.
While HSS tools remain the primary choice for miniature machining due to their low cost, resharpenability, and adaptability for custom form tools, carbide insert tools are invaluable for specific applications. They maintain a sharp edge when cutting hard or abrasive materials, reduce tool wear, and allow for faster machining—reasons why they're widely used in professional machine shops.
Note: Tool orientation is named by the direction the chip exits the tool. A right-hand tool has its cutting edge on the left, and the chip peels off to the right.
Updated Note: The previously used straight-groove chip breaker insert shown in some images is no longer available. All current inserts now come with the spider web-style chip breaker as shown here.


Carbide Inserts (thread, groove)
These Carbide inserts are used in the Insert Tool Holder and are used for either threading or grooving.
Thread Cutting
- 60° threading insert for cutting outside threads (P/N 22675)
- .031" insert (P/N 2269)
- .062" insert (P/N 2270)
- .094" insert (P/N 22694)
- .125" insert (P/N 22695)
- .031" radius insert (P/N 22692)
- .062" radius insert (P/N 22693)