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
In stock
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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


Carbide Insert RH 80° 3/8″ Boring Bar w/2 Flats
Sherline’s gang-tooling tool post (P/N 5930) was specifically designed for customers converting their Sherline lathe into a chucker-style or gang-tooling lathe. Since most parts produced on a chucker lathe are 1/2" (13 mm) in diameter or smaller, and the center-to-center spacing on our gang-tooling post is 1.5" (38 mm), we identified a practical opportunity: our boring bars can double as both boring and outside diameter (O.D.) turning tools.
To support this dual use, we modified our standard boring bars by adding a second locating flat. This allows them to be mounted with the insert face up or face down, providing flexibility for front- or back-side operations. For example, right-hand 80° and 55° boring bars can now be used effectively on either side of the part (see Figure 1).
These 3/8" diameter boring bars are designed to hold a 2-sided 80° carbide insert, secured with a Torx® screw. Each holder includes an 80° carbide insert and a Torx driver.
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Each holder is 3-1/4" long and can bore to a depth of just over 2" when secured with two set screws.
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Constructed from 1144 Stressproof® steel with a black oxide finish for strength and corrosion resistance.
See instructions below for additional guidance on using two-flat boring bars with gang tooling setups.
Pro Tip: Consider using the boring bar with the insert face down to help reduce chip buildup on the insert during cutting. This orientation can improve chip evacuation and extend insert life.

FIGURE 1—55° boring bars used as examples. The left-hand tools are used as turning tools, while the right-hand tools are used as boring tools.
Note: The straight-groove chip breaker shown in some older images is no longer available. Current inserts feature the spider web-style chip breaker as shown here


80° RH and LH Tool Holders w/Carbide Inserts
These holders are available individually in right-hand and left-hand configurations, or as a matched pair. Each includes an 80° carbide insert, a hold-down screw, and a Torx® key for installation.
Specifications & Features:
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3/8" square shank, compatible with standard 3/8" insert tool posts
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5° offset angle provides better tool clearance for complex operations
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Tip height is 0.375" from the base, meeting industry standards
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Constructed from case-hardened steel with a durable black oxide finish
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80° inserts are ideal for roughing cuts
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55° insert holders are also available for sharper corner access
For example, when the holder is squared with the crosslide, it allows you to turn an O.D. up to a shoulder, then finish the shoulder by backing the tool out—while maintaining proper clearance throughout the cut.
Advantages of Inserted Tip Carbide Tools
Although more expensive than high-speed steel (HSS), carbide inserts offer key benefits:
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Each insert can be rotated 180°, giving you two cutting edges per insert
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Maintain a sharp edge when cutting exotic alloys or abrasive materials
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Enable faster cutting speeds and improved surface finishes
While HSS tools are ideal for general use due to their affordability and ease of resharpening, carbide tools are essential for challenging jobs, which is why they're widely used in professional machine shops.
Note: Tool orientation is based on the direction of chip flow. A right-hand tool has its cutting edge on the left, with chips exiting to the right.
Chip Breaker Update: The previously used straight-groove chip breaker is no longer available. Current inserts now come with the improved spider web-style chip breaker, as shown in the updated product images.


55° Carbide Insert-10 Pack
While not inexpensive, carbide inserts offer excellent value—each insert provides four cutting edges, significantly reducing the need for frequent sharpening and saving valuable time.
Carbide cutters perform well on hard-to-machine materials like cold-rolled steel and are also effective on aluminum, brass, and leaded steels, offering exceptional durability. However, for the finest finishes on softer metals, a well-sharpened high-speed steel tool still delivers superior results.
This is the 10-pack of replacement carbide inserts for the following tool holders:


Carbide Insert LH 80° 3/8″ Boring Bar w/2 Flats
Sherline’s gang-tooling tool post (P/N 5930) was specifically designed for customers converting their Sherline lathe into a chucker-style or gang-tooling lathe. Since most parts produced on a chucker lathe are 1/2" (13 mm) in diameter or smaller, and the center-to-center spacing on our gang-tooling post is 1.5" (38 mm), we identified a practical opportunity: our boring bars can double as both boring and outside diameter (O.D.) turning tools.
To support this dual use, we modified our standard boring bars by adding a second locating flat. This allows them to be mounted with the insert face up or face down, providing flexibility for front- or back-side operations. For example, right-hand 80° and 55° boring bars can now be used effectively on either side of the part (see Figure 1).
These 3/8" diameter boring bars are designed to hold a 2-sided 80° carbide insert, secured with a Torx® screw. Each holder includes an 80° carbide insert and a Torx driver.
-
Each holder is 3-1/4" long and can bore to a depth of just over 2" when secured with two set screws.
-
Constructed from 1144 Stressproof® steel with a black oxide finish for strength and corrosion resistance.
See instructions below for additional guidance on using two-flat boring bars with gang tooling setups.
Pro Tip: Consider using the boring bar with the insert face down to help reduce chip buildup on the insert during cutting. This orientation can improve chip evacuation and extend insert life.

FIGURE 1—55° boring bars used as examples. The left-hand tools are used as turning tools, while the right-hand tools are used as boring tools.
Note: The straight-groove chip breaker shown in some older images is no longer available. Current inserts feature the spider web-style chip breaker as shown here