Cutting tools not included.
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This tool holder is designed to hold 3/8″ square tools on the “back” side of the part. The rear-mount tool holder is slightly taller than our standard #7600 Tool Post, allowing the tool to be mounted upside down and used on the backside of the crosslide. The round hole is for holding boring tools on center (tool not included) like Sherline’s own right- and left-hand 55° inserted tip tool holders.
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Always wear safety glasses when operating machine tools. |
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| Body Material | Aluminum |
|---|---|
| Body Coating | Black Anodized |
| Body Dimensions (H x W X D) | 1.75″ x 1.25″ x 1.25″ |
These 3/8" diameter boring bars hold a carbide insert secured with a Torx screw. Each comes with either a 2-sided 55° or 80° carbide insert and Torx wrench. The 55° LH boring tool will fit into a 3/4" starting hole. The 80° holder will fit into a smaller 1/2" hole. The 80° holder offers a little more strength for roughing cuts while the 55° insert will cut into sharper corners. The 3-1/4" long holder can bore a hole a little over 2" deep with two fastening screws tightened on it. The holders are made from 1144 Stress-proof steel with a black oxide finish. Available individually.
These LH boring bars are not intended to be used for boring on a standard Sherline lathe, as the spindle is not reversible without electronic modifications. They were developed for a Sherline tool that is now in development where they will be used as a turning tool from the backside with the bit upside down. Watch for the introduction of this new “chucker” lathe soon.
Though relatively expensive, if a cutting edge of a carbide insert becomes dull or chipped, the insert can be removed and rotated 180° to expose two new cutting surfaces, providing, in effect, two tools for the price of one.
The primary method of cutting metal on miniature machine tools is usually with high-speed steel tools as they are inexpensive, easily resharpened and can be ground into "form" tools for special jobs. However, inserted tip carbide tools can be lifesavers for some jobs. Though more expensive and not able to be resharpened, carbide tools hold their cutting edge when cutting exotic metals like stainless steel or titanium or abrasive materials like carbon fiber and can speed up the cutting process. This is why they are used for most cutting tasks in the modern professional machine shop.
NOTE: A tool is named by the direction from which the chip leaves the tool; so a right-hand tool has its cutting edge on the left and the chip peels off to the right.
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 55° carbide insert, secured with a Torx® screw. Each holder includes an 55° 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
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.
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:
