Negative Rake Carbide Insert Bits, 10-Pack | Fits AMMCO Brake Lathes | Part #6914-10

Brake Lathe Details

Replacement negative rake carbide insert bits for AMMCO bench brake lathes equipped with negative rake tool holders. The negative rake geometry generates a stronger, more shear-resistant cutting edge than positive rake bits, making it the preferred choice for tougher, harder-grade rotor castings and older composition materials where edge survival is the priority over cutting speed. Industrial-grade carbide with extended edge life under heavy load.

Part #: 6914-10
Quantity: 10 inserts per pack
Rake geometry: Negative
Material: Industrial-grade carbide
Application: Heavy-duty rotor resurfacing on AMMCO brake lathes with negative rake holders
Lathe compatibility: AMMCO bench brake lathes using negative rake tool holders (such as 10701, 10702, 6999)
Function: Shear-resistant edge for harder rotor materials and longer cut life under load
Recommended use: Hard cast iron rotors, older composition rotors, demanding fleet service

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Frequently Asked Questions (FAQs)

Will these handle the "hard spots" on high-carbon rotors?

Yes. High-carbon performance rotors often develop hardened areas from heat cycles. Our negative rake geometry maintains constant cutting force to shear through these spots cleanly, whereas sharper positive rake bits often skip or fracture upon impact.

Why is "Virgin Micro-Grain Carbide" better than recycled carbide?

Recycled carbide has inconsistent density, which leads to thermal cracking and edge failure. Our virgin micro-grain structure stays sharper longer and can handle the "interrupted cuts" of a rusted rotor without the tip snapping off.

How many cutting edges are available on these bits?

These are 6-sided indexable inserts. Because the geometry is symmetrical, you can use all three points on the top face, then flip the bit over to utilize three additional points on the bottom face. A single 10-pack provides 60 fresh cutting edges, offering the lowest "cost-per-cut" in the industry.

How do these Negative rake compare to Positive rake vbits in terms of surface finish?

'-Negative Rake: Uses a scraping action. It is more durable and better for heavy material removal, but it may require a slower feed rate on the final pass to achieve a mirror finish.
-Positive Rake: Uses a shearing action. It cuts cleaner and cooler with less pressure but is more susceptible to edge wear and "chipping" if it hits a hard spot or a heavy rust scale.

Why am I getting "chatter" with my Negative Rake bits?

Chatter with this style of bit is usually a sign of improper tool height or loose dampening. Since negative rake bits require more force to push into the metal, any play in your lathe