LMT Onsrud 63-631 1/2" Solid Carbide Single-Flute Upcut O-Flute Router Bit for Aluminum – 1-1/8" Cut Length, 1/2" Shank, 3-1/2" OAL

The LMT Onsrud 63-631 is a 1/2" solid carbide, single-flute upcut spiral O-flute router bit from Onsrud's 63-600 aluminum series, made for routing aluminum sheet and plate on a CNC router. The polished single O-flute gives the chip a huge, open path out of the cut, so aluminum does not weld to the edge the way it does on multi-flute tools. With a 1-1/8" cutting edge and a full 1/2" shank, the 63-631 is the size you reach for when cutting 1/4" to 1" aluminum plate, thick ACM panel, or heavy non-ferrous stock where a 1/4" or 3/8" O-flute would flex or run out of reach.

LMT Onsrud 63-631 specifications

What the 63-631 is designed to cut

• Aluminum sheet and plate (5052, 6061, 7075 and similar)
• Aluminum composite material (ACM, Dibond, Alucobond)
• Brass, copper, and other soft non-ferrous metals
• Hard plastics and solid surface when a large single-flute is preferred

Why a single-flute O-flute for aluminum

Aluminum is gummy. A two- or three-flute end mill at router spindle speeds packs chips into the flutes, heats the edge, and the aluminum welds itself to the carbide. A single O-flute has one large, polished gullet, so each chip is thicker and leaves the cut immediately. That lets you run a real chip load at 18,000 RPM and higher without recutting chips. Use an air blast or mist to keep the cut clear, climb cut where the machine allows, and avoid dwelling in the cut.

Fitment

The 1/2" shank requires a 1/2" collet: ER20, ER25, ER32, or a 1/2" router collet. It will not fit ER11/ER16 spindles or 1/4"-collet trim routers. For 1/4" and 3/8" versions of this geometry, see the LMT Onsrud 63-620 and 63-625.

Frequently asked questions

Can a hobby CNC router run a 1/2" aluminum bit?
Only if the spindle has a 1/2" collet and the machine is rigid enough. On lighter machines, the 1/4" 63-620 is a safer choice; the 63-631 is intended for rigid gantry routers and industrial machines cutting plate.

Do I need coolant?
Not flood coolant. Compressed air or a light mist to evacuate chips is enough for most sheet and plate work. Dry cutting in aluminum without air risks chip welding.

What is the difference between the 63-631 and the 63-631ONX?
The ONX version carries LMT Onsrud's ONX coating for longer life in production aluminum sheet. This listing is the standard uncoated 63-631.

Genuine LMT Onsrud tooling, manufactured in Waukegan, Illinois, USA.