Part Galling (or Loading)

Broach teeth are mutilated

• Repair teeth; heavy face grinding may be necessary.

• Check your handling and set-up practice.

• Consider follower supports.

Hard fixtures or liner bushings

• Use liner bushings having a maximum hardness of Rc 32.

• Use softer hole fixtures.

Improper face (hook) angle

• Check your sharpening practice.

• Verify actual face angle against the broach print.

• Review the broach design.

Negative face (hook) angle

• Make sure the gullet radius on the grinding wheel is not too large.

• Dish-out the back of the grinding wheel.

Deep (or shallow) face angle radius

• Check your sharpening practice.

• Check the size on the grinding wheel against the size shown on the broach print.

Rounded cutting edges

• Check your method of dressing the grinding wheel.

• Used the root (gullet) diameter for a steady rest instead of the broach OD.

Burned cutting edge

• Check for loading on the grinding wheel.

• Do not sharpen off as much stock in one pass with the grinding wheel

Insufficient backoff

• Check with the broach manufacturer or supplier.

• Verify that the broach print specification is correct.

Incorrectly ground chip breakers

• Set the centerline of the chip breaker grinding wheel as far back as possible behind the broach cutting edge.

Poor coolant practice

• Use recommended coolant.

• Check coolant chemistry.

• Make sure coolant is clean (no tramp oil or excess swarf).

• Check for leaks of hydraulic oil into the coolant.

Porous forgings

• Check the forging practices.

• Eliminate variations in the work material by checking all pre-broach operations.

• Use material with a high standard of cleanliness.

• Examine material for slag or other foreign matter.

• Check the part for pieces of high-speed or carbide tools that may have broken off in a pre-broach operation.

• Check the micro structure of the part.

• Avoid spheroidal structure (lamellar pearlitic structures are the most desirable).

Streaks in the Part

• Lands may be too thick for the degree of part softness.

• Review the broach design.

• Remove burrs with a wire brush, fine grit stone, or vapor blast.

• Broach a cast iron blank.

• Pickle the forgings.

• Alter the part processing sequence.

• Clean the broach before using it.

• Pickle the forgings.

• Install filters or magnetic chip separators.

• Pickle the forgings.

• Specify roto-kut or hole-hog broaches to be designed for this condition.

Abrasion of Broach Surfaces

Excessive scale on the parts

• Pickle the forgings.

• Specify roto-kut or hole-hog broaches to be designed for this condition.

Scale in the coolant

• Remove slag by installing a filtering device.

Cold-worked surfaces

• Check microhardness of parts; change processing methods if necessary.

• Specify broaches designed for this condition.

Broach condition

• Check broach hardness.

• Check face angle sharpening.

Broach Breakage

Broach is overloaded

• Broach parts with a length of cut no greater than that for which the broach was designed.

• Do not broach more than one part unless the tool was designed for it.

Broach is dull, mutilated, or improperly sharpened

• Keep broaches sharp (pull loads are significantly increased by dull or abraded broaches).

Interrupted stroke

• Do not stop then start a broach in the middle of the cutting cycle.

Broach was backed through the part

• Remove the parts from the broaching machine before the broach is returned to the cutting position.

Broach passes completely through the guide hole

• Set the machine stops so that the broach remains in the fixture guide hole at the end of the stroke.

Loose fitting (or sharp edged) key

• Fit the key snugly and round the edges on broaches with key-type pull ends.

Crooked holes in part

• Check forging, piercing, or drilling operations.

Off-square locating surfaces

• Avoid overloads by providing accurate work and fixture locating surfaces

Hard holes in parts

• Check hardening processes to assure parts broached after hardening have machineable holes.

• Correct machining practices that work-harden surfaces.

Stripping the part

• Make sure the part is removed before the broach begins its return stroke.

Insufficient backoff angles

• Compare backoff angle with the broach print specifications.

Sharp corners on broach pull end

• Make certain corners on broach pull ends have chamfers or fillets.

Broach Drifting

Eccentric face grind

• Check broach sharpener center runout.

• Clean centers of broach.

Small broach body

• Specify broaches with body diameters that assure adequate stiffness.

• Do not back taper body between splines.

• Provide adequate supporting means for long or heavy broaches on horizontal machines.

• If cast parts are used on a vertical machine, use an equalizing type (dish) fixture.

• Use rigid, hard fixturing to prevent part movement during broaching.

• Correct part processing methods to provide needed concentricities.

• Correct the hardening processes.

• Review the broach design for a minimum of 2-3 teeth in contact.

• Sharpen broach only after cleaning centers and verifying center runout.

• Make sure broach is sharpened concentric to outside broach diameters.

Rings In Broached Hole

Surging broach feed

• Specify round broaches with staggered tooth spacing.

• Specify flat broaches with increased shear angle on cutting teeth.

Excessively sharp broach

• Vapor blast the broach to slightly dull the edges.

• Lightly stone the outside diameters.

• Run a wooden block along the broach teeth.

High backoff angle

• Review broach design

Rough part locating face

• Provide square locating face on the part, or use equalizing-type (dish) broach fixture

Unsupported broach or part

• On a horizontal machine, the broach must be supported until the last cutting tooth is through the workpiece.

Chatter Marks in Broached Part

Too few teeth in simultaneous contact

• Review broach design.

• Specify shear teeth.

• Review face (hook) angles.

Excessive part hardness

• Correct hardening practices

• Design rigid fixtures so that parts are held in firm position during broaching.

• Reduce or increase broaching speed.

• Check the hydraulic system.

Broach Stuck In Workpiece

Insufficient machine capacity

• Provide broaching machine with more tonnage.

• Resharpen broach to eliminate dullness.

• Redesign tool(s) to require less tonnage.

Clogged chip gullets

• Check sharpening and chip breaker practices.

• Review broach design.

Power failure

• Check power supply.

NOTE: If the broach is stuck in the workpiece, do not try to back the broach out of the workpiece under power. Remove the workpiece and broach and then try to separate them. If that can not be done, the workpiece may have to be broken to separate it from the broach.