MILLING
PROBLEMS
|
POSSIBLE
CAUSES
|
POSSIBLE
SOLUTIONS |
1. ROUGH
FINISH
|
Dull cutting
edge
Wrong feeds & speeds
|
Resharpen
to original tool geometry.
Increase speed - also try reduced feed.
|
2. EXCESSIVE
CUTTING
EDGE WEAR
|
Wrong feeds
& speeds
Rough cutting edge
Insufficient coolant
|
Increase
feed (should always be over .001" per
tooth) - especially when machining ductile
or free machining materials. - Also try
reduced speed.
Lightly hone cutting edge with fine grit
diamond hone.
Increase coolant flow - review type of coolant.
|
3. CHIPPED
CUTTING
EDGE
|
Poor chip
removal
Recutting work hardened
chips
Vibration
Incorrect carbide grade
|
Use tool
with larger flute space - larger
diameter or fewer flutes.
Increase coolant flow.
Increase rigidity of set-up, especially worn
tool holders.
Change to tougher carbide grade.
|
4. CHATTER
MARKS
|
Insufficient
machine
horsepower
Vibration
|
Use tool
with fewer flutes as correct speeds &
feeds must be maintained.
Consider climb milling.
Use larger diameter cutter.
Resharpen tool with more clearance.
|
5. GLAZED
FINISH
|
Feed too
light
Dull cutting edge
Insufficient clearance
|
Increase
feed.
Resharpen tool to original geometry.
Resharpen tool with more clearance.
|
6. POOR
TOOL LIFE
|
Excessive
cratering
Milling abrasive material
Milling hard material
Insufficient chip room
Milling surface scale
Delayed resharpening
Thermal cracked carbide
|
Increase
speed or decrease feed.
Change to harder grade of carbide.
Decrease speed and increase feed.
Increase coolant flow.
Climb milling better than conventional
milling.
Reduced speed - rigidity very important.
Use larger diameter tool.
Conventional milling better than
climb milling.
Prompt resharpening to original geometry
will increase total tool life.
Increase coolant flow at all times.
Climb milling is cooler than conventional
milling.
|
DRILLING
PROBLEMS
|
POSSIBLE
CAUSES
|
POSSIBLE
SOLUTIONS |
1. CHIPPED
CUTTING
EDGE
|
Excessive
feed
Excessive lip relief
Vibration
Thermal cracking carbide
|
Reduce feed.
Reduce lip relief to provide smaller
chisel angle.
Frequently a worn drill bushing - REPLACE.
Maintain adequate coolant flow at all times
to avoid thermal shocking carbide.
|
2. SHORT
TOOL LIFE
|
Drill Dwelling
Only one lip cutting
|
Maintain
adequate feed at all times.
Regrind with equal lip heights and chisel
in center.
|
3. DRILL
WALKS
OR DRIFTS
|
Unequal lip
heights
Worn drill bushing
|
Regrind with
equal lip heights and chisel
in center.
Replace drill bushing.
|
4. OVERSIZE
HOLES
|
Unequal lip
heights
Excessive lip relief
Worn drill bushing
|
Regrind with
equal lip heights and chisel
in center.
Reduce lip relief to provide smaller chisel angle.
Replace drill bushing.
|
5. ROUGH
FINISH
|
Dull cutting
edge
Inadequate coolant
|
Regrind with
fine grit diamond wheel.
Review type of coolant and maintain
adequate flow.
|
REAMING
PROBLEMS
|
POSSIBLE
CAUSES
|
POSSIBLE
SOLUTIONS |
1. POOR FINISH
|
Unequal chamfers
Incorrect margins
Excessive spindle runout
Chatter
|
Regrind reamer
with equal chamfer angle.
Regrind reamer with narrow margins for
reaming lower tensile materials.
Increase reamer back taper (will lose size faster).
Reduce speed and increase feed rate.
Use power feed unless material is hard.
Use right or left spiral fluted reamer.
Grind secondary lead angle immediately back of
45° chamfer.
|
2. OVERSIZE
HOLE
TAPER HOLE BELL
MOUTH HOLE
POOR FINISH
|
Misalignment
Insufficient cutting action
|
Use bushing
- .0002"/.0003" over reamer diameter.
If hole location varies, use floating reamer holder.
Increase reamer back taper (will lose size faster).
Specify reamer with positive radial rake to reduce
cutting pressure - may produce slightly larger
diameter holes.
|
3. EXCESSIVE
TOOL
WEAR
|
Insufficient
stock for
removal
Excessive reaming
pressure
Misalignment
|
Decrease
previous operation drill size to
allow more material for removal by reamer - leave
about 3% of hole diameter for cast iron and more
stock for non-ferrous materials.
Increase feed rate.
Reduce stock to be removed by increasing previous
operation drill size - leave about 3% of the hole
diameter.
See problem #2 above.
|
4. CROOKED
HOLES
|
Not drilled
straight
|
Correct previous
drilling operation - reamer
will follow the drilled hole.
Increase reamer attack angle (chamfer) to 120°/180°
included angle.
|
5. TOOL BREAKAGE
|
Excessive
reaming
pressure
Misalignment
|
Reduce stock
to be removed - see problem
#3 above.
See problem #2 above.
|
