Printed from Kezuriba (kezuriba.net/en/maintenance/milling/troubles/)

Quick troubleshooting guide for a manual milling machine

Look up likely causes, what to check, and what to do from the symptom. For intervals, oil types, tightening torques, and tolerances, your machine's instruction manual comes first. The values here are examples from published materials (instruction manuals of overseas small turret mills, an inspection report from one domestic maker, and so on) and differ by model. Adjust gibs and the spindle head only with the spindle and feeds stopped and the power off

Table, saddle, or knee is heavy or will not moveCommon

Likely cause	What to check	Action
Clamp (lock) stays tight	Clamp levers of the table, saddle, and knee	Loosen the clamp. Overtightening the saddle clamp can alone make the table a little stiff^[1](1 source, for reference)
Chips are packed in the ways	Ends of the ways, around the chip wipers	Remove chips often. Blowing with compressed air drives chips under seals and into fits^[1][2]
Not enough oil on the ways	Oil level and discharge of the one-shot lubricator or automatic lubricator	Send oil to the ways with the lubricator. Set the automatic lubricator to a sufficient discharge (if too low, the gibs and ways wear faster)^[1][3]
Gibs overtightened	Gib adjusting screws, heaviness when moved by hand	Loosen slightly and measure the play again. Overtightening prevents an oil film and increases friction^[3][4]
After gib adjustment, the loosened-side screw was not tightened	Screws at both ends of the gib	The wedge-shaped gib wedges into the gap and will not move. Retighten the screws at both ends and redo the adjustment^[3](1 source, for reference)

Dimensions or squareness are off, holes become slottedCommon

Likely cause	What to check	Action
Saddle (Y) gib fits poorly	Front-back runout of the saddle (guideline 3–4 µm; 10–30 µm if poor)	Adjust the Y-axis gib. If it is not seated, cuts in the Y direction will not be square to the X axis^[3](1 source, for reference)
Knee (Z) gib overtightened	Runout when the knee is moved up and down (vertical gap)	Overtightened, the knee tilts each time it moves up and down and holes become slotted. Adjust to within 5 µm as a guideline^[3](1 source, for reference)
Knee (Z) gib too loose	Perpendicularity of the table top to the knee motion (is the front edge low?)	The whole knee sags and tilts forward downward, and uneven wear progresses. Adjust, and if uneven wear has progressed, consult about repair^[3](1 source, for reference)
Feed screw play (backlash) was picked up in climb milling	Amount of lost motion, cutting direction	Normally feed against the cutter rotation (conventional milling), where the cutting force pushes the backlash to one side. For climb milling, remove as much backlash and deflection as possible^[5][4]
Vise fixed jaw is not parallel to the table travel	Put an indicator on the fixed jaw and feed the table	Re-square the vise (guideline: within 0.0005 in over a 6 in jaw; Washington State course material)^[6][7]
Misidentified the source of the backlash (the Z gib was loose, but the spindle head or column tilt was blamed and corrected)	Did you measure to confirm the cause before fixing it?	Do not jump to conclusions: measure gib play and squareness separately, then fix^[4](1 source, for reference)

Steps appear at each pass of a face mill or fly cutter, or the cut surface is tiltedTurret type

The step gets larger as the tool diameter gets larger (because the tram error is an angle)^[8]

Likely cause	What to check	Action
Spindle head is not square to the table (tram error)	Compare left/right and front/back readings with a tramming indicator	Adjust the spindle head tilt and nod (for the procedure, see Care of spindle, arbor and feed). The head drifts with use, so check it from time to time^[8][6][7]
Machine is not sitting level	Level on the table top	Level the machine before correcting tram. Support it evenly at the 4 corners^[8][1]

Chatter, heavy vibration, or poor surface finishCommon

Likely cause	What to check	Action
Belt tension is wrong, uneven belt wear (hard spots), or unbalanced motor or spindle pulleys	Belt tension and condition, pulleys	Adjust the tension. Replace the belt. Balance or replace the pulley^[1](1 source, for reference)
Gib is loose	Play on each axis. Tormach says that if chatter occurs during straight feed on one axis, suspect a loose gib on the opposite axis	Adjust the gib^[1][9]
Tool or workpiece holding is not rigid enough	Fit of the collet and holder, tool stick-out, how the vise or clamps grip	Use a collet and holder that fit, and shorten the tool stick-out. Grip the workpiece firmly. Clamp the axes you are not using (Baileigh)^[9][1]
Tool wear or chipping	Wear, chipping, and thermal cracks on the cutting edge	Resharpen or replace. A dull edge softens from the heat (U.S. Army manual)^[9][1][5]
Low air pressure on the power drawbar, or cracked or missing disc springs in the drawbar	Air pressure (90 psi or more), number of disc springs and cracks	Set the air pressure. Replace the disc springs (Tormach recommends replacing them once a year)^[9](1 source, for reference)
Spindle speed or feed is wrong, or the tool is turning the wrong way	Cutting conditions, spindle direction	Use the correct spindle speed and feed. Match the rotation direction to the tool^[1](1 source, for reference)

Tool slips or pulls out in the colletTurret type

Likely cause	What to check	Action
Collet is not seated all the way into the spindle taper	Drawbar tightness	Pull the collet in and tighten it with the drawbar^[1](1 source, for reference)
Collet diameter does not match the tool shank	Nominal size of the collet	Use a collet that matches the shank diameter^[1][6]
Oil or dirt on the collet, spindle or shank (including the rust-preventive oil on a new tool)	Inside of the collet and the tool shank	Remove oil and dirt, and keep the inside of the collet and the shank dry^[1][10]
Drawbar thread, seat and washer are dry or galling	Galling on the drawbar seat, wear on the thread	Apply anti-seize. Re-machine a galled seat on a lathe, and if the thread is worn, replace the drawbar (and collet)^[10](1 source, for reference)

Tool gets hot or the workpiece burnsCommon

Likely cause	What to check	Action
Spindle speed is too high	Conditions table	Reduce the spindle speed^[1][5]
Tool has gone dull	Cutting edge	Sharpen or replace^[1][5]
Feed is too slow	Feed rate	Raise the feed until the chips clear out^[1](1 source, for reference)
Not using cutting oil or coolant (when cutting steel)	Cutting oil supply	Use cutting oil or coolant^[1][5]

Spindle motor stops or speed will not riseCommon

Likely cause	What to check	Action
Feeding too hard	Feed rate, depth of cut	Reduce the feed^[1](1 source, for reference)
Tool has gone dull	Cutting edge	Sharpen and keep the tool cutting^[1](1 source, for reference)
Motor cannot reach full speed, or motor failure	Motor	Repair or replace the motor^[1](1 source, for reference)

Loud noise, or rattling from the spindle headTurret type

Likely cause	What to check	Action
In high speed (direct drive) the clutch engagement is shallow (clutch wear)	Does the noise occur only in the high-speed range?	Raise the detent plate to compensate for clutch wear. If neutral can no longer be found, flip the detent plate over^[1](1 source, for reference)
Workpiece is mounted poorly	Vise, clamps	Secure it firmly with a vise or clamps^[1](1 source, for reference)
Motor noise	Motor bearings	Inspect the motor bearings^[1](1 source, for reference)

Quill auto feed does not stop (does not disengage automatically)Turret type

Likely cause	What to check	Action
Feed trip is out of adjustment	Set screw under the trip rod, position of the quill stop nut	Adjust with the set screw and confirm that it trips automatically in both the up and down directions^[1](1 source, for reference)

Machine will not runCommon

Likely cause	What to check	Action
Voltage differs from the nameplate, plug or outlet is wired wrongly, or power is off	Nameplate voltage, voltage on each phase, the main power supply	Match the supply to the nameplate. Correct the wiring (electrical work is done by a qualified person)^[1](1 source, for reference)
Power feed circuit breaker has tripped (only the table feed does not move)	Power feed breaker	Push it in to reset^[1](1 source, for reference)

Causes on the side of machining conditions and tools are covered in the Machining Troubleshooting Encyclopedia .

📚Sources

Items without a mark are those on which two or more materials from different publishers agree. Values and intervals are governed by each machine's specifications. The text is summarized in Kezuriba's own words.