Machine guides › General horizontal borer

How to operate a horizontal borer

General steps that apply to most manual and CNC table-type horizontal boring machines. Your own machine’s manual comes first.

Setting up

• Check the machine is level and the table, column and headstock ways are clean and oiled. Clear swarf from the table T-slots before you clamp anything.
• Check the spindle taper and the tool shank are clean and undamaged. Seat the tool fully and tighten the drawbar or drift-key retention as your manual describes.
• Know where the axis locks are. Lock every axis you are not feeding: the headstock on the column, the table slides and, where fitted, the spindle sleeve. Unlocked axes are the most common cause of chatter on a borer.
• Plan the job so that the spindle stays as short as possible. Every extra length of spindle or bar sticking out reduces stiffness.

Tramming and indicating the work

• Clamp the work lightly first. Mount a dial indicator in the spindle and sweep a datum face or edge while you move the table, then tap the work square before tightening the clamps fully.
• To pick up an existing bore, sweep it with the indicator by turning the spindle by hand, and move the headstock and table until the reading is even all round.
• For a rotary table, indicate the table centre and its zero position before you set the work on it.
• Re-check the indicator after the final clamping: heavy work can move as it is clamped.

Line boring with an outboard support

• For long or in-line bores, use a line bar carried in the spindle and supported at the far end in the outboard (end) support bearing.
• Align the end support to the spindle with an indicator before you pass the bar through. The bar should turn freely by hand with no tight spots.
• Set each cutter on the bar to size with a setting gauge or micrometer and lock it. Take a test cut and measure before you commit to the full length.
• With the bar supported at both ends you can usually run nearer the normal speed. Without support, a long bar needs the slower speeds shown by the calculators.

Using the facing head

• The facing head is used to face large surfaces and to bore or recess large diameters. Its radial slide carries the tool out from the centre as the head turns.
• Engage and disengage the facing head drive only as your manual describes, normally with the spindle stopped.
• Set the slide stops and check the tool clears the work and the clamps through a full turn by hand before you start the motor.
• An offset slide and tool are out of balance. Use the head’s own, slower speed range, keep the slide no further out than needed, and use any balance weights provided.
• Work out the speed from the diameter the tool is actually cutting at, not the size of the head.

Spindle extension

• Feed the spindle out only as far as the cut needs. Stiffness falls off quickly as the spindle extends.
• Where the job allows, move the table or column instead of extending the spindle, and lock the spindle sleeve once it is in position.
• If the cut starts to chatter as the spindle extends, slow the spindle, reduce the depth of cut, or move the work closer.

Speeds and feeds

• Use the RPM calculator or speeds & feeds with a horizontal borer chosen in the machine picker. Enter the bar overhang and bar diameter, and tick the facing head box if you are using it.
• Our speed reductions for long bars (by overhang ÷ diameter, L/D) and for the facing head are rules of thumb est., not published data. Start lower and work up while listening to the cut.
• Geared machines have fixed steps. Pick the nearest step at or below the suggested speed, and change gear only as your manual describes.

Safety

• Keep clear of the rotating spindle, the facing head and any bar sticking out. A turning facing head can catch clothing well away from the cutter.
• No gloves, loose sleeves, ties or jewellery near the spindle. Wear eye protection, and safety boots when handling heavy work.
• Use proper lifting gear and rated slings for heavy work and fixtures. Never stand under a suspended load.
• Stop the spindle before measuring, clearing swarf or adjusting the tool. Use a brush or hook for swarf, never your hands.
• Know where the emergency stop is, and keep the area round the table travel clear.

Shutting down

• Stop the spindle, withdraw the spindle and return the axes to a safe position. Isolate the machine.
• Clean the table and ways, then oil them as your manual lists.