1. Horizontal Milling Operations
Unit 67

2. Objectives Set a cutter to the proper depth
Mill a Flat surface on a workpiece
Perform operations such as face, side, straddle, and gang milling

3. Milling Machine One of most versatile machine tools found in industry
Two basic types of milling are:
Plain milling
Surface cut parallel to periphery of cutter
Surfaces may either be flat or formed
Face milling
Surface cut is at right angles to axis of cutter

4. Procedure to Set Cutter to the Work Surface
Before setting depth of cut, check that work and cutter properly mounted and cutter revolving in proper direction
Raise work to within .250 in. of cutter and directly under it
Hold long piece of thin paper on surface of work
Start cutter rotating

5. With left hand on elevating screw handle, move work slowly until cutter grips paper
Stop spindle
Move machine table so cutter just clears end of workpiece
Raise knee .002 in. for paper thickness
Set graduated collar on elevating screw handle to zero.
Move work clear of cutter and raise table to desired depth of cut

6. Procedure for Milling a Flat Surface
Most common operation and generally machined on workpiece with helical milling cutter
Remove all burrs from all edges of work with mill file
Clean vise and workpiece
Align vise to column face of milling machine using dial indicator

7. Set work in vise using parallels and paper feelers under each corner to make sure that work seated on parallels
Tighten vise securely by hand
Tap work lightly at four corners with soft-faced hammer until paper feeler are tight
Select plain helical cutter wider than work to be machined

8. Mount cutter on arbor for conventional milling
Set proper speed for size of cutter and type of work material
Set feed to approximately .003 to .005 in. chip per tooth
Start cutter and raise work, using paper feeler between cutter and work
Stop spindle when cutter just cuts paper
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

9. Raise knee .002 in for paper thickness
Set graduated collar on elevating screw handwheel to zero
Move work clear of cutter and set depth of cut using graduated collar
For roughing cuts, use depth of not less than .125 in and in. for finish cut
Set table dogs for length of cut
Engage feed and cut side 1
Set up and cut remaining sides

10. Face Milling
Process of producing flat vertical surface at right angles to cutter axis
Cutters inserted-tooth cutters or shell end mills
Face milling cutters made in sizes of 6 in. diameter and over
Less than 6 in diameter usually called shell end mills

11. Procedure for Face Milling
When facemilling large surface, use inserted-tooth cutter and mount it into spindle of machine
When milling smaller surfaces, face milling cutter should be 1 in. larger than width of workpiece
Set speeds and feeds for type of cutter and material being cut

12. Set up work on milling machine
Use cutting fluid if cutter material or work will allow
Take large rough cut as possible to bring surface close to within .030 to .060 in. of finish size
Set depth of finish cut and machine surface to size
After completing operation, clean and store cutter and equipment in proper places

13. Side Milling Procedure
Often used to machine vertical surface on sides or ends of workpiece
Set up work in vise and on parallels
Tighten vise securely by hand
Tap work lightly at four corners with soft-faced hammer until paper feelers are tight between work and parallels
Mount side milling cutter

14. Set proper speed and feed for cutter
Start machine and move table until top corner of work touches revolving cutter
Set crossfeed graduated collar to zero
Move work clear of cutter with handwheel
Set required dept of cut with crossfeed handle
Lock saddle to prevent movement during cut
Take cut across surface

15. Procedure of Centering a Cutter to Mill a Slot
Locate cutter close to center of work
Using steel square and rule or gage block, adjust work to center by using crossfeed screw dial
Lock saddle to prevent movement during cut
Move work clear of cutter and set depth of cut
Proceed to cut slot using same methods as for milling flat surface
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

16. Straddle Milling
Involves use of two side milling cutters to machine opposite side of workpiece parallel in one cut
Cutters separated on arbor by spacers of required length
Used for milling square and hexagonal bolt heads
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

17. Points to be Observed When Straddle Milling
Select two sharp side milling cutters, preferably staggered-tooth, of suitable size
Mount cutters with suitable arbor spacers, as close to column as work will permit
Mount arbor support as close to cutters as possible to provide rigidity for cutters
Center cutters on workpiece in proper location

18. Tighten saddle lock to prevent any movement during cut
Set cutter to work surface
Move table so cutter clears end of work
Set depth of cut required and tighten knee clamp
Set proper speeds and feeds for cutter size and type of work material; check cutter rotation
Use good supply of cutting fluid and complete straddle milling operation in one cut

19. Gang Milling Fast method of milling used in production work
Performed by using two or more cutters on arbor to produce desired shape
Diameter and width of each cutter same
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

20. Points to be Observed To Avoid Problems During Gang Milling Operation:
Select cutters close to same size and number of teeth to allow maximum speeds and feeds
Mount correct cutters on arbor as close to machine column as possible
Fasten arbor support close to cutters
Set spindle speed to suit largest-diameter cutter
Be sure work fastened securely and work-holding devices will not contact cutters
Use good flow of cutting fluid

21. Sawing and Slitting
Used for milling narrow slots and for cutting off work
Fragile cutting tools because of their thin cross section
Break easily
To get maximum life from slitting saw, take the following precautions:
Never key slitting saw on arbor unless it is mounted in special flanged mounting collar

22. When selecting slitting saw, choose one with smallest diameter that will permit adequate clearance between arbor collars or supports and holding devices and work
Mount saw close to column face and have outer arbor support close to saw
Always use sharp cutter
Be sure table gibs are drawn up to eliminate play between table and saddle
Operate saws at approximately 1/4 to 1/8 feed per tooth
When sawing or slitting fairly long or deep slots, climb-mill to prevent cutter from breaking