https://labsafety.tamu.edu/training/shopsafety/default.asp
Machining
Two introductory projects
1. Support post for mirror mount
2. Vertical micro-rail mount
Certification
• Required by TAMU
• Complete course at
http://engineering.tamu.edu/safety/new/templates/tool_shop.htm
– submit printout of completed exam
https://labsafety.tamu.edu/training/shopsafety/default.asp
Dress code
• No exposed toes
– No sandals, no shoes with any openings in front
• No exposed legs
– No shorts, skirts, etc
• Will make storage space available in lab
General machine shop skills
Safety is first
• Always follow shop rules
• Never reach toward moving machine part or tool
• Rehearse procedure before turning machine on
• Anticipate hazards
• Never rush a machine – machining should be relaxing
Machines to learn how to use
• Band saw
• Lathe
• Drill press
• Mill
Measurements
• Optics table – metric, Machine shop – inches
• Fractional inches
• Binary but expressed as reduced fractions (ex: 1/4, 5/64)
– Hard to tell which is larger
•
Thousandths of an inch = mils
First pieces to make
• Mirror mount post -- round
• Lens mount post =-- square
Project 1 – Mounting post
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Start with round stock ~ 1-1/2 inch diameter
Cut longer than desired length on band saw
Band saw safety & care
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Set blade guard as low as possible
For round stock – hold in vise
Keep piece in contact with saw table
Fingers away from blade – push stick ?
Lubricate blade
Ease up pressure near end of cut
Listen for bumping sound – metal caught in blade teeth
Mounting post
Band saw rough cut
Face off one side on lathe
– Make end face perpendicular to cylinder axis
– Triangular tool mounted in tool holder
•
Lathe safety
– Spin work once by hand after every change in setup
– Keep hand on power switch when starting first time
– Stand clear of rotating piece – pieces can fly off
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Face off other side
Shorten by removing material
Measure and face off
Lathe
• Round pieces
– Work piece moves
– tool is stationary
Mounting post – part 2
After face off – machine recess
• Insures broad area contact on mount assembly
– Alternative – grind mating parts on optical flat
Cut recess
Recess
(dimple)
• Press tool into face with lathe spinning
• Take off ~ 40 mils, up to half diameter of piece
Start screw hole with center drill
• More rigid than ordinary drill Center drill
• Insures hole is in center
Finish screw hole with number drill
• Number keyed to intended thread size
With recess
• Ex: #7 drill for ¼-20 threads
Drilling procedure
• Lubricate and drill 1st half inch
• When metal chips slow down – remove, clean, lubricate
Ring of
• Repeat more often as hole gets deeper
contact
points
End view
No recess
Single contact
point
Tapping
Tap
holder
Cut screw thread – special tool = tap
• Usually final operation
• Most difficult (least dangerous)
• Broken taps common
• Many tap extraction tools – rarely work
• Usually must start over
How to save tap
• 1. Treat like piece of glass of same size and shape
• 2. Use special tap lubricant – some dissolve aluminum
• 3. Use tap guide to start – tap must be aligned along hole axis
• 4. Frequently back tap out 1 turn – especially when deep
• 5. Choose tap holder
– Long holder gives better control over torque
– But easy to give too much torque
Long
tap
holder
Prevent
bending
motion
Tap
guide
Piece
Project 2 – Micro-rail vertical mount
Start with 1-inch square stock
• Cut in band saw
• Square off ends in mill
• Also machine recess grooves on ends if necessary
Milling machine safety
• Mount work securely
• Don’t take off too much on one pass
Drill holes in one end and two along one side
• Side holes must be spaced by whole inches
• Must be precise
• Measure, mark, punch, then drill
• Punch makes small dimple – guides drill bit
Drill press safety
• Hold work in vise
• Ease up pressure before going through
Hit with
hammer
Punch
Tip makes
dimple
Workpiece
Mill
• Square pieces
– tool moves
Drill press
• Drill holes
Safety review
• 1. Always wear safety glasses
• 2. Never reach toward or point at moving parts of machines
• 3. Lathe
– Mount workpiece and tool tightly
– Spin chuck once by hand just before starting
• 4. Mill
– Mount workpiece tightly
– Make translation stages stiff
• 5. Drill press
– Use vise for small work pieces
• 6. Band saw
– Keep hands far from blade