MIT LEAP Group Machining FAQs
Working in a machine shop for the first time, or even the hundredth time, can be a daunting experience! To help make machining less intimidating, we have compiled answers to common questions asked in a machine shop. This guide is meant to be used by students, hobbyists, or industry professionals looking to sharpen their skillset.
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Questions
General
What is the difference between the collets used on the mill and those used on the lathe?
What is the difference between the chucks used on the mill and those used on the lathe?
How do I know if a cutting tool (bit, end mill, insert, blade) is dull?
What does “squaring a block” mean?
What is the difference between a countersink and a counterbore?
Noises
Is it easy to break a tap, drill, or end mill?
What is this cyclical sound I’m hearing?
What are good noises? What should milling sound like?
Why does the spindle sound bad?
Why does the spindle sound bad?
Inspection
What measuring equipment should I use for specific tolerances?
What features can I measure with calipers?
How do I read analog calipers?
How do I read vernier micrometers?
How do I interpret the numbers on a bolt?
Filing
What are the different kinds of files? And how do I know when to use them?
How do I know if the file is dull?
How do I hold my part while I file?
Why do I need a handle on my file?
Edge Finding
How fast do I run the spindle when using an edge finder?
What is the diameter of an edge finder?
How far below the surface of my part should the edge finder be?
Parallels and Vises
What size parallels should I use?
Should the parallels be able to slide in and out when the vise is tightened?
Why is my part not sitting flat on the parallels?
How much of my part should sit in the vise?
Can I drill into the vise or the parallels?
How do I know how tight to clamp the vice?
How do I hold a round object in a vise?
Drills and End Mills
How do I decide which end mill to pick?
How do I choose what size end mill to use?
Why choose a two flute end mill vs. a four flute end mill?
Could I drill with an endmill?
How do I know when my cutter is dull?
Why is carbide tooling more prevalent than high speed steel?
Loading Tools on the Mill
How do I load a tool into the machine?
Why are drill chucks used vs collets to hold tools on the mill?
Milling Techniques
How do I counteract backlash on a manual machine?
Which direction should the spindle be rotating?
How do I know if the spindle is spinning the right way?
How do I make this face perpendicular to the other one?
Why are the tools set to different RPM’s?
What is the difference between speed and feed rate?
Depth of Cut on a Mill
How much material should be removed for a finish pass?
What’s the max depth of cut I can take when using a face mill?
What’s the max depth of cut I can take when side milling?
Should I measure my part before taking a finish pass to ensure accuracy?
How much material should be removed for a roughing pass?
Where should the center of the spindle be if I want to mill the side of a part?
Center Drilling
How shallow do I center drill?
X, Y, and Z on a Mill
What do the digits of precision of the DRO mean?
Why is the zero corner most often at the top left-hand side of the workpiece?
How do I keep consistent zero if I switch out parts?
How do I define the Z axis zero?
What are the units on the vertical knee crank on a mill?
Tapping
Why are there different types of taps, and how are they different?
How do I make the threads go all the way to the bottom of the hole?
When tapping, what is the purpose of ½ turn forward and a ¼ turn back?
How do I set up a tap on the mill?
Do I need lubricant when tapping?
What lubricant should I use when tapping?
Why is it necessary to countersink or deburr the top of threaded holes?
What’s the appropriate countersink amount?
Why are 10 turns of a 6-32 tap equivalent to approximately .300”?
Threads
What is the purpose of thread relief?
Why am I cutting the major diameter of the thread undersize?
Chips
Lathe Set-Up
Why do we use collets vs. chucks to hold parts on the lathe?
How far can my part stick out?
What if my part has to stick out further than recommended?
How do I insert the collet into the lathe?
Which direction should the spindle spin? What if it’s going backward?
How do I change the speed on a Sharp 1340F lathe?
The lathe is on but my part isn’t spinning– what do I do?
How do I attach my part to a center (dead center or live center)?
How do I get the live center or drill chuck out of the tailstock?
What are the parts of a lathe?
What are the different types of lathe tools, and when should I use each?
Lathe Techniques
How do I determine an acceptable depth of cut?
Should I adjust the feed rate before the finish pass?
How much stock should I leave for a finish pass?
What determines my surface finish and how “nicely” my part turns out?
How do I inspect for concentricity (alignment of a cylindrical or spherical part)?
Why is the tailstock moving backwards as I try to drill into my part?