Threads Flashcards
Week 2
What are threads for?
Fastening and Motion
Fastening = nuts and bolts
Motion = levers, screwjacks, feed screws (think auto feed on the lathes)
What type of threads are used on a 4 litre milk jug?
Multi-start threads
What are the advantages of multi start threads?
More starts = steeper lead angle = faster travel
Thread forming:
Commercial threads are _______
&
Threads on a lathe are ________
Thread forming:
Commercial threads are ROLLED
&
Threads on a lathe are CUT
What is the thread angle for Metric and Unified Threads?
60* included angle
What angle do you set your compound rest to when cutting threads on a lathe?
29* from straight in
29* avoids rubbing that would occur at 30* which makes for a better finish and better tread
Is your lathe Inch or Metric, or both? Name the appropriate pitches for each.
Inch = TPI
Metric = threads per mm
Lathes can be both metric and imperial or only one. Be sure of your units before setting thread pitch.
What tool do you use to check thread depth?
Thread pitch gauge
How do you know when to engage the half nut when turning a thread?
Monitor the Threading Dial, as it runs off the feed screw.
For exactly when, James recommends using the same number each time you engage the half nut.
(though, there are many options and your mileage may vary, review Casperson’s for detailed diagrams and charts)
How do you cut a thread deeper when threading on the lathe?
Increase the depth on the compound slide, and cut again!
When setting up TPI for threading, what part of the lathe is adjusted to ensure correct thread pitch?
The gear box
The lathe must be switched to threading mode, then set the gearbox to the appropriate thread pitch desired.
For the vise operations, what
if 500 RPM is normal, use ~120 RPM (or something slower to become more comfortable)
True or False: When increasing the depth of thread, you should be removing the same amount of metal each pass
False: ensure that you are reducing the amount of material as you reach final measurement.
