×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

ACME Screw Thread Inspection

ACME Screw Thread Inspection

ACME Screw Thread Inspection

(OP)
   I wanted to see if any one had any recommendations for inspecting ACME screw threads.  My company has some parts with a 1"-5 ACME thread class 3G called out and we really don't have or know of a good way to inspect.  I realize there are standards under ANSIB1.5 and others that define geometry of screw threads, but what are the common ways that these are inspected.  My manager thought maybe we could measure the distance over wires.  Possibly OK for the external thread, but what about internal threads.  Any thoughts?  Thanks in advance.

Pete

The pessimist says the glass is half empty.  The optimist says the glass is half full.  The engineer says the glass is twice as big as it needs to be.

RE: ACME Screw Thread Inspection

If this is an external thread then the best is to purchase ring (female) GO and NO-GO gages. If it is an internal thread then you need a GO and NO-GO male gages.

RE: ACME Screw Thread Inspection

The 3G designation for both the screw and nut is v.important to the final function.

Aside from the usual thread variables: pitch diameter (which can be measured over pins) and thread pitch the major and minor diameters are also critical.

The reason is:
What are the radial loads on the screw?
If the design has no radial load, (like on a lathe lead screw)the root and crest clearances can be large. But if there is side load you must decide to take that load on the crest or root - if taken on the thread flank you get wedging - rapid wear and trouble.

This provision of a crest and root wear surface is one reason acme threads are chosen.

Of course, accurate go nogo gauges are nice but only justified for volume inspection. We have potted the screw/nut in hard epoxy then milled and polished a diametral section and scanned the image at 1200 dpi. Taking it into AutoCad allows good analysis.

Now, if anyone knows about lubricants for acme screws, I'm all ears...

RE: ACME Screw Thread Inspection

One question I would have is what frequency of inspection are you looking at.

If it is just one time for one piece, then you can use over pins or even optical methods.  (For internals - use dental filling material (Reprocil) to  produce a zero shrink cast reproduction of the internal thread as an external.  Then measure the cast as a male thread, remembering that the tooth is really the space.

If you are looking at measuring on an ongoing basis, I would suggest you look into a gauge made by Johnson Gage to do this.

http://www.johnsongage.com


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources