Modeling Machine Screws

Ball Screws were used because of the obviousness of requiring a radius
in the plane at right angles to the helix.

If you have a high helix ACME or multiple thread in a V form and take
a longitudinal section through the axis of the thread, your thread
forms will definately look "funny".

Bo

 

Briancad,

If you have specific questions about screw thread metrology please
send me an email I am happy to help.

 

Bo,

This thread is about modeling machine screws so I don't want to drift
too far.

I don't quite understand your statement. What you describe is not how
to view a thread form so all threads viewed in this manner SHOULD
"look funny".

Acme is just a thread form, multi-start threads are just threads with
different start positions. Neither is a big deal. I feel you are
making this task more difficult for yourself than it needs to be.

Tom

 

When machining high helix thread forms, there is often excessive
chatter due to unequal rake angles on the leading and trailing edge of
the tool. To over come this, the profile of the tool is often canted
forward into the helix, so that the rake angle is neutral ie. The top
of the tool is 90deg to the face of the helix. This changes the dims
of the tool and can be difficult to calc. manually, but are not too
hard to grind on the average tool and cutter grinder. Ball forms are
even more complex to achieve this with and probably can not be ground
on the average tool and cutter. Probably they could be ground on a
CNC grinder (they seem to be fairly common these days.)
I've never machined a ball screw, is there any lurkers out there who
have?

Dominic V.
Nybro Holdings

 

In all my prototype machining on manual lathes, I have cut both single
lead and double lead V threads cutting on only one edge and using
29-30 degree infeed, specifically to eliminate chatter.

I think I first learned that way back @ Oregon Inst. of Tech. in my
first machine shop class.

Bo

 

I suppose it depends on if you want to measure a thread, right?
Can you answer the original question or only say "Use a comparator"
without saying how or what you are looking for/measuring & how?

 

Are you certain? Other than the thread form.

BTW, IIRC The balls in a ballscrew/nut don't bottom on the threads
(or are not supposed to .... but who knows about Tom's?)

 

I suspect Tom likes them that way <G>.
Even for low helix angles.

 

Correctly or incorrectly?

Hence your posts on optical comparators.

Probably not.

Probably is when the scrap comes back from the customer with
irate notes & calls.

So what is the 60 degree V aligned with?
And how could you make such on a lathe with a 60 degree
included angle insert?

 

Thus evading the question as well as delving into metrology
rather than how to model (correctly)...

BTW, Anyone that models threads, bolt heads, etc. when
such are not the product being designed (and even then a callout
to the standards might be better) is just adding complexity & entity
count to part databases for no good purpose & wasting computer
clock cycles, memory & disk space, usually.

 

You posted some sily stuff again?

One tired typo ... unlike your turning of negative diameters & a
multitude of nearly worst practices.
Bet your machine "operators" are always adjusting, fudging & editing code.

I hope I'm not flying in planes with your "parts" I think.

So you "inspect to guage" .... that can be wrong too.
BTW, In the US "gage" is often used. Even though such

DANGER, WIL ROBINSON !!!

If the thread's axis went left to right your "perpendicular" would be
up & down or similar.

"Perpendicular" means "at a right angle". HTH.

1 axis + 1 axis + 1 axis +1 axis + 1 axis = (1 + 1 + 1 +1 + 1) axis =
5 axis you say?
Just like 1 apple + 1 apple = 2 apple?

A picture = 1,000 words, eh?

Depends on how things are made.

You need to consider first & second derivatives <G>.

HTH

 

Snipped Cliff's BS and guess what?

Nothing left,
Tom

 

So Cliff, you are promoting people use optical comparators
incorrectly?

Seems like your two lines of g-code with 5 mistakes in it may look a
little funny as well.

Tom

 

Cliff,

As per your normal MO you can't follow or comprehend a thread. You are
repeating what has already been posted and as your usual you ignored
the OP Authors follow up posts.

Tom

 

Cliff,

Your having trouble reading & comprehension again I see.

Your question has been asked and answered, re-read the thread.

Tom

 

Cliff,

You should know the answer to these questions before you represent
yourself as a expert.

Tom

 

<Snipped the Cliffdribble;>

Dear Cliffused Cliff;

The OP author stated:

"The models do require that the threads be "real". The threads made
for asthetic purposes are easy enough to make, in that they are
nothing more than annual grooves. This method would be unacceptable
for this job."

So Cliff, maybe modeling the thread to reflect how it's made is
"real".

Also unlike you I modeled a bolt and emailed it to the OP with jpeg of
the sold. The model included the imperfect threads near the head so
that it is "real". You know, that would be the allowable (actual)
imperfect threads caused by the chamfer on thread roll dies and/or on
a lathe where the threading tool pulls out.

Cliff, when was the last time you modeled a part in SolidWorks?*
Have you ever modeled a part in SolidWorks?*

Tom

*Famous Cliffism:

I have never answered a direct question on Usenet and do not
believe there is a good reason to start doing so now.

 

Cliff,

I forget out of the 5 mistakes you made, which is the 1 you are
admitting to?

Tom

 

Cliff,

Don't you ever get tired of being wrong?

Have you ever worked in a job shop?

There are different types of gauges in this world. Tri-Roll indicating
gauges, set-plugs, etc.

Often times on special threads Customer Supplied Gauges are used
because they don't want to spend an extra five to twenty-five hundred
dollars for a duplicate set.

Other customers REQUIRE job shops to use their gauges.

Tom

 

DANGER is running your Cliff-Code, two lines of sample G-Code with 5
mistakes in it. You know the code that proved you don't know to
program a cnc lathe and never have even though you proclaim yourself
to be an expert.

You don't think Aerospace Fitting and Fastener Companies checked our
parts?

Out of millions of parts if the customer finds ONE bad part we would
most likely lose the customer. If there is a failure in the field we
lose the customer for sure.

Tom