Print Inspection Requirement to measure Thread Pitch for an 0-80 Thread

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RoscoeSplevins

We have a print inspection requirement to measure thread pitch for an 0-80 thread. Hell, 80TPI looks like a surface finish probem! Mitutoyo pitch mic has a minimum of 60 TPI. Anyone have suggestions?

Thanky
 
S

Sturmkind

Re: 0-80 thread measurement

Hi, Roscoe!

The originating patents on variable thread measurement for both ID and OD threads are held by Johnson Gage http://www.johnsongage.com/. If anyone can help you out, they can! Their folks are very knowledgeable and quick to respond.

I am not directly associated with this company but they have helped me out tremendously in the past.

Best of luck!
 
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RoscoeSplevins

Re: 0-80 thread measurement

I took a quick look at the Johnson Gage products. Far too expensive for our comany! And a little too complicated. We need a simple, quick, and easy solution.
 

Stijloor

Leader
Super Moderator
Re: 0-80 thread measurement

I took a quick look at the Johnson Gage products. Far too expensive for our company! And a little too complicated. We need a simple, quick, and easy solution.

The simple solutions may not always be available. Measuring is knowing and that does not always come "cheap."

Stijloor.
 
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RoscoeSplevins

Re: 0-80 thread measurement

Exactly our issue. we don't know and we are cheap !
 
S

Sturmkind

Re: 0-80 thread measurement

Bob is 100% right. Threads (or gears) and cheap don't mix.

Caution about ring gages:

A) They are what drove me to Johnson Gage to begin with as they are a composite gage that do not detect conditions that can (and did) result in a customer concern.

B) They can be very tricky to set to the masters because they are so dependent upon touch and feel time-to-time and inspector-to-inspector.

My experience was that when 'best' set, both GO and NO-GO artificially rejected parts that were, in truth, fully conforming (up to about 14% of production). When the rings were set to pass most OK product, they also passed non-conforming product on to the customer.

Another option would be optical scanning. Johnson may be willing or know of another source who you could 'job out' this as both a means to verify the ring gage 'best' set and to satisfy your customer concern for sufficient thread form analysis. It could be a compromise that is financially acceptable to your company but minimizes your risk.
 

bobdoering

Stop X-bar/R Madness!!
Trusted Information Resource
Re: 0-80 thread measurement

If you are really good you can section them and measuring them on an optical comparator. But, that takes some technique - you have to hit dead center on a gnat's knee.
 
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RoscoeSplevins

Re: 0-80 thread measurement

We were avoiding thread ring gages also. Especially with this small a thread. Never fully trusted our calibration of ring gages. As stated, very operator dependent, very subjective.
 
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