Does China have their own standard for Acme threads? 3

[aroundhere]

I am retrofitting some parts. All is fine until I got to the threads. I ran the od and pitch on a acme ans stub acme thread calculator, but the numbers dont jive. Does anyone if China uses a standard different from the standard U.S. acme or stub acme threads? It is measuring out at 64.8mm od X 4.0 pitch (2.55" x .157").

thanks

 

[MikeHalloran]

In cases where they make both parts, Chinese manufacturers tend to be a little slack about meeting standards.

I see no indication that this will change, ever.



Mike Halloran
Pembroke Pines, FL, USA

 

[Cockroach]

The chinese standard, is not a standard by our definition in North America or Europe. They tend to follow the literature put out by other jurisdictions, yet do not have compliance to that standard. Although getting better than what I have seen in the past, quality and assurance control safeguards are still lacking.

In general, knock off copies are said to be interchangeable and they never are. Reverse engineering is a black art, they are not particularly good at it in comparison to India for example.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[KENAT]

Are you sure it's ACME not some kind of Metric?

Not sure it would make much difference but I've never really played with the trapezoidal metrics so don't know.

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[aroundhere]

I have searched to see if their is a metric type of thread similiar to an acme or stub, but cant find anything. After measuring the part, it almost looks like a stub acme that they modified to take the minor down .040". Its almost like they took an average of acme and stub acme.

For people that use metric only. Is there a metric type of acme or do you just use a 2G acme, but use metric dimensions?

Thanks again guys,

 

[KENAT]

If by ACME you mean more generally trapezoidal thread form take a look at:

http://www.roymech.co.uk/Useful_Tables/Screws/Trapezoidal.html

It appears to show a 65 X 4 thread which is close to what you have when you take into account likely tolerance.

Or you may be able to google something better that actually gives you the tolerances etc.

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[mrainey]

Tr65 x 4-7e
Allowance,0.095
Major Diameter Max,65.000
Major Diameter Min,64.700
Pitch Diameter Max,62.905
Pitch Diameter Min,62.605
Minor Diameter Max,60.500
Minor Diameter Min (Ref),60.030
Root Radius Max,0.250
Root Radius Min,--
Flat At Root,1.330
Thread Height (Basic),2.250

Tr65 x 4-7H
Minor Diameter Min,61.000
Minor Diameter Max,61.375
Pitch Diameter Min,63.000
Pitch Diameter Max,63.400
Major Diameter Min,65.500
Flat At Root,1.330
Thread Height (Basic),2.250

Pitch,4.000
Lead,4.000
Starts,1
Lead Angle,1.160

Included Angle,30.0000


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[KENAT]

Thanks mrainey

So aroundhere ringing any bells yet?

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[aroundhere]

Yes Kenat...They had to have been shooting for the 65 x 4 on the chart. The numbers are very close to the Tr65 x 4-7H that mrainey supplied. I am going to assume that the small tolerance difference is just the chinese way. Thanks alot guys, I believe you hit that one right on the head.

They (chinese) are getting better in the quality. They still match drill alot of parts at assy and sometimes no 2 parts are the same.

thanks

 

[juergenwt]

aroundhere - Just a chance, but look at DIN 380 Flat Metric Trapezoidal Thread.
Basic profile is like regular metric trapezoidal thread DIN 103 except minor dia..
Din 103 Basic Profile Thread Depth = 0.5 x P.
Din 380 Basic Profile Thread Depth = 0.25 x P
mrainay is correct on DIN 103