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Measuring Threads

Measuring Threads

Measuring Threads

(OP)
We have a situation where we may have to produce a family of parts with variable metric threads depending upon a number of design conditions.

The thread may be large (M60 to in excess of M300) and at this size plug and ring gauges are both cumbersome and expensive.

What alternatives to other people use to not only verify the nominal size and pitch of a thread but also the fit tolerance?

RE: Measuring Threads

M300! This company has thread measurement equipment but I'm not sure they can go that big. You could call and see if they will do a special for you.

http://www.geninsp.com/laserlab

 

Harold
SW2009 SP4.0 OPW2009 SP2 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600
www.lumenflow.com

RE: Measuring Threads

Harold provided a good source for non-contact measurement.  For traditional contact measurement, try Johnson:

http://www.johnsongage.com

RE: Measuring Threads

Three wire measurement.  This can be performed over the bed of the lathe or manually by your QA/AC department.

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

RE: Measuring Threads

Just remember that thread wires can be cumbersome to use on large diameters, and that they tell you nothing about the root geometry of the thread.
 

Software For Metalworking
http://closetolerancesoftware.com
 

RE: Measuring Threads

I agree with cockroach for limited production three wire verification with mic's is ok. It is common practice.

I also agee with mrainey need to verify the thread geometry
make sure it's the correct included angle, Major dia. & root.
which is easy to do in a optical comparator. directly or by dentist mold. It has happened, where the 3 wire check verified correctly, but the geometry was off, there fore
it would not assemble correctly.

To my experience for large threads ground threads is better than single point from a lathe or mill,
but single cut threads are good to if done by an experience
machinist. so it can be debated.

RE: Measuring Threads

I would suggest that an M300 thread may not be the best
solution to your problem.

Perhaps if you could illustrate the application and constraints eg. accuracy required.

RE: Measuring Threads

(OP)
Thanks for all the replies.

The large thread needs to be an 7H6g fit, so that's the level of tolerance we are working to, it's for a pressure vessel where the end is screwed into the shell.

I've also heard of snap gauges.

The optical comparison interests me, developing it a little further, is there a digital method of the same technique? For instance, taking a digital photograph and checking that against a template or series of templates?

RE: Measuring Threads

There are probably integrators that would set up the whole thing for you but if you are interested in DIY you might look at these products:

http://www.colorado-video.com/

We've used the image combiner with good success.

Harold
SW2009 SP4.0 OPW2009 SP2 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600
www.lumenflow.com

RE: Measuring Threads

A CNC Turning Centre equipped with an inspection probe(Renishaw) could machine the component and inspect the thread.

RE: Measuring Threads

They did similar to mfgenggear at a previous place on 13.5" ACME threads or something like that.  They used the dental mold stuff to get an inverted copy of the thread then put that up on the optical comparitor.  I think I prepared a segment of the thread form in CAD that they used on teh optical comparitor but I can't remember the details.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Measuring Threads

Yes the thread geometry can be printed from cad at 50 x size or which scale fits in the comparator.
the thread can then be viewed with the overlay on the optical comparator screen.

if the threads measure to the correct 3 wire verification
your as good as gold.

low tech for small quantities.

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