gage screw correct name & where to find

[KENAT]

I don't really have any inspection experience being on the design side but am helping a manufacturing intern design a crude go-gauge for a granite part with a number of threaded inserts. We want to check the position of inserts is OK.

http://www.tec-ease.com/tips/june-03.htm

shows something like what we'll be creating at bottom right, though ours will have 12 or more holes to check.

What is the correct name for the gage screws used in the link. They don't have to be exactly like that, any variation that will work is fine. I tried some google searches and couldn't find quite the right thing. I may resort to shoulder screws as the +0 -.001" on the shank might be OK but I'd prefer to use proper gage screws which should have slightly better tolerances and better coaxiality etc.

Thanks

KENAT,

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[PSE]

Kenat,

Are you perhaps thinking of True Position Locators? A link to a potential source is below.

http://www.lavezzi.com/QA/LavTruPos.html

Regards,

 

[KENAT]

Thanks, if I understand correctly those are designed for use with gauge balls and either CMM or other inspection methods.

We're looking at an actual go gauge as the part to be checked is part of a vendor supplied assembly.

KENAT,

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[CoryPad]

Fixed limit internal thread gage. See page 5 of this catalog:

http://www.greensladeandcompany.com/pdf/GC Catalog.pdf

Johnson Gage is another respected provider of these gages:

http://www.johnsongage.com

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MadMango]

Most go/no-go gauges for threads have to be screwed-in, is this what you want, or do you simply want to check to positional location of threaded holes? If the latter, then you might look into "slot pins".

Example:

http://www.misumiusa.com/CategoryImages/Metric_2008_pdf/METRIC0993.pdf

 

[KENAT]

We're primarily interested in the location/position of the threaded holes. However, I believe we want to pick up on the actually pitch dia rather than just on the minor dia so using 'slot pins' doesn't look like the way to go.

I already suggested picking up on the minor dia with pins as it would be a lot quicker but I'm not sure that will be adequate.

I just found out that this whole thing is a complete mess, we aren't even sure what locational/position tolerance we're trying to verify!

KENAT,

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[MintJulep]

Didn't the gizmo's I linked to on the other thread (now gone) located on the pitch diameter?

 

[KENAT]

They pick up on the pitch dia but they aren't suited for use in a go fixture like that in my link above. As far as I could tell the intent was that you put them into the threaded hole and then put a gauge ball on top or similar then do your inspection.

I'm looking for something you put up against the face, put 'gauge screws' in all the holes and if you are able to do this then you're good to go.

KENAT,

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[MadMango]

You might be able to use some form of captive screw (clearances equal your tols), and kludge something together if you just want to make sure the locations are accurate enough. I've done this for flat plates with threaded holes using cage nuts or PEM fasteners.

 

[MintJulep]

They have cylindrical features on the tops of the heads. I presumed them to be coaxial with the pitch cylinder of the thread when installed.

So screw a gizmo into each hole and try to set a gage plate over them all. Doesn't that have the same result?

http://www.vermontgage.com/prices/threads/index.html

The TPLs suggested by PSE above would seem to allow the same.

 

[KENAT]

The ones I looked at they didn't spec out the OD in the catalogue, doesn't mean it isn't controlled tho' I suppose. The geometry on some of them wouldn't suit the kind of fixture in my link too.

They were also a bit expensive considering I'll need a bunch of them. $85 or so a pop for around 20 to make a gauge for a product that isn't selling well in this economic climate may not be viable.

KENAT,

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[ajack1]

I have always known them as emel bolts, named after someone who I worked with many years ago but not for long from Hemel Hempstead (you need to know the accent) who always turned bolts down like this as he could never drill holes that lined up.

On a slightly more serious note why would shoulder screws not work, would the .001” limit really matter? If so you could cylindrically grind them to a certain size, you can also buy them with different thread specs at a cost.

 

[KENAT]

ajack, emel ampsted, I get it;-).

Having got definitive tolerance information on the part being inspected I think I can get away with using 'precision' shoulder screws. I'm a bit concerned about the coaxiality of the screw thread to the shank but it'll probably be OK. Turned out the tolerance was looser than I'd initially been led to believe so I have a bigger tol budget and can accomodate the .001.

Sounds like concensus is that the screws often shown in illustrations like that in my link are usually custom.

Thanks all.

KENAT,

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[MintJulep]

If you start with a sufficiently large box of shoulder screws you should be able to select enough that are nearer the +0.

Ajack,

How do you grind something larger?

 

[KENAT]

Having just looked around who got laid off and what section has been all but closed I'm not entirely sure I need this anymore but thanks all!

Kenat

KENAT,

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[ajack1]

I have often wondered that myself MintJulep.;-)

I was actually thinking of grinding it smaller by say .005” and then making the gauge to suit, surely it is the relationship between the body of the shoulder screw and the hole in the gauge that matters not the actual sizes?

 

[CoryPad]

Screw threads have their own variations, so I don't see how using commercially produced (usually low cost and low quality) shoulder screws is the correct choice. Thread gages are made, sold, and used for a reason.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[KENAT]

Cory, I'm obviously having trouble explaining my needs. What has been showing up on searches for 'gauge screws' etc. and the links you and others have kindly provided do not fulfill my needs.

Basically some kind of precision shoulder screw is pretty much what I need, ideally with a head like a thumbscrew to ease use (captive would be nice too but typicall captive techniques wouldn't work well for this appliation).

The self centering thread on some of the 'hole location gauges' would be nice to overcome the concerns of truely centering on the thread but the 'head' & shank geometry of these do not meet my needs.

As to the other thread gauges that typically appear to be a hex with threads on either end, these also do not meet my needs.

I also have concerns over using off the shelf shoulder screws as I'm not sure of the thread form & coaxiality of thread to shank. However, having found a bit more information on how this gauge is to be used they'll probably be adequate.

ajack, that's what I'd thought of doing with the shoulder screws, turning them down to get a tighter tolerance, if I was going to do that though I'd also want to closer control coaxiality to the thread and I'm not sure how practical that is at the tolerances I'm looking at and the likely budget.

KENAT,

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