Would anyone care to share their experience of the dimensional accuracy of the conical Luer fittings that I perhaps naively believed should have an included angle represented by a 6% slope?
Briefly, we have an issue relating to the mating of an OEM supplied female Luer non-return valve with 'standard' disposable syringes as found ubiquitously throughout the world's healthcare system.
Until very recently I had not needed to consult ISO 594/1 which describes typical dimensions of male and female conical fittings and goes on to describe the requirements in terms of gauging, air & liquid leakage, separation force and stress cracking. So far so good.
However having assembled a collection of disposable syringes made by five different manufacturers and measured the dimensions of the male conical fittings using Vernier callipers it is clear that that actual included angles of this admittedly small sample vary from 4.25 to 5.14%. These items may all meet the gauging and other requirements of the standard, but they certainly don't approach 6%. I do not possess the requisite ring and plug gauges to assess this point at present. Clearly fittings with a more acute angle than nominal would be expected to enter into a mating fitting further than one closer to the nominal.
Is it possible that a female fitting similarly departing from the nominal in the obtuse direction, but still meeting the requirements of the standard would result in the two components bottoming out before a secure joint is made?
Is the range of angles represented by my sample common or expected and would they normally be expected to mate satisfactorily with female fittings that might exhibit a similar variability?
Any experience that you might care to share will be gratefully received.
Mike
Hello,
I realize that this is an oldish thread and that the OP may not be around any more, but I think my comments below may still be relevant as general ones.
Luer tapers (ISO 594-1) are not formally defined in terms of slope %. Although the Luer taper is termed as a "6% taper", it's dimensionally defined (including tolerances) through diameters and lengths. A carefull telerance analysis of the various cases could yield the resulting allowed % range, however, to determine whether a given (actual) taper meets the dimensional requirements of the standard, it'd have to be judged by the dimensions specified in the standard, not by the slope % alone.
Further, I find that measuring a Luer taper with Vernier calipers, for formal purposes (such as determining compliance with a standard's requirement), would likely be inappropriate, because (a) taking measurements off a taper is not very reliable this way, especially when the diameter is specified at a certain location along the taper; (b) The real precision of most Vernier calipers would not suffice; and (c) the gauge R&R rating of such measurement would most likely be too low.
Theoretically, any combination of an ISO 594-1 compliant male Luer tip and an ISO 594-1 compliant female Luer bore would not bottom out before a secure connection is achieved (I refer to "secure" as meaning "meeting all functional / performance requirements specified in the standard"). However, construction materials of both fittings, and the presence of any use liquids / contamination (serving as lubricants), have a significant bearing on the actual axial travel under a given engagement force. As noted in another post, the common use of semi-rigid (viscoelastic) materials such as PE and PP complicates the theoretical analysis and takes it beyond a simple dimensional analysis that may have sufficed for steel (such materials also introduce time dependency). It's also true, and not uncommon through the industry, that fittings
not meeting the standard's dimensional requirements
do meet its functional / performance ones.
Cheers,
Ronen.
Read their Scope before sending gages to them. 
Because of the difficulties of measuring Luer Product Fittings, as stated in previous post by Ronen E, the three ISO 594/1 gages are only part of the measurement requirements.
