huangyhg

need to delcare chamfer on screw clearance hole?
quick question:
when working with nx 6 i noticed that when creating a screw clearance hole it put a small chamfer on both sides of the hole. for a #10 hole the chamfer was 0.015in by 45 deg. when i create the drawings to get this part fabricated will i have to declare this small chamfer or is it assumed by just the deceleration of the hole on the drawing?
thanks!
i can't recal if you get the lead in by default if the thread is called up properly. check out asme b1.1, or if you don't have it i'll try and make time to look.
kenat,
i didnt' see anything in b1.1.
y14.6 shows how to dimension it but not explicitly how big it should be.
grailo,
you will need to specify any chamfers that you want.
kenat,
grailo is talking about clearance holes, not a threaded hole. clearance holes get chamfers to provide clearance for the underhead fillet on screws. tapped holes get chamfers to avoid having a sharp first thread.

doh, yeah my bad, should have re-read the question.
cory's right, you'll need to specify it if you want it. asme y14.5m-1994 1.8.11 & 1.8.12 detail how to spec it. essentially, in the order hole, c'bore, csk. my machineriy's handbook has table 5 from ansi/asme b18.3-1998 which gives the sizes of csk needed for common socket head cap screw sizes.
not sure how i got a star when not answering the question asked.
kenat,
if you have a note calling for a break edge unless otherwise specified, the chamfer on a clearance hole may not need to be called out, if the default break edge is large enough for the screw head fillet.
peter stockhausen
senior design analyst (checker)
infotech aerospace services
i do not like that break edge note. how do you inspect the break edges? do both sides really need to have a chamfer for the clearance hole? this makes the machinist setup up on that hole twice. once to drill the hole and chamfer. then unclamp the part, then clamp it again, find the holes center and add the other chamfer. i would only add the chamfer on the side that mates with the screw head. unless the part can be installed either way i would only include the chamfer on one side.
i detect thread hijacking. break edge is a whole other topic, so to discuss that, i suggest starting a new thread.
anyway, from my experience, unless you are using very very tight clearance holes, there should be no need for the edge of the hole to be affected unless you are using a particular type of bolt, machine screw, or screw that requires it.
i would also say that it is not automatically added. there might be a setting in nx where you can disable its inclusion.
matt lorono
cad engineer/ecn analyst
silicon valley, ca
sorry bout the possible thread hijacking my bad. if you do not think the chamfers are needed take them out.
there is an option for this in nx6 which can be turned off, which is what i have done. on non-critical features, it is as annoying as someone modeling all of the edge breaks.
good to know you got shoes to wear when you find the floor."fff"> - robert hunter

another star? i don't understand you people sometimes.
kenat,

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