Need to Delcare Chamfer on Screw Clearance Hole?
Need to Delcare Chamfer on Screw Clearance Hole?
(OP)
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!
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!





RE: Need to Delcare Chamfer on Screw Clearance Hole?
KENAT,
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RE: Need to Delcare Chamfer on Screw Clearance Hole?
Y14.6 shows how to dimension it but not explicitly how big it should be.
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I believe the chamfer will generally be put in to help with the thread forming process, at least if tapping.
We don't explicitly call it out on our drawings, if you really need to control it though then it should be on the drawing.
KENAT,
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RE: Need to Delcare Chamfer on Screw Clearance Hole?
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.
RE: Need to Delcare Chamfer on Screw Clearance Hole?
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,
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RE: Need to Delcare Chamfer on Screw Clearance Hole?
Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
RE: Need to Delcare Chamfer on Screw Clearance Hole?
RE: Need to Delcare Chamfer on Screw Clearance Hole?
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
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Need to Delcare Chamfer on Screw Clearance Hole?
RE: Need to Delcare Chamfer on Screw Clearance Hole?
"Good to know you got shoes to wear when you find the floor." - Robert Hunter
RE: Need to Delcare Chamfer on Screw Clearance Hole?
KENAT,
Have you reminded yourself of FAQ731-376: Eng-Tips.com Forum Policies recently, or taken a look at posting policies: http://eng-tips.com/market.cfm?
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Need to Delcare Chamfer on Screw Clearance Hole?
Using a chamfer is helpful for any size clearance hole. For example, large clearance holes usually are there because the mating parts can have variable positioning, which means the screw may be on the outer edge of the hole rather than the center. The chamfer prevents the screw underhead fillet from being damaged by tightening against an unchamfered hole.
RE: Need to Delcare Chamfer on Screw Clearance Hole?
"it is considered good practice to countersink or break the edges of holes which are smaller than (D Max + 2F Max)in parts having a hardness which approaches, equals or exceeds the screw hardness. If such holes are not countersunk, the heads of the screw may not seat properly or the sharp edges on holes may deform the fillets on screws thereby making them susceptible to fatigue in applications involving dynamic loading." where D=Bolt MMC (i.e.: .164 for #8) and F= the maximum fillet of the screw head (i.e. .012 for #8). Therefore the countersink dia. for a #8 screw is .188 minimum. PS not sure what OP means by deceleration.
RE: Need to Delcare Chamfer on Screw Clearance Hole?
"If it's not on the print, it had damn well better not be on the part."
Okay, I paraphrased a little, but you get the point.
Mike Halloran
Pembroke Pines, FL, USA
RE: Need to Delcare Chamfer on Screw Clearance Hole?
Matt Lorono
CAD Engineer/ECN Analyst
Silicon Valley, CA
Lorono's SolidWorks Resources
Co-moderator of Solidworks Yahoo! Group
and Mechnical.Engineering Yahoo! Group
RE: Need to Delcare Chamfer on Screw Clearance Hole?
If you need the chamfers, or are added because of a machining process, call them out on the drawing.
Chris
SolidWorks 09, CATIA V5
ctopher's home (updated Aug 5, 2008)
SolidWorks Legion
RE: Need to Delcare Chamfer on Screw Clearance Hole?