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General Fabrication Any Fab that does not fit into another Forum

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  #1  
Old 10-30-2015, 05:55 PM
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Allowance for powder coating?

You make a part and you drill a 3/8 hole for a bolt.
The part will be powder coated how much oversize should the hole be to allow for the coating?

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Old 10-30-2015, 06:19 PM
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Depends on the coating and how much room you need for misalignment of mating components. If you're talking about a electrostatic spray applied polyester coating, I would count on around 0.002-0.005in thickness and use a 0.397in hole (X-size drill, finished diameter after coating would be in the neighborhood of .387-.393). You should talk to your powdercoater about thickness though.
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Old 10-30-2015, 06:24 PM
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Quote:
Originally Posted by TheBandit View Post
You should talk to your powdercoater about thickness though.
Prolly I should but the OFN is faster

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Old 10-30-2015, 06:27 PM
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Well that is what I would have done back when I was building automation machine frames and powder coating them cardinal blue. For non coated stuff, i always used "close fit" specs which would be a 0.386 W size drill. Your results may vary according to what powdercoating you use and how well controlled your hole positions are between mating components.
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Old 10-30-2015, 06:34 PM
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Quote:
Originally Posted by TheBandit View Post
Well that is what I would have done back when I was building automation machine frames and powder coating them cardinal blue. For non coated stuff, i always used "close fit" specs which would be a 0.386 W size drill. Your results may vary according to what powdercoating you use and how well controlled your hole positions are between mating components.
On my industrial stuff I just mask the holes, but this is being coated for weather protection...
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Old 10-30-2015, 09:56 PM
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alwaysFlOoReD alwaysFlOoReD is offline
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I really wish the manufacterers of the painted screws I use for work would think ahead like this. They have a robertson head and the paint prevents proper engagement to the screwdriver. I did send a message to the supplier many years ago but nothing has ever changed.
Rant over.
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  #7  
Old 10-30-2015, 11:49 PM
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JaysinSpaceman JaysinSpaceman is offline
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For weather protection don't use any locking washers, I've seen a number of otherwise nice installations quickly ruined by lock washers cutting through the coating and inviting rust. That said most of my bolt holes for structural stuff have around 1/64" clearance and powder doesn't even come close to causing a problem. I have had problems though on alignment dowel holes but usually if you ask your coater they will put silicone plugs in the holes before they coat it. It's a nice way to do it because it only masks the hole and not the area around it. My guy always plugs threaded holes but I do have to ask him to do the clearance holes if I need him to.

Jaysin
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Old 10-31-2015, 10:33 AM
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Originally Posted by JaysinSpaceman View Post
For weather protection don't use any locking washers, SNIP<
Jaysin
Lock Washers are like putting a band-aid on suspenders!

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Old 11-02-2015, 12:22 PM
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CarterKraft CarterKraft is offline
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lock washers are like putting a band-aid on suspenders!

edxactly
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