ran into a problem??????

**hoytheld** · 10-01-2009, 05:32 AM

I machined an item from 6061 aluminum. basically it is a ring (doughnut) with 6 bolt holes in the face, then counter sunk so the bolt head lays flush with the face.

I shot gloss black on them last night and had poor results. Around the machined edge of the countersink, the powder appeared to flow away...so...in essence, there is a hairline silver ring around each counter sink.

here is how I prepped:

1) scorch brited part
2) used brake cleaner
3) heated part to dry off any residue
4) powdered...cured

question: should I media blast the entire part to ensure the crisp edge of the counter sink gets etched?

Thanks

**hoytheld** · 10-01-2009, 05:40 AM

ok....just remembered the search function!!! powder does not like 90 degree edges! I will take some emery cloth and make that machined edge to a slight rounded surface....sound ok? The counter sunk hole is 3/8" OD x .150" deep...so I think that's my only option is to put emery cloth on my finger tip and twist my finger tip in the hole to round over the edge

**SCOTTRODS** · 10-01-2009, 07:25 AM

Originally Posted by hoytheld

ok....just remembered the search function!!! powder does not like 90 degree edges! I will take some emery cloth and make that machined edge to a slight rounded surface....sound ok? The counter sunk hole is 3/8" OD x .150" deep...so I think that's my only option is to put emery cloth on my finger tip and twist my finger tip in the hole to round over the edge

If you can machine it perfectly "square edged", you should be able to round that same edge just a little with your machining stuff..... Either way, you have found the answer, knock the corner off a little to get no "picture framing"

**SCOTTRODS** · 10-01-2009, 05:32 PM

Originally Posted by SCOTTRODS

If you can machine it perfectly "square edged", you should be able to round that same edge just a little with your machining stuff..... Either way, you have found the answer, knock the corner off a little to get no "picture framing"

I knew what I was talking about, but used the wrong terminology when answering this early before work,.... It's not called picture framing. It's just poor edge coverage. Thanks H-daddy for the PM correcting my terminolgy.

**hoytheld** · 10-02-2009, 04:13 AM

Originally Posted by SCOTTRODS

I knew what I was talking about, but used the wrong terminology when answering this early before work,.... It's not called picture framing. It's just poor edge coverage. Thanks H-daddy for the PM correcting my terminolgy.

hell....I wouldn't have known the difference. I have the parts stripped...will round edges and give it another go!!

Thanks

**FigureLLC** · 10-02-2009, 04:15 PM

yup, you nailed it. just round off the corners a bit. some powders are more tolerant to edges than others. gloss black it's apparent, flat black not so much. depends a lot on the individual powder.