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Old 03-24-11, 06:56 AM   #1
trayraynor
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Powder Coater Error - Eccentric Bottom Bracket

Just got the frame back from the powder coater (it sure looks nice); but the sprayer failed to cover the two bosses used by the eccentric locking screws (see photos). I'm thinking I'll use a small diameter drill bit and progressively ream the opening sufficiently to allow me to poke and scrape the threads clean - all w/o messing up the finish around the boss.

Does that seem like the best approach? Any other thoughts or suggestions?
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Old 03-24-11, 07:07 AM   #2
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gentle use of the right size tap?
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Old 03-24-11, 07:18 AM   #3
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Rack the bike in a workstand so that anything in the holes will drip down into the BB. Start from the INSIDE of the BB with a little lacquer thinner on a Q-tip.
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Old 03-24-11, 07:49 AM   #4
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If lacquer thinner even discolors the powder it will never hold up. Period. Depending on the base of the powder aircraft stripper may soften it. Looks like a hard spot for a tap - but that will be the best. Powder coat is what I do. We coat for CAT, CNH, Deere etc.

Here's a pic of some valve covers for a airplane we coated.

Best,

marc
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Old 03-24-11, 08:06 AM   #5
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If I go at this mechanically, using a drill bit to effectively tap the hole -> followed by aircraft stripper from the inside of BB, do you think that will work? I've never heard of aircraft stripper, is this sold in relatively small volume containers? Any suggestions on what type of shop would carry this?
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Old 03-24-11, 08:12 AM   #6
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I agree that if you get the right size tap and work from the inside. You may have to cut (grind) the tap down lengthwise to fit inside and maybe grind some flats on it to get a small wrench on it. If you could find a stripper that would work, I think it would be difficult to keep if off the areas you want coated. Good luck.
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Old 03-24-11, 08:14 AM   #7
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Try auto parts stores for the a/c stripper.

marc
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Old 03-24-11, 10:47 AM   #8
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The drill bit approach has the (high) risk of damaging the threads in the frame. You need those threads to hold the set screws.
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Old 03-24-11, 10:53 AM   #9
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Are the holes filled or simply covered?
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Old 03-24-11, 11:03 AM   #10
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Trayraynor - have you tried poking something thru from the inside? Had they just coated the threaded hole it doesn't look right. They may have left a plug or cap or something in the hole.

marc
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Old 03-25-11, 12:21 AM   #11
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Does your frame have the correct diameter bore to fit a Bushnell eccentric?
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Old 03-25-11, 06:26 AM   #12
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Heat gun/hot hair drier and a dental pick will get it open enough to get the tap through it. Air craft stripper is messy, it's hard to control and can take more off than you intend.

+1 on the Bushnell eccentric.

You will also want to run a tap and light cutting oil down every threaded hole on the frame as well as chase the rear bottom bracket threads/face (assuming external BB cups) and head tube reamer. These are all things frame builders *should* do after a frame goes to the paint shop. Since yours was refinished, you'll get to do it.
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Old 03-25-11, 06:42 AM   #13
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I would first try picking at it with a sharp awl or scribe. This material is quite brittle and sometimes the adhesion is inconsistant. I have found that very often I can chip it out. If you can get the first few threads, you might be able to chase out the rest with the screws. In fact, this may work to your advantage...sort of like locktite
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Old 03-25-11, 07:27 AM   #14
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Well, sitting here now just a bit chagrined... using an awl, I was able to poke through the bubble of coating and exposed the hole. Indeed, a plug (rubbery/cork like substance) must have been inside the thread (funny 'cause this is not an issue on any of the other threaded bosses on the frame). I then used a clean exacto blade and cut some of the material away. Looks like I'll need to pick at it, using tweezers and I'll see how that goes. If I have trouble picking out material to get the threads clean, I'll try dabbing some Goof Off (using a Q-tip) inside the hole to remove any persistent junk... it appears the tap will not be necessary (sigh), and will forgo the aircraft stripper.

The Cutting Oil sounds like an interesting idea... I haven't attempted to thread any other bolts yet, so I'll swing by the hardware store this morning and see if I can p/u a small can.

Re. the Bushnell Eccentric, it appears that by using the Bushnell I would not need to worry about the existing threaded lock bolts, do I understand this correctly?

Thanks for all the input, looks like my weekend assembly will proceed as originally planned (whew)!
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Old 03-25-11, 01:30 PM   #15
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trayraynor, Like I said, try a machinist's scribe-the kind that is used to do layouts on steel with machinist's blue. It is strong, but quite thin and comes to a fine point. With it, you might be able to chase out most of the thread. It sounds like your powdercoater used small tapered plugs, sort of like miniature rubber stoppers, which is typical. They might have been narrow and therefore went further into the hole than ideal and got painted over. They should come out pretty easily, leaving, perhaps, just a bit of fused powder that slipped through.
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Old 03-25-11, 03:48 PM   #16
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You are correct, with the bushnell you'll abandon the threaded pinch bolts. The Bushnell eccentric is a really nice piece of engineering.
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Old 03-25-11, 03:52 PM   #17
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USPSPRO, I've a question for you. Can you please pm your e-mail address to me.

Sorry for the hijack but my limited number of posts prevents me from sending a pm.

Thanks
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Old 03-28-11, 08:57 AM   #18
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Hi All,

I want to thank you for your input. Over the weekend I used a set of taps and chased each of the threaded bosses and the bottom bracket. Used the cutting fluid and it all came out clean; I mounted the BB and it fits perfectly! I really appreciate all the advice.

Cheers!
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