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Thread: The hole is too big
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19th Jul 2007, 02:53 AM #1Product designer retired
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The hole is too big
Dear members,
I have just bored a 10mm hole in a piece of brass, and plow me, it turned out to be 10.2 in dia. Is there any way I can reduce the dia?
Is there an internal 1-piece knurling tool that I can introduce into the bore to shrink the dia?
Yeh, I know, I can always bore it out, and fit a bush, or simply start again. Prefer not to.
Any clever answers, would be appreciated.
Regards,
Ken
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19th Jul 2007, 05:21 AM #2New Member
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Re internal Knurling tool
I saw pics of one made from the striker wheel off a disposable butane lighter. Just turn a shoulder on a piece of keystock and drill and tap for a socket head capscrew. Use just like a small boring bar.
I will look for picture.
alabamaed36046
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19th Jul 2007, 09:21 AM #3Andy Mac Guest
Hi nekmerj,
Butchery I know, but you could hammer the brass with a ball pein around the margin of the hole and it will push out, squeezing the hole smaller.
Now where's my striped apron...?
Cheers,
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19th Jul 2007, 11:23 AM #4
Further to what Andy said, if you have any big bearing balls lying around, you can use one on each side of the hole, hammering briskly to swage the hole smaller. Butchery might be too kind of a word for this, however.
Would a 0.004 shim stock strip do you? That would take your dia to 10 mm and be no more inelegant than the knurl.
Greg
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19th Jul 2007, 11:59 AM #5Senior Member
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19th Jul 2007, 01:24 PM #6Most Valued Member
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first thing to work out why is your bored hole oversize,correct that problem before trying any solution,and if your making that optical aligning tool why not just make your lens and punch to suit your oversized bore.
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19th Jul 2007, 02:50 PM #7
Machinery's Handbook devotes a paragraph to "Accuracy of Drilled Holes." Factors cited include: accuracy of the drill point; size of the drill; length and shape of the chisel edge; whether or not a bushing is used to guide the drill; length of the drill; runout of the spindle and the chuck; rigidity of the machine tool, workpiece, and the setup; also the cutting fluid used, if any. "The diameter of the drilled holes will be oversize in most materials."
JoeOf course truth is stranger than fiction.
Fiction has to make sense. - Mark Twain
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19th Jul 2007, 06:09 PM #8
If you're really desperate to save pitching the brass, a sleeve would be the most elegant solution.
'What the mind of man can conceive, the hand of a toolmaker can achieve.'
Owning a GPX250 and wanting a ZX10 is the single worst experience possible. -Aside from riding a BMW, I guess.
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19th Jul 2007, 08:27 PM #9Senior Member
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19th Jul 2007, 08:34 PM #10
You may be able to run a couple of rows of centre punch pricks around the insides of the hole. So if its only to locate something that should do but if its to run a shaft in you need to bush it
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20th Jul 2007, 06:34 PM #11
Yeah, I know, MH. But you'd have to admit, knurling a bore just so it's not oversize... uggh.
Might suck doing the extra work, Ken, but it'd be worth it over knurling.'What the mind of man can conceive, the hand of a toolmaker can achieve.'
Owning a GPX250 and wanting a ZX10 is the single worst experience possible. -Aside from riding a BMW, I guess.
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20th Jul 2007, 09:41 PM #12Senior Member
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20th Jul 2007, 10:27 PM #13
Anything's possible. -You should know that.
Time and inclination, however, are another story. -Something I'm sure you'd also already know.
Can't say I've ever heard or seen it done either, so it may just be a delusional myth.
One of the lads I work with once bored an oversized hole in a piece of expensive high-tensile for a foreigner. Poor bugger was shattered when he first measured the bore. He did manage to save it, however. Ended up running a 2mm parting wheel down the length to split one side, heated it up in the furnace, gave it a squeeze in the press and then brazed the small gap up. Bore didn't exactly resemble round any more, but it was small enough to re-bore true and to the correct size.
OD did end up smaller as a result, but he still had enough meat left on to clean it up to size.
Quite the save, I thought.'What the mind of man can conceive, the hand of a toolmaker can achieve.'
Owning a GPX250 and wanting a ZX10 is the single worst experience possible. -Aside from riding a BMW, I guess.
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21st Jul 2007, 12:42 AM #14
You haven't mentioned the thickness of the brass stock, I think, nor its function. If the diameter is critical, you could possibly braze to restore most of the metal, then drill a smaller pilot hole and ream to the exact diameter. (Assuming you have a suitable reamer, of course. Grizzly #G9418 is 25/64" (9.9219mm) at US$7.95 plus shipping etc.; Oz engineering shops may have metric sizes.)
JoeOf course truth is stranger than fiction.
Fiction has to make sense. - Mark Twain
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21st Jul 2007, 09:15 PM #15New Member
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Internal knurling is not only possible , but widely used in engine rebuilding to re-condition valve guides. The tool is pretty simple and resembles a reamer that has wood screw threads on it. I would suggest a quick visit to an automotive machine shop in your area to see if they can help you either repair your part or direct you to a supplier of the tools.
I am a thirty year tool maker so if I can offer any help just let me know.
BTW when trying to bore a hole to size it is good practice to "sneak" up on it once you are within about .010".
Reamers are also pretty cost effective and much more forgiving.
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