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Old 09-18-2010, 10:24 PM   #11
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Default Re: miniature boring bars

I needed to bore a small, shallow fit, so I took an old end mill and ground all of the flutes off
but one. Then I ground clearance behind that flute to make it a small boring bar.

It worked great!
But, it wasn't my own idea.
A guy I used to work with came up with that solution to boring a small hole on our CNC turning center.

Thanks B.Todd!


Seriously, how many times can THAT happen in one day?
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Old 09-19-2010, 02:58 PM   #12
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Default Re: miniature boring bars

I've had pretty good luck boring using carbide end mills. I have lots that have one edge chipped. I arrange the bit in the lathe tool holder in such a fashion that the remaining sharp edge is doing the cutting/boring. I find carbide end mills in the small sizes pretty stiff. Hard to find any other material in small sizes that stiff. And, the angles seem about right for boring too.
Hey, check out my v8.

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Old 09-19-2010, 04:46 PM   #13
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Default Re: miniature boring bars

I've been known to use old end mills as well-- set 'em at a bit of an angle to provide clearance and away you go.
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Old 09-27-2010, 02:26 AM   #14
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Default Re: miniature boring bars

Thanks guys, for all your helpful responses
I apologize for not replying back earlier, but I forgot about this thread, then tonight I was looking at this area of the forum, and seen the title "miiniature boring bars", and it caught my attention, then when I seen it was started by me, I figured I would open it up to review it again.
And I seen the added helpful replies.
So that's why the late affirmation.

Jim your V-8 looks and runs like a real champion..
Great job on that build...

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Old 11-04-2010, 10:38 PM   #15
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Default Re: miniature boring bars

Bit of a late bump for this thread but....

Why not use a piece of stock silver steel to form your tool? For example take a piece of Stubs 5mm, heat to bright red, flatten one end then use the grinder to make it into a nice cutting shape (harded/hone as required). I've made a few of these for boring smallish holes and they work well - the problem with most standard tools I've tried is that they wont fit in the 'ole.

Just a thought

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Old 11-05-2010, 12:04 AM   #16
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Default Re: miniature boring bars

For small boring jobs those Micro 100 solid carbide are the _its for the job. From .125 and up, on ebay I paid like $4 for the little guys, mostly use .230-.490 sizes, generaly around $10 on the bay. There is a guy selling on the bay where he says the bits were used once to cut plastic, I doubted it was true but I bought 2 lots of 5each for $25. The bits did not appear used, and were perfect except no boxes.
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Old 11-05-2010, 01:22 AM   #17
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Default Re: miniature boring bars

You must have experience with huge machines. I have only worked on my two Sherlines, and a 1/8 boring bar is quite normal sized... I ground an other small boring bar today, this time I took photos.


take care,
tom in MA

tom in MA, US
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