Boring bar sizing

Wreck™Wreck said:
Boring bars are the easiest tool to size.
If it will not fit into the hole it is to big (Minimum bore diameter) if it will not cut to depth it is to short (Depth/Length of cut) if it still does not perform and both of these parameters are met it will then take a bit of work.
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Great advice, Wreck - made me smile!! :)
 
I would make go and no-go gauge pins to do the measuring.
 
This would require making .1873 No Go and .1860 Go pins, fussy work with a lathe.
This also does not tell you the bore size just that it is within the range.
 
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AGCB97 said:
In the last table of this document, what is a' heavy metal shank'?
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Haven't read the link but a heavy metal boring bar is usually made of tungsten. They are between steel and carbide in modulus of elasticity (stiffness) and cost. They're intended to give you a bit more overhang capability at a lower cost than a solid carbide bar.
 
Wreck™Wreck said:
This would require making .1873 No Go and .1860 Go pins, fussy work with a lathe.
This also does not tell you the bore size just that it is within the range.
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He does not need to measure the hole. He only needs to be within the fit tolerance for the bearing.

I don't find making pin gauges that much trouble. For those who do not machine for a living its not always practical to spend that kind of money on bore gauge with a limited measuring range for a few parts.
 
jbolt said:
He does not need to measure the hole. He only needs to be within the fit tolerance for the bearing.
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I realize this, I simply like having a number so that there is a basis for the next move if any. - .0014 is a considerably tight bore for an annular bearing of that size.
 
mikey said:
The shank is 1/8" in diameter; this is the part that must fit into your boring bar holder. The "0.0600" part should be the size of the cutting tip. You will need to drill a hole larger than this to begin boring. I should think a #45 or #46 drill should be large enough. Its hard to tell from the pic but this looks like a positive lead bar, which means the end of the bar is angled so that the tip leads the way; this allows you to cut to a flat bottom without rubbing, among other things.

This tool has a neck 0.250" long so that is your limit for the deepest bore you can make. The overall length of the tool is 1-1/2".

You will need a sleeve to use this in your boring bar holder. It is solid carbide so it should be sharpenable with a diamond stone.

Another brand to look at is Micro 100 - their bars are top of the line and is the brand I prefer for these tiny bars.
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Hey Mikey, sent you a PM. How goes the "PROJECT". Any new updates you're willing to share ???
 
RandyM said:
Personally, I'd think you'd be better off reaming the hole rather than boring it.
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What Randy suggests is what I would do. With the tailstock properly aligned, I'd drill a 11/16 hole (3/16 - 1/64) and then ream the hole with a 0.1865 (3/16 - 0.001) reamer. Done!
 
Might be an interesting exercise to ream a hole only 0.095" deep (I assume just less than half of the bearing ball will protrude) with a 3/16" undersize reamer. Not sure the cutting edges would even engage at such a shallow depth. I think the only way to make this hole is to bore it. That isn't the challenge; the challenge is to measure it accurately with the equipment a hobby guy has available. I think this is going to come down to a go/no-go gauge.
 
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