Boring Bar Diameter

JPMacG

JPMacG

Active User
H-M Supporter - Silver Member
Joined
Mar 22, 2014
Messages
847
I'm asking about the nominal diameter of a boring bar, i.e. 3/8", 1/2", 3/4". Are boring bar shanks typically sized to be a good fit inside these diameters? For example, will a 3/4" boring bar shank fit into a boring bar holder that is reamed to .7500?

I ask because I am making a 3/4" boring bar holder and I have a .7500 reamer. I don't yet have the boring bar.

Revised for clarity.
 
Last edited:
Sorry, apparently my question was not clear. I'm asking about the boring bar holder, not the hole that is being bored.
 
Last edited:
But you don't have a 3/4" boring bar?
You should be fine. You're going to split the holder, right?
 
It all depends on the actual size of your boring bar, if it is an accurate ground size, you will need a little clearance to be able to insert the bar, like perhaps a thousandth, otherwise you would be looking at what amounts to a press fit.
 
I thought the industry standard might be to undersize a boring bar shank so that it fits a holder. For example, I have a kit of 1/2" boring bars with shanks that measure .499 and they fit nicely in the "1/2" socket of my boring head.

I'll hold off until I have the 3/4 bar and can measure it. I plan to get the bar at Cabin Fever Expo in mid January.
 
JPMacG said:
I thought the industry standard might be to undersize a boring bar shank so that it fits a holder. For example, I have a kit of 1/2" boring bars with shanks that measure .499 and they fit nicely in the "1/2" socket of my boring head.

I'll hold off until I have the 3/4 bar and can measure it. I plan to get the bar at Cabin Fever Expo in mid January.
Click to expand...

It's common for tooling blanks to be .001 undersized and the holder to meet the nominal dimension.

As for industry standards, the only standards I am aware of start with specific references like DIN/EN-ISO in front of them, there are no gentleman's standards in industry. Standards are either called out and subscribed to, or they're not standards- They're unqualified customer expectations. Sorry for the mini ISO 9001 rant, I can't help it.
 
Or another away of saying it, assume nothing. Measure it and get a reamer that's 0.001" over the measured value. (Measure it a few times!) Or hope you get lucky. Sometimes that happens.

What's the old saw? "Assume makes an A$$ out of you and me."
 
You must log in or register to reply here.
Back
Top