# Would a 3" boring head bore from 0 to 3"?



## LEEQ (Feb 2, 2014)

I'm considering finally investing in a micrometer adjustable boring head. I can't seem to tell if they will go all the way in as tight as a 2" model. As my first boring is already 2", I would like to get the bigger set if it will increase my range. I have a 1" drill for a clearance hole in the event of 3/4" boring bars. Does anybody have these?
'


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## Tony Wells (Feb 2, 2014)

Normally there are multiple holes that allow you to put the boring bar in whatever position needed to get the hole size you want to work. They are not designed to go down truly to "zero", as in making the initial hole, but when using them "backwards", to turn OD's, the pretty much you can put the bar with tip in, and get to zero diameter.

Also, some of the larger heads have a hole in the end so that you can put a bar in horizontally and reach out quite a ways. Much larger than the OD of the head. Limit there is the rigidity of the bar and head.


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## xalky (Feb 2, 2014)

I have a 2" boring head that takes !/2" diameter bars. The range that you can put in these is quite large. On the small side your limited only by the size of what will fit in the hole your trying to bore. On the large end, I could probably go about 9" diameter, maybe even bigger, with a longer boring bar, by putting the cutter in perpendicular to the axis of the boring head. Thats with a 2" boring head. A larger boring head will give you a little more rigidity for sure, but you might be limited by the rigidity of your machine spindle.


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## LEEQ (Feb 2, 2014)

It's no big iron by any means, but it is a Bridgeport. I'm thinking on the 3 hole on bottom, one through the side, 3" models. For a few bucks more I would rather have the more rigid tool, if I can get down to a similar size bore on the low end.


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## Tony Wells (Feb 2, 2014)

Those do adjust down pretty small, but your real limit will only be the bar size. I have a couple of adapters that reduce a 3/4 (I think) hole down to a smaller bar, and certainly you could make a split bushing to put virtually any mini or micro bar in a larger head and do just fine. So in reality, you only gain size, not lose when you select a larger head. Some of them do not have a "tenths"  style adjustment, so you need to have better eyes to start splitting thousands easily. Not a big drawback, in my view.


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## Bill Gruby (Feb 2, 2014)

I believe that the 3 inches is referring to the Boring Head Diameter itself, not it's boring range. Yes it will bore 3 inches and more.

 "Billy G"


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## LEEQ (Feb 2, 2014)

I will use a magnifier  if it will keep me in this price range. Thanks guys.


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## george wilson (Feb 2, 2014)

How large you can bore depends also upon how SLOW you can get the spindle of your mill to revolve. Try to bore a hole that is too large for the slowest speed to handle,and you will get a howling squeal that will make a mess of the hole and will burn out the cutting edge of the tool.


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## bjmh46 (Feb 3, 2014)

LEEQ said:


> I'm considering finally investing in a micrometer adjustable boring head. I can't seem to tell if they will go all the way in as tight as a 2" model. As my first boring is already 2", I would like to get the bigger set if it will increase my range. I have a 1" drill for a clearance hole in the event of 3/4" boring bars. Does anybody have these?
> '




I will tell you that my experience with  Bridgeport Series 1 class machine is that I used my 3" head about 1 out of ten times I needed a boring head.  One problem, aside from the larger overhang of a 3" head vs. a 2", is that you are forced to run very slow due to the imbalance of the greater mass offset.  There are times when you may need the 3", but I'd get the 2" head first.  I like the Criterion dbl series.

Bob


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