Boring head question

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just got a small mill and learning.....Boring heads...they come is different sizes 2"....3" and so on. what is the difference? If i get a 2" does that mean i can go no smaller than 2" I can see were one would want a larger head for a bigger hole so that ya don't have to extend the boring bar as far out...what should i know before i buy one, ain't nothing cheap anymore....what is a good make, i will be buying used, hopefully lightly used....
Reply:I've used only criterion boring heads.These are very well made,and expensive.I'm assuming the size is the maximum dia.because the boring bar can be movedto the center of the boring head,making the minimum dia. limited only by the size ofthe boring bar.(I could be wrong) .Miller a/c-d/c Thunderbolt XLMillermatic 180 Purox O/ASmith Littletorch O/AHobart Champion Elite
Reply:Boring heads are sized..2" head VS 3" head..3 wins because of the size..They both take metal off by the thousandth..Depends on how many thousandths they can go before you are out of thread to move it...They will hold the same boring bars and with a little finageling you can do whatever you want with either size..I make my own boring bars and with that capacity from 1" to 10" is not a problem with either head but bigger is better....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Oh, and if you can inspect it before buying,look for broken gibs.(Little wear strip in dovetail)I've seen a few broken ones. IIRC people loosen the wrong set screw and when they adjust thedia. the gib slides out a little.Tightening  a set screw on the unsupported gibbreaks it.Miller a/c-d/c Thunderbolt XLMillermatic 180 Purox O/ASmith Littletorch O/AHobart Champion Elite
Reply:Usually the  holes for the boring bar are larger for a larger head; maybe 3/8" for a 2" head vs 1/2" for the 3" head. The larger one will be a bit more solid and will have more travel, as stated above. Different types of shanks are available for both; straight to fit a collet, R-8 to fit Bridgeport quills, and possibly Morse taper too. The shanks generally screw into the head; sometimes they are very tight, and used ones can be bent from misuse.
Reply:O.K.  I need a R8 shank, i will try to get a 3"....I assume the boring bars i have for my lathe also are used in the mill boring head, right? I believe mine are 1/2"...
Reply:I was planning to get a 2 or 3 inch boring head when I saw an ad for a larger mill near here.Picked up the mill and a pallet of taper 45 tooling, including a 4" boring head...It takes 1" boring bars. So far I've made a sleeve so I can use my 1/2" boring bars, but I'm getting my pennies saved up for a 1" set!Bigger is definitely better! You can always make some sleeves so that you can use 3/8" or 1/2" bars in a 3/4" or 1" (or larger) head! Of course, the 1" head takes up more room under the spindle, so I'm sure there will come a time where I'll be wanting a smaller one too...does it ever end????Andrew
Reply:"so I'm sure there will come a time where I'll be wanting a smaller one too...does it ever end????"NEVER
Reply:Andy, It never ends trus me... I am sure if I added all the tools together I would have at least twice what I paid for the mill in tools alone.  The when you add in a dividing head and tailstock with plates and a riser,and a DRO, and, and, and, and........Well you get my point.  Its a nasty addiction, but you will never go to jail for it either.  Have fun, and keep buying tools!!!!BobI'm spending my Kids inheritance, I dont like him that much anyway!!!!!!Enuff tools to do the job, enough sense to use em.Anybody got a spare set of kidneys?  Trade?
Reply:then there are these Wohlhaupter heads for boring and facing, considered by many machinists to be the ultimate boring head.http://cgi.ebay.com/6-TAPER-24-375-D...efaultDomain_0These have a feed in the head such that the cutter can be made to move out uniformly as the head rotates in the mill. Because the cutter dia can feed out and in while in use, many tricks can be performed with a Wohlhaupter including reaching down inside a bore to cut a snap ring or O ring groove.  Preset stops on the head give a repeat max diameter and an auto return function brings the cutter back in at a high ratio after hitting the stops to reset on a smaller diameter for the next operation.I have a 3 1/2 " version .
Reply:BTW, don't be put off by the price of the Wohlhaupter, I have seen the 3/1/2" size sell for as little as $300. The new 3 1/2 set sells for about $4,000.This one has been for sale at $2950 for months. The $2950 price relates to a new cost of over $7000 for the 5 inch size. Reality is that the market for this stuff is not great right now.