# Boring Head Interchangeability



## Plum Creek (Dec 12, 2016)

I need to cut 4,  5" holes in 1" low carbon steel.  The holes are near the ends of 24" material, so they won't fit on the rotary table on the Birmingham mill.  I have several insert type Valenite boring heads ranging up to 3", but no drive.  Since these are more of a commercial line there seems to be a lack of used R8 drives available. I was wondering if the 3" might fit a (3") Criterion drive?   I can't seem to find any specs on the dovetail mount.


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## Bob Korves (Dec 12, 2016)

R8 arbors to fit a boring head should be pretty universal, though there are several thread sizes.  What kind of connection is on the top of your boring head(s)?


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## Plum Creek (Dec 12, 2016)




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## Plum Creek (Dec 12, 2016)

Pics and no text. Interesting, its usually the other way around. 
Thanks Bob for the reply. 
Im attempting this with my cell phone so pardon my errors. 
As pictured, all I have is the head from the dovetail down.


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## Bob Korves (Dec 12, 2016)

It is not much good without the other parts, though you can try to make some...  or find some...  You are missing much more than just the arbor...


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## Plum Creek (Dec 12, 2016)

I thought that would probably be the case. I guess I was hoping that there might be some standardization and my heads would fit a Criterion.  I hate to spend money on waterjetting the holes when I could buy or make a tool. 
I have another week or two before it becomes time critical. 
Thanks


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## Tony Wells (Dec 12, 2016)

That appears to me to be a boring head intended for use on a fixed bar. I have a couple of Sandvik heads like that. They are not intended to fit the sliding dovetails of a boring head at all.


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## Plum Creek (Dec 12, 2016)

Hi Tony
Not that they are correct, but I have seen pics of them attached to cat 40 And cat 50 collets. 
I have a variety of them mostly in the 3T6 family.  HBN 44 is the one that was pictured. I will post a pic of the entire lot.


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## Plum Creek (Dec 12, 2016)




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## Tony Wells (Dec 12, 2016)

Correct. What you have, with the Vari-Set, is a combination purpose head. It can be affixed to a holder that might vary anywhere from R8 up, depending on what diameter it is. Those can be set much like a standard boring head. Or it an be used on a solid bar for use in a lathe. I have 2 of them, one I'll probably never use, as it is left handed. But the other, even though it is set up for my least favorite style insert (triangle) I will use for roughing on the larger lathe I have. It's a 4" diameter, so I will have to build a special holder for it, or remove the Aloris and fabricate an alternate mount. If I were being realistic, I'd admit I'll never get to it. But it's there if I ever have a job come in that needs it.


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## Bob Korves (Dec 13, 2016)

Wow, I sure had that figured wrong...  Never saw any like it, though they look really useful in a bigger shop or factory.  They also look more versatile across machine platforms than the boring heads we are used to seeing.  Thanks for the education!


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## Tony Wells (Dec 13, 2016)

Not all of them are adjustable, however. If you notice there is a socket cap screw from the face of the head to lock it into position. The bar that has the mating dovetail is split and expands to hold it. There is some adjustment in one of the heads you have, the one with the small, round insert holder protruding at an angle. I can't see it on that one, but some versions of that style have what they call "micro-adjustment" which extend or retract the holder mounted in the head. All around, it's a versatile tool system. But I agree, Bob....not all hobbyist will have a use for them, or even the machine large enough for them. Or I should qualify that by saying the larger end of the system. The smaller, R8 and possibly some with 30 and 40 taper machines could use some of them.


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## Bob Korves (Dec 13, 2016)

Yes, I suppose much of that sort of tooling actually in use is in a production or intensive dedicated repair environment.


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## Tony Wells (Dec 13, 2016)

Such is the case with most modular tooling systems. You start with the bar or holder, for either lathe or mill, then select the currently needed head. It's a money saver in the long run. One bar, for example, to set up the one 4" head I have, is about $3k, last I checked. It was about 4 feet long. That sounds like a lot, but if you see it the way Sandvik wants you to, you will see that one bar as capable of being used to bore, thread, groove, face, etc. without having to have separate bars. Just swap heads when you need to run a different operation. Naturally if they are all on the same part the money logic fails, but for many production jobs, a single function is all you need at one time. So you can save some money. Often though, you have to consider the fact that if you have a turret style CNC lathe, it has to be able to swing that 4 foot bar around without colliding with anything. Not many lathes can swing it. So there's little use in mounting up 2, 3 or 4 of these bars in the first place. Same deal on a slant bed with a turret. Rarely do you hang a bar out as far as you can, but on that style turret, there isn't a lot of clearance _behind_ the toolholder, so you can't just choke up on the bar like you'd want to to minimize the overhang. Most shops discourage sawing off the excess just to get a tool to index. So what are you going to do with all that extra bar hanging out the front? Chances are it would run all over stuff while the other tools were in the work anyway.

If/when I do need to use the head I have, I haven't decided whether to go the whole dovetail route, or simply weld it onto a bar. I probably won't be buying alternate heads for it. Then again......


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## T Bredehoft (Dec 13, 2016)

I once used some of those heads, one operation I did on the Lucas 4" Horizontal. Rough boring the mains on a compressor frame. We had a set of extensions on which we'd put one of the bars with the boring head on the end, bore no. 1, put an extension in and bore no. 2, the saddles were almost four feet apart. one rough pass, about 3/16 on a side. 
My employer also bought the "Micro Adjust" heads, and I made bars for them. Broaching a 3/16 keyway in a 3 ton arbor press at about 30 degrees is some kinda fun.


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## Plum Creek (Dec 13, 2016)

Ahhhh ok, thanks Tony!     That explains why nobody except scrappers, bid on them.  
Bob, you were right, they came from a machine/equipment repair shop a few years ago. The bars were probably included in another lot.
So, basically the operational difference between this system and a rotary system like Criterion is adjustability and the lack of an indicator.
I haven't completely given up on getting a bigger milling machine yet, so I think for now I will sort through them and get rid of the duplicates. 
Two of the heads were crashed so I may experiment with them to weld up a fixed 80mm MT3 for the lathe.
That leaves me back at square one for the 5" holes. 
I learned a lot! Thank you both!


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## Christian Poulsen (Dec 13, 2016)

At 1st read I'm not quite following "R8 drive", Criterion drive, but I just thought I'd throw in my 2 cents...
I often times use flycutters (3 set screws, with lathe tool bits) for boring (I made a few diff sizes up to a 4")...The shanks are all 3/4" that I would put in a R8 collet in my old Jet mill....I scale the toolbit from center in a lathe for initial size/cut (under) and swing the flycutter around with a o-1" indicator (flat tip in it) and set 0 and leave it...then, after a bore (bores) in the mill, I slide the tool bit out as needed on the lathe (measurement/adjusting by the indicator that I have left set up on the lathe...

...I like the above (while not as handy) as being more rigid for boring thicknesses that my flycutters can get thru rather than adjustable boring heads.

...Note: Of course the proper grind for boring (not much diff than turning (except more nose r for finish) on the carbide (Smiley face here) lathe tool bits in the flycutters is a must....


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## Plum Creek (Dec 13, 2016)

T Bredehoft said:


> I once used some of those heads, one operation I did on the Lucas 4" Horizontal. Rough boring the mains on a compressor frame. We had a set of extensions on which we'd put one of the bars with the boring head on the end, bore no. 1, put an extension in and bore no. 2, the saddles were almost four feet apart. one rough pass, about 3/16 on a side.
> My employer also bought the "Micro Adjust" heads, and I made bars for them. Broaching a 3/16 keyway in a 3 ton arbor press at about 30 degrees is some kinda fun.


Tom,
I wasn't familiar with Lucas and had to look that up.  wow thats quite a machine!
I haven't tried broaching yet, so its hard to imagine how that was accomplished..


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## Plum Creek (Dec 13, 2016)

Christian
Basically I was asking if my Valenite cutter heads would interchange with heads on a bar style Criterion head.  Criterion cutters are readily available with R8 mounts. They're both use dovetail mounts for the heads, and I was hoping that there might me be some standardization between boring heads.  Apples and oranges as the saying goes.
I will give the flycutter some thought. Thanks


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## 4GSR (Dec 13, 2016)

Plum Creek,

A buddy of mine works at a shop over in Taylor.  He can plasma cut the holes a little under size for you if you are interested.  In fact, they could machine them to size for you too.  I don't know what he would charge, but may be worth it in the long run if you don't want to tie up your own time in doing them. 

I have a spare 3" Criterion boring head if you like to borrow it.   Ken


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## Plum Creek (Dec 15, 2016)

Hi Ken
Thanks, I will keep those options in mind. My goal is to keep cost as low as possible as well as build machining skills.
I'm retired so in general the time consideration is just the delicate balance between learning and paying someone else, which sometimes is considerably cheaper.
I don't know anything about plasma cutting or how much it would harden the edges. I was considering water jet as a backup, because when I torch cut the components I experienced hardening well beyond what I would expect for A36.  HSS cutters really didn't like it.
So for a little background. This is a mesquite grubber attachment for the excavator. The 5" holes go "through the ears" for the pin bosses which I am turning on the lathe.  I can fit to the hole but the holes need t
be aligned through both plates (ears) (the uppermost part of the cardboard mockup pic) for proper pin alignment. The first pic in this thread are the cut plates.
The second pic here is a medium hardness shaft that I am considering turning down to a single piece R8 boring head holder.  Any thoughts?


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## 4GSR (Dec 15, 2016)

I would go rent a mag base drill and buy an annular cutter for the hole size needed and get after it.  A annular cutter of that size probably around $75 - $100.  One cutter should do the job.  Use a good cutting oil with the cutter.  Ken


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## Plum Creek (Dec 16, 2016)

Ken, thats another good option! I will check into that.


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## Plum Creek (Apr 4, 2017)

Nearly finished with the project. 
I ended up tacking the two parts together and mounting them on the rotary table using a centering pin. I rotated and remounted for the area that remained due to contact with the column. 
There are some obvious mistakes in the construction but I think It will work ok.


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## dlane (Apr 4, 2017)

Plum creek, I'm just curious are you affiliated with plum creek shooting club off of namless rd?


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## Plum Creek (Apr 4, 2017)

No, but I have to admit I had to look that up because I had never heard of it.  Plum Creek headwaters near Kyle and runs through the ranch near Uhland.


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