Criterion Boring Head Models?

Just FYI, the Wohlhaupters are made in Czech Republic and an entire kit like the one I have is typically about $800 used in good condition. The Narex versions are made in Japan are are typically twice the price of the Wohlhaupter. I believe this is the same Narex that Mark has if you want a new one - you buy the spindle arbor separately to match whatever taper you have.

www.penntoolco.com

Narex Universal Boring & Facing Head Set, 0-9" Range - VHU-36 - 85-050-036

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rwm said:
Do they make an integral shank that cannot be removed or are they all removable? I have heard both stories.
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Criterion did not make any of the DBL series with integral shanks that I know of. All the DBL-202 heads have a threaded back that takes a 7/8-20 adapter.
rwm said:
Also- Any reason I would not want the 203 model? I will need to buy boring bars anyway so I could buy 1/2 or 3/4". My mill is a PM 727v so the 3" head is probably overkill but is there a downside if I get one at a good price?
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This is an extremely complicated question that would take an article all by itself to answer fully but I'll try to hit the highlights.
  • Boring on the mill is not the same as boring on the lathe. A boring head has mass, as do the boring bars used in them. Unlike boring on the lathe, there is an additional force, Centripetal Force, that is generated as the mass of the head and bars extends beyond center. Centripetal force is a real thing and must be contended with. While it is not a cutting force, it does impact on what and how much we can do.
  • Centripetal Force = Fc = MV squared/R, where M = mass, V = velocity, and R = radius. You can see that Fc increases with the square of the velocity that the head spins at so even small changes in speed can have big effects on Fc. Likewise, mass, which represents the weight of your boring bars, will increase Fc as the size of the bars increase. Fortunately, going for bigger radii does not increase Fc. What you need to remember is that as Fc increases, the potential for vibration increases and at some point that vibration is going to limit what your mill can handle. Go big enough and fast enough and the mill can walk across the shop - I've seen a Bridgeport mill move sideways this way. Now, imagine if you had a 3" boring head using an inserted carbide boring bar boring a 3.5" hole in 6061-T6 at the recommended speed for that insert. Do you really think your PM727 can handle that without moving around your shop? My RF-31 is near 800# and it cannot do it using a 2" head without excessive vibration, which is why I use a 2" head that takes smaller cobalt boring bars and have no issues at all boring out to around 3".
  • A DBL-202 head can bore a hole 0.050 to 3.00" using the two central holes. It can go from 2.875" to 6.687" using a bar in the horizontal hole. The 202 head is sized very well for a mill in the PM727 class. So, ask yourself just how big a hole do you need to bore. It isn't about how big a hole you may need to bore someday; that day will probably never come. Be realistic and choose wisely.
  • Going with a bigger head will require bigger, heavier bars that will limit how big a hole you can bore before vibration becomes a real problem. You will compound this if you go with brazed or inserted carbide boring bars that require higher cutting speeds to perform well. Some guys think that because an inserted bar will cut at low speeds means its okay but compare the finish and accuracy of in inserted bar used at improper speeds vs a good cobalt bar and you'll see why bar choice makes a big difference. I highly recommend you go with a high quality cobalt set and use the smallest bars you can practically use. For example, I have both the DBL-202a and 202b models. I own Borite cobalt boring bar sets for both and have yet to find a hole that exceeds the reach and capabilities these bars. Whenever I can, I use the 202a head with the 3/8" bars and have had superb results.
So, for me, I have no need for a 203 head. My mill can handle a 202 head just fine and each of my 4 Criterion heads are extremely accurate. I have yet exceed the limits of the 202 series but I'm a wimpy hobby guy so there is that.

Insofar as boring/facing heads go, we all want one and I would take one in a heartbeat if offered one but I have not found the instance where I couldn't do what needed doing with my regular heads. For me at least, these heads fall into the "want", not the "need" category.
 
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David, I believe that Wohlhaupter is made in Germany, the Narex is the Czech Republic. Wohlhaupter is more common, but I usually see them as the head only without the accessories and they can run in the $400-800 range for the head with arbor. Narex are less frequently seen on eBay, and either are pretty beaten up or as a set they can run much more these days. You can look up the specification online, but I would I would stick with a Wohlhaupter UPA 2 or 3, or a Narex VHU 36 or 56. Finding one with an R8 arbor is rare. I bought mine several years ago as a complete set, and was like new, but had damage to the drive indexing pins which I had to replace. It was not disclosed by the seller, so as usual they plead ignorance and I did not find out about it until I went to use it months after the sale. I paid $750 for mine at the time, I do use it to bore and surface on the mill. They work well but they can be damaged if the release clutch is not set correctly. They allow much wider boring capacity then the criterion 2" and 3" boring heads.
Nice Wohlhaupter on eBay, just the head with arbor. Both have bolt on arbors, an R8 adapter for the Narex is around $250.
www.ebay.com

wohlhaupter boring and facing head UPA2 | eBay

Very nice west German made tool. Looks new, light use if any. Has R8 shank but can be removed to original taper shank if needed.
www.ebay.com

Narex VHU36.jpg
Narex R8 Arbor installed.jpg
Wohlhaupter eBay listing looks like it has an R8 arbor.
Wohlhaupter UPA2 eBay 165832321100.jpg
 
Very informative guys! I have a much better understanding now. Mikey- thanks for going into the practical physics. I had not thought about the rotating mass and the size of my mill. I think I should stick to a 202 or even a 202a. Wohlhaupter as nice as they are, may be out of my budget.
 
I know the Criterion, and the Wohlhaupter are nicely made tools, but do they do anything that my old Enco doesn't? They all seem to be the same basic design, and mine seems to do everything I ask of it. Mike
 
The larger boring heads can handle larger jobs, but it's usually possible to accomplish a lot with what you have. I bored out a spacer for the Bridgeport with a DBL-202. Sure, I had a 6" boring bar hanging out the side of it, but it worked. Thankfully I only needed to take off about 20 thou.

I've heard that the Enco heads are good quality. The really fancy Wohlhaupter etc can face as well, you hold a ring on them and it adjusts out so you cut a wider arc every time around. Some even let you adjust the feed rate etc.. Way cool, but out of the price range I'm willing to pay as a hobbyist for the few times I would use that feature. I did build an MLA kit version, fun project with very nice castings. Heavy, but the Bridgeport doesn't mind, and I doubt I'll ever spin it faster than 500 RPM or so.
 
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