Modified boring head, what were they thinking?

Cannonmn · Oct 28, 2020

Here’s a Criterion boring head that when new had a 2 1/4-10 threaded arbor, probably 50 taper. Somebody’s welded in a round 1=1/2” shaft. Round, not even a flat or two. It won’t work as-is, too much torque for round. Maybe customer is supposed to create flats on it? Am I missing something here?

NICE CRITERION DBL 206 BORING HEAD 2 " CAP W/ 1 1/2 " SHANK | eBay

Milland · Oct 28, 2020

What??! That setup worked fine in my Rong-Fu Mill-Drill, I'm only selling it because I needed a bigger boring head.

Conrad Hoffman · Oct 28, 2020

Yeah, that sure knocks the value down; the asking price is nuts.

Milland · Oct 28, 2020

Not sure why it's listed as being a 2" capacity either. It's a 6" body, 1.5" bar holes. Maybe a 2" adjustment on the radius?

MattiJ · Oct 29, 2020

Cannonmn said:
Here’s a Criterion boring head that when new had a 2 1/4-10 threaded arbor, probably 50 taper. Somebody’s welded in a round 1=1/2” shaft. Round, not even a flat or two. It won’t work as-is, too much torque for round. Maybe customer is supposed to create flats on it? Am I missing something here?

Too much torque says who?
1.5" endmill holder with two setscrews torqued to 70ft/lbs clamps with something like 20000 lbs force. 0.1 coefficient of friction and it should still hold about 3000 in-lbs = 250 ft-lbs max torque. That is still about 5 horsepower cut at 100rpm. Boring heads are typically used with rather light cuts.

Rigidity sucks for sure compared to proper one and if used in end mill holder the setscrews might bite in the shaft.

UncleFrank · Oct 29, 2020

We had Criterions with round shanks for collets. We'd drill/rough bore first and leave about .015 for finish.

yardbird · Oct 29, 2020

My guess is they didn't have a machine that would fit it. Either turn it down to fit what you have and use it or it's junk. I don't necessarily think of those as being tools used for hogging so as long as you have some sense I don't see spinning it in whatever is holding it. I wouldn't give $600 for it.

Brent

Cannonmn · Oct 29, 2020

MattiJ said:
Too much torque says who?
1.5" endmill holder with two setscrews torqued to 70ft/lbs clamps with something like 20000 lbs force. 0.1 coefficient of friction and it should still hold about 3000 in-lbs = 250 ft-lbs max torque. That is still about 5 horsepower cut at 100rpm. Boring heads are typically used with rather light cuts.

Rigidity sucks for sure compared to proper one and if used in end mill holder the setscrews might bite in the shaft.

Thx for the needed facts, I’m currently working with same model heads and “guessed” the torque could be much higher, was concerned about how to make/adapt an arbor for the arbor-less one. I want to preserve the female threads in the head. Being able to use various geometries above that makes the project a lot easier.

For example I considered using a nice-condition nmtb50/1.5-in. (female) Weldon arbor by making a short adapter piece with the threads on one end and the 1.5 in., two-flats male on other end. Or, if the tool-holding end of my 1.5-in. Weldon holder isn’t too hard to thread, just turn down and thread the O.D. to 2 1/4-10. I’ve never even seen a 1.5-in. two-flats Weldon cutter so “using up” that arbor is a no-brainer. Think I can find pic of it, later.

gbent · Oct 29, 2020

Why do you think its on ebay? The grinding on the bottom suggests a significant oops as well.

If you are going to run left hand rotation, either weld or locktite the shank to avoid unpleasant surprises.

Nmbmxer · Oct 29, 2020

Perhaps he was using it to turn and OD with the bar flipped over and spindle in reverse, a standard shank might unthread... [too slow I see]

Tools make money, that is their purpose. If bending a wrench makes it faster to remove a fastener, bend the wrench and buy a new one with the time saved. I don't understand why some here put tooling/machines on such pedestals. Joe Rong Fu didn't use that tool in his basement, that's a big boring head and a large shank and there was assuredly a purpose. Even if modifying it was simply faster than making a new threaded shank and shop rate covered the difference.

Cannonmn · Oct 29, 2020

FWIW here’s the arbor I identified as 1.5” Weldon because of the two pairs of setscrews, however I see how you could use it with round shank as well.

John Morris has shared 3 photos with you! | Flickr

In my second-guessing on the Eboo ad, seller probably got the damaged head alone and wanted to make it more sale-able, so welded in the round shank. Guessing that due to fresh weld and lack of setecrew or other Holding marks on shank.

FredC · Oct 29, 2020

I clicked the link and looked at the boring head a while ago and I already got an ad from Ebay on the same item. I just wanted to see how screwed up it was!

Milland · Oct 29, 2020

FredC said:
I clicked the link and looked at the boring head a while ago and I already got an ad from Ebay on the same item. I just wanted to see how screwed up it was!

You have this quaint idea the computer is YOUR property, don't you...

john.k · Oct 29, 2020

When I was at the refinery ,maintenance guys there would buy a new Wohlhaupter boring and facing head ,and weld it to piece of pipe for some one off job,then toss it in the scrap.

GregSY · Oct 29, 2020

I have a friend who was hired by the biggest University in Texas to do a job for their research lab that involved moving earth around a few times a week for about 6 months. They asked him what tools he needed, and he made a small list that included a John Deere tractor, 30+HP diesel with front bucket. When he showed up to start, they had bought a brand new John Deere diesel tractor for the job.

He used it and when the job came to a close 6 months later, he asked them where they wanted him to leave the tractor. The University guy looked at him and said, "Oh...that was expensed as part of the job tooling. Could you get rid of it?"

Needless to say, he disposed of it at his spread...

john.k · Oct 29, 2020

Local Uni was like that ,catch was everything had to be smashed unusable and then taken by the period contract scrap dealer......Waste of money is no-problemo ,cant have any hint of corruption,tho.

ratbldr427 · Oct 30, 2020

You have to use a little common sense; any machine chuck that will hold a 1 1/2" shank will hold many times over the breaking force of any cutting tools that will fit in that head. You will destroy the tools before it slips.

1 Jaw Chuck (Chuck Evans) · Oct 31, 2020

For a NMTB or Cat 50 spindle, a TG 150 or TG 200 collet would hold that nicely.

The ebay one posted is way overpriced, but is exactly what I look for in tooling. I've gotten great deals on boring heads with odd shanks, Flash Change, Pratt Whitney Jig Bore, and MT5.

With just a little bit of lathe work, many of those oddballs can be made
into 3/4" or 1-1/4" straight shanks. One or the other will fit all of my machines.

Best score was a D'Andrea Boring and Facing head. Flash Change 40 taper. Can't remember the price but after it arrived I found that there was a 3/4" straight shank in there.

Chuck
Burbank, CA

Garwood · Oct 31, 2020

2 minutes with a bridgeport or vise in a vmc will have a nice flat on that shank that 40 HP won't twist.

Looks like a real nice weld. Wouldn't bother me a bit to buy or use that boring head, but I'd probably only go to $200 or so on the price.

I have turned lots of oddball taper and even bent tool shanks into straight shanks with a flat. Then it works in anything.

I have many larger sized Devlieg bars/heads with round shanks that I use and most of them do not have set screw flats. Luckily I have big machines and big collet holders.

Ox · Oct 31, 2020

Yep, I have a a few holders that will chuck that right up in TG150's.

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I am Ox and I approve this h'yah post!

Modified boring head, what were they thinking?

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