Criterion Boring Head Questions

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rronald

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I needed to bore a hole and decided to go for the used "old American" item rather than the import. I managed to purchase an Criterion Model 1-1/2 Boring Bar with a 3/4" Shaft. Perhaps I should have held out for the more-common larger model, but this one was only $70 and seems to be in reasonably good condition. I've already managed to bore a hole and I like the tool and the boring process.
s-l1600.jpg
However, there are a few issues:

1) The arbor/shank is 3/4" and is incredibly long. I use ER40 collets, but their max depth can only take about 1/2 the bar. Is there any reason not to cut off some of the length so that I don't have to run the head on the mill up an extra 3 or 4 inches? I'd probably just bandsaw it off and then grind the face on the remaining length flat on the belt grinder. But I could mount the body in a 4-jaw chuck and part it off.

2) The current set up has a flat brazed carbide tip on a 1/2" shank. It's seen better days. How do I get the boring bar out? There's a set screw, but it didn't move easily with hand pressure. Oddly enough, there are many threads on the internet about getting the arbor off Criterion heads, but I couldn't find anything about removing the boring bar. If it's just tight, it looks like it would be easy to press out. But I thought it would be wise to ask first.

3) Any advice on good boring bar options. I have several for the lathe...but they are only partially round (have some flats on the diameter). Will they work?

4) One of the threads on Criterion boring heads mentioned BBs on the tip of the set screws. Mine has no BBs, but the set screw for the boring bar is clearly made for one. Any ideas on how to size the proper BB? The screws for the ways also don't have BBs and it doesn't necessarily look like they should be there.
 
That set screw is holding the bar in.

No reason at all not run a shorter shank but I'd keep that one and buy a shorter one. That long shank might be handy someday.

I use lathe bars in my boring heads all the time. Even solid carbide indexible bars.

Here is mine.20240801_093900.jpg
 
Nice find.

There is really no reason that you can't cut the shank shorter, I have modified boring heads like that in the past with no ill results. As for the getting boring bar out, it may be that it has been in the head for so long that it has corroded into the hole. I would put home penetrating oil on it from the end and in through the set screw hole. Give it some time to work and then clamp the bare in a vise and twist it loose. Lastly I have had my Criterion boring head for about 40 years and have never run across ball bearings retaining the boring bar. Standard set screws have a recess in the end that looks like it could be for a set screw but it is for gripping when tightened.

Good luck with the boring head and I am sure once you get the bar out and clean out the hole, it should allow bars to slip in and out easily.

Richard
 
The tolerances of the hole in the boring head and the diameter of the boring bar are pretty tight. Thus, if the setscrew holding the boring bar in creates a burr on the bar, which it will, that can make it tough to get out. Force helps.
 
APT boring bars are pretty awesome too.

BTW: forget the silly bb thing.

I have several hss boring bars I bought on Ebay as well. Great for low pressure applications.
 
Ken from ontario said:
Borite also gets my vote, one other option is Mesa tools:
www.mesatool.com

BORING BARS | mesatool

www.mesatool.com www.mesatool.com
I use this 1/2" bar with the same model boring head as yours, no regrets so far.
Click to expand...
I have reduced my shank/arbor length by about 50% and I pressed out the old boring bar. The problem with getting it out is that there was a cover (perhaps a dust cap) in the head bar holder on top of the hole for the bar. Seemed like the cover was pressed sheet metal. I mangled that cover, but I'm pretty sure it's not a problem to leave it out. And the boring bar slides in and out nicely now.

I'm trying to pick an indexable boring bar, perhaps based on the recommendations in this thread. But, I've been looking at pictures and I'm pretty sure that the original bar I got with the head is Right Handed. And, the 1/2" one linked to is Left Handed.

Do I have the "hand" correct? And, if I do...are you running your boring head using a left hand bar? Do you need to run the spindle with the opposite rotation from normal milling cutters and such?
 
rronald said:
I have reduced my shank/arbor length by about 50% and I pressed out the old boring bar. The problem with getting it out is that there was a cover (perhaps a dust cap) in the head bar holder on top of the hole for the bar. Seemed like the cover was pressed sheet metal. I mangled that cover, but I'm pretty sure it's not a problem to leave it out. And the boring bar slides in and out nicely now.

I'm trying to pick an indexable boring bar, perhaps based on the recommendations in this thread. But, I've been looking at pictures and I'm pretty sure that the original bar I got with the head is Right Handed. And, the 1/2" one linked to is Left Handed.

Do I have the "hand" correct? And, if I do...are you running your boring head using a left hand bar? Do you need to run the spindle with the opposite rotation from normal milling cutters and such?
Click to expand...
I run right hand bars for internal boring.
 
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