Criterion DBL-202 question

[techymechy]

I’m looking to purchase a DBL-202 boring head. It has a 7/8 x20 TPI mount.

I see that I can buy a 7/8x20 TPI shank from SHARS. Are these shanks standardized and will the Shars fit the Criterion head?

I haven’t ever purchased a boring head before.

Thanks for your advice.

 

[sfriedberg]

Yes, the Criterion-style boring head shanks are industry standard. There are two or three sizes, but anybody's 7/8-20 R8 shank sold for use with boring heads should fit. (There is always the possibility of lousy manufacture, but I would trust Shars to get the shank right, even if I was doubtful about a Shars clone of the Criterion head.)

BTW, the highschool where I help out has a real Criterion head and an import clone. To a casual visual inspection, they are identical, but once you start working the slides you realize the import clone is really bad. You can tell that the main slide has a pronounced taper, binding at one end and rattling around at the other. The sides are out of parallel by probably 0.005 to 0.010" in the 2" length of the slide. The true Criterion head, in comparison, has consistent light drag from one extreme to the other if you have the gib adjusted nicely.

 

[techymechy]

Thank you for the reply.

Do you have thoughts for which boring bars to get for my first set? I am look at a set with carbide inserts:

Shars 4pcs 1/2" Indexable Boring Bar Set + TCMT Inserts + Certificate $77 Off S] | eBay

INSERT STYLE TCGX, TCMT. TCMT Inserts. Weldon shanks allow the operator to set positive or negative rake. A new cutting edge may be presented by simply indexing the insert. Easy reference guide for insert number, screw, and other accessories is printed on the tool shank.

www.ebay.com

Or:

NEW 6PCS 1/2 SHANK INDEXABLE BORING BAR AND 6 TBGT06/09/11 CARBIDE INSERTS | eBay

(TBGT09 TPGT1103 ). 6PCS 1/2 INDEXABLE BORING BAR. INDEXABLE NO BORING RANG BORING DEPTH INSERTS BORING AP BORING FEEDmm/rev CUTTING SPEEDm/min WRENCH. BJ1210-40 10 -13 40 TBGT0601 0.07-0.25 0.05-0.010 100-200 T6.

www.ebay.com

the more expensive set allows smaller bore holes.

I have a Hardinge TM that has limited Z height so I don’t expect that I’ll ever be boring deep cylinders.

What are your thoughts for a boring bar set?

 

[MrWhoopee]

Since you have limited Z height, I would order a straight shank instead of R8. It's already enough of a fight with a bar in the boring head.

 

[techymechy]

Thanks for the reply.

I am ordering a straight shank. I have a M Head on a Hardinge TM mill.

As far as boring bars, the majority of my work will be with low carbon steel and aluminum. I don’t know if I should use the carbide inserts or try to find a HSS boring bar set.

 

[EmGo]

As far as boring bars, the majority of my work will be with low carbon steel and aluminum. I don’t know if I should use the carbide inserts or try to find a HSS boring bar set.

Mostly carbide. Once in a while for some special reason, HSS is useful. But 90% of the time carbide works best.

Oh, inserts. Mmmm. I prefer the brazed carbide for these smaller holes. Insert bars cost more and work worse. Maybe around 3/4" or so they start to make sense ?

 

[Gordon Heaton]

Since you have limited Z height, I would order a straight shank instead of R8. It's already enough of a fight with a bar in the boring head.

I'm missing something... why would a straight-shank gain Z over an R-8 if the mill has an R8 spindle? Is is just that the straight shank is shorter, allowing for easier insertion? BTW, mounting the head before mounting the bar takes care of a lot of height issues.

 

[sfriedberg]

The majority of my boring bars for use on the mills are either HSS or brazed carbide, because they are for fairly small diameters. I do have a few larger carbide insert bars for use with a Tree taper boring/facing head and a Narex boring/facing head, both heads being larger than a DBL-202.

I bought a lot of my small boring bars used, and regrind them as needed. I trawled through the catalogs a couple of months ago and was not impressed with the design/build quality shown in the photos I found for new bar sets, either HSS or brazed carbide. I ended up recommending a set of brazed C2 carbide bars to the highschool where I help out, as they cut mostly aluminum.

I use carbide insert bars pretty much all the time on the lathe, except for the very smallest bores, but those bars aren't as well suited to a boring head.

 

[techymechy]

Thank you folks!

The brazed carbide boring bars are significantly lower price than the inserts. I’ll look for a good C2 brazed set.

Any recommendations?

 

[MrWhoopee]

I'm missing something... why would a straight-shank gain Z over an R-8 if the mill has an R8 spindle? Is is just that the straight shank is shorter, allowing for easier insertion? BTW, mounting the head before mounting the bar takes care of a lot of height issues.

Yes, a straight shank can be cut to less than half the length of an R8, reducing the necessary clearance (and cranking). In the case of my chucks, it amounts to 2.75 in. or more.

 

[JohnEvans]

Just remember you lose the edge on a brazed tool you will need a diamond wheel to get it sharp again and if chipped a green wheel also. Also with insert bars check price and availabilty for replacement inserts, some are common and reasonable others not so much.

 

[EmGo]

Just remember you lose the edge on a brazed tool you will need a diamond wheel to get it sharp again

Yeah, and you need abs to drive a car, and gps to take your boat out of its berth, and you damn well better not ride a bike without a helmet!

This is overkill. You do need a green wheel to grind carbide, those are not expensive. A Leonard Lap is nice but in no way is it necessary. Don't worry about not having a diamond wheel.

 

[Doozer]

I don't think a diamond wheel is overkill for sharpening carbide.
To be successful in achieving a sharp edge that is not chipped,
you at least need a perfectly smooth dress on your SC wheel,
on a grinder with no vibration, and the wheel should have good
balance. A slow speed diamond wheel is so much more forgiving
with how many variables that must be controlled, the chances of
success are much greater and easier. I can't think of any negative
trade offs when using a diamond wheel over a SC green wheel.
All said, I think it is better for the application. Even price is not
an issue as it used to be, as there are many new diamond wheels
on the market for less than $100, and the usage time over a SC
wheel is a lot more, so there is value there as I see it.
So yes, do not worry about a diamond wheel, but for my money
the pragmatic approach is to go with the performance advantage
of a diamond wheel.

-Doozer

 

[techymechy]

Thanks folks.

I have a green wheel but no diamond wheel. I have one of those HF green tool grinders and it works surprisingly well.

To get to specifics, would this arbor work on my Criterion DBL-202? The head has a 7/8" x 20 TPI receptacle.

1/2" Straight Boring Shank for 7/8''-20 Thread Threading Precision Boring Head | eBay

1/2" Straight Boring Shank. 7/8" - 20 Thread. Unit Weight: 13 Ounce Estimate Only . Small Freight Item.

www.ebay.com

I'll look for a C2 or C6 brazed carbide boring bar set. I understand that C6 is probably better for my application (I'll primarily be machining low carbon steel and aluminum).

Dave

 

[EmGo]

To get to specifics, would this arbor work on my Criterion DBL-202? The head has a 7/8" x 20 TPI receptacle.

1/2" Straight Boring Shank for 7/8''-20 Thread Threading Precision Boring Head | eBay

1/2" Straight Boring Shank. 7/8" - 20 Thread. Unit Weight: 13 Ounce Estimate Only . Small Freight Item.

www.ebay.com

It'd work, but your mill is a Bridgeport-type ? R8 ? You can go at least 3/4" and I am pretty sure 7/8" with R8.

The stiffness of the pterodactyl is equal to the fourth power of the diameter of his shaft, or something like that.

 

[MrWhoopee]

It'd work, but your mill is a Bridgeport-type ? R8 ? You can go at least 3/4" and I am pretty sure 7/8" with R8.

The stiffness of the pterodactyl is equal to the fourth power of the diameter of his shaft, or something like that.

Agree, I would go 3/4".

 

[stephen thomas]

I'd go 7/8" if it *has* to be straight shank.
Otherwise, R8

Must be the odd guy out - I like Borite bars and their triangular positive inserts for straight boring in most of the simple heads. However, for small holes a shop ground bar is often necessary.
For the Tree or Wohly, i tend to grind my own, including often HSS, to get the geometry pointing per my preference.

PS, there's at least a dozen diamond wheels here, many shapes, grit, dress.
I avoid using them as much as possible anymore, and always use mist and usually supplied air hood. Sometimes just a cartridge respirator. Rubber gloves.
Read up on the dangers of carbide & cobalt dust in your environment, including through your skin.

Green wheels do not "sharpen" carbide.
They erode the binder enough that the carbide falls out, and the shape more or less takes an edge-like form.

smt

 

[techymechy]

Thanks. I have a Bridgeport M head on Hardinge TM mill and the maximum collet size is 1/2”. Hence, the 1/2”’arbor. I have the unobtanium B3 spindle on my head.

I never knew that green wheels didn’t sharpen carbide.

 

[eKretz]

Green SiC wheels suck for grinding carbide when compared to diamond wheels. Hands down in every way, diamond is better. If all you have is SiC wheel, you'd be well advised to use a diamond hone afterwards for the final edge at least.

 

[EmGo]

Green SiC wheels suck for grinding carbide when compared to diamond wheels. Hands down in every way, diamond is better.

And better yet is to shitcan all that crap and bring in a new Makino We should cut the guy some slack, he's just barely buying his first boring bar ...

If all you have is SiC wheel, you'd be well advised to use a diamond hone afterwards for the final edge at least.

Ja, that's a good compromise. Those filey things are not too expensive and should help sharpen up the edge goodly.