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ed_h
03-07-2015, 10:03 PM
I recently bought this Interstate NBN-6-2 boring bar to do some fairly deep boring on a project.

It seems to cut OK, but I soon found that the cutting tip is a little behind the shank diameter. In other words, with the bar square to the work, the shank hits the edge of the hole cut by the insert.

Did I have an unrealistic expectation, or am I overlooking something stupid?

Ed

http://bullfire.net/Misc/SDC12551.JPG

lakeside53
03-07-2015, 10:26 PM
You are generally depth limited to 2.5 -3 times the diameter, so it looks "about right". Of course, we all cheat on that now and then ;), but you can't with this bar. I have a few limited like that, but also many that are not.

If it bugs you grind off the front edge.

I have solid carbide bars that are good for 10X diameter... love those.

JRouche
03-07-2015, 10:47 PM
I have a gang of boring bars. From some really nice and small 1/4" to for me, heavy duty 1" in steel and carbide, heavy that carbide 12x1" bar. Ironically the carbide insert is mounted on a tool steel "holder" that is the end of the carbide bar. Still gotta use some steel, I think it cushions the insert also.

It was interesting AND informative with what Lakeside said. I have never seen a boring bar with built in limits. I don't suppose its a bad idea for the market they work with. I learned something new today. Good Day.. JR

Black_Moons
03-07-2015, 10:57 PM
Yep that is just how they work. that is why round bars and a holder are popular, you can get the EXACT stickout you want. Although having a non fixed height (as tool can rotate) is a blessing and a curse.

You are generally expected to get a whole set of different length carbide insert bars.. and different diameters. This is why I find the $20 9pc brazed carbide boring bar sets such a great deal. You get a size/length for most occasions. When you need a big hole turn to your carbide insert bars, only need a few then (as they are pricy) of various stick out lengths.

PixMan
03-07-2015, 10:59 PM
Interesting design. Ironic, made in USA to a crappy Chinese standard?

Send it back and get a name brand that takes a CCMT/CCGT, a CPMT/CPGT, or WCMT/WPGT.

Failing that, are you sure you've got it in the correct orientation? If you are holding it in a QCTP block type 1 or 2 using set screws on the flat top of that bar, all you should have to do is set center height and go. If holding it in a No.4 boring bar holder be sure that flat is level then set to center. If the steel of the bar still rubs then it's a POS and you should get rid of it.

Mike Amick
03-07-2015, 11:05 PM
I may do it totally wrong, but a lot of times I angle my BB. Is this a no no ?

lakeside53
03-07-2015, 11:14 PM
It's fine unless you want the insert to cut the bottom of a hold shoulder dead straight etc.

elf
03-07-2015, 11:54 PM
It seems to cut OK, but I soon found that the cutting tip is a little behind the shank diameter. In other words, with the bar square to the work, the shank hits the edge of the hole cut by the insert.



Isn't that what grinders are for? :)

lakeside53
03-08-2015, 12:52 AM
YEP! I've modified many tools to get into a tight space...

ed_h
03-08-2015, 01:41 AM
It just seems like a silly limitation. The bar is 5" OAL, but it's mostly shank that can't go into the bored hole. Moving the insert tip out maybe 0.020" would have avoided the problem.

I can grind it, but I shouldn't have to. This bar wasn't cheap by my standards--$40+ without the insert.

Ed

RussZHC
03-08-2015, 07:17 AM
What lakeside said...Micro 100 for one makes a lot of their smaller brazed tip boring bars in a configuration that does the same thing, IMO its two things, the limitation as lakeside said but in
Micro 100 example perhaps that even the smallest bars have a common shanks size of 1/2" so you don't have to putski around with shims/spacers/split thingies in the holder (I don't have any of those Micro 100 boring bars but it could be that the larger diameter is of a length that allows good clamping and the rest can go into the bore without hitting, tough to tell scale looking at sellers photos)

Baz
03-08-2015, 08:46 AM
Interesting observation I have not encountered not having insert holders. It seems to be the all too common result of a designer being far removed from the actual use and no hint of proper field testing.
Ok you wouldn't expect people to think of trialing such a simple item but it would have shown up the shortcomings and lead to a decent product. So often I have bought somthing (normally rather more complex) and wished I could be a reviewer for a magazine that tested products and was permitted to make honest reports rather than sucking up to the advertising revenue.

JohnMartin
03-08-2015, 09:32 AM
Boring bars are always limited by a compromise between diameter and rigidity.

I won't say that you are being unrealistic, but the specs for that bar should have stated its maximum boring depth, which would be limited to the length of the reduced shank portion. If that reduced shank portion was larger, it wouldn't be able to bore to the same minimum diameter. If it was longer, you would lose rigidity. If the full sized shank part was smaller, you would again lose rigidity and it wouldn't fit into standard boring bar holders. What it comes down to is that the manufacturers expect you to match the boring bar to the job, and buy more of their expensive boring bars.

If no maximum boring depth was listed for the Interstate bar, you may have a legitimate gripe with the seller. Many if not most other makes do list maximum depths in their specs.

Again, boring tools are always a compromise. Had the reduced shank portion been longer, you might have been complaining about excessive chatter.

PixMan
03-08-2015, 10:31 AM
Let's back up one minute.

It occurs to me (far too late) that every insert or solid carbide boring bar I've ever bought or used gives a minimum bore diameter that it's rated for. In this case, I looked up that boring bar on MSC's website (the Interstate brand is theirs) and it clearly states "minimum .430" bore" for that one.

What size hole are you trying to stuff it into?

Ed ke6bnl
03-08-2015, 10:39 AM
I may do it totally wrong, but a lot of times I angle my BB. Is this a no no ?

Just a nooby but I do this most of the time

ed_h
03-08-2015, 10:57 AM
What size hole are you trying to stuff it into?

Trying to stuff it in a 0.500" hole. I believe the 0.430" is the size necessary for the insert to clear.

I get the issues with rigidity etc. My point is that just moving the cutting point outward by maybe 0.020 would have avoided the problem. Keep the reduced diameter the same, or even beef it up a little if necessary. That way, I get to decide how deep is too deep.

In this particular job, I was boring Delrin, so the limitation of the bar was way too restrictive.

Ed

Rich Carlstedt
03-08-2015, 11:54 AM
Time out fellows
Yes, the toolpost can be turned slightly, as many do for use. Thats Ok, except it requires resetting for other tools in most cases
Look at the design ...It is a bar turned down on the end, and milled to accept an insert.
Simple and cheap form to manufacture. It is not a design problem, it is an answer for an inexpensive application.
If you want a bar thet is offset ( by forging) they make them...but they cost more.
http://www.iowa-industrial.com/Eastern-Iowa-/Earth-Moving-Equipment-/Myford-glanze-12MM-indexable-boring-tool-image-No.jpg

So the options are:
Offset the toolpost or
Buy a offset boring bar or
Grind off some of the shank or
Heat the end of the shank , and forge/bend the head to an offset on the existing bar

Rich

dp
03-08-2015, 12:00 PM
Since others have answered the question I'd suggest that bar is overkill for turning plastic.

sarge41
03-08-2015, 04:32 PM
ed_h: The longer the reduced portion of the bar is, the more apt to get vibration. This is bad for the insert. This is why it is done thus. An aside, why don't you make your own. Getsome good steel of the desired size, such a 4140-SAE. They are not hard to make and you will have a better bar than what you would have paid $40.00 for. I have made several over the years. Good luck.

Sarge

Forrest Addy
03-08-2015, 05:43 PM
It just seems like a silly limitation. The bar is 5" OAL, but it's mostly shank that can't go into the bored hole. Moving the insert tip out maybe 0.020" would have avoided the problem.

I can grind it, but I shouldn't have to. This bar wasn't cheap by my standards--$40+ without the insert.

Ed'

So move the tip out 0.020". The relieved part of the bar is relatively long. Locally heat it near the shoulder and offset the tip portion. Keep the insert pocket cool so you don't draw the temper. Don't just go at it with a torch and a hammer. Think about it; maybe make a bending fixture like a plate with three pins in it.

Make the first bend of the offset at the intersection of the angle made by the chip relief (just past the insert pocket apex) to the straight part. Make the next bend right next to the shoulder.

Longer overhang means greater tendancy to chatter so be prepared. One reason yesteryear's boring bars were made so long is so washers or rings could be placed on the far end of the bar to damp conducted chatter. A couple of thick 1 1/2" merchant sized flat washers washers on a 18" long 3/4 dia boring bar would buzz and murmer but the chatters was greatly reduced. This did nothing for tool deflection of course but the finish was better and you could take slightly heavier cuts at higher speed. Regardless single point boring deep holes is time consuming.

CCWKen
03-08-2015, 07:10 PM
I'm glad I don't have to put up with that crap. I'm old-school with ground bits. :)

ed_h
03-08-2015, 07:47 PM
All the suggestions on how to "fix" this supports the notion that the design could have been better in the first place.

I appreciate the input, guys.

Ed

kevkeller
03-09-2015, 06:40 AM
If you're boring Delrin you can make a boring bar out of any metal. I've used CR steel from the local hardware store and ground a point on it. I've bored and threaded.

Doozer
03-09-2015, 08:23 AM
It is frustrating when members suggest a million fixes for a purchased
product that was clearly (to me) designed with a significant limitation.
Yes the OP could grind it or even bend it, but he should not have to.
Please post the brand of the bar so I don't ever buy one.
I am going to guess APT. Am I correct?

-Doozer

PixMan
03-09-2015, 08:39 AM
He did post that, it's MSC's own "Interstate" brand. I take that as MSC's translation of "made to a Walmart standard of quality to achieve the desired price point while maintaining a healthy profit margin."

Even though it shows "made in USA" I have my doubts because of the poor milling and the ridiculously large screw holding the insert down. That's why I said "made in USA to a Chinese standard", or something to that effect.

Lew Hartswick
03-09-2015, 08:40 AM
If you're boring Delrin you can make a boring bar out of any metal. I've used CR steel from the local hardware store and ground a point on it. I've bored and threaded.
In about 1960s somewhere a friend and I did a small production of special parts that required an annular slot in Nylon and the tooling was made from BRASS . Worked a charm. :-)
...lew...

vpt
03-09-2015, 08:44 AM
I'm glad I don't have to put up with that crap. I'm old-school with ground bits. :)


Yes. Although I have a few carbide bits for tough stuff I like hss for many reasons including I can grind whatever bit I need.

http://img534.imageshack.us/img534/2110/hydraulicram014.jpg

http://img713.imageshack.us/img713/4528/excursioncargo015.jpg

http://img849.imageshack.us/img849/5379/hydraulicram018.jpg

sawlog
03-09-2015, 09:47 AM
It is obvious the bar is designed to have a limited boring depth. You get what you pay for, however if you purchase something cheep enough you can modify it fit your needs. With that in mind I would just chuck the sucker up in my lathe and turn the back down as far as I needed it to be.

JohnMartin
03-09-2015, 11:46 AM
All the suggestions on how to "fix" this supports the notion that the design could have been better in the first place.

I appreciate the input, guys.

Ed

The design was fine. This boring bar was not the proper one for your particular task.

It was made to enter a bore of a certain minimum diameter, and bore to a certain maximum depth. With a standard sized shank. Yes, they could have made it with a longer reduced shank. But then you'd get increased deflection and chatter. Maybe not a problem in Delrin, but definitely a problem in other materials.

Many of the manufacturers of these small reduced neck boring bars offer them in several different neck lengths - i.e. boring depths. You pick the one with the minimum depth that will do your job.

Boring bars always involve a compromise.

iMisspell
03-09-2015, 11:48 AM
Ironically the carbide insert is mounted on a tool steel "holder" that is the end of the carbide bar. Still gotta use some steel, I think it cushions the insert also. its possible a manufacturing decision also, eayer and faster to mill out the insert pocket in steel.

But, you can also send out a bar which was trashed and just have the steel end repaired/replaced for fraction $$$ of a whole new bar. As you know, them carbid bars are not cheap compaired to steel.


_

lakeside53
03-09-2015, 12:14 PM
The design was fine. This boring bar was not the proper one for your particular task.

It was made to enter a bore of a certain minimum diameter, and bore to a certain maximum depth. With a standard sized shank. Yes, they could have made it with a longer reduced shank. But then you'd get increased deflection and chatter. Maybe not a problem in Delrin, but definitely a problem in other materials.

Many of the manufacturers of these small reduced neck boring bars offer them in several different neck lengths - i.e. boring depths. You pick the one with the minimum depth that will do your job.

Boring bars always involve a compromise.

I agree. I've had several from major brands like that also, and many that do not have that restriction. If you were only boring steel, it would be fine.

lakeside53
03-09-2015, 12:16 PM
It is obvious the bar is designed to have a limited boring depth. You get what you pay for, however if you purchase something cheep enough you can modify it fit your needs. With that in mind I would just chuck the sucker up in my lathe and turn the back down as far as I needed it to be.

It would be much better to just grind off a portion of the interfering edge; reducing the entire shank will make for more deflection. You could of course use a 4 jaw to offset it and only turn the interfering edge.

Rosco-P
03-09-2015, 12:42 PM
I recently bought this Interstate NBN-6-2 boring bar to do some fairly deep boring on a project.

It seems to cut OK, but I soon found that the cutting tip is a little behind the shank diameter. In other words, with the bar square to the work, the shank hits the edge of the hole cut by the insert.

Did I have an unrealistic expectation, or am I overlooking something stupid?

Ed

I'd phone them and return it.
For $49 and change, I think it's reasonable to expect better. The description and diagram on the Enco catalog page could use some improvement.
http://www.use-enco.com/CGI/INPDFF?PMPAGE=196&PMCTLG=00


It would be much better to just grind off a portion of the interfering edge; reducing the entire shank will make for more deflection. You could of course use a 4 jaw to offset it and only turn the interfering edge.

They could have and should have manufactured it that way so Ed wouldn't have to do just that.

Doozer
03-09-2015, 12:50 PM
... You could of course use a 4 jaw to offset it and only turn the interfering edge.

Like.

-D

lakeside53
03-09-2015, 12:56 PM
I

They could have and should have manufactured it that way so Ed wouldn't have to do just that.

Or.. Ed could have bought a bar more suitable for what he wanted. I have bars from Mitsubishi just like that (at 2-3X the price), so they are made for a purpose. These are "mini bars" designed to go into small holes (0.286 minimum if I'm looking at the correct bar on Enco) and have 1/2 inch shanks. Ed's hole is 0.5 inches. Buy something with smaller shank if you can handle the deflection. BTW.. why a negative rake holder for Delrin? I'd have gone for positive rake and very positive inserts.

This is what I think he has : http://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO=949229&PMAKA=377-1020

I have over the years collected over 20 insert type boring bars... not counting the brazed on types for boring heads. You can't get what you need for every circumstance with just one bar.

PixMan
03-09-2015, 01:31 PM
A steel, non coolant fed 3/8" boring bar that takes CPxT21.5x inserts or WCxT21.5x inserts, from a high qality American maker can be had for the same price. They have a minimum bore of .400", and I can assure you they need NO modification. Those ANSI/ISO standard inserts, with two or three edges, can be had in every kind of grade and chipbreaker imaginable for any material and/or cutting condition.

http://www.ultradexusa.com/ULTRADEXUSA.2011.2.A.BORINGno.pdf




I have over the years collected over 20 insert type boring bars... not counting the brazed on types for boring heads. You can't get what you need for every circumstance with just one bar.

True, no way one boring bar will suit every job that comes down the road. I don't have twenty, but a few and adding more all the time. This doesn't show the little 1/4" one I have, nor the growing collection of Micro 100 solid carbide, but from 5/16" up to 1-1/2" bars, I'm covered. Old photo, a couple more have been added since.

http://img.photobucket.com/albums/v466/kenm10759/Dads%20shop/IMG_1251-r.jpg

CCWKen
03-09-2015, 01:34 PM
Just a quick question; Who made the rule that a boring bar must be parallel to the hole axis? Mine never are and solves the clearance issue. :)

lakeside53
03-09-2015, 01:41 PM
Not if you are trying to stuff a 0.5 shank into a 0.5 hole :)

ed_h
03-09-2015, 02:02 PM
Here's the boring bar:

http://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO=948859&PMAKA=377-1000

No mention of limited boring depth.

Getting it to work isn't the problem. There are a number of ways to fix it, including some of the good suggestions here. It's just a nuisance irritation.

By the way, I bought the bar as a general purpose tool. The problem just happened to show up while working some Delrin.

Ed

PStechPaul
03-09-2015, 02:22 PM
It says the lead angle is -5 degrees. It might be possible to tilt the bar by 4 degrees and have the shank clear the hole while also boring a flat bottom. Another possibility might be a larger insert, if it fits, or the bar could be modified so that it will. I don't have any insert tooling and I'm happy with the mostly HSS and some brazed carbide tip stuff I have, but I may get some insert tooling at some point so it's good to learn more about it.

Forestgnome
03-09-2015, 04:01 PM
Most boring bars will specify a length of cut (LOC). Doesn't look like this one does, but the specs of minimum bore diameter=0.4300 and shank diameter=1/2" should tell you something.

Doozer
03-09-2015, 04:52 PM
Mitsubishi was mentioned as a nice small dia bar.
Wanted to add that I have a few Sumitomo bars that are very nice.
One has a carbide shank with a steel head, with a trigon insert that
will fit down a 5/16" hole. I have another that takes a diamond shape
carbide insert, of about the same size. I think they are called out as
.093 IC inserts. I must admit, when you get that small, it is probably
time to use Micro100 bars. That also being said, Micro100 makes
short bars in 1/2" diameter for a bit more general size stuff. These are
their solid carbide offerings. I know they make brazed in models also.

-Doozer

onemoretime
03-09-2015, 06:30 PM
*The NBN identified bars are "necked" as shown. They have a limited boring depth when orientated parallel with the spindle axis and a minimum bore slightly less than the shank.

*The NBS bars are not "necked," and the cutting edge is located outside of the full length shank profile. The minimum bore is slightly more than the shank diameter.

Unfortunately, these facts are not listed or listed inaccurately in all of the distributor catalogs I know of for these bars. This problem should not be confused with quality. The bars themselves are very well made. The insert pocket is accurate, of correct angles and machined well. The metal stock exhibits no questionable characteristics, and the hot black-oxide coating is well done. The screw is hardened and does not break prematurely when used with a correctly matching carbide insert. It is #4-40 with an 82 degree countersink angle.

PixMan
03-09-2015, 07:55 PM
Mitsubishi was mentioned as a nice small dia bar.
Wanted to add that I have a few Sumitomo bars that are very nice.
One has a carbide shank with a steel head, with a trigon insert that
will fit down a 5/16" hole. I have another that takes a diamond shape
carbide insert, of about the same size. I think they are called out as
.093 IC inserts. I must admit, when you get that small, it is probably
time to use Micro100 bars. That also being said, Micro100 makes
short bars in 1/2" diameter for a bit more general size stuff. These are
their solid carbide offerings. I know they make brazed in models also.

-Doozer

The top four bars in the photo I posted of (most of) my insert boring bars are solid carbide or carbide with a small coolant hole through them, with steel heads brazed on. The steel heads hold the insert better because it's very expensive and difficult to get good insert pockets in carbide. Plus with steel heads you can drill the coolant hole at an angle to get coolant from the center hole of the carbide bar out to the insert, and braze a new steel head in if it gets worn or trashed.

I've since added one bigger and one smaller than those. None cost me more than $75 on eBay, some of them brand new old stock. I do agree that Micro 100 solid carbide is the way to go for smaller and shorter holes and have a growing number of them. I've used those for years "at work."

PixMan
03-09-2015, 08:06 PM
*The NBN identified bars are "necked" as shown. They have a limited boring depth when orientated parallel with the spindle axis and a minimum bore slightly less than the shank.

*The NBS bars are not "necked," and the cutting edge is located outside of the full length shank profile. The minimum bore is slightly more than the shank diameter.

Unfortunately, these facts are not listed or listed inaccurately in all of the distributor catalogs I know of for these bars. This problem should not be confused with quality. The bars themselves are very well made. The insert pocket is accurate, of correct angles and machined well. The metal stock exhibits no questionable characteristics, and the hot black-oxide coating is well done. The screw is hardened and does not break prematurely when used with a correctly matching carbide insert. It is #4-40 with an 82 degree countersink angle.

Is that a typo? I have never seen the minimum bore diameter of an insert (or any type) boring bar be less than the shank diameter.

I will dispute the use of a #4-40 82 screw there. The vast majority of ANSI/ISO compliant "screw down" inserts have between 40 and 60 countersinks, which would help explain why that one is sticking up and likely has a circle around the bottom of the 82 where it met the smaller diameter 60 countersink on the insert.

CCWKen
03-09-2015, 08:22 PM
Not if you are trying to stuff a 0.5 shank into a 0.5 hole :)

Well, like Pixman I have more than one boring bar. They're not all .5". :rolleyes:

lakeside53
03-09-2015, 09:00 PM
Here's the boring bar:

http://www.use-enco.com/CGI/INSRIT?PARTPG=INLMKD&PMPXNO=948859&PMAKA=377-1000

No mention of limited boring depth.

Getting it to work isn't the problem. There are a number of ways to fix it, including some of the good suggestions here. It's just a nuisance irritation.

By the way, I bought the bar as a general purpose tool. The problem just happened to show up while working some Delrin.

Ed

But it does say min bore 0.430, and 0.5 shank, so somewhere you have to be limited 'cos you can't get the 0.5 shank into .430 hole. The limitation is of course the neck-down point.

ed_h
03-09-2015, 09:47 PM
Of course the .430 is just the smallest hole the insert will go into. As soon as the insert cuts, the hole is bigger.

Ed

lakeside53
03-09-2015, 10:04 PM
Yes, but it would have to cut 35 thou doc to make it just fit a 0.5 shank... Might work for delrin or some AL, but with the insert steel will likely chatter or worse ... and... with deep cuts and maxed out bars there no way to get the chips and swarf out. I fight this all the time... even with insert stick out, the back of the bar can hit the minimal bore for a given cut.

I like my carbide bars for tight holes - skinny and able to cut 10X diameter in depth. Sometimes I cut with 2 different bars - skinny to get the bore big enough to stuff in a more rigid bar.