1" boring bar recommendations

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Alan H.

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Got a hankering to buy a 1" boring bar for general purpose to have on hand. By the way, I have an Aloris BXA 4-D boring bar holder.

Borrowed my son's Kennametal and it was very well made and has a high price tag to go with it. I am thinking for my needs something less expensive would be adequate.

What bar and insert style/size would you recommend for general purpose work. I have 1/2" and 3/4" bars now and want to put a 1" one in the tool box.
 
Are you talking about a steel bar, Alan? If so, a 1" steel bar has a theoretical depth capacity of 4", while a 1/2" carbide bar will theoretically bore 2" deep. Since a boring bar is limited by depth and not bore ID, the modulus of elasticity of the bar is what really matters. Maybe look at carbide bars?
 
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Mike,
Yes, thinking about a steel bar. Sorry should have been more clear.

BTW, what's the depth for a 3/4" and 1/2" steel bar respectively?
 
Alan H said:
Mike,
Yes, thinking about a steel bar. Sorry should have been more clear.

BTW, what's the depth for a 3/4" and 1/2" steel bar respectively?
Click to expand...

Steel bars can theoretically be extended in a 4:1 ratio, or 4 times the bar diameter from the holder. So, for a 3/4" bar, you have 0.75 X 4 = 3" max bore depth. For 1/2", 0.50 X 4 = 2". For carbide, the extension capability is 8 - 10:1, so for a 3/4" carbide bar, you can go out 7.5" beyond the holder, and 5" for a 1/2" bar. All of this has to do with the modulus of elasticity of the bar material; hardness of the bar has nothing to do with it. Hence, mild steel and a hardened bar will have the same extension capability.

I guarantee you that one day you will need to bore a deep hole that will be beyond the extension capacity of your steel bar. You can still bore it but deflection is going to be more of an issue at that point and the walls of the bore may not be straight or of a consistent ID. When this happens, you will buy a carbide bar so you can get on with it and that steel bar will sit in a drawer.

Rather than go big, I say go carbide when considering depth capability. Again, a bar is not limited in the size of the bore it can cut; it is the depth capacity that is the key limiting factor. Of course, there are many other considerations when choosing a boring bar but you seem to be looking at size so I just wanted to raise the extension capability issue.
 
Alan H said:
Got a hankering to buy a 1" boring bar for general purpose to have on hand. By the way, I have an Aloris BXA 4-D boring bar holder.

Borrowed my son's Kennametal and it was very well made and has a high price tag to go with it. I am thinking for my needs something less expensive would be adequate.

What bar and insert style/size would you recommend for general purpose work. I have 1/2" and 3/4" bars now and want to put a 1" one in the tool box.
Click to expand...

I have a Kennametal 1" MCLNR boring bar that I got for $100 brand new. If you're patient you can find one for a good price & it doesn't have to be Kennametal. It seems like 1" MCLNR boring bars are an industry standard size, almost all of them that I have seen (at the time when I was purchasing) ar 12" long.

I prefer the SCLCR boring bars that use CCMT inserts. I only use CCGT inserts in them. My 3 smallest indexable bars all use the same size insert, 21.5x. I choose that route so I could use the same insert in all of them. My next largest is a 3/4" SCLCR that uses 31.5x inserts. I use this size CCGT inserts for turning quite often so again convenient.

Now my 1" MCLNR uses CNMG inserts which is not needed on my 1236 but I use CNGG or CNMP positive & ground geometry inserts so it's much more free cutting.

Bigger/thicker isn't always better though. A couple of weeks ago I had to bore a 3.25" ID tube 6061 that was 12" long boring from both end. The 1" Kennametal steel boring bar chattered as it got close to the 6" depth. I switched to my 3/4" solid carbide bar with CCGT insert & it took care of it no problem even with a 1/32" nose radius (32.52) insert. Could barely tell where the 2 bores met each other.

These are all my current indexable boring bars, all but the Kennametal are solid carbide.

20170526_145124.jpg



Alan H said:
BTW, what's the depth for a 3/4" and 1/2" steel bar respectively?
Click to expand...

That will vary on workpiece material & insert type. For example a boring bar using DCMT inserts will be much more free cutting than one that uses CCMT inserts. All my boring bars use 55° diamond inserts. All but one (the 1" Kennametal) uses CCMT inserts as noted & seen above. A smaller nose radius will cut even more freely when you need to bore deep.

My take on boring bars is buy the longest you can find and/or afford. Even if you think might not need the length or it might not work well you never know when that extra length will come in handy & might work for the situation.

There was a seller on ebay years ago that sold solid carbide boring bars quite often. They always varied in lengths so you had to pay attention to the listings. I'm very happy with my 3 smallest indexable boring bars that are seen above. Got them for $30 - $50 ea. I for get who the seller was but I suspected it was a secondary account & name for JTS machinery. Funny cause I inquired once about a specific size boring bar, they quoted me like $300. I waited & they ended up listing the size boring bar I was looking for but in an even longer length for $50. That was for the 1/2" boring bar.
 
Okay friends, now you have me wanting some carbide bars too. That's the danger of asking questions here. You need the cash flow to deal with the answers!

Seriously, I appreciate the feedback and it is very helpful.

So if you were to go for carbide in 3/4" and 1/2", what would be the minimum lengths you would find acceptable? In my case, a BXA holder eats up 3" of the bar for a full grip.
 
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Most 1/2" carbide bars will be 6-8" long. Most 3/4" bars will be 10" long but often shorter. Look at it this way. You want the bar to be able to extend fully beyond the holder so 8" is just right for a 1/2" bar and 10-12" long is just right for a 3/4" bar.

What will happen if you have to bore a hole 4.5" deep but only 5/8" ID? Can't do it with a steel bar but you could pull it off with a 1/2" carbide bar. If you can, spend the money on a carbide bar. Know what you want and watch ebay until you find the bar at a price you can handle.
 
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mikey said:
.......................................What will happen if you have to bore a hole 4.5" deep but only 5/8" ID? Can't do it with a steel bar but you could pull it off with a 1/2" carbide bar. ..................
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Back in the day when carbide bars were unheard of, you had no choice but use what you had. Generally a homemade bar of what ever steel you had on hand. I remember doing bores in the 5/8 - 3/4 diameters by 3 to 4" deep using a steel bar and high speed steel tool bit. Had to play around with tool bit geometry to get it to cut without chatter. It did work! Today, well, too spoiled to using carbide tooling.
 
If interested I've got a large box of Everedes which take the triangular inserts, if that would work for you.
Various diameters and lengths with several duplicates.
PM me, if I have extra of whatever you might be looking for, then I'm sure we can get you a price which fits your needs and budget.

Daryl
MN
 
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