# Which Boring Bar?



## Spokerider (Feb 3, 2020)

Guys,
 I just picked up a Craftsman 101. lathe, and, well, I have lots to learn! 
 I'm in the process of researching tooling for this little lathe, and would like to know what you'd recommend for a boring bar. 
 Do I buy the bottom-of-the-barrel china stuff.....the kit with brazed on carbide tips? Or, get a quality bar with carbide or HSS inserts?
 The problem is, being totally new, I don't know what I want or need. What to get to begin with? 

 I have an OXA tool post holder for this lathe, and it came with the 3/8ths / 1/2" boring bar tool holder.

 I see a guy can part with many thousands on the tooling alone, and since I don't have bottomless pockets, I would like to purchase tooling that will not only be appropriate for beginning, but remain somewhat useful as my experience grows.

 Thanks for yer thots.


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## Janderso (Feb 3, 2020)

Spokerider said:


> Do I buy the bottom-of-the-barrel china stuff.....the kit with brazed on carbide tips?


The problem with these cutting tools is the geometry is off. They braze a hunk of carbide on a piece of steel and sell it as a ready to go tool.
I have them, I also have a diamond wheel to shape them to perform the task I am trying to achieve. You will need to adjust the cutting relief angles in addition, the boring bars have the cutting point positive of center line. Someone will explain better.
I think many of us are tempted with the cheap off shore tooling and some of it is just fine! 
I'm a hobby guy, I don't have the experience of others, this is my opinion on part of your question.
Welcome to the site. Great group!


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## benmychree (Feb 3, 2020)

With that sort of lathe, stick with HSS tools for the most part.


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## francist (Feb 3, 2020)

Spokerider said:


> being totally new, I don't know what I want or need.



This is the crux of the matter -- why not wait until you actually need one before buying something? 

With something like a boring bar, it's unlikely that you will need just one, unless or course you only ever bore one depth of hole. You will likely need a variety of sizes and lengths and possibly different materials too. You can also grind your own from HSS blanks which is also a nice way to go. Gives you the ability to tailor your tool to the job at hand. Afterwards it goes into the drawer for the next time.

As far as the inexpensive brazed-on carbide ones go, unless you have a means to correct the grind yourself I expect you will be frustrated right off the bat. The grinds on these tools is typically very poor. Far better to stick with a high-speed variety and actually get results and then go from there. You can also get the type that have interchangeable HSS bits on each end (one at 90 degrees, the other end at 45 degrees) and they work fine too. I have one for the longer reach stuff. There's a lot of variety to choose from, including indexable carbide, so unless you just want to spend some money you might be better off waiting until you have a better idea of what you need to bore. 

-frank


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## DavidR8 (Feb 3, 2020)

@francist I was looking at the boring bars for HSS on the KBC site. 
Thought it would be easier to make one. 
As you have one, is the hole for the HSS round or square?


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## francist (Feb 3, 2020)

I have one that I bought from KBC not long ago -- 5/8" diameter I think and about 6" long. The holes are square and take 3/16" square blanks. That being said, if you're making your own a round hole works just fine too. There was a post here just the other day (maybe the other forum?) where someone made one with a round hole for broaching. Once the set screw is in place and tightened I think it holds the blank quite rigidly. The KBC is "ok" but not stellar in the fits for the blanks. It works though.

You can also grind them from square HSS -- I have one I ground both ends on like that and it's my favourite for being able to control the cutting angles. It's also quite stiff (HSS vs carbon steel). I'll post a photo maybe when I get home later. It's lasted me for a number of years already.

-frank


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## francist (Feb 3, 2020)

Okay, my less-than-extensive collection...

The one on the top is from KBC and is 1/2” diameter, not 5/8” as I said earlier. It does take 3/16” square HSS though.

The next one down is a home-made one from a previous owner of the lathe. It sings like crazy because it’s so flexy but I have used it in a pinch.

The double-ended one is what I use most and is just ground from a square 5/16 HSS tool blank. I use the 4-way style of tool block, so it’s tailored to fit that height. That’s why there’s flats on two sides of the upper KBC bar too, so it fits my tool blocks on height.

The last one is one of two I bought from KBC as well. I use them in the boring head on the milling machine and they’re ok. They’re HSS, made in India I believe.

The nice thing about the long bar at the top is although it may not be the snazziest tool in the world it’s really economical to use. Want a boring bar, put a couple angles on a piece of tool bit and there you go. Want an internal threading bar, grind a bit to a 60 degree corner and you’re away. Same for internal thread relief, o-ring groove, whatever. I even used it to come from the side and turn a diameter that was too large to get the tool post in front of. Very useful tool for not many dollars.

-frank


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## DavidR8 (Feb 3, 2020)

Thanks Frank, the top one is the one I saw from KBC. I didn't realize it had flats milled on it.
I might try my hand at making one...


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## francist (Feb 3, 2020)

@DavidR8 It doesn’t when you get it, I put the flats on to work with my tool blocks. It’s round when you get it.


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## Chewy (Feb 3, 2020)

I have the 1/2" & 5/8" boring bars from PM.  They use CCMT inserts.  Withe that said, I just bought a 45 & 90 degree 5/16" boring bar from KBC.  It uses 3/16" round HSS.  Don't know how it works as they were out of round HSS.  Haven't had time to find an old drill bit and grind it. The shank size of the bar determines the "stick-out" that you can get.  After a certain length you get chatter.


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## Mitch Alsup (Feb 3, 2020)

The trick with boring bars is that they are never SMALL enough, big enough is rarely a problem.
I have a number of insert boring bars (bottom feeders from china:: 6mm, 7mm, 8mm, 10mm, 12mm) that are perfectly capable of 0.31 and larger
But I have needs to bore holes of 0.247,5 as races for 1/4" ball bearings pressed in with thumb pressure.
measuring that small ID accurately enough is also a big problem.

For big stuff, I will drill 1/2, 3/4 and 7/8 before starting to bore with a 16mm boring bar.
I generally use CNMG inserts but will substitute CCGT when doing aluminum or brass.


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## Janderso (Feb 3, 2020)

Mitch,
You said it. I have a pretty good selection of boring bars but they are usually too big.
I found I use this one quite often.


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## Janderso (Feb 3, 2020)

This is what I meant about the geometry is off with the cheap brazed carbide boring bars.
Criterion on the left, cheap brazed carbide on the right.


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## DavidR8 (Feb 3, 2020)

The one on the right looks like a tooth off an excavator bucket!


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## Janderso (Feb 4, 2020)

DavidR8 said:


> The one on the right looks like a tooth off an excavator bucket!
> 
> 
> Sent from my iPhone using Tapatalk


I should expand my thoughts on these two examples.
You can always get your tool height correct and adjust the cutting relief etc. on the lathe but if you are going to bore with these on the mill, that excavator bucket isn't going to cut it's going to be a problem!


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## pontiac428 (Feb 4, 2020)

Cheap brazed carbide does pretty good for the money once you re-grind the working end to proper angles... at least up to the quality of the carbide material itself.


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## benmychree (Feb 4, 2020)

francist said:


> I have one that I bought from KBC not long ago -- 5/8" diameter I think and about 6" long. The holes are square and take 3/16" square blanks. That being said, if you're making your own a round hole works just fine too. There was a post here just the other day (maybe the other forum?) where someone made one with a round hole for broaching. Once the set screw is in place and tightened I think it holds the blank quite rigidly. The KBC is "ok" but not stellar in the fits for the blanks. It works though.
> 
> You can also grind them from square HSS -- I have one I ground both ends on like that and it's my favourite for being able to control the cutting angles. It's also quite stiff (HSS vs carbon steel). I'll post a photo maybe when I get home later. It's lasted me for a number of years already.
> 
> -frank


There is literally no difference in stiffness between HSS and carbon steel, hardened or unhardened, it is explained in the book "Tool Steel Simplified", which unfortunately, I cannot find just now, it can be proved by taking samples of HSS or any other hardened steel and comparing them by fastening them to a stationary object, and some distance away, attaching equal weights to each at a given distance from the attached end, and noting the deflection; until the tensile strength of the soft sample is reached, they will deflect equally, then the soft sample will take a permanent set or bend.
The only way to get a stiffer boring bar is to substitute carbide for steel.


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## mikey (Feb 4, 2020)

Spokerider said:


> I'm in the process of researching tooling for this little lathe, and would like to know what you'd recommend for a boring bar.
> Do I buy the bottom-of-the-barrel china stuff.....the kit with brazed on carbide tips? Or, get a quality bar with carbide or HSS inserts?



Spokerider, you are going to find that this is one of the most difficult questions to answer because boring is a somewhat complex process and there are a lot of "it depends" thrown into the mix. If I asked you what you plan to bore with it, my guess would be that you're not sure but you just want to have it on hand for when you need it. At least that was my thought when I was a new guy with a new lathe. Little did I know how little I knew.

I put some thought into this and, knowing what I know now and considering the size of your lathe, I would recommend you buy a set of cobalt boring bars from LMS. They will allow you to bore a reasonable range of holes to respectable depths and should be capable of pretty good accuracy if you do your part. They also have shanks to fit the tool holder you have. I strongly recommend that you NOT buy inserted HSS or carbide tools at this point unless you understand what you're buying and how to use it.

I'm all for shop made tools and grinding your own so I don't want to take anything away from the input you've gotten but new guys need decent tools to learn with and they are just not capable of grinding them yet. I would rather see you learn to use the lathe at this point, and that includes boring. Later on, when you have some ideas about tool geometry and some grinding equipment available, you can give it a go. I, and all the other guys, will help where we can.


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## francist (Feb 4, 2020)

benmychree said:


> no difference in stiffness between HSS and carbon steel


That is correct. I did find a slight difference in Young's modulus between the two but for all intents and purposes they are even. The stiffness appears to be concentrated between my ears, for the most part.


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## benmychree (Feb 4, 2020)

Yes, that is correct, modulus of elasticity is what I was unable to remember earlier --- I first became aware of it from the Tool Steel Simplified book back in the 1960s during my apprenticeship; very few machinists knew or believed that it could be so ----


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## Spokerider (Feb 6, 2020)

Thank you gents for chiming in. 
 mikey, you know exactly what I'm asking, lol. Yes, I have no idea what I'm doing, and just want to learn to use my lathe, including boring a few holes just to see "how it works". 
 I like your suggestion to avoid the insert type bars at this point and go with some decent quality bars as with the cobalt set that LMS carries. 
 Learning to grind my own is also going to happen in due time. I have a bunch of blanks that I need to learn to grind for the basic cuts too. 

 I have so much to learn......but this is why I'm here!

 Thanks guys.


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## Liljoebrshooter (Feb 6, 2020)

I would recommend you buy some of the cheap insert bars when you can get them to learn with also.  You will crash something somewhere and you'll do it with a $12 bar and not a $50 or $75 one.
The solid carbide ones like the Micro 100 are excellent but there is zero forgiveness with them.  They break before you even realize what happened.
I also agree with never having one that is small enough to fit into the bore.

Joe


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## mikey (Feb 6, 2020)

Spokerider said:


> I have so much to learn......but this is why I'm here!



Me, too!


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## Liljoebrshooter (Feb 6, 2020)

Also if you haven't already seen it ,  search for the thread "A boring Primer "  that Mikey wrote.   It has some great information about boring a hole on a lathe.
And yes that thread cost me some money after reading about some good quality bars and I just had to try a couple.  I bought a small. 250"  diameter solid carbide bar that is just incredible.

Joe


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## mikey (Feb 6, 2020)

Thanks, Joe!


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## mmcmdl (Feb 6, 2020)

Liljoebrshooter said:


> Also if you haven't already seen it , search for the thread "A boring Primer " that Mikey wrote. It has some great information about boring a hole on a lathe.
> And yes that thread cost me some money after reading about some good quality bars and I just had to try a couple.



Atta boy Mike !


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## DavidR8 (Feb 6, 2020)

@Spokerider our esteemed friend @mikey started an amazing thread on grinding your own tool bits. 
I highly recommend checking it out in the beginners section. 
Be warned it’s a 1,000 posts long but well worth the time. 


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## mikey (Feb 6, 2020)

Thanks, Dave and David. I write too much. What is the equivalent term for verbal diarrhea as applied to the keyboard?


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## Liljoebrshooter (Feb 7, 2020)

Yes,  lots of writing but a huge amount of very good information that is easy to understand.   The pictures also help to see what the small details are. 

Joe


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## ACHiPo (Feb 9, 2020)

mikey said:


> Thanks, Dave and David. I write too much. What is the equivalent term for verbal diarrhea as applied to the keyboard?


Au contraire mon ami!  Keep writing.  Please!


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## martik777 (Feb 12, 2020)

I use these holders and inserts in a semi -production shop with 1144 and 4140 steel - no issues. Buy the whole set or as needed 10mm or 12mm shafts: (and get a box of each type of insert)









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I now only use HSS for form tools or special setups

When I need to bore less than 3/8" I use a 4 or 5mm carbide endmill


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## neilking (Feb 17, 2020)

I've had pretty good luck with the cheap braised carbide boring bars. They work really well on aluminum but have to take pretty light cuts on steel

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## neilking (Feb 17, 2020)

Used it to make a bearing removal/install tool and to make a new bearing
	

	
	
		
		

		
			








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## neilking (Feb 17, 2020)

I'm not really disagreeing with anyone because I don't enough.

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