Which Boring Bar?

[Spokerider]

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.

 

[Janderso]

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!

 

[benmychree]

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

 

[francist]

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

 

[DavidR8]

@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]

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

 

[francist]

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

 

[DavidR8]

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...

 

[francist]

@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.

 

[Chewy]

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.