boring bars

[ShawnR]

Hi All

Question for you all. I have a set of boring bars, 1/2" shaft. I see many of them advertised, some with holders, and some without.

https://www.kbctools.ca/itemdetail/1-4526-500

I am wondering how most of you use them. I saw an add with them just mounted in a tool holder so I tried it. Seemed to work ok, but it looks ....unprofessional..which describes me perfectly so that might be ok....

I asked a machinist friend how to use them, he said he would make a holder or grind/mill a flat on them. When I started looking at my tool holder, I would have some options. A slit square holder might be best but does not leave much room to shim to find center. Being round, I can rotate them to adjust the centre... Is this the idea with their design?

I am using them on a small 9x18 lathe. The tool holder opening is .875"

Thanks,
Happy holidays
Shawn

[ShawnR]

This one looks like it might be the most favourable option for me? Is this common? It is the one that I thought might lead to more chatter or flex? but then boring cuts are supposed to be light, right?

Cheers,

Shawn

[LKeithR]

The bars you've shown in the ad are normally used in a boring head on a milling machine; they're not meant to be used as boring bars on a lathe. Anything that's meant to be used on a lathe will come with a flat already ground on at least one face. The holder you've shown in the last picture just adds extra overhand and flex. It will work with small bars and light cuts but it's not necessary.

If you're just getting started I would highly recommend that you invest in a couple bars which use insert tooling. In the long run you'll be glad you did...

[digr]

This is what I made

[ShawnR]

Originally Posted by LKeithR

Anything that's meant to be used on a lathe will come with a flat already ground on at least one face.

I might mill a flat on them then.

Thanks. I might investigate some index cutters too but have none now. Still grinding carbide bits. As much as I have had the lathe and small mill for years, still just a hack with them. Nice to do stuff on them though.

digr, Thanks for that. I might explore something similar. It is all good practice for me.

Cheers,
Shawno

[ShawnR]

This looks like a simple solution too. I guess I should have surfed longer...

https://www.model-engineer.co.uk/for...s.asp?th=55077

[greywynd]

It may also change depending on what sort of toolpost you have. If you have a quick change just adjust the holder up and down for centre.

You could also make a little ‘vee-block’ for under it, and still setscrew down on the round, gives a little more room for shimming. I’m guessing you have a turret style tool post for your lathe.


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[ShawnR]

Yes greywynd. Here is what I have. The 3/8" bar has been my go to for years. I always dreaded using it, being so lightweight and a tiny cutter, but it got the odd job done when I needed to. I found the other ones tucked away in the back of the drawer last week so figured I should learn how to use them. I don't recall where or when I got them from. I had a couple of boring jobs to do and they worked great! Despite not having a holder. As I mentioned in the first post, it did not seem right, but actually worked well.
I will go take some photos of the project and post later.

Thanks
Shawno

[camdigger]

Originally Posted by LKeithR

.....If you're just getting started I would highly recommend that you invest in a couple bars which use insert tooling. In the long run you'll be glad you did...

I am definitely not sold on insert tooling. I have several low to mid range (in cost) holders that either use obsolete/difficult to find inserts, or don't perform well. Any insert I have looked at runs $1.5+ per cutting edge. A lot of cash on a hobby budget for something that may or may not have the right geometry to perform well on my equipment with the random material I end up with.

Ordering from Banggood and the like might be lower cost, but stretches delivery time to months and those places have not always supplied the correct items - how many f''n Chinese dumpling makers do I need?

My boring bars are almost all plain bars out of the scrap bin or bargain bin that use 3/16" or 1/4 HSS blanks. Those bars run from 1/2" to 7/8" bars. I have a few boring tools ground directly into HSS blanks for small bore work.

I save the boring tools like those in the OP for use in my cheapo boring head in the mill.

My $.02 CDN as a hobbyist. Someone with a larger tooling budget, quicker access to tooling at reasonable cost, and that puts a dollar value on time spent grinding tool bits may have different priorities.

[Ironman]

I'll throw my vote in for insert stuff. The biggest cost is the holder as they invented way too many types.
A box of 10 inserts will last me years, unless i do something stupid. They can take interrupted cuts, cutting weld hardened steel, machine high speed steel, and do it with a 2x overspeed. I never worry about rpm.
I just got almost finished with a box from years ago, and I spent 10 bucks from Banggood for replacements. We shall see how they last.