Which boring bar set

[Swifty]

But CNCJunior you have only instanced what is essentially a very small piece of carbide. The rest is steel and roughly the same as it would have been had it all been steel. What you are calling carbide- simply isn't.

Norman

Norman,
With all respect, I think that you are missing some points. You stated that there is only a very small piece of carbide, with the rest being steel, and it simply is not carbide.

What I have posted about, together with MachineTom and CNCjunior is solid carbide boring bars. The whole bar is carbide, with replaceable carbide tips.

You also intimated that I only had a mere 35 years experience and that your experience goes back to the mid 30's, intimating that you have a lot more experience in these things. You then go on to mention that you worked as an accountant. I was a toolmaker for 35 years, mostly working 50 hour weeks. The last 20 years that I worked, I owned my own toolmaking business employing 7 toolmakers and 2 trade assistants. So I think it is fair to say that I have a reasonable amount of experience in machining metals and the tooling to use.

You have also stated that you are now 82 years old, but your first experience with carbide was back in the mid 30's, this would have made you about 5 years old at the time.

The postings about solid carbide boring bars were just from people making general comments about them, not saying that they were the answer to everything. Yes they are expensive, but most home machinists are not working with tool steels, some already 30 rockwell C in their soft state, just brass, aluminium, bronze, mild steel and cast iron to name a few.

We all have to sit back, relax and try to share knowledge together in what is a great forum.

Paul.

 

[MuellerNick]

That rule of 3 times the diameter for steel shanks and 5 times for carbide is a bit … well … not too useful.

For example, I'm boring spindle mount castings. Boring depth is 170 mm, the boring bar is ø 40 mm. No problems. It is simply stiff enough for the cutting forces.

A few weeks ago, I bought a used boring bar at at dealer. Saw it, realized that it must be different. Guessed it was a de-vibe bar. Shuck it and it rattled. I was only asked for 20 €. Back home, looked it up in the catalog. The shaft alone costs 990 €, the head (that was included) 230 €. They say, it is good for 4 times stick out. That's the same nonsense. It is good for more stick out with the same cutting forces.

So with a carbide bar, or a de-vibe bar, you can have more stick-out with the same cutting forces. Or, you can have more DOC with the same stick out. More DOC is less time and that is more money earned. That is the main reason for all that fancy stuff.

Sure, there is a point where you can't reduce DOC even more. That's when you have to use carbide bars.


Nick

 

[Swifty]

Hi Nick,

Never worried about the ratio of overhang to bar diameter, just tried to bore holes without chatter. Always seemed to be pushing past ideal set ups, trying to bore small dia holes way too deep.

Paul.

 

[kvom]

There are boring bars that are 100% carbide as well as steel bars with carbide inserts. My two larger bars are steel with inserts, and since they are 3/4" diameter I can use them equally on the lathe and in my mill boring head. I have two solid "micro 100" bars that are solid carbide and are very small. One has a 1/4" shaft, but only 1" depth. This is useful for smaller holes that are not as deep. My other micro bar is 1/8", and I've never had a use for it.

In any case, the 3/4" bars can bore deep holes, even at full extension. You just need to take very shallow cuts when near the target diameter to avoid the bars themselves distorting/chattering.

 

[Tin Falcon]

We all have to sit back, relax and try to share knowledge together in what is a great forum.

Well put.

the tiny solid carbide bars are not too bad as affordability.

the lager ones are expensive and new even at a discount probably out of reach of most HSM guys. but not a bad idea to know they exist. in case you find a deal on one.
The rules of thumb are guide lines. lots of variables tool stick out is probably the most basic. and do not forget you can make or grind your own bb as well.
Tin