Boring bar offset

For the tool bits in my round boring bars I started with a long tool bit that made it easy to shape. Then put it in the boring bar and cut off the end of the tool bit. I found that a sort of left hand shaped tool bit worked best for me.
 
We would make very large boring tools
(18"-48") with some of these or similar for the old boring mills...
I need to find a picture.
Amazing to watch a boring mill turn a 10 inch diameter bearing HUB with a shop made bar and a cartridge mounted on it!20230513_210537.jpg
 
I'm no expert on boring but seem to get it done OK. I have an assortment of inserted bars and a few I've made using a HSS square, inserted into a steel bar. All work OK as long as the tip is engaging the work at the correct angle. I choke-up on the bars to limit overhang so a long bar works fine for a 1" deep hole. I've made carbide tipped bars by silver soldering scrap carbide on. Work at least as well as the import stuff. Worth the time? Not really but had to see if I could.
 
The ones I'm asking about in my original post are for lathe use. I have another set for my mill boring head. I've used them and they worked just fine. I'll need to spend more time using them to really feel like I knew they are working well, though.

The sets from KBC and LMS don't have any info on where the cutter bit is located. I think I have a set from KBC and another Chinesium one.

What about this one:
https://www.kbctools.com/itemdetail/6-870-062
It's about $50, 6" long, but a smaller dia shank (3/8"). I was thinking I'd like a thicker shank (3/4"). It states the centerline is 1/4"; is this where the cutter is located?

Would I buy just one boring bar, or is it better to buy a few? I'm thinking I'd use one for boring deep (6" or more) holes and another for boring holes in the mid-range (3"-6") and maybe another for shallower holes. Or, could I just use a long one for all the holes and mount it so it only sticks out to the depth needed? I'm leaning towards just one.

They are $26 each at McMaster, about $12 at KBC, and $5-$15 at LMS. Are those reasonably inexpensive? Would you recommend buying them in bulk? I've only used them a few times and I broke the one I was using; good thing it had 3 sides!
There is a whole lot to buying a boring bar. Rather than launch into a long discussion, can I ask you to read this first? The article will answer a lot of the questions you're asking.

The cobalt boring bar sets have the top of the cutting tip ground on the centerline of the boring bar so they will work well on the lathe or in a boring head on the mill. I have all kinds of boring bars but still use cobalt bars a lot, especially when I am doing close tolerance work.You might try them.
 
There is a whole lot to buying a boring bar. Rather than launch into a long discussion, can I ask you to read this first? The article will answer a lot of the questions you're asking.

The cobalt boring bar sets have the top of the cutting tip ground on the centerline of the boring bar so they will work well on the lathe or in a boring head on the mill. I have all kinds of boring bars but still use cobalt bars a lot, especially when I am doing close tolerance work. You might try them.
Thanks so much for the reading material. I've read it over twice and I'm still processing it all. I hope others find this useful; I sure did!

I thought it might help if I showed you all what I'm making:
DSC01215 (2).JPG
This is a boring bar holder for my Atlas Craftsman 12" (no hole for the boring bar yet). I have a QCTP, but it holds the boring bar holder out a little far to the side (not depth) and so it flexes. I thought if I made one that had the boring bar centered more over the compound it would be stiffer. The block is about 2". After reading the boring primer, that means about a 1/2" diameter boring bar and a 2" hole depth.

There is no height adjust on this so I need to get the hole right. I thought I would chuck up a drill bit in the lathe and make a hole in the block while it was mounted to the compound, then put the boring bar in the hole, and be done. I need a boring bar with the top of the cutter on center. I thought I could rotate it as needed to make any minor adjustments. Seems I may be going about this wrong. I might need to make due with my existing set-up and learn better technique.
 
Personally, I would stick with the QCTP and try an Aloris 4D boring bar holder. It will allow you to use sleeves for smaller bars and still handle a 3/4" boring bar. If you take the recommended depths of cut for the insert, the QCTP should handle it
 
My boring bars are all offset as shown in this end view. The shank is 0.750" in diameter:
View attachment 447386

Is this a standard, or all all boring bars different depending on what company makes them?
It might be as simple as rotating the bar till the cutting edge hits center or a few thousands above center. Unless bar has a flat forcing it above centerline. I silver solder tips on bars often and do this all the time.
 
I haven't been able to find what SCLCR means. Thanks
 
it means the bar uses a CCMT/ CCGT 80deg single sided insert and is a right hand cut with a 5deg clearance at the front of the insert/ bar. The number after is the size of the insert and the size of the bar (usually in metric if it's an import). So 06 = 06 or 22.5x insert size, 10 = 10mm diameter.
 
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