Boring bar offset

After some thought, I've decided I'm looking for the following:
-a set of 3 SCLCR carbide bars 8-12" long that should cover my needs:
-1/4" diameter bar
-1/2" diameter bar
-3/4" diameter bar. I can wait on this one, but if I see a deal, I'll get it.
-Should I get a 3/8" diameter bar in addition or instead of any of the others?

For inserts, I think I like the CCMT32.50. I'll go with the smaller nose radius (0, 4th digit). I will consider a bigger insert size (CCMT4, etc.) as well. I can't tell if bigger diameter bars always use bigger inserts or not. I'd like to keep the inserts all the same size. Tell me if that's not realistic or advised.

The 2.5 (5/32" thick) inserts are available at Little Machine Shop, so if I need something else, that makes it easy and cheap to get something.

Thoughts? Am I on the right track?

This one is for @davidpbest
I was looking on Ebay and found a seller that has quite a bit of what I think I need.
mmtoolscarbide

These sellers also seem to have a decent selection:
dans_discount_tools2
rwksurplus

Do you have any feedback for these sellers and can you recommend anyone else I should look at?

Thanks!
 
I emailed mmtoolscarbide and got these offers. Thoughts?

1/4" CCMT #2. non coolant. around 5-1/2" OAL. $115

1/2" CCMT #2. non-coolant. 7" OAL. $130

1/2" CCMT #3. non coolant. 8-1/2" OAL (only 1 left) $180

3/4" CCMT #3. non-coolant. 7" OAL. $230


$475-$525 for all 3.

Here are the inserts he has:
inserts on ebay.jpg


 
They all seem pretty expensive to me, but maybe that is the going price for the Good Stuff! I'm still using the boring bars I got from Precession Mathews when I got my lathe.
 
Yeah, the more I think about it, the more I think I don't need to spend this kind of money. Precision Matthews has reasonably-priced ($70-$160) boring and turning sets (1 or more steel bars, bit holders and inserts) that would probably suit my needs just fine. I don't even have a particular need for a boring bar at the moment; I've been using the non-insert ones when I do. The only issue I currently have is when I need to bore a smaller diameter hole; the boring bits I'm using are a little big to fit in smaller holes. I've been using drill bits to get close to any needed diameters and that has worked okay so far.
 
I don't think you'll find a 1/4" bar with 32.xx inserts, pretty sure they're 25.xx or smaller.

those prices aren't unreasonable, but here's an alternative - buy a cheap set of steel SCLCR bars, some silver braze (45-50%) and black flux then carbide rods in whatever size you need. Then it's a fairly straightforward process of cutting the business end off the steel bar and brazing it onto the carbide rod. I don't see many 3/4" carbide rods around, but you may be able to find a trashed extended reach endmill and use the other end (what I've done before). Probably cost you about $100 all in, depending on how much you can get the carbide rods for. I might even have some suitable candidates in amongst my "for resharpening only" endmills.
 
A few comments. First, small holes one is usually better off either drilling/reaming if it is a common size, boring would be for an odd size. You are limited to depth you can bore, carbide is about 8X the diameter, and the smaller the bar the more likely it is to snap. Small diameter I prefer a solid carbide micro-boring bar (no insert). A SCLCR-2 boring bar takes a 21.5X insert, A SCLCR-3 will take a 32.5X insert. You do not need all kinds of inserts, I would recommend a CCGT coated, it will work well in a range of materials, so the Kennametal CCGT32505LF KC730 coating. Inserts should last a long time, don't waste your money getting all kinds of inserts. My experience with Cobra carbide inserts was they were very poor, not recommended. I would not get a lot of boring bars, I usually recommend a 3/8", 1/2" or 5/8" and a 3/4", depends on the size of the lathe and how big and deep you need to bore.

https://www.ebay.com/itm/325154605725 or https://www.ebay.com/itm/195642254119
 
A few comments. First, small holes one is usually better off either drilling/reaming if it is a common size, boring would be for an odd size. You are limited to depth you can bore, carbide is about 8X the diameter, and the smaller the bar the more likely it is to snap. Small diameter I prefer a solid carbide micro-boring bar (no insert). A SCLCR-2 boring bar takes a 21.5X insert, A SCLCR-3 will take a 32.5X insert. You do not need all kinds of inserts, I would recommend a CCGT coated, it will work well in a range of materials, so the Kennametal CCGT32505LF KC730 coating. Inserts should last a long time, don't waste your money getting all kinds of inserts. My experience with Cobra carbide inserts was they were very poor, not recommended. I would not get a lot of boring bars, I usually recommend a 3/8", 1/2" or 5/8" and a 3/4", depends on the size of the lathe and how big and deep you need to bore.

https://www.ebay.com/itm/325154605725 or https://www.ebay.com/itm/195642254119

I have to agree here.
keep the types and sizes of inserts to a minimum.

For lathe work I have 3 types of inserts.
21.5X for all my turning and boring tools, a single type and size of parting insert, and a threading insert that works for multiple tpi.


Don't get carried away by getting big inserts either. Most of the time you paying extra for carbide you will never use. Very few hobbyists need the doc capacity larger inserts can provide.
 
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