PDA

View Full Version : Boring bar question



outsider347
11-16-2012, 10:29 PM
Looking to purchase my first boreing bar setup. My lathe is a 12" atlas/cman / AXA and I use it for hobby work. Primary use is making spacers needing .500 + id

I see all types of versions & variations available, not sure what I need

thanks

danlb
11-16-2012, 11:47 PM
You generally want as stiff as possible so you can go as deep as possible.

The general rule is that a bar can bore some multiple of it's diameter without chatter. I think it's 5 or 5 times for steel, 8 or 9 times for carbide.

If you are only boring a hole 1/2 inch deep, then just about anything will do the job. Get the biggest that will fit inside the hole.

I kind of like my SCLCR style solid carbide bars that take CCMT carbide inserts. They work well and the inserts are easy to find.

Dan

RussZHC
11-17-2012, 12:42 AM
Related: I found myself needing larger drills...if your largest drill is 1/2" and you need to get to say 1.5" bore, it takes awhile :rolleyes:, if you are mostly through boring lots of variations will certainly work, if you are wanting a truly flat bottomed bore from time to time and using inserts you will have limited choice (STFC/STFP spring to mind). As mentioned, stiffness is the primary concern after size.
Basic is often a bar with a broached hole at each end, typically 90 degree at one end, 45 degree at other using lathe tool bits you already have, even more basic is sort of a longish "shank"
"J" with the end of the curl ground to cut.
Back in the day any number of manufacturers had boring bar "posts" which usually allowed 3 or 4 sizes of bar to be clamped, now any quick change post has option of a holder with a hole that can be bushed smaller etc.

Rich Carlstedt
11-17-2012, 05:15 PM
For a beginner, I think a SET of boring bars made for a mill boring head will work great.
The come in hish speed steel, colbalt, or carbide tipped and you can get American made or imported depending on your wallet
Go about haalf way down the page and a photo will be seen. The set displayed is rather large, but take your pick

http://www.use-enco.com/CGI/INPDFF?PMPAGE=202&PMITEM=375-2300

It does lack the ability for deep bores, but generally new fellows don't do deep bores

Rich

Click next to the "202" at the top of the page to see more

justanengineer
11-17-2012, 08:50 PM
If you understand or care to learn about cutting tool geometry, you can also make your own from pretty much any scrap of steel and use a HSS bit. Ive got quite a few that Ive acquired used, but occasionally still find myself making one.

darryl
11-17-2012, 09:14 PM
I know it's just a typo- but hish speed steel, how fast is that?:)

Yeah, you can make a boring bar to suit providing you have a cutting bit to stick onto it. I have all manner of home-made ones, plus a set of carbide ones. For the carbide, I made up a holder which would mount directly to the cross slide, with a cross hole drilled to take the shank diameter of the set- 3/8 in this case.

My most used 'boring bar' is a piece of bar which has been cut to fit into the tool post. One end has been drilled to accept 1/4 inch diameter shanks, and the other was drilled for 3/16 diameter shanks. Each has been cross drilled and tapped for set screws. I'm currently using a carbide shank in the larger end, and have ground a sort of D bit onto the end of that. It's been my favorite boring tool for years now. Maximum depth of cut with it is about 1 inch, so that's the limitation there, but it's very stiff as most of the 'stick-out' from the tool holder is the larger size of the bar I used as the holder.

Since the other end is drilled smaller, I can use 3/16 drill bit shanks as cutters. I had some long HSS bits I got from boing surplus years ago, and have been making special cutters from it for boring in very small diameter holes, etc.

For deep boring I use the carbide set. I pick the shortest one I can that will still go the distance. Because the compound is not used as part of the tooling holder path, the rigidity is enhanced. I don't really like the boring bar set I got, but that's another story. If I mount a good quality tool in the holder, I can get a beautiful finish and a straight and accurate hole. This is my second favorite boring tool.

JoeLee
11-17-2012, 11:57 PM
Buy a bar that takes a standard common type of insert like the TPG style. Avoid any bar where you have to buy the special size inserts from the mfg.

JL................

+ or - Zero
11-18-2012, 04:24 AM
This may not be the best possible boring bar, but it's fast cheap and really does work quite well:

Grab an appropriate size Allen wrench, cut the short end down to the size you want, grind the cutting shape you want, and bore away. As the diam gets bigger use larger Allen wrenches, eventually you will have lots of sizes.

Just a real good bang for the buck, not meant to be the end all of boring bars.

PixMan
11-18-2012, 07:07 AM
Buy a bar that takes a standard common type of insert like the TPG style. Avoid any bar where you have to buy the special size inserts from the mfg.

JL................

Good advice. The only manufacturer I know making those proprietary style insert boring bars and inserts is Circle. What's dangerous is that they use what looks like common TPGT, CCGT and similar shape inserts, but theirs are odd thicknesses, side clearance angles and I.C. (inscribed crcle) sizes.

If I'm not mistaken , right now Enco has a sale on Seco bars that take the common CCGT/CCMT 21.5x size inserts. They are stronger at the tip than the TPG and TPGT (no hole and hole style 11 side clearance angle), though have only two cutting edges vs. three.

loose nut
11-18-2012, 08:50 AM
They come in hish speed steel, colbalt, or carbide tipped

The HSS or Cobalt work great and are very easy to sharpen, just touch up the end. If you don't want to spend the money on them then take a dull endmill and grind off all the flutes but one (two flute would be best type to start with) and you have a good, short, boring bar

JoeLee
11-18-2012, 09:23 AM
Good advice. The only manufacturer I know making those proprietary style insert boring bars and inserts is Circle. What's dangerous is that they use what looks like common TPGT, CCGT and similar shape inserts, but theirs are odd thicknesses, side clearance angles and I.C. (inscribed crcle) sizes.

If I'm not mistaken , right now Enco has a sale on Seco bars that take the common CCGT/CCMT 21.5x size inserts. They are stronger at the tip than the TPG and TPGT (no hole and hole style 11 side clearance angle), though have only two cutting edges vs. three.

Your right, there are a lot of look alike copies out there with limited grades of carbide and radius. Thickness usually isn't a problem if it's the clamp type but some of the inserts that are held in place by a torx screw have different size holes and counter seats and you'll have problems securing the insert.
I have a nice bar made by APT that takes the standard TPG style insert. Inserts that vary a bit in thickness aren't a problem. The bar came with 3 different anvilles, positive, negative and neutral rake. I use it for just about all my boring. It's about 6" in length and 3/4" in dia.
Only draw back is the minimum starting hole has to be I think 7/8".

JL.........................