Problems with boring on a lathe.

[swatson144]

The red set is as worthless as anything I have ever seen. The set in the wooden stand will work well. Most of the Chinese boring bar sets I have seen were never ground. The rough carbide blank was brazed on and called done requiring the owner to finish them. I think if you have a look under strong magnification you'll see what I mean edges are round and dull. Usually they are also over square vice square or slightly under. A little grinding will likely make a world of difference.

 

[kkcalvin]

Thanks for the help guys.

1. I'll try to find something that I tried to bore out to show, but most of the things I just threw out. It's been a while since my last boring operation.

2. I had no idea that I had to grind the carbide boring bars. Now I'll need to find a diamond grinding wheel. I think I'll also practice with HSS grinding.

3. FarFar that's a very nice setup you have. I use AXA piston type too post with boring bar holder for 9/16" to 3/4" bars and 101 holder for 1/2" carbide and 3/8" HSS bar. I'ts not Aloris but still pretty solid and major improvement over stock tool holder.

4. Just to clarify things, you guys set up boring bars to the center. Some instructions that I found tell you to set up bar slightly above center. That might be part of my problem.

 

[rgray]

I make boring bars and sell them on Ebay. My user name there is russ_gray .. They are round bars from 1144 stressproof steel and that may not work to well with the tool holder you have. They are intended for the QCTP tool holders. They have broached square holes so accept standard square hss bits.
Have been playing with making hardened tool steel bars in the 3/8 size as I have noticed flex in them when boring hard steels....they seem fine in regular steel and great in aluminum.

 

[swatson144]

Thanks for the help guys.

2. I had no idea that I had to grind the carbide boring bars. Now I'll need to find a diamond grinding wheel. I think I'll also practice with HSS grinding.

YMMV but I just went out and took a macro photo of one of my brand new un used china BB sorry raining out so poor lighting but you should get the idea.


Not optimal! Good bars don't have this kind of finish and can be used as received but cost many times the price of these. You get what you pay for, but to me a quick touch up is well worth it.

A diamond wheel helps but isn't really needed, an SC wheel will work with some honing. Heck in a bind I'd just use about any old wheel considering how little you have to do.

I usually set mine flat and dead on center and then tweak depending on the performance and chips. Nice thing about boring is you usually have several cuts to get it right.

Steve

 

[OrangeAlpine]

I was taught to set the bar slightly above center. That way, as the bar flexes, it tends to lessen the cut and does not hog in.

Bill

 

[rammed]

+1 on slightly above center. I get good results with chinese boring bars doing that. I never use HF cutting tools.

 

[Syaminab]

Thanks for the help guys.

1. I'll try to find something that I tried to bore out to show, but most of the things I just threw out. It's been a while since my last boring operation.

2. I had no idea that I had to grind the carbide boring bars. Now I'll need to find a diamond grinding wheel. I think I'll also practice with HSS grinding.

3. FarFar that's a very nice setup you have. I use AXA piston type too post with boring bar holder for 9/16" to 3/4" bars and 101 holder for 1/2" carbide and 3/8" HSS bar. I'ts not Aloris but still pretty solid and major improvement over stock tool holder.

4. Just to clarify things, you guys set up boring bars to the center. Some instructions that I found tell you to set up bar slightly above center. That might be part of my problem.

Calvin, you may also set the boring bar as angled as the diameter lets you, that increases rigidity more than running fully parallel to the wall you are boring lessening vibration.
regards

 

[darkzero]

I suppose I have "more expensive" boring bars than the ones mentioned already. But I found them on ebay for great deals. They are all solid carbide & work very good for me so I have no plans in upgrading them for a long time if ever. I guess I'm spoiled as I started off with using solid carbide on my mini lathe so I have no experience with any others.

My 5/16, 3/8, & 1/2 bars all use the same size 21.5x CCMT/CCGT inserts which is nice cause I don't have to purchase different inserts for them. My 3/4" x 10" boring bar is also solid carbide & uses 31.5x CCMT/CCGT inserts & again I don't have to purchase yet another different insert since my turning tools use them.





My largest bar so far is 1" x 12", it's steel & uses CNMG/CNGG 43x inserts, yet again, I use the same inserts for my turning tools as well.





For smaller boring I use the solid carbide bars by Micro 100. They are very high quality, very sharp, & are plentiful on ebay for great deals.





Check out Mesa Tools for boring bars & turning tools. They are very nice for their price & are US made. Many people are happy using them. http://www.mesatool.com/


FarFar, I really like your boring bar holder!

 

[kkcalvin]

Thanks for all the help. Steve I like your idea about saw blade sharpener on your homepage. I have few dull saw blades anyway so I will get one of of those. It's actually cheaper than a new 10" blade.

Kris.

 

[hecirp]

What material are you boring, and what final hole size, and how deep a hole?
The boring bar should extend from the tool holder only slightly more
that the final hole depth. What size drilled hole are you starting
with? If the final size is a large hole and the starting hole is
small, you may need to start with a small shank boring bar, and then
switch to a large shank as soon as possible. The bit tip needs to be
right at center height to avoid digging in if too low, and rubbing and
chatter if too high.
There are several books available for learning. The best IMO is book
from England by Sperry, called, (I think), The Amature Lathe. That
will show you in detail how to grind HSS bits which are probably what
you should use on a small lathe. A 3/8 and a 1/2 steel boring bar,
with slots set 90 degrees one end and 45 degrees the other end for 1/4
or 1/8 in HSS bits work great. These are 50 cent items at garage
sales and swap meets or a nice afternoon project to make. You do not
have to have square holes for the bits, just clamp down tight with a
set screw at the end.
My mentor keeps reminding me that you will learn more and faster by
always experimenting on scrap first.
Sorry about the length of this missive, but if you are a newby, these
things are important to know. Also join a home machinists club if
there is one in driving distance.
Good Luck and have fun,
Harvey