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Silverback
02-03-2009, 05:09 PM
This may be a stupid question, but that's never stopped me...

My 2" boring head has 4 holes in the carriage, 3 facing straight down, and a 4th perpendicular to the other 3, which when mounted in my mill would be oriented horizontally.

Are these things designed to be used with a boring bar mounted horizontally? It seems like a stupid question but you always see pictures of them being used with the bar sticking straight out, and never out the side, so I wonder if it would even be rigid enough to give you a clean cut like that. In this case I'm trying to figure out the easiest way that I have to open up a large, center bore in an aluminum piece to 4.774

Walter
02-03-2009, 05:31 PM
In short, yes it's meant to be used.

I use the horizontal setup quite often to knock out radius's (Radii?) in the 5 + inch range.

And the stupid question is the one that goes unasked.

--me

piniongear
02-03-2009, 05:38 PM
.

My 2" boring head has 4 holes in the carriage, 3 facing straight down, and a 4th perpendicular to the other 3, which when mounted in my mill would be oriented horizontally.

Are these things designed to be used with a boring bar mounted horizontally? It seems like a stupid question but you always see pictures of them being used with the bar sticking straight out, and never out the side, so I wonder if it would even be rigid enough to give you a clean cut like that. In this case I'm trying to figure out the easiest way that I have to open up a large, center bore in an aluminum piece to 4.774
Yes you are correct. The normal way you see the boring bar mounted in the head is to have it inserted into the center bottom hole.
Here I have a bar in 3 of the 4 holes to show how they mount.

http://i12.photobucket.com/albums/a214/piniongear/Bridgeport%20Milling%20Machine%20Photos/DBL-203Dwith3barsLarge.jpg

The pic above has a boring bar stuck into the different holes you can use to bore a hole. For demo only please. Only one boring bar is used at a time.

This will get you a hole somewhere close to 1-1/2 inches diameter, depending on the head. You can move the boring bar to the hole on the outside (still a vertical mount) to obtain a larger diameter hole.

Then if you need a really large hole, remove the boring bar and install it in the horizontal hole. This is where you get your 5 to 6 inch diameter holes from.........pg

interrupted_cut
02-03-2009, 05:56 PM
Don't you end up with the cutter facing the wrong way when you put it in the side hole? I've done this, and run the mill in reverse to make the cut, but that was (just) before I found out that the arbor was held to the boring head with a righthand thread. Are there commonly available boring bars with "lefthand" cutting edges?

Bill Pace
02-03-2009, 06:04 PM
Don't you end up with the cutter facing the wrong way when you put it in the side hole? I've done this, and run the mill in reverse to make the cut, but that was (just) before I found out that the arbor was held to the boring head with a righthand thread. Are there commonly available boring bars with "lefthand" cutting edges?


Heh, Thats what I ran into also.....

SGW
02-03-2009, 06:11 PM
The one time I had occasion to use the side hole, I made a "left-hand" boring bar by silver soldering a chunk of carbide to a piece of 1/2" drill rod.

Silverback
02-03-2009, 06:17 PM
huh... now you guys have me wondering how my boring head is held onto it's R8 shank. Just when you thought you had your problems solved...

Liger Zero
02-03-2009, 06:22 PM
I know right? Ask one question 30 more come up. :D

JCHannum
02-03-2009, 06:24 PM
Most boring heads are threaded to the shank. Right and left hand boring bars are available, usually in inserted carbide.

The cross hole can be used with a short stub of a cutter ground from a broken or dull end mill with the proper size shank, or a suitable cutter silver solder as SGW suggests.

lane
02-03-2009, 06:25 PM
If it unscrews . You do not have it screwed together tight enough. Once together right it is almost impossible to ever get it apart again.

piniongear
02-03-2009, 07:40 PM
Don't you end up with the cutter facing the wrong way when you put it in the side hole? I've done this, and run the mill in reverse to make the cut, but that was (just) before I found out that the arbor was held to the boring head with a righthand thread. Are there commonly available boring bars with "lefthand" cutting edges? To answer your question regarding left hand/right hand...........
The drawbar is a right hand thread (on a Bridgeport anyway).
What is the purpose of the drawbar?
It is used to draw the R8 end of the boring head up tight into the spindle.
What holds the R8 in place?
The taper of the spindle engaged with the R8 shank is the answer to that one.
The drawbar is not what holds the R8 in place. The taper does.
So, you can run the mill in a clockwise or counterclockwise direction(s) and the drawbar is not going to 'unscrew.'


http://i12.photobucket.com/albums/a214/piniongear/Bridgeport%20Milling%20Machine%20Photos/TwoWeldonFlats.jpg

Moving on to the left hand/right hand regarding the boring bars.......
Take a look at one of your boring bars. See the two Weldon flats on the shaft of each one?
Know what those are for?
The flats are 90 apart and this is how you mount a boring bar to run CW or CCW.
Hope that explains the mystery some to those of you who are not so familiar with boring heads and bars..........pg

Carld
02-03-2009, 07:43 PM
If your running scared of it coming off locktite it on but it takes a heck of a hit to loosen it without the locktite.

I make many of my own boring bars for my boring head. I do have two sets of factory brazed boring bars that I use most the time.

I have used every hole it the boring heads at one time or another. It is a very usefull tool.

JCHannum
02-03-2009, 08:09 PM
To answer your question regarding left hand/right hand...........

I believe the concern is with the mounting of the boring head on the arbor, not the drawbar threads. Most boring heads are threaded for mounting to the various arbors. While they are usually tight, running in reverse can cause them to unscrew with unpleasant results.

Dave Converse
02-03-2009, 08:33 PM
In short, yes it's meant to be used.

I use the horizontal setup quite often to knock out radius's (Radii?) in the 5 + inch range.

And the stupid question is the one that goes unasked.

--meI've used the horizontal hole in my Chi-Com 4" boring head to mount a 1" bar with an HSS cutter..............all to function as a big fly cutter. Worked great in single pass finishing the surface of a table I fabricated for my vertical bandsaw.

Walter
02-03-2009, 08:51 PM
My boring head is a very nice 3 inch Japanese (metric) version (The price was Very right).... Built to accept 18mm shank tooling, so it won't fit standard 3/4 inch bars. I've always made my own and been very happy with them.

I always get a chuckle when I run the boring head on a job, more often than not I get one smart@ss at work that tells me my drill is bent, and two or three that come to look and end up semi mesmerized, almost always followed by "what the H*ll are you building now?" comments *grin*

TriHonu
02-07-2009, 11:28 AM
Here are a couple of tips I have picked up along the way.

1. You can mount a flycutter in your boring bar head in one of the vertical holes to extend the cutting diameter of your boring head. The head continues to spin clockwise and won't unscrew from the shank.

2. For manual mills without power down feed, it is sometimes hard to achieve a good surface finish with single point boring bars. You can mount an end mill in one of the vertical holes in the boring bar head. Insure you have the tip of one flute aligned with the outer cutting radius. The end of the mill will remove the majority of the cut while the side of the mill will clean the edge of the hole like a reamer.