Horizontal Boring

[blockmanjohn]

Hi, I have a Uni-Vertical mill with a Bridgeport type H head on it. I need to bore a 2" hole in an engine casting but it is too long to mount vertically in my mill. It is also too large and irregular to safely mount in my lathe.

The head on my mill rotates 90 degrees and I was thinking of doing the boring horizontally. I have a boring bar holder for my mill, but I was wondering if there were any things I would need to pay special attention to for this operation. I have never tried this before, and I want to be sure to do it safely and effectively.

Thanks, John.

 

[john_reese]

Once you have the mill trammed so the bar is parallel with the table it should work fine.

 

[kvom]

I would try it on some scrap material first. In addition you might look for a 2" adjustable reamer once you've bored it close, esp. if you don't like the finish or accuracy you're getting. Esp. check for taper.

 

[Blogwitch]

I too have something very similar to a Bridgeport and I am sure if you can get the piece part up in the air for about 6", you should be able to carry out the method you suggest.Maybe you could make a pair of holding cradles out of wood..

I am lucky in that I have a 90 degree head for my mill, plus a boring head that will take a 1" diameter, 12" long boring bar.

There are many ways to part a feline from it's coat.

John

 

[blockmanjohn]

Thanks for the great advice. I was hoping there would be no problems with doing this.

Exactly right. I will have to lift the work about 6" and I never considered wood for the build up. That's the way I'm going to go.

One other thing. I have a 3 axis magnetic DRO on my mill. The controller will calculate and index bolt hole circles in the X-Y plane.

I need to layout and drill a bolt hole circle on a vertical axis of the work. Can I just switch the X for the Z plug at the controller to achieve this?

Just hoping some one else has done something like this.

Thanks, John.

 

[Blogwitch]

John,

As I said, I too have a problem with a large cast iron cylinder, and I was going to use a couple of bored wooden stands for it to sit on while it was bored to size.

This is the cylinder (the rule is 7"+ long) and a 12" x 1" boring bar (to reduce cutting flex) would be used.in the boring head.

Great minds think alike.

John

 

[Wizard69]

Thanks for the great advice. I was hoping there would be no problems with doing this.

Exactly right. I will have to lift the work about 6" and I never considered wood for the build up. That's the way I'm going to go.

The problem would be in getting the casting setup accurately enough and to the degree required by the engines design. The use of wood may or may not help here. It really depends upon how accurately the bore must be made with respect to other datums.

One other thing. I have a 3 axis magnetic DRO on my mill. The controller will calculate and index bolt hole circles in the X-Y plane.

I need to layout and drill a bolt hole circle on a vertical axis of the work. Can I just switch the X for the Z plug at the controller to achieve this?

Interesting idea which may or may not work. It likely would be far easier to just calculate the bolt hole positions and move to the required locations. With a 3 axis DRO this should be a snap.

Try searching for bolt hole calculators on the net if you don't want to do it by hand. Little Machine Shop has one http://littlemachineshop.com/mobile/bolt_circle.php but there are many others online. Programs that work in excel or other spread sheets can often generate coordinate tables that make it dead simple in conjunction with a DRO.

Just hoping some one else has done something like this.

Thanks, John.

I haven't done boring as you describe but have seen plenty of examples on the web. Do your setup right and you should be good. The biggest problem is that you will not have a smooth feed unless you have some sort of drive attached to the axis. As KVOM alluded to above you may want to have a reamer available if this is needs to be a high quality surface.

 

[bazmak]

I dont think i would use timber for any accurate machining.I would look at
fabricating a a cradle from steel scrap.Cheap and nasty but less
chance of flex thru compression.Only my thoughts

 

[Blogwitch]

Bored or shaped wooden holders are standard practice when holding castings on the saddle of a lathe for line boring, there is no difference in using the same technique on a mill. I have a large amount of red oak that I used to use for such jobs and never had any problems.

Once you have done your boring, it is then a simple exercise to accurately mount up on the lathe (using centred wooden plugs each end of the bore) to skim up the outside.


John

 

[john_reese]

Another option on a turret mill is to fixture the work off the edge of the machine table. With part of the work held below the table you may have enough headroom to bore with the spindle vertical. The fixturing can get complicated,

Blogwitch comment about boring in the lathe is worth considering. It allows you to use a bar supported on the outboard end by a center. That is a real advantage on long bores. Unfortunately many lathes do not have a means of fastening work to the saddle or cross slide,

 

[blockmanjohn]

I just got off the phone with DroPros. They supplied the 3-axis mill kit that I installed. They said it would be no problem to switch the x or y axis plug with the z axis plug, in the back of the controller, to be able to lay out vertical bolt hole circles. Just for what it's worth. John.

 

[deverett]

As a follow on from John Reese's suggestion of between centre boring in the lathe, here is my solution.
I have a Harrison M300 that does not have a tee-slotted cross slide. It has half dovetails down each side to secure attachments so I used these to secure a home made auxiliary boring table. Instead of tee slots in the steel, I drilled/tapped a series of holes in convenient places. Ideal for holding castings.


Dave
The Emerald Isle