PDA

View Full Version : Boring Head/Bar Question



texjames
06-29-2011, 10:42 PM
I am still learning and want to use this borite boring bar in my boring head to open up some holes.It don't have the flat like the other bars i have to index it with the set screw.Whats the trick on bars without a flat? Thanks
http://i113.photobucket.com/albums/n225/texjames/1e0d4944.jpg

TGTool
06-29-2011, 11:29 PM
The trick is to lay a scale across the flat formed by the cutting edge or insert and rotate to make sure that the scale is parallel to the sides of the boring bar. Since your insert has positive rake built in and probably a little side clearance this should work. If the side clearance in a small hole is insufficient and the heel of the insert drags on the side of the hole you'll have to rotate slightly in the direction for a negative top rake and you'll still be alright. If you were using a HSS boring bar, you could rotate just a little in the forward direction to create a little positive rake but you can't do much before running into clearance problems. The parallel positioning is probably your best bet.

Carld
06-29-2011, 11:45 PM
I will add, stick the bar in the hole of choice and then back it out about 1/8" because sometimes it interferes with the motion of the head adjustment.

texjames
06-30-2011, 12:26 AM
Thanks TG can ya explain the "scale" a little more i don't think i'm following on that part.Sorry i'm so dense.Waiting til 60 years old to learn how to use a Milling Machine.Been wanting to do this a long long time.

DATo
06-30-2011, 04:10 AM
Don't mean to butt in but I think what TGTool is saying is that if you lay a scale (or any other flat thing) along the flat side of the insert while it is loosely held in the boring head the long side of the scale will visibly amplify the amount of error. So, for example, if you hold the 1" section of a 6" scale against the flat of the insert and look at the boring head's dial the 6" end of the scale will be pointing either to the left or right. When you've adjusted the tool to the point that the scale is pointing directly at you it will mean that the insert is inline with the centerline of the boring head. It is not necessary that the insert be PERFECTLY set. If you can get reasonably close "by eye" it will cut just fine.

Toolguy
06-30-2011, 10:05 AM
Non machinist types usually think of a scale as something to measure weights. What we call a 6" scale, they call a 6" ruler. I don't know if that is the case here, but I have run across this on occasion.

texjames
06-30-2011, 11:04 AM
Non machinist types usually think of a scale as something to measure weights. What we call a 6" scale, they call a 6" ruler. I don't know if that is the case here, but I have run across this on occasion.
OK thanks.Thats what was throwing me.I looked in all my reference books for
"Scale"...Machinerys handbook, Machine Shop Trade Secrets, Machine Shop Basics,and Machine Shop Essential Q&A and could not find anything on "Scale".I was pretty sure it might be a steel rule but not sure.
So steel rule, machinist square, or a short parallell just to get the cutter close
should do the trick.Thanks for all the input and helping a newbie out you guys. :)

TGTool
06-30-2011, 05:35 PM
Yes, sorry, some folks would call it a rule. It can be any straightedge as noted but many machinists carry a 6" scale (ruler) in a pocket for quick checks so it's always the first thing I reach for.

This is a picture showing the rule lined up so it can be compared with the flat sides of the boring head. It's easy to tell parallelism or not. In this case the tool is set for a slight positive rake as shown by the larger gap on the left than the right.

http://i48.photobucket.com/albums/f244/TGTool/P1010408.jpg

texjames
07-01-2011, 06:08 PM
First time boring a hole in a VW engine case.Turned out great.
Took all morning to bore the holes through the blocks the case is setting on.Those are bolted down to the table with T-slots.My center tool holder for my dial indicator did not work i got to rethink that.That magnesium cuts pretty huh?
http://i113.photobucket.com/albums/n225/texjames/4f0f69ca.jpg
http://i113.photobucket.com/albums/n225/texjames/82df1f57.jpg
http://i113.photobucket.com/albums/n225/texjames/7f239556.jpg

Bmyers
07-01-2011, 06:25 PM
That magnesium cuts pretty huh?

Looks good and the chips are fun to burn

tdmidget
07-01-2011, 08:28 PM
Yes, sorry, some folks would call it a rule. It can be any straightedge as noted but many machinists carry a 6" scale (ruler) in a pocket for quick checks so it's always the first thing I reach for.

This is a picture showing the rule lined up so it can be compared with the flat sides of the boring head. It's easy to tell parallelism or not. In this case the tool is set for a slight positive rake as shown by the larger gap on the left than the right.

http://i48.photobucket.com/albums/f244/TGTool/P1010408.jpg
A machinist calls it a rule. A scale is that triangular device that is used to convert one system to another or to "scale" a measurement up or down, most often in drafting, now done with a couple of keystrokes.
When in doubt, check your Starrett catalog.