Help, Problem Boring a Hole !!

Sandia

Sandia

Active User
Registered
Maybe you guys can tell me whats going on here. I was boring a hole in 6061 aluminum, the hole is 1.5" in diameter and .500 deep. I was using a new 3/4 boring bar and taking a .030 doc each pass. The problem I was having was each pass I made the cut would not bottom out in the hole. Each successive pass was about .005 shallower than the previous cut. Even though I was bumping up against the carriage stop. Can't figure what was going on.
 
Maybe you are running into the area of the tool that doesn't cut therefore it just rubs or the holder itself is rubbing. Could also be a chip getting in the way.

When I use a end mill to bore a large blind hole I have to feed from the center out to the ID of the hole to clean the bottom up to get it flush very once and a while, otherwise the same thing happens.
Pierre
 
Make sure your boring bar holder is nice and tight. The force of the cut would tend to push it in to the holder reducing its reach. Also check how tight your toolpost is.
 
Sounds like a tool clearance problem. What style tip did you use? The angle of the grind is not allowing you to hit the inside corners. Common problem. Also, are you cutting down the length of the hole or are you cutting from the center outward and working your way back? Many ways to skin the cat.

Also, 30 thou DoC is a bit deep even for aluminum with a boring bar. Might want to knock that down to around 15 or 20. -That's not the cause of your problem though.

Ray
 
Depending on the machine, even 0.100 per side may not be excessive. I regularly take that much, and more. We don't know enough. The OP didn't give information about his machine. Nor how much bar is hanging out, what type of insert, if an inserted bar, or what style of grind if a brazed bar or HSS tool in a holder. A picture is worth a thousand words.

Does seem likely to be a clearance issue. When it hits the travel stop, are you sure it's actually on the stop, or just stopped cutting? You might check the compound locks if you have them. If they are loose, and the compound screw has backlash and it is not taken up in the right direction it could allow the compound to work its way back. Depending on the angle, this will effect the diameter you are cutting as well.
 
Something is moving. Either your workpiece is not gripped tightly enough, the bar is sliding in the holder or the tool post is rotating, but something is moving even on that light of a cut. Like Tony said, a pic would help.

Tom
 
Ditto on the more info. .030 is a light cut. Also ditto to Tom, something is definitely moving somewhere.

"Billy G"
 
Tony Wells said:
Depending on the machine, even 0.100 per side may not be excessive. I regularly take that much, and more. We don't know enough. The OP didn't give information about his machine. Nor how much bar is hanging out, what type of insert, if an inserted bar, or what style of grind if a brazed bar or HSS tool in a holder. A picture is worth a thousand words.

Does seem likely to be a clearance issue. When it hits the travel stop, are you sure it's actually on the stop, or just stopped cutting? You might check the compound locks if you have them. If they are loose, and the compound screw has backlash and it is not taken up in the right direction it could allow the compound to work its way back. Depending on the angle, this will effect the diameter you are cutting as well.
Click to expand...

Thanks for the replies fellows. Tony here are a few pics, maybe you can see something I don't. I know nothing was loose on the setup.

DSC_0112.JPG DSC_0119.JPG DSC_0115.JPG
 
That type of boring bar has a taper on the leading edge. It is going to leave steps on each pass. You have to clean that up when done.
 
You must log in or register to reply here.
Back
Top