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Boring Bar Tool Set Up...?
- Thread starter EmilioG
- Start date
- Joined
- Dec 20, 2012
- Messages
- 9,422
Nothing wrong with an inserted tip boring bar, provided it is made for use in a boring head. Most boring tool makers have these. If you have it then use it. Heck, even the cheap Chinese brazed carbide bars will work fine for this job.
You have align the face of the bar with the spindle centerline if you want the adjuster on the head to read correctly. That way, any adjustment you make will put the cutting tip at the outside of the cut, like this:
Speeds are harder to suggest because it depends on the hole size, bar size, extension, depth of cut, etc. I usually start at about half the usual turning speed and for this project I would start at about 700 rpm or so. Then adjust up or down based on results. When the bar cuts well there will be little resistance to feed, the finish will be good and there will be a slight hiss when the bar cuts well. Keep in mind that the bigger the hole, the greater the centrifugal force and vibration becomes an issue at higher speeds. If the machine starts to vibrate, lower your speed.
Keep in mind that increasing rpm will increase the centrifugal force at the tip. Increasing speed for the same depth of cut will result in a deeper cut. Okay, that's confusing. Say you've found that a 0.020" depth of cut at 1000 rpm works for you. On the finish pass, say you have just 0.020" left to go. If you just dialed in the 0.020" cut and made the pass at the same speed the bore will probably come in on size. If you decided to increase speed to improve your finish, however, and went up to 1300 rpm then that same depth of cut will take you well over size. This is why it is best to find the best combination of depth of cut and speed that produces an adequate finish during the roughing phase of the process. Once you have it then you can proceed to bore at those settings.
On the other hand, it can be useful if you are a small amount under final size. If you made your finish pass but are still a tiny bit undersize you can increase rpm 50-100 rpm for another pass without changing the depth of cut setting and if you're lucky you will hit the bore dead on. I do this all the time but I admit it depends on the phase of the moon and wind direction more than anything else. In other words, luck, plus having done this many times before.
Whenever you're boring with a new setup or a bar you haven't used before it is a good idea to rough small so you have enough material to find a combination of speed, feed and depth of cut that produces a cut that is predictable. Then you can use that information to come in on size. Boring, be it on the lathe or mill, is not about hogging. It is more about finding the right cutting conditions that give you predictable cuts so you can plan an approach to final size. In other words, boring is a planned approach to a precision result.
The best idea is to practice on scrap until you figure out your speeds and depths of cut. None of this is hard and once you see how it works you'll wonder what all the fuss was about.
You have align the face of the bar with the spindle centerline if you want the adjuster on the head to read correctly. That way, any adjustment you make will put the cutting tip at the outside of the cut, like this:
Speeds are harder to suggest because it depends on the hole size, bar size, extension, depth of cut, etc. I usually start at about half the usual turning speed and for this project I would start at about 700 rpm or so. Then adjust up or down based on results. When the bar cuts well there will be little resistance to feed, the finish will be good and there will be a slight hiss when the bar cuts well. Keep in mind that the bigger the hole, the greater the centrifugal force and vibration becomes an issue at higher speeds. If the machine starts to vibrate, lower your speed.
Keep in mind that increasing rpm will increase the centrifugal force at the tip. Increasing speed for the same depth of cut will result in a deeper cut. Okay, that's confusing. Say you've found that a 0.020" depth of cut at 1000 rpm works for you. On the finish pass, say you have just 0.020" left to go. If you just dialed in the 0.020" cut and made the pass at the same speed the bore will probably come in on size. If you decided to increase speed to improve your finish, however, and went up to 1300 rpm then that same depth of cut will take you well over size. This is why it is best to find the best combination of depth of cut and speed that produces an adequate finish during the roughing phase of the process. Once you have it then you can proceed to bore at those settings.
On the other hand, it can be useful if you are a small amount under final size. If you made your finish pass but are still a tiny bit undersize you can increase rpm 50-100 rpm for another pass without changing the depth of cut setting and if you're lucky you will hit the bore dead on. I do this all the time but I admit it depends on the phase of the moon and wind direction more than anything else. In other words, luck, plus having done this many times before.
Whenever you're boring with a new setup or a bar you haven't used before it is a good idea to rough small so you have enough material to find a combination of speed, feed and depth of cut that produces a cut that is predictable. Then you can use that information to come in on size. Boring, be it on the lathe or mill, is not about hogging. It is more about finding the right cutting conditions that give you predictable cuts so you can plan an approach to final size. In other words, boring is a planned approach to a precision result.
The best idea is to practice on scrap until you figure out your speeds and depths of cut. None of this is hard and once you see how it works you'll wonder what all the fuss was about.
- Joined
- Jul 20, 2014
- Messages
- 1,386
Thank you. I totally get.
Thank you for taking the time to write all of that for us. One last question before I take the plunge, ha ha.
Would the use of a dial indicator be better than the dial on the head?
If I had a Narex or Wolhaupter, no problems, but I'm using an old APT.
Hell, I'd be so happy with a Criterion DBL 202.
I'll report back soon. First, I'm taking the APT apart to clean and oil.
Anyone here own an APT boring head?
Thanks so much Mikey. You're the best.
Thank you for taking the time to write all of that for us. One last question before I take the plunge, ha ha.
Would the use of a dial indicator be better than the dial on the head?
If I had a Narex or Wolhaupter, no problems, but I'm using an old APT.
Hell, I'd be so happy with a Criterion DBL 202.
I'll report back soon. First, I'm taking the APT apart to clean and oil.
Anyone here own an APT boring head?
Thanks so much Mikey. You're the best.