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parting
- Thread starter geraldsd
- Start date
- Joined
- Mar 10, 2013
- Messages
- 324
Hi ,
I am new too.
When I was parting a part on Sunday I had to re think my set up by asking myself and just going over the basics in my head.
1) is your parting cutter sharp?
2) is it at the correct cutting height for your part ?
3) are you using any or the best type of cutting oil or lube?
4) best rpm for aluminum ?
After re thinking things I got it working nicely.
I had to sharpen my cutter and found I was using the wrong oil.
(WD-40 works great for Aluminum)
I am new too.
When I was parting a part on Sunday I had to re think my set up by asking myself and just going over the basics in my head.
1) is your parting cutter sharp?
2) is it at the correct cutting height for your part ?
3) are you using any or the best type of cutting oil or lube?
4) best rpm for aluminum ?
After re thinking things I got it working nicely.
I had to sharpen my cutter and found I was using the wrong oil.
(WD-40 works great for Aluminum)
- Joined
- Nov 16, 2012
- Messages
- 5,596
Hi. Good luck with everything and don't forget to post a few pics when you're all done...
Here's a thread with parting information. I happen to like post #14 myself
http://www.hobby-machinist.com/showthread.php/13207-Parting-off-question?highlight=parting
Here's a thread with parting information. I happen to like post #14 myself
http://www.hobby-machinist.com/showthread.php/13207-Parting-off-question?highlight=partingI am parting mild steel. I sharpened the cutter first. The cutter is slightly below the center line. It is also square. I am using oil. I Have a SB 9A and am turning at the slow setting. I had some Remoil (remington gun oil that I was using while cutting.
You are correct...it is an excellent thread. Need to get that band saw that I want...
Hi. Good luck with everything and don't forget to post a few pics when you're all done...
Here's a thread with parting information. I happen to like post #14 myself
Double check the tool height. I was taught to use a six inch pocket rule. Put the rule between the tool and part. With the motor off close the gap until the rule is pressed between the tool and part. If the rule is straight up and down then your tool is at the correct height. Also I never let the parting tool blade extend to far either. About a half inch longer then the radius of the part is enough.
A little tip if your part has a hole drilled in the center I use a small diameter bar stock chucked in the tail-stock drill chuck. Insert the bar stock inside the hole until it is deep enough to caught the part when it is cut off. Saves diving in the shavings searching for it. Good luck
I am having a problem adjusting my tool the slight amount up to make the center line. I guess that I really need to take some photos. I saw a youtube video describing the technique that you just described. You did a very good job btw...
- Joined
- Dec 17, 2012
- Messages
- 630
Parting should be a pleasure. If you have things set up well, it should be a non issue. I regularly part 2 in. steel on my lathe and I don't have near the lathe you have. (I have a little 7x14 mini-lathe.)
Tool height is important but not really directly a cause of chatter. If it is too high, you will ride the relief on the bottom of the cutter and just rub instead of cut. Too low and you will part but leave it connected in the middle with a little stem.
The most important thing is everything must be rigid. Chatter is vibration. If it can't vibrate, it can't chatter. Lock down anything you can.
Make sure that your tool is exactly perpendicular (square) to the work piece.
Make sure that your tool is vertical in the holder and not slanted.
Make sure that your tool is sharp.
Make sure that you only have as much parting tool exposed as you need. If it isn't extended, it can't flex. When parting larger pieces, I extend the blade about 1/2 in. and cut to depth, stop, pull out and extend the blade another 1/2 in. (or even less if it is tough steel) and repeat until I get all the way through.
You need even light, even pressure. Feed too fast and the cutter will dig in and flex and possibly even break. Push too hard and you will flex the blade and it will begin to vibrate and bounce around in the slit from that as well. Too slow and it will just rub and get hot. The chips should just peel off the work like peeling an apple. Just let the cutter do the work like using a hacksaw.
Sometimes you will just hit some harmonic and it will vibrate no matter what you do. In that case, change the speed. Faster or slower doesn't really matter. Just the change is important.
Be generous with the lube. Lube always makes things work better in every circumstance. It doesn't matter what it is really. There is no material left when you are done to worry about finish. I just use whatever is handy. Oil, WD40, threading lube, motor oil.
Don't let chips build up and go on the sides of the cutter. Keep it cleaned out.
Things that are nice:
Use as thin of a tool as you can. Use as tall of a tool as you can. If it can't touch, it can't rub. A tool that is narrower at the bottom will have less friction. If you are grinding your own, you can also make the tip wider than the body of the blade. You can make a V in the tip to have the chips curl into the center. You can also angle the cutting edge a little. If the right side is a little longer, the off cut will be severed first and not leave a little nipple on it. Then the left side will clean off the spindle side. Just a tiny bit is all that is needed. Do it too much and it will try to cut at an angle. That is not good. Only a degree or so is enough.
Tool height is important but not really directly a cause of chatter. If it is too high, you will ride the relief on the bottom of the cutter and just rub instead of cut. Too low and you will part but leave it connected in the middle with a little stem.
The most important thing is everything must be rigid. Chatter is vibration. If it can't vibrate, it can't chatter. Lock down anything you can.
Make sure that your tool is exactly perpendicular (square) to the work piece.
Make sure that your tool is vertical in the holder and not slanted.
Make sure that your tool is sharp.
Make sure that you only have as much parting tool exposed as you need. If it isn't extended, it can't flex. When parting larger pieces, I extend the blade about 1/2 in. and cut to depth, stop, pull out and extend the blade another 1/2 in. (or even less if it is tough steel) and repeat until I get all the way through.
You need even light, even pressure. Feed too fast and the cutter will dig in and flex and possibly even break. Push too hard and you will flex the blade and it will begin to vibrate and bounce around in the slit from that as well. Too slow and it will just rub and get hot. The chips should just peel off the work like peeling an apple. Just let the cutter do the work like using a hacksaw.
Sometimes you will just hit some harmonic and it will vibrate no matter what you do. In that case, change the speed. Faster or slower doesn't really matter. Just the change is important.
Be generous with the lube. Lube always makes things work better in every circumstance. It doesn't matter what it is really. There is no material left when you are done to worry about finish. I just use whatever is handy. Oil, WD40, threading lube, motor oil.
Don't let chips build up and go on the sides of the cutter. Keep it cleaned out.
Things that are nice:
Use as thin of a tool as you can. Use as tall of a tool as you can. If it can't touch, it can't rub. A tool that is narrower at the bottom will have less friction. If you are grinding your own, you can also make the tip wider than the body of the blade. You can make a V in the tip to have the chips curl into the center. You can also angle the cutting edge a little. If the right side is a little longer, the off cut will be severed first and not leave a little nipple on it. Then the left side will clean off the spindle side. Just a tiny bit is all that is needed. Do it too much and it will try to cut at an angle. That is not good. Only a degree or so is enough.
I want to echo what David wrote. I was having a terrible time parting on my 7x12 mini lathe, and frustrated by tool chatter in general. Then, I added and started using a carriage lock. What a difference! Like night and day. Suddenly the problems with chatter and the tool grabbing improved dramatically. Then I did the extended travel mod to the cross slide and in the process changed the leadscrew nut to a spring-loaded anti-backlash nut. And presto, another very nice improvement in all operations. The most recent mod was to change the spindle bearings to tapered roller bearings, and one again (yes, you guessed it) an improvement in everything. The project I keep putting off is to improve the fit of the carriage, and now I expect another improvement in performance. It's nice when the improvements from each of these steps is immediate and significant. All have improved rigidity, and as David said, rigidity really is everything.
bix
When I read about locking the carriage it made a lot of sense to me as well. I have a lot to learn, but that did make sense. My South Bend was made in 1952, and it had the original belt on it. I broke that belt and have ordered another one. I did play around with the parting tool rotating the chuck with the parting tool against the piece. With very minute adjustments I could make the chuck feel totally different. I actually could cut quite a bit. I will approach things differently when I get her cranked back up...