Parting tool trouble

[Bustednuklz]

Thanks for all of the input. Many new things to try.
Nothing broken on the lathe, just had to restart it
I thought about flex, and even tried with a live centre as an experiment. Still chattered.
I had no intention of cutting all the way through with the centre, but thought it was worth a try.
I will check the cutter for taper, and make sure that it is square.
Never really had a chance to see if the lathe was slowing down, it shut down all together.
I will make sure that the carriage is locked.
Thanks again for all the advise
I will post my progress
Steve

[wrustle]

Steve,

Nothing can be more frustrating than trying to get a parting tool to cutoff properly when first learning how to do it.

I do not know your level of machining experience so I apologize in advance if I am insulting your intelligence.

Here's a drop dead simple trick I have always used for setting the height of my cutoff tools in a manual lathe.

Again, I do not know what lathe you're using but the principle still applies to most I would imagine.

The first thing you need to do is make sure your tool post is square to the chuck. I always held a 1-2-3 block against the face of the chuck and brought the tool post up against the end of the block. Be sure the tool post is loose enough to swivel without being overly sloppy. With the tool post brought to bear against the block, you should be able to hold the tool post there with your finger pinning the 1-2-3 block against the chuck and snug up the tool post nut. Bring the carriage away from the block and finish tightening the tool post.

Now put in a face off tool and with any piece of stock in the chuck, face to clean and be sure there is no tit left on the face. If so adjust the height of your facing tool and face again.

Once you have established your facing tool to be on center, turn the spindle off. With your face tool away from the face move the crossslide in so the tip is near the center of the piece, then with the carriage bring the tool tip in so it just touches the face. Again.....spindle off!

Now with the tool against the face, turn the crossslide out to drag a line across the face of the piece. It only needs to be about a quarter to three eighths of an inch.

Move the tool away from the face with the carriage, and replace the facing tool with the cutoff tool.

Now bring the cutoff tool with the carriage and cross slide so the tip is close enough to your drag line to compare the height. You should adjust it so it is either right on the center to just a tad below (not even the thickness of the drag line) and now you should be all set.

This might sound very complicated at first, but once you know the method, it can be done in less than a minute and with great results.

Also realize depending on the type of cutoff holder you have, you may need to do this everytime you change the length of the tool sticking out of the holder if it's at an angle.

On that note, also only have as much of the cutoff tool sticking out as you would need to part off the piece. Parting off a 1" Dia. piece? Stick the tool out no more .562". Keep your tool as rigid as possible!

Wait.....did I really just say that..............

Best Regards,
Russ

[Mayhem]

That is a great tip on setting the tool hight Wruss - I'll have to try that,

[Highpower]

(04-05-2013, 07:54 PM)Bustednuklz Wrote: Good day to all
I am having a chatter problem while trying to use my parting tool (cut off tool) on a mini lathe. It is a 7x10 lathe.

Steve, also check the retaining plates on the saddle (that ride on the underside of the bed ways) for looseness or cracks around the screw holes. They are often made of cast iron and are known to crack, allowing vertical movement between the bed and the saddle. If you grab the saddle and rock it fore and aft on the bed, can you feel any play?

Saddle strips

Been there done that. I made new plates from mild steel and did away with the "adjusting" screws. I just shimmed them so that there is minimal clearance. (.0005" - .001")

[Bustednuklz]

Thanks for all of the advise here.
Thanks Wrustle for the step by step instructions. You by NO means insulted my intelligence.
I think that I on the right track but had 3 things that needed 'fine tuning'
1. tool was almost square when i was trying it, but I had not taken the time to make sure that it was square.
2. I had the cutter to far out of the holder and probably allowed for flex and chatter
3. Feed speed was way to slow. started cutting and then just give it the beans.....presto

Now if the cops show up, they are going to think that I am making slugs to rip off the vending machine, since there are so many little quarter sized discs in the shop (Do vending machines even take quarters any more??)

Highpower.. thanks for the link- lots of great ideas

Now the big question...........How to remember this the next time I run into this?
More reason to practice!!
Thanks to all
Steve

[Mayhem]

Glad you were able to sort out your problems.

[DaveH]

Always good when things work out

DaveH

[DaveH]

Steve,
Oh, by the way those disc's can make fine washers.

DaveH

[Ozwelder]

Hi,
I have taught my seniors (well most of them)at high school to part off with HSS, without too many dramas.If they were able to manage this ,it should not be a problem for most once the basics are used and confidence is gained.

The following should help.

1. Ensure job is held securely in chuck jaws with a minimum of overhang. Don’t use your live centre ,it’s a recipe for an accident.

2. Ensure tool is sharp, square to work and is at center height (or very slightly below).
With cutting edge slightly below, there is a tendency for the tool to flex away from the
work reducing damage of “dig in” if it occurs.

3. Ensure top slide is retracted so there is a minimum of overhang.

4. Move tool into position with saddle and then lock to bed.

5. Set speed. Say 83 ft minute for your aluminium.
If chatter is experienced, feed rate should be slightly increased and not a slower speed selected. It takes a while to develop confidence but a constant feed provides best results. I hand feed because I can feel the load against the cross slide wheel. I parted off a 1 5/8" washer in 316 S Steel tonite, using a hand feed, with no problems .If big lazy C shaped curls are coming off,you are on the track.

6. Lubrication. If fitted, coolant is set to flow in order to float the swarf away from the cut but if not available, use a small brush (or old toothbrush) and plenty of lathe cutting oil. WD 40 works ok on aluminium as does kerosene.

7. When parting off large diameters, take side by side cuts in initial stages to increase clearance and reduce possibility of swarf jamming in the cut and causing damage to the job or tool.

8.Can’t peak for carbide as I have not used it, but HSS works well for me. Its ground on the front for clearance.Sometimes a tiny dip ground in the top behind the cutting edge works well as a chip breaker.If you have a Dremel tool ,do it with that.

I hope it helps you

Ozwelder