Parting tool chatter

[SmithDoor]

Here photos I found
Show the higher angle

Dave

 

[SmithDoor]

OK. A36 is listed as structural steel, so I would expect it to be ugly to part-off. And DOM tubing has a welded seem. I haven't tried parting it, but I imagine the weld would provide an interruption to the cut, being harder than the rest of the tube. I can see that introducing chatter.

They both fun cut .
I have Manufacturer door and crane wheels 26" diameter x 6" wide using A36, plunge cut for double flanges.

Dave

PS: I still have a full package of carbide inserts for plunge cutters that did not work.
I first cut the outside face with carbide. Then plunge with hand sharpen HHS tool bit.

 

[SmithDoor]

Website for books on old machine tools
http://vintagemachinery.org/mfgindex/detail.aspx?id=2185&tab=3
Dave

 

[justisla]

I have just been through this thread & cannot see anyone mentioning making 2 cuts.
I have had a very elasticated Warco 240 MV from new. (My Drummond M seemed more rigid.) One can watch the cutter dipping visually millimetres, not thous. I cannot run a low revs because the variable speed motor will constantly stop. That happens even for simple turning operations. That can make parting off an "interesting" activity to say the least.

If the metal removed can help cause a cutter to jam- & I believe it can- then making a second cut to increase space for the chips to clear makes sense, does it not?
I have found that I do better if I cut to a depth where I feel things getting tight when hand feeding (that is really a mixture of, nerves, feel, revs dropping & tool dipping) I withdraw the cutter, move over a cutter width, go in again but deeper. I can usually do this fairly fast & confidently, because the chips are clearing quickly. Then go back to the first cut again cutting deeper. Alternating, until finished, or giving up & resorting to the hacksaw.
Seems to work for me- most of the time that is

 

[Steamchick]

Stiffness in the lathe is everything under heavy tool loads like parting-off. I have had various small lathes, fro a 1960s right-hand thread lathe with 3 in swing (my Grandfather's), and Unimat from 1960s to my current Chinese 6 in swing. None of these small tools work like big stiff lathes for parti -off. On a single piece of steel I have had 3 cuts consecutively where the part "worked Ok", next dug -in and next was best and fastest feed rate. The "worked Ok" cut was at a slower feed speed (by hand), because the workpiece was projecting more from the chuck, the next final was Ok when I figured a feed-rate that worked, and the last was close to the chuck.
I feel that the last time I sharpened my tungsten a carbide tool I must have got the grinding "just right" as it is set on a back tool post. My notion is that as the cuts were on different projections from the chuck that affected the total stiffness of the lathe and the bad cut was at a point where something was resonating at that stiffness. THe other cuts at different system stiffnesses didn't hit the resonance and therefore cut Ok.
Certainly, there is always a sweet-spot for feed rate , part rotational speed, etc. And the lathe bed stiffness is the thing you can't change. On smaller lathes I have seen the bed twist under dig-in loads, and this will happen on any lathe if you can get a high enough load. All the advice about tool rake, sharpness, finish, feed rate being higher, etc. is valuable as all these factors contribute to dig-in and chatter. But there are limits on every lathe and set-up where too high a feed will dig-in, and if you have any significant play you will get chatter. I suspect the initiator for resonance is the torque variation (quite a high frequency) from the poles of the motor, or belt drive resonance, or something relating to a ripple on the rotational speed. This excites resonant frequency or harmonic based on the stiffness of the whole lathe. Once initiated the resonance causes a ripple on to pressure which in turn causes momentary dig and release.... This then accelerates into chatter. CHANGE SOMETHING to change the stiffness and the chatter seems to magically dissapear. But what to change can be any of these various factors that make it work. It is a bit of a black at for the less experienced (I.E. me!).
Thanks for you advice - it has helped me.
Discuss.
Ken

 

[SmithDoor]

Stiffness in the lathe is everything under heavy tool loads like parting-off. I have had various small lathes, fro a 1960s right-hand thread lathe with 3 in swing (my Grandfather's), and Unimat from 1960s to my current Chinese 6 in swing. None of these small tools work like big stiff lathes for parti -off. On a single piece of steel I have had 3 cuts consecutively where the part "worked Ok", next dug -in and next was best and fastest feed rate. The "worked Ok" cut was at a slower feed speed (by hand), because the workpiece was projecting more from the chuck, the next final was Ok when I figured a feed-rate that worked, and the last was close to the chuck.
I feel that the last time I sharpened my tungsten a carbide tool I must have got the grinding "just right" as it is set on a back tool post. My notion is that as the cuts were on different projections from the chuck that affected the total stiffness of the lathe and the bad cut was at a point where something was resonating at that stiffness. THe other cuts at different system stiffnesses didn't hit the resonance and therefore cut Ok.
Certainly, there is always a sweet-spot for feed rate , part rotational speed, etc. And the lathe bed stiffness is the thing you can't change. On smaller lathes I have seen the bed twist under dig-in loads, and this will happen on any lathe if you can get a high enough load. All the advice about tool rake, sharpness, finish, feed rate being higher, etc. is valuable as all these factors contribute to dig-in and chatter. But there are limits on every lathe and set-up where too high a feed will dig-in, and if you have any significant play you will get chatter. I suspect the initiator for resonance is the torque variation (quite a high frequency) from the poles of the motor, or belt drive resonance, or something relating to a ripple on the rotational speed. This excites resonant frequency or harmonic based on the stiffness of the whole lathe. Once initiated the resonance causes a ripple on to pressure which in turn causes momentary dig and release.... This then accelerates into chatter. CHANGE SOMETHING to change the stiffness and the chatter seems to magically dissapear. But what to change can be any of these various factors that make it work. It is a bit of a black at for the less experienced (I.E. me!).
Thanks for you advice - it has helped me.
Discuss.
Ken

Something just trying different ways.
Mind was broken blade and later reading that was right way.

Biggest thing is to have fun.
I forget that and taken a long time to get back to having fun.
It fun just trying

Good luck
Dave

 

[goldstar31]

.
I feel that the last time I sharpened my tungsten a carbide tool I must have got the grinding "just right" as it

Ken

I'm left guessing about your technique. Vaguely, I am left wondering what thickness is your carbide parting tool and secondly, what or how you are regrinding a carbide parting tool. I think that I shall not be alone in this.

Moi? I'm really a HSS guy but I DO have ability to /access to CBN and diamond stuff too.

Here, in the wilds of sometimes sunny Gosforth and in severe lockdown and shielding, I'm trying too keep a degree of sanity starting on Worden tool grinnder- theoretically to do hss stuff.

Regards


Norman

 

[SmithDoor]

I have use both
Carbide is great for speed and life but it break faster.
Most time I use HSS low cost and does not break as often as carbide.
I can get better finish use HSS tool bits and I grind to shape faster than carbide

When do use carbide I braze carbide to steel for rake and shape I want but for long runs.

Dave

I'm left guessing about your technique. Vaguely, I am left wondering what thickness is your carbide parting tool and secondly, what or how you are regrinding a carbide parting tool. I think that I shall not be alone in this.

Moi? I'm really a HSS guy but I DO have ability to /access to CBN and diamond stuff too.

Here, in the wilds of sometimes sunny Gosforth and in severe lockdown and shielding, I'm trying too keep a degree of sanity starting on Worden tool grinnder- theoretically to do hss stuff.

Regards


Norman

 

[tornitore45]

Talking about carbide for parting...

I saved a 10" carbide tipped saw blade for wood.
I am not inclined to resharpen some 40 teeth but I cut out several 1/2" strips each one with one tooth radially down to the center.

Once sharpened with a diamond stick, they make excellent parting or growing blades.

One plus is that the teeth of wood saws have alternate beveled (set) teeth with a straight raker in between. So you can have a choice of a tool that leaves the "pip" on the chucked part or on the falling off part.

 

[dkwflight]

Hi
You also might do a hone with a diamond stone on the cut off tool. It helped me in one instance.
You also might be able to make a jack to support the toolon your carriage.
Good Luck
Dennis

 

[SmithDoor]

It just finding how too use the cutoff equipment.

Now how about the little tip left after cutoff.

When first just joy of cut is great but do that thousand times with tip leftover

Dave

 

[Ken I]

Mauro, thanks for reminding me to get MAIG and complete an idea from years back - to make a part off tool from a circular saw blade vis :-

I mostly use the 3/32" HSS blade and holder (top right) and was hoping this 2mm wide blade would be better.

For my first attempt, I was deliberately belligerent with the blade (stress test) without coolant - probably overheated and the tip came off.

Test #2 was done with care and coolant - it works but all in all is more trouble than my 2.4mm (3/32") blade.

So I'm going to call it a failure although the occasional job might still pop up where it might be useful.

Next I'm going to make a holder to take the standard 3/32" beveled blade and mount it at 5-7° so I don't have to grind the rake in the top and use the bevel as a chip narrowing device.

Regards, Ken

 

[Bentwings]

I have a mini-lathe with (as explained by someone else) the rigidity of a wet noodle but I can part off quite well with the sharp blade but I use a diamond honing stick as it needs to be sharper than what my grinder can do. Honing all my cutters is essential with this lathe.

When I worked in the shop we had a number of brand new tool room lathes were snugged up the ways it seemed like daily finally the solution was to simply place a large chunk of steel plate on the carriages. I suppose you could say the machines wore out more but loss of production made this a moot point. I rented time at a horrid shop on his old mill. It chattered something terrible so I tightened the gibs as much as practical and set about 100 lbs chunk of steel on the table. Chatter gone. There was a mild confrontation but he was a business man too so we compromised budgets I said I’d clean the mess his helper made when I was done . Saved him half hour wage and it took me a few more minutes to finish the job that I made a couple hour engineering pay. ( very high rate for skilled toolmaker-with eng degree. Ya just gotta know how to bargain.LOL

 

[tornitore45]

Ken I due to the aggressive rake of a wood saw it is best used on aluminum. Aluminum can be cut with wood tool at wood speed. Lacking a metal band saw I use my 10" table saw for aluminum all the times.

I used the recycled carbide wood saw to cut cooling fins in cast Iron because HSS can be a problem with cast Iron

 

[Bentwings]

Mauro, thanks for reminding me to get MAIG and complete an idea from years back - to make a part off tool from a circular saw blade vis :-
View attachment 117440
I mostly use the 3/32" HSS blade and holder (top right) and was hoping this 2mm wide blade would be better.

For my first attempt, I was deliberately belligerent with the blade (stress test) without coolant - probably overheated and the tip came off.

Test #2 was done with care and coolant - it works but all in all is more trouble than my 2.4mm (3/32") blade.

So I'm going to call it a failure although the occasional job might still pop up where it might be useful.

Next I'm going to make a holder to take the standard 3/32" beveled blade and mount it at 5-7° so I don't have to grind the rake in the top and use the bevel as a chip narrowing device.

Regards, Ken

I just saw the picture of the saw blade. In view of the riots here we were discussing over lunch defensive weapons. Even at my age being ex relief baseball pitcher I’d guess I could throw that thing through a 1/4” piece of plywood at 20 feet. Hate to be on the receiving side of that tool. Bedside gun is nice but very difficult to leave in very accessible position. I don’t sleep with leather gloves on but I could present that thing effectively.

 

[Bentwings]

I just saw the picture of the saw blade. In view of the riots here we were discussing over lunch defensive weapons. Even at my age being ex relief baseball pitcher I’d guess I could throw that thing through a 1/4” piece of plywood at 20 feet. Hate to be on the receiving side of that tool. Bedside gun is nice but very difficult to leave in very accessible position. I don’t sleep with leather gloves on but I could present that thing effectively.

Sorry off topic but not off mind these days.

 

[tornitore45]

I like my tool lower than center, so the pip is difficult to avoid. The only choice is on which part you get it. By adding a little front angle one can steer the pip on one side or the other but is hardly worth the trouble.
I like my 0.040" blade and adding a front angle makes it flex and does nor cut straight.

 

[SmithDoor]

Do not worry
This is a good group.
Soon or later it will happen.

Dave

Sorry off topic but not off mind these days.

 

[jack620]

If you're still getting chatter after trying all the tips given here, I recommend making a solid toolpost mount to replace the topslide/compound.

 

[SmithDoor]

Here my cut off blade as the last time it was used.
Note the hook at the end.
Cuts A36 like butter and no chatter

Dave