Parting off vs bandsaw

Parting off is usually faster if you have the tool available and setup (quick-change). Sometimes you can even get a nice usable surface from the part off.

Also, it can be difficult to hold the stock material in the bandsaw because of a large vice and small stock length...

Regards,

Robin

Yesterday I parted off for the first time... That was my question as well

- wouldn't it be easier to just saw it off and then face the part?

As far as I can tell, the advantages would be that you don't need a parting off tool, and it's easier on the nerves (would be for me anyway - does parting off get easier on the nerves the more you do it?).

The disadvantages being difficulty holding some work (as Robin already mentioned) and when you take a workpiece out of the chuck and then put it back in (if you'd be putting it back in the lathe to face it after cutting it - I guess it depends on how precise you have to be) it's hard to get the work to sit exactly the same way in the chuck (or so I've been taught

- is there a quick way to get it in the chuck exactly the same way?)

Sorry for the huge run-on sentence with all those brackets... :)

chem

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-> I am not a machinist, just a student in a pre-apprentice machining course. Any advice, opinions, etc, are taken from my very limited knowledge base and should be treated accordingly.

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I don't think I've ever seen a part go flying after being parted. The curls of chips can hit you though.

However, you're probably not right in front of the cut because of the coolant spraying everywhere anyway. Gets interesting when you get into carbide tools. They're really capable of going fast enough to launch chips rather than just drop them.

So yes, it gets easier.

A standard 3 jaw chuck will never really center the part very well. Newer ones are usually better, but if you want it within something like .0005" you'll need a collet or (even better) an independant 4-jaw.

Regards,

Robin

So how does one hold the piece that's being parted to prevent it from falling and denting itself in the case of something soft like aluminum, or landing on the ways and denting them in the case of something more substantial?

Obviously, I'm another newbie...

Regards,

Peter

I'd say just put something under it to prevent it from hurting itself or others ;-)

You sometimes see people grab parts that are falling off with their hands. I don't think that's very safe, but YMMV. Some CNC lathes have part catchers that extend at the right time and catch the part. You could make yourself something of a net...

To be honest, most people don't have the capability to part off workpieces capable of hurting the machine when they fall off (that would have to be a pretty big part - try getting the stock through the spindle, and good luck with your parting blade).

I find pieces really don't tend to hurt themselves very much. Aluminium and brass will dent, perhaps, but they'll dent anyway from being used and handled.

Certainly not rules, but I've never found it to be an issue.

Regards,

Robin

What I often do is to drill the ID of the part to just past the depth of the parting (assuming that I need to produce a hollow part). Then I chuck a rod in the tailstock chuck (most recently, it was the T-handle of the chuck wrench) and extend that into the hole far enough to catch the part -- ideally not deep enough so the parting tool will hit the rod. I needed to bore these parts out afterwards to make a

1"x12 internal thread, so the fact that I would lose a bit of the centering by re-chucking was no significant problem. I was using hex stock of whatever the size is which will just fit through the spindle when the collet drawbar is out, and using a 6-jaw with adjust-tru feature to hold the workpiece.

When doing parting off of short parts which have been drilled and tapped (turret work), I usually use a hex Allen key, with the long arm sticking up and held in my hand, and the short arm in the hole (a loose fit, not something close enough so a chip would cause it to bind), and this catches the part and allows me to transfer it to a stainless steel basket (brass stock, FWIW), so the remining chips can fall on out.

The biggest that I've tried to part of was 6". I could not reach in far enough with a parting tool, the 4x6" horizontal/vertical bandsaw would not cut to the center, and a hacksaw was taking *way* too long, so I proceeded to drill the center to 1", and then bore out in increasing sizes until it finally fell off from the earlier work. Luckily, the intended center hole was larger than the solid slug left by the reach of the parting tool. This 6" stock was on a 12" Clausing, FWIW.

Indeed so.

Enjoy, DoN.

Mainly precision. It is hard to set a piece so the cut length is accurate to less than a thousandth on the bandsaw. It is fairly easy when using a parting tool in the lathe. Also, it you're making a bunch of parts from a bar, it is lots quicker to cut them off on the lathe rather than have to dismount the bar, mount it in the bandsaw vise, do the cut, then put the bar back in the lathe to make the next piece, etc.

Gary

Parting of a reasonable sized stock for a lathe of a particular size and condition is fairly easy and repeatable. Reasonable size relates to the lathe's capacity, and condition refers to rigidity of the setup. Spindle speed is another factor.

A recent thread "Armstrong Armstrong Armstrong" had numerous replies for attaining predictable results.

A lathe technique that's been repeated often here in RCM is.. for parts that will have a center hole, drill the hole first, then cut the section off. This works very well, particularly for numerous parts such as washers, bushings etc.

WB ..............

One of my ex coworkers used a bandsaw when cutting round stock once.

ONCE.

As soon as the stock touched blade it twisted in his hands... and severed his thumb!

I was told to use cutting oil instead of coolant, but then again, maybe that's called coolant too, is it?

I shouldn't read newsgroups until I've had my first coffee... I read that and thought you'd said 5 thou... Lol... I was thinking it must have been luck that we were getting within +/- a couple of thou on our 3-jaw lathe projects at school.

chem

A vertical bandsaw?

And... eww... How did his thumb get severed? Did it go through the saw blade? Or did a sharp end on the stock rip it off as it was twisted?

chem

snipped-for-privacy@yahoo.com (Miki Kanazawa) wrote in news: snipped-for-privacy@posting.google.com:

And this is why we have such things as V-blocks and Vices. Put the V-block in the vice then stock, then CLAMP, then saw. If you can't get close enough to the cut with the vice to support the piece at the blade properly, turn the vice upside down, with a modified (short- sided) v-block and the workpiece resting on the saw table. The vice will still provide enough support to keep it from spinning, and make controlling the part during the cut easier.

/| |\/ | |____|

Usually most folks shy away from parting off in a lathe due to their not knowing how to properly set up the tooling etc and having a bad experieince doing it. Done correctly in a lathe, its a simple and great way, and perfectly safe. parting off in a bandsaw, means having to remove part, possibly reindex it in the lathe, and then remachine the cut ends. This is all extra work and steps, when usually just a parting tool in a lathe does it all at one time. Visit my website:

expressed are those of my wifes, I had no input whatsoever. Remove "nospam" from email addy.

When the stock twisted, his hand twisted with it, dragging his thumb to the blade.

A doctor managed to reattach it. The doc's comment was, "Hmmm... that's a clean cut!"

Rarely do you find an application or operation in precision manufacturing that will always work only one way. Oil is ok but if you're parting off something of a significant diameter, your oil will leave with your chips and your cutter will be starved (I've never seen a manual machine with flood oil - _very_ messy).

If I'm feeling lazy or not interested in getting sprayed with coolant, I'll part off with no fluids at all. Once you know what it should feel, look and sound like, you can do it under most conditions. A high spindle speed will pretty much always cause trouble though...

Essentially, you have to plan your work such that you are never required to get a part centered in a 3-jaw. Some people will try and hit the piece into being centered while in the chuck, but I'm fairly sure this doesn't result in the part's axis being concentric with the axis of the spindle.

If you want to be able to remove the part and replace it in the machine accurately, the best option is to turn between centers (used in a cylindrical grinder working on a hardened part, it is difficult to detect if a part was removed). Next is the 4-jaw independent chuck. Takes a while to learn how to use it and it will almost certainly mar the surface being clamped, but you can center a part far beyond .0005" easily. Collets are pretty good, but due to their limited clamping range, you either have to have lots available, or design your parts to fit the ones you have.

Regards,

Robin

It took a moment for me to realize he must have had his thumb in line with the blade for it to be cut off when the piece turned.

That's why I always use a piece of scrap as a push piece between the stock and my fingers when using a verticle bandsaw. Also, my fingers are NEVER in line with the blade, even if they are protected by the scrap.

Paul

You're kidding. Never?

I will only run oil in my manual lathe.

If you have the option of running your parting tool upside down, that can overcome many of the inherent problems when parting. Oil/coolant flows more freely in the cut and chips fall away readily, instead of gathering on the top, as sometimes happens.

mj

As do I on the Hardinge's. Full flood, with splash guards.

I concure.

Gunner

'If you own a gun and have a swimming pool in the yard, the swimming pool is almost 100 times more likely to kill a child than the gun is.'" Steven Levitt, UOC prof.

I have a rule in my workshop at work that no round stock is to be cut on the vertical bandsaw without being clamped in a vise to prevent this type of injury. We use one of the project vises being made by the local community college, as it will lay flat on all sides, and allows a variety of workholding positions. Mostly it is used upside down with the round stock flat on the bandsaw table. Our bandsaw has a flatbar removeable insert in line with the blade, and I tell all new trainees that I call that area the "dead zone" to get their attention, and that they are to never have their body parts in line with that bar when sawing in case the blade breaks and they surge forward.

RJ