Lathe slug stick out

I have a batch of 6061 parts to make that I have always done on my mill despite being obvious lathe parts. I finally managed to get my Emco 220P lathes running and would like to turn them loose on this job. Problem is these lathes have a 1" bore, and these parts are made from 2" bar...

There are two parts in this assembly, one is about 1/8" thick and the other is 3/16", 1.95" finished OD with a 1" hole through the middle, and I need 100 assemblies total. At that size the amount of time and material lost from cutting a bar into 200 thin wafers would be ridiculous, so I'd like to cut them into slugs and get a few parts out of each.

In my mill I cut them into 4" pieces and using a slitting saw to part off I was able to step down and get 5 or 7 assemblies out of each before I reached the vise.

What would be a reasonable length to have engaged in the chuck and how much could I safely leave sticking out? I have some 3" step collets and they're about 1-1/8" thick. Or should I get the broom ready and spend a day cleaning up around the saw?

I think you could hang it out 6" + with a power 3 jaw. Collet sounds like a shitshow to me

I do have a little 95mm Rohm 3 jaw but the drawbar for the collet chuck on the machine I'd like to do this on is kinda stuck so I was hoping to avoid changing that out...
What kind of clamp:stickout ratio is advisable for that kind of setup? And some kind of reduction in spindle speed as well?

So im hearing you want to run a collet because thats whats stuck on the draw tube?

I would go 1:1 engagement on the collet. What kind of collet? 16c? So stick 2” into the collet for max rigidity/ safety

Rule of thumb is 3-5:1 stick out. So for 2” bar anywhere from 6-10” should be safe.

You can bore a separate emergency collet for the 2 ish inch drops you end up with leftover. Just grab onto an 1/8” or so, let them pile up and swap collets when you run out of the full cut lengths. Eat up the drops that would end up in the bin instead of being parts.

Just write a sub program that runs the whole part and adjust the # of loops depending on what stock length you end up with. Start at 6”, if it doesn’t chatter keep adding an inch and see when it acts up.

Nothing is set in stone, risk/reward for how many parts you can run vs rigidity. If the tolerance is open go for it, tight tolerance not so much. Use the scientific method like they taught ya in grade school you’ll figure it out.


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Eric-
Assuming what you are making is essentially fancy washers, I would start with a piece that you predrilled to a little under your target ID.
Use the tailstock and a step collet to support the slug.
Turn to diameter,
part to finished ID,
retract tailstock
bore to finished id ( which should cut off the first washer)
rinse and repeat for how many you can fit on the slug.
The Emco has a pretty good subroutine loop.
Hahn Rossman

Hi Lostfab:
You wrote: "At that size the amount of time and material lost from cutting a bar into 200 thin wafers would be ridiculous, so I'd like to cut them into slugs and get a few parts out of each."

Do you think you will waste less material slicing them off the bar with a parting tool?
The skinniest parting blade I have is a Sandvik that's 0.084" wide.
If you cut slugs and then part them off, you'll waste the bar ends, and the rule of thumb is, the shorter the bar, the more you waste.
If you get 5 parts from a short slug and have to throw away a bar end you couldn't hang onto anymore, you will waste more than if you make a long slug, get ten parts and then have to throw away a bar end.
If you can get a hundred parts before you have to toss a bar end you waste even less.

So there are a couple of ways you can do this if you can't feed a full length bar through the spindle.
None of them is efficient, but I assume you don't care all that much, so long as it's not too bad.

Also, your lathe is tiny, so you really can't go balls out.
I had one of those machines once upon a time with the cute little 3 3/4" diameter Rohm chuck on it, and it was a sweet little toy but nothing to part 2" bar with if you want any sort of efficiency.
I seem to remember mine had something like three tired little German ponies to drive it and wasn't really very rigid.

Since your OD is non standard and I assume you want to turn it to finished size, you could saw all your washers by ganging up a few bars with big hose clamps and slicing off the baloney slices say 5 at a time with a decent horizontal bandsaw if you have one.

Even better if you have a cold saw, because you can slice them very square and close to thickness.
Or you can find a sawing service that can slice them for you.

Now the turning of the ID and faces is simple.
The OD can be turned 20 at a time on a mandrel because you've got a tailstock.

A second way you can try is to make bandsaw slices that are two parts plus a parting blade allowance wide.
Now you can turn one and bore it.
Do that enough times for all your blanks.
Now bore a pot collet and chuck all your slugs on the finished side.
Turn the second part and then part it off right next to the collet so there is almost no cantilever to flip the part out of the collet.
Face one, then un-chuck it, chuck up the second one and face it too.

I know, I just contradicted myself about the shorter the slug, the greater the loss.
But this presumes a bar end that you cannot use.
The way I'm describing uses one part to act as the "bar end" for the other part, so the only waste is the sawcut at each end of the slug and the width of the parting blade in the middle.
With the part off blade snugged right up against the collet face you should (might) get away with it.

Of course, you could always just get a bigger lathe, but that would be cheating.

I'd saw single part slices or have them sawn for me, and get or make a 1 inch mandrel.

A hundred assemblies like you're describing is a morning's work on the little Emco, but not if you try parting them off any distance from the headstock bearings.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Marcus, good point about the parting vs. saw cutting.
I had a bigger lathe but got these because small lathes would be perfect for the little widgets I usually need but typical now that I have small lathes I've got some bigger parts...
Hahn, I kind of generalized the shape of the parts, the thicker one is a thru bore for a bearing, the thin part continues that bore but then has a flange to capture the bearing, and a step on the OD, so they aren't all the same size or or shape OD/ID. I could probably rig up a mandrel but I think I'll start by trying something like the two-for-one setup. I have access to an auto saw so I can at least be efficient about one part of this job...

For aluminum, 4xD is about right, so 8" protrusion beyond the face of the chuck jaws, and clamp onto about 2".

So 10" OAL per slug.

Before saw cutting all your slugs, maybe experiment with longer ones and see what you can get away with. Every little bit means longer cycle times and less waste.

The remnants will be 2" and change. If you want to want to squeeze out every little bit, you can clamp onto about 1" of remnant and get a few more parts out. There will be much less leverage acting on the bar when it's only 2" long vs. 10". Might be more hassle than it's worth though.

Hi Orange Vise:
Are you aware how tiny an Emco 220 lathe is?
It's basically a training lathe from the 1990's (I think) marketed to trade colleges.
The chuck is under 4" in diameter.

The one I had was great for making tiny brass parts but struggled with anything much over an inch in diameter.
If you rip the enclosure and controller off it, you can put the whole machine on the kitchen table...it's not that much bigger than an Atlas/Craftsman 6 x 18" with some tin around it.

Hobbyists love them because they are so well built: that makes them a popular retrofit machine.
Parting off a 2" bar is a major accomplishment for a little machine like this...doing it any substantial distance from the spindle bearings is not for the faint hearted.
I didn't own mine for long enough to really test its limits...others would be better positioned to comment than I.
But this is not a CNC lathe like you're thinking of.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Eric-
I wonder if you could prep blanks by waterjet? If you upload a napkin sketch, people probably have great ideas.
Hahn Rossman

I would blank out of plate stock with the water jet, emergency collet on the od to face and finish the bore, use an expanding collet holding on the i.d. and face and turn the od. Turns it into a simple two op job, and others have stated the obvious, an Emco that size isn't going to part off that large of stock with any efficiency.

Hi Brian and Hahn:
I'm wondering why both of you are advocating for waterjetting round blanks out of (relatively) expensive plate and accepting all that waste stock (plus the cost of it and the garnet that has to be tossed and etc etc), when the OP has access to a decent saw, and can make baloney slices from (relatively) cheap 2" aluminum round bar pretty efficiently with relatively little waste on a low tech platform.
His worst complaint about sawing them from bar is that he will have to man a broom to sweep up afterward.

I can't personally bring myself to consider waterjet from plate as the best way forward to getting something he can turn.
He still has to turn the OD's so no gain there.
He still has to face both sides so no gain there either.

So what do you see that I'm not seeing?

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Yeah, no kidding.

Making round parts from plate is generally a very poor way to do it.

Waterjetting anything that can be done any other way is terribly inefficient.

Well, you would have to do the math, but if you stagger one row into the gaps of the previous row so things are as tight as they can be, I'm not so sure you are wasting much material over an .080-.100 kerf on the bandsaw. The water jet is kind of like a 3D printer, set it up, walk away and come back when it is done... and it's fast. Not so sure a saw is as non-labor intensive.

At least at the prices that I get stuff water jetted, I would prefer to be handed all the blanks ready to drop into the lathe and do two ops and be done. No fuss, no muss, no parts getting cut out of square because the blade wandered... just seems simpler to me. That, or he can check with his material house and see what they charge to slice them up.

implmex said:

Hi Brian and Hahn:
I'm wondering why both of you are advocating for waterjetting round blanks out of (relatively) expensive plate and accepting all that waste stock (plus the cost of it and the garnet that has to be tossed and etc etc), when the OP has access to a decent saw, and can make baloney slices from (relatively) cheap 2" aluminum round bar pretty efficiently with relatively little waste on a low tech platform.
His worst complaint about sawing them from bar is that he will have to man a broom to sweep up afterward.

I can't personally bring myself to consider waterjet from plate as the best way forward to getting something he can turn.
He still has to turn the OD's so no gain there.
He still has to face both sides so no gain there either.

So what do you see that I'm not seeing?

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Click to expand...

OK Brian, that makes perfect sense.
I understand exactly why you're advocating this path now, and I think the OP is going to have to game out both approaches if he is super concerned about getting the best price/performance ratio he can.
As you correctly point out...there is value in getting a box full of blanks ready to turn, and you've described a viable way to get those blanks.

I do wonder though, if a sawing service would be more expensive or cheaper than a waterjet service...I've ordered sawcut round blanks before and was very satisfied with what I got (they were cold sawn and were very accurate), but I've never done the same for waterjet cut blanks I intended to turn, so I don't have a good point of comparison from my own experience.

Thanks for explaining your reasoning; you've given me a new point of view to use when it's my turn to decide on something like this.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Chuck on a 1/2” and hang it out 4” start with round tube if its similar price face, turn, bore, repeat. If you can get a good enough finish on the parting tool you can 1 op them.

Hi Marcus,

There are a lot of factors to consider, if he can do the parts with 1/8" and 3/16" plate and still clean up the faces, then I'd say it is probably the way to go. If he can't clean them up and has to buy the next stock thickness of plate, probably not a good idea.

I have done this both ways, water jet and saw cut. My material supplier (Coast Aluminum here in Phoenix) doesn't really charge me much for saw cutting if I'm buying 300-600 pounds of aluminum. They bandsaw cut some of the larger blocks I get, and do use an automatic cold saw on others. The blade kerf is closer to 3/16" or more, and I'm paying for that aluminum for them to cut, so again, going to have to push the calculator a bit to see which way is cheaper, which if it's a constant repeat job, it might be worth it.

implmex said:

OK Brian, that makes perfect sense.
I understand exactly why you're advocating this path now, and I think the OP is going to have to game out both approaches if he is super concerned about getting the best price/performance ratio he can.
As you correctly point out...there is value in getting a box full of blanks ready to turn, and you've described a viable way to get those blanks.

I do wonder though, if a sawing service would be more expensive or cheaper than a waterjet service...I've ordered sawcut round blanks before and was very satisfied with what I got (they were cold sawn and were very accurate), but I've never done the same for waterjet cut blanks I intended to turn, so I don't have a good point of comparison from my own experience.

Thanks for explaining your reasoning; you've given me a new point of view to use when it's my turn to decide on something like this.

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Click to expand...

Brian said:

Hi Marcus,

There are a lot of factors to consider, if he can do the parts with 1/8" and 3/16" plate and still clean up the faces, then I'd say it is probably the way to go. If he can't clean them up and has to buy the next stock thickness of plate, probably not a good idea.

I have done this both ways, water jet and saw cut. My material supplier (Coast Aluminum here in Phoenix) doesn't really charge me much for saw cutting if I'm buying 300-600 pounds of aluminum. They bandsaw cut some of the larger blocks I get, and do use an automatic cold saw on others. The blade kerf is closer to 3/16" or more, and I'm paying for that aluminum for them to cut, so again, going to have to push the calculator a bit to see which way is cheaper, which if it's a constant repeat job, it might be worth it.

Click to expand...

I buy mostly from Coast in Portland. Cold saw kerf is .120". I regularly have 12' bars made into 1" slugs. Results are pretty good and they don't charge for the cold saw.

I do agree that thin parts should be made from plate, but the OP is not making parts that thin.

When I need to make round parts from aluminum thinner than 1/4" and under 4.5" diameter I have them punched from sheet on a CNC turret punch. An Amada 357 has a cyclic rate of 350 strokes per minute. It takes two hits to make a washer. With 2000 IPM positioning you should get about 150 washers per minute coming out the bottom of the punch. Turret punch uses no garnet, tooling lasts forever in aluminum and it's probably more accurate than waterjet.

To cut down on stock usage, you may want to consider these as opposed to a collet.
Chop a 3-1/4" long slug, and grip the last 0.06 or 0.1" using the versa grips.
Run as many parts as you can, using a 0.06" wide parting blade, and leaving 0.01 to clean on the face of each part.
Since you are only going 0.43" deep from the OD to the ID, a 0.06 part blade should work great.
If parting the 1/8" thick washers, I would plan for 0.2" per part, total stock usage. From 3.25" you should yield 15 pcs.

Doug.

Have a look at this thread:
Talon grip chuck jaw)s (stupid question)

As mentioned before this lathe is small, like really small...95mm 3 jaw chuck or a 5c collet. I really like the idea of using versa grips and may try that in the future, but I don't have any soft jaws for the chuck right now.

I used to have access to a fiber laser and I think even with the homie hookup it would probably cost double to get plate cut than it did to buy a 12' stick and the beer I drank while I waited for it to cut on the auto saw.

I think I may have been too fixated on the material being lost, I remembered a Maritool post where he mentioned a job making small fittings that somebody else passed on because they were unprofitable, but he factored in the money recycling would bring in and made it work. This isn't quite the same but when I did the math on how many pieces fit in a bar, and how much a bar cost I realized I don't really need to worry on this job.
I ended up cutting 1-1/8" slugs, gripping 1/2", face and cut the thin part, part off, face and cut the thick part, toss the 1/2" in the solids recycling bin and carry on. Two-for-one is good enough for me until I find another lathe with a similarly small footprint, but a larger bore!

Thanks for the input everyone, always get great ideas from this place.