So I’m starting to settle into our new house and fired up the lathe which I haven’t used a whole lot since buying it. I came to the realisation that I need more tooling so I have one or two things on order. In the meantime I’ve been doing bits and pieces getting used to how it works. Today I was taking a few mm off a bit of copper. Something unusual happened (at least I think it’s unusual) see pics. I want to know if this kind of thing is normal? I tried to bend it with my finger which I could but it was still stiffer than I was expecting. I wasn’t getting much (if any) chatter so the material was curling off in coils. I’m curious if the tool bit should be pointing the other direction? The results weren’t causing any problems, I’m just curious.
I didn’t use enough lube on this next pass and I got a bit of chatter this time.
That’s a boring bar, typically used for cutting inside a hole, like reaming it out after drilling to make a battery tube or the like.
The steep angle on that bit leading away from the cut is what’s making that happen. I’m also very new, so I’m sure someone else will have something to say about my response, but you need to use a different bit for that type of cutting action if you expect a different result.
Edit:
If you’re squaring the end of the bar or just trying to clean it up on the end, a bit with more of a 90º angle to it will do a cleaner job. You also don’t want a long edge dragging at the rear of the bit, minimize the cutting surface contact for a cleaner cut and less load on the machine, less heat in the part as well.
I’m not a machinist but I do have some (but still small) experience around and with a lathe.
I think you have used the wrong tool, or tried to remove too much material in one pass.
What I mean by that, if you look at the 3rd picture you can see that the angle is precisely the same as that off the insert.
So it looks like that the tool was cutting the copper but only with the tip of the insert, the rest of the copper was pushed away with the side of the insert.
A boring bar? I thought they had left , right and neutral angles to suit which way you want to cut. I have a bar that’s definitely for boring as it has a rounded shaft. I guess the answer seems more obvious to me now I have slept on it and read your replies. At the time I was like ‘cool, that’s weird’. Anyway, thanks for the replies.
For some reason those pictures won’t load for me so can’t say much about the tool. I can say I’m not a very experienced machinist either but when I’ve turned copper in the past I’ve found you need the right cutting lube to get a nice clean cut. Stuff I’ve used for steel an aluminum and such just wasn’t cutting it (pun intended). While probably not great for most other materials soap works great for copper. Yes real soap from a bar (not detergent or that fake soap), I just put some in a spray bottle and added just enough water to make it come out kind of like a thick slime. Frankly I was quite surprised how well it worked.
My boring bar is round, yes, but it has that carbide diamond on it. I find it works great for a plunge cut inside, but not for much else unless I take care to keep the angle of the lead edge away near perpendicular to the material. If you think about it, moving the bit across the face of the turning part it has to cut towards the center and left, on the spinning bar, so the edges needed are left and front. In those pictures you had a long cutting edge on the left, dragging after the initial cut, and then a very acute angle away from front or lead edge, which is why it ramped.
Yeah, I haven’t been doing this long either so while I know what I want to say, I’m finding it somewhat difficult to find the correct descriptors…
Angled bits and bitholders are made for specialized work, about 30 degrees is the sharpest I’ve seen. If the bit is closer to 90 degrees it’s a boring bar.
Didn’t know about the copper lube, learn something new every day!
If I read that diagram right, I was doing a right side face cut and the directional arrow looks like the same as what I was doing……? I must be reading that wrong.
You had it set up to reduce diameter, traveling the length of the bar, not dress the face going across the bar. That’s the difference. They don’t, for whatever reason, show a face cut scenario.
You have to have cutting tool in the direction of travel. Face cutting, you’re going forward, into the metal, so you need a sharp edge in that direction to peel metal away, instead you had a sharp angle away that wedged itself into the metal and any deeper of a cut (bit to the left) it would probably have jammed. At any rate, going from outside to middle on a face means you’re cutting forward, so that needs to be the lead edge ^ not < or >
Edit II: The picture shows a side facing, that means that they’re cutting into the metal, reducing diameter along it’s length, then facing the shoulder that results. This facing action takes place pulling the bit away from center, at the end of the cut. This is not the same as facing the end of the bar. Best bet is to watch a video showing stock facing on the lathe.
Edit: Shoot TexasLumens (Dan) a message, he sells lathe’s and cnc machines for a living, traveling across the country setting em up in businesses. He could say it more clearly and has tons of experience.
(I downloaded the picture and saved it, that should tell you something, LMAO)
but… in the picture? i ended up mainly using the “round nose” tool, that cuts both ways. Its my most versatile tool, i would say.
not being a DEDICATED right or left tool, it doesnt produce the best finish, but, very acceptable results. Really light finishing passes with it work well. I mount it “straight in” at the work.
i also use it for “facing”, by mounting it facing the end of the piece.
i also have a dedicated boring tool, i use it for boring, naturally. Those 2 tools cover 95% of my work right now… I should add i am mainly machining plastic and softer metals, like aluminum and the odd piece of brass. I should add that i did one piece of steel rod with that round nose tool, it turned and faced and even cut a channel for an o-ring.
it just seems to be my most versatile tool, for now.
I’ll try a different hosting site if I get time tomorrow Steve. Currently uploaded to my Google account.
Hmm… a round bit. I don’t have one but I may add it to the next order. At the very least it sounds like a good way to cut O-ring grooves. Thanks sedstar.
Nice images now. The images look like nothing more than the habits of copper. This looks to be soft copper and that machines like bubble gum. Try speeding the lathe up and using lighter cuts. The less tool surface contact that you have with copper the better. Cuts like you are making in your third image will usually cause misery in copper. Use a different technique and lessen the amount of tool surface contact. For best results, see if you can find some C145 Tellurium copper. This is much easier to machine than the soft gooey stuff. Plus... you will have the fun of picking the chunks out of your fingers. Great entertainment. Tellurium makes little curled chips like some steels when you cut it.
About every material works a little differently. The hardest ...in my opinion... to work are these soft gooey metals like soft copper. Copper is a poor place to start learning because of this. Once you get a feel...and that's exactly what it is... "A feel" for your machine, tooling and good cutting materials... like 6061 or 7075 aluminum, this copper work will come easier. In just awhile, you will know when you are creating yourself a problem. Remember that the 20XX series of aluminum alloys...and many others are just like that copper. Cut yourself some good aluminum alloy...perhaps some brass... just play a little... get a feel for what you are doing, then come back to the bubble gum. Every minute you stand at that machine will benefit you. None of us (that I know of) were born with the experience you need to gain. It just takes time at the cranks. TL
Thanks MrsDNF but I doubt there is much I can tell you about a lathe that you don't know. Looking at your work... you could sure teach me some things though!! I enjoy sharing. That is what makes the world turn. TL
Great entertainment. Tellurium makes little curled chips like some steels when you cut it. 
Every minute you stand at that machine will benefit you. None of us (that I know of) were born with the experience you need to gain. It just takes time at the cranks. TL