We all know the first cut is the deepest . My machining instructor used your gear cutting video as a guide to formulate or gears , thank you for your videos
Once again, a great video. Excellent technical content, and great training delivery. I't's amazing how quickly material that you learned 50 years ago comes back to you with just a little refresher training. Many thanks.
I never learned much about cutting speeds, but I have always paid attention to the chips and finish. Also paid great attention to the sounds from the machine. So I guess I am on the right track. Now if I could get my head around the arithmetic, I might do a better job. Thanks Marc.
11:40 The spindle motor and feeds motor on decent mills are the same motor. It's only cheap mills like Bridgeport that have separate motors. Although the separation has its plus points !
Good vid Marc. I need to grind/get some larger radius tools for my finish passes. I have my changegear atlas set to 5 thou feed. Slow for roughing but almost too fast for finishing.
Excellent. What I take from this presentation is that one should change the tool bit for the finishing pass for a tool with a large tip radius. This means you would have to plan ahead for re-registration of the tool bit to ensure enough material remain for at least two passes, unless some can suggest a re-registration approach which does not require a cut and measure and measure approach.
IMO, it's not the radius that matters but how quickly the tool leaves the work. A pointed tool leaves the work quickly and offers little to no polishing action. A tool that's square on to the cut but has an end almost parallel with the work should provide a polished finish.
Wait! Should i use a smaller nose radius or larger for finishing?! Differed sources say different things and I'm very new to this. Somebody please suggest
Hi, for finishing use a bigger radius and a shallow cut. There is however a limit to how shallow you can go. The last thing you want is rubbing. Rubbing equals heat that cannot be evacuated in the chips and will never give a good finish. Thanks for a great question, happy machining Marc (THATLAZYMACHINIST)
@@drazenkosutic I've only just joined the party ;) I noted you'd not had anyone else respond. Chatter/vibration is something you 'tune' with a machine - how tight the gibs are, how well clamped non-moving axes are and how stably stacked the various bits are too - not to mention the tightness of spindle bearings.
The back rake on drill (clearance from cutting lips) will effect the bite taken by drill, there are specifications as to the angle needed for different size drills
Welder by trade , and you just gave away the secret to a good weld at the very end . 😁 And maybe many other activities or skills we do in through out life
Now I have a problem, I rough cut several passes to get closer to size then take a smaller cut, a finishing cut. This cut will get me to size but will be smaller than ideal. Solution?as it relates to chip size
johnvallesfarm Just leave more material on, enough to take 3 or 4 finishing cuts. Make sure your last 3 or 4 cuts are at the same depth and sufficient enough to produce a good chip that will leave a nice finish.
THATLAZYMACHINIST Hello, its more my process. Again related to depth of cut verses chip size. As a hobby I try to be constant in my process, master a way of working by repetition for lack of experience. So I establish a roughing setting for my inventory of a metal ( cold rolled) I have in stock. I gradually increase speed for it’s decreasing diameter but I , as my routine, creep up to my final dimensions. My finish cuts vary as needed but are as a rule are less than ideal chips and more akin to tiny ribbons or dust. New to my dro, I need to plan ahead to achieve more ideal chip size or use various files and sandpaper to desired fit. I like carbide but I realize my lathe isn’t fast enough for prescribed settings. I shoot for 2 to 5 thou final cut. Just need more lathe time.
Like most things... it depends. For example, you could have a large casting bolted to a lathe face plate and because of it's shape you can't run it more than 60rpm max. And you have to drill a 1/2" (12.5mm) in the work. You drill at slow speed..but you can use drills with a point ground for tough materials as that will make the cutting faces of the flutes slightly shorter. And you can power feed the drill from the carriage so that the feed is accurately controlled and you don't let the drill dig into the work. The main thing is to work smoothly and do what you can to dampen vibration in the work... at slow speeds the excitation frequency generated by the tool may be getting into the realm of the natural frequency of the work. Wrapping the work with rubber belting or similar often helps dampening the work (A must do for things like turning brake drums). This is a place where speeding up the work slightly (if you can) is more likely to stop the vibration of the work than slowing down the rpm.
Thanks for info, but was wondering if there is such a thing as a minimum rpm to get the chips going - or is there minimum rpm where below which the surface finish isn't what it should be.. I'm only using lathe/mill for hobby projects, I'm in no rush to get the max feeds,etc :)
I would say that the limiting factor in running very slow speeds is the rigidity of the machine. When the excitation frequency generated by tool in the work gets very low, you are getting into the natural frequency of the machine tool and the machine starts vibrating in response to the excitation. At slow cutting speeds you still have to keep the feed high enough to get ahead of the work hardening zone just ahead of the chip. That's the reason you often will have longer tool life with higher feed rates.. stainless steel is a good example. Light feeds in stainless will burn up carbide just as fast as it will high speed steel. I would follow Marc's advice about numbers from speed and feed tables..they are for a production environment where cutting time and tool life are important. Like he said, 2/3 surface speed table values is a good place to start with in a home or job shop. 80% recommended feed rates are a good place to start...more if the machine and tool will stand it as it is important to stay ahead of material work hardening. The slower the surface speed you run, generally the smaller the nose radius of the tool you want to run. This is to reduce vibration excitation from the cutting tool. The rate of heat generation is reduced which helps to keep the nose of the tool from overheating.
We all know the first cut is the deepest . My machining instructor used your gear cutting video as a guide to formulate or gears , thank you for your videos
Once again, a great video. Excellent technical content, and great training delivery. I't's amazing how quickly material that you learned 50 years ago comes back to you with just a little refresher training. Many thanks.
Legend . Absolute blessing of information, thank you
Thank you very much Marc. All the information you've given in your free training courses is invaluable. Wishing you the best.
Your videos have been helping me so much sir.
I have been following u for 3 years Thanks for share all that information.
Well done. Very informative
Learning more from you than in my Machine Tool Technology classes. Just Saying
Thanks for another clear and excellent presentation
Great video as always, Marc! Thanks for sharing.
Cheers
Jimmy
I never learned much about cutting speeds, but I have always paid attention to the chips and finish. Also paid great attention to the sounds from the machine. So I guess I am on the right track. Now if I could get my head around the arithmetic, I might do a better job.
Thanks Marc.
Excellent work as usual Marc!
Great video, thank you.
Very good instructions, thanks again !
11:40 The spindle motor and feeds motor on decent mills are the same motor. It's only cheap mills like Bridgeport that have separate motors. Although the separation has its plus points !
Awesome video, thank you very much for sharing your knowledge with us.
Good vid Marc. I need to grind/get some larger radius tools for my finish passes. I have my changegear atlas set to 5 thou feed. Slow for roughing but almost too fast for finishing.
Thank you!!!
Excellent. What I take from this presentation is that one should change the tool bit for the finishing pass for a tool with a large tip radius. This means you would have to plan ahead for re-registration of the tool bit to ensure enough material remain for at least two passes, unless some can suggest a re-registration approach which does not require a cut and measure and measure approach.
IMO, it's not the radius that matters but how quickly the tool leaves the work. A pointed tool leaves the work quickly and offers little to no polishing action. A tool that's square on to the cut but has an end almost parallel with the work should provide a polished finish.
Dear Marc, thank you very much
Lesson: 44
Awesome take on the Cheryl Crow song “first cut is the deepest.” Lol.
I think there's a typo at 5:33 in the surface speeds. For 50 ft/min the metric would be about 16 m/min. not 6 m/min.
15·25 m/min ! Yup !
❤
Wait! Should i use a smaller nose radius or larger for finishing?! Differed sources say different things and I'm very new to this. Somebody please suggest
Hi, for finishing use a bigger radius and a shallow cut. There is however a limit to how shallow you can go. The last thing you want is rubbing. Rubbing equals heat that cannot be evacuated in the chips and will never give a good finish. Thanks for a great question, happy machining Marc (THATLAZYMACHINIST)
Is there some way to relatively simply calculate impact of machine rigidity on feeds and speeds?
I'd say no - too many variables ! Like weights of various parts and how loose the slides are.
@@millomweb Thanks for reply, a bit late😁, but appreciated, thanks
@@drazenkosutic I've only just joined the party ;) I noted you'd not had anyone else respond.
Chatter/vibration is something you 'tune' with a machine - how tight the gibs are, how well clamped non-moving axes are and how stably stacked the various bits are too - not to mention the tightness of spindle bearings.
What does DOC translate to in a drilling operation?
Diameter of the cutting edge - for a new hole. Enlarging a 1/2" hole to 3/4", DOC would be the difference of the 2 holes: 3/4 - 1/2 = 1/4"
The back rake on drill (clearance from cutting lips) will effect the bite taken by drill, there are specifications as to the angle needed for different size drills
Welder by trade , and you just gave away the secret to a good weld at the very end . 😁
And maybe many other activities or skills we do in through out life
Now I have a problem, I rough cut several passes to get closer to size then take a smaller cut, a finishing cut. This cut will get me to size but will be smaller than ideal. Solution?as it relates to chip size
johnvallesfarm Just leave more material on, enough to take 3 or 4 finishing cuts. Make sure your last 3 or 4 cuts are at the same depth and sufficient enough to produce a good chip that will leave a nice finish.
Hi John! Do you have any numbers (dimensions), the type of material being cut and the size of the part?
THATLAZYMACHINIST
Hello, its more my process. Again related to depth of cut verses chip size. As a hobby I try to be constant in my process, master a way of working by repetition for lack of experience. So I establish a roughing setting for my inventory of a metal ( cold rolled) I have in stock. I gradually increase speed for it’s decreasing diameter but I , as my routine, creep up to my final dimensions. My finish cuts vary as needed but are as a rule are less than ideal chips and more akin to tiny ribbons or dust. New to my dro, I need to plan ahead to achieve more ideal chip size or use various files and sandpaper to desired fit. I like carbide but I realize my lathe isn’t fast enough for prescribed settings. I shoot for 2 to 5 thou final cut. Just need more lathe time.
Cuz , 👍🏽👍🏽 good eats 🇬🇾🇬🇾🇬🇾🇬🇾
what about the minimum rpm on lathe?
Like most things... it depends. For example, you could have a large casting bolted to a lathe face plate and because of it's shape you can't run it more than 60rpm max. And you have to drill a 1/2" (12.5mm) in the work. You drill at slow speed..but you can use drills with a point ground for tough materials as that will make the cutting faces of the flutes slightly shorter. And you can power feed the drill from the carriage so that the feed is accurately controlled and you don't let the drill dig into the work. The main thing is to work smoothly and do what you can to dampen vibration in the work... at slow speeds the excitation frequency generated by the tool may be getting into the realm of the natural frequency of the work. Wrapping the work with rubber belting or similar often helps dampening the work (A must do for things like turning brake drums). This is a place where speeding up the work slightly (if you can) is more likely to stop the vibration of the work than slowing down the rpm.
Thanks for info, but was wondering if there is such a thing as a minimum rpm to get the chips going - or is there minimum rpm where below which the surface finish isn't what it should be.. I'm only using lathe/mill for hobby projects, I'm in no rush to get the max feeds,etc :)
I would say that the limiting factor in running very slow speeds is the rigidity of the machine. When the excitation frequency generated by tool in the work gets very low, you are getting into the natural frequency of the machine tool and the machine starts vibrating in response to the excitation. At slow cutting speeds you still have to keep the feed high enough to get ahead of the work hardening zone just ahead of the chip. That's the reason you often will have longer tool life with higher feed rates.. stainless steel is a good example. Light feeds in stainless will burn up carbide just as fast as it will high speed steel.
I would follow Marc's advice about numbers from speed and feed tables..they are for a production environment where cutting time and tool life are important. Like he said, 2/3 surface speed table values is a good place to start with in a home or job shop. 80% recommended feed rates are a good place to start...more if the machine and tool will stand it as it is important to stay ahead of material work hardening.
The slower the surface speed you run, generally the smaller the nose radius of the tool you want to run. This is to reduce vibration excitation from the cutting tool. The rate of heat generation is reduced which helps to keep the nose of the tool from overheating.