How to operate any machine tools quickly but relatively safely...
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  1. #1
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    Default How to operate any machine tools quickly but relatively safely...

    So I borrowed a friend's lathe, because I really don't have one, and I need to make a fly cutter since I can't find one in NT40 (in fact I had no way to buy a fly cutter at all in Taiwan, nobody knows what it is, and Aliexpress doesn't have one either. In Taiwan they just use face mills when they need to surface something). I ended up making a straight shank one (because it was 10 times easier to do, and a fly cutter don't see that much force anyways).

    I figure I just use the lathe but the guys I am borrowing the lathe from is a rather experienced machinist, and of course in their view I am just way too slow. So instead of letting me continue they just went and took over my project. They machined this: (I plan on finishing the work on my mill by cutting an angle, and milling in the slot for the tool bit, as well as the set screws)

    img_0844.jpg

    If you notice, there is a roundover, don't know why they put that there (I would have been happy with a chamfer so I don't cut myself on it). The kicker is, they did this without a forming tool. The guy simply turned the wheels and made the roundover by hand. He did it without crashing the lathe too.

    How do I learn how to do that, and how do I machine quickly enough without breaking something? I never used a 16x40 lathe before (only one I used was a 12x28) so naturally I work slow and take light cuts at slowish speed. The HSS blank I ground flat out sucked, and the carbide insert on his machines work 10 times better. He told me forget grinding HSS blanks and just go with inserts...

    I felt like I'm the most incompetent machinist in the world right about now...

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    First you get good, then you get fast. Worry about the first part and the second will come naturally (eventually).

    Trying to run before you can walk is an excellent way to end up posthumously immortalized in one of those stick figure safety posters.

    If you BSed your way through the interview enough to get the job and now the chickens have come home to roost, well you got what you deserve. If not and you were hired with a lack of experience there should be a bit of time allotted to getting up to speed.

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    Tell that to a boss when they're paying you for your time and you're taking too long because you're not that good yet...

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    Quote Originally Posted by taiwanluthiers View Post
    Tell that to a boss when they're paying you for your time and you're taking too long because you're not that good yet...
    So keep rushing until you lose a finger or hand and then slow down because you're crippled.

    There is no trick for going faster that doesn't involve skipping steps or earned experience.

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    I'm sorry, I don't really understand your situation. You're borrowing a lathe but the lender won't let you use it to make your own parts?
    If you're not able practice at a slow and deliberate pace, you will never be able to learn how to do any craft well, much less well and quickly. Having a mentor helps a LOT, but it is possible to self instruct with online resources, although it is a slower path and has some potential pitfalls. But you will need to practice first and foremost, in an environment that allows you to work slow enough that you can be safe and plan out what you are doing.

    Don't take this the wrong way, but your tooling choices (ground HSS blanks and fly cutters) kind of sound like you're most familiar with hobbyist tools and skills, which will not deliver the most productivity (speed/qty). Like the your machinist friend said, carbide insert tooling can be run faster and harder. it's very worthwhile to invest the time you would spend grinding blanks into learning about insert types and geometry if you're trying to maximize productivity. Likewise, most of the professional machining world has moved on to using inserted face mills rather than fly cutters, which is why you are having trouble finding fly cutters for sale.
    Lots of resources out there for learning about modern tooling, Sandvik has a good free online course, you can go through most of the major manufacturers' catalogues online, also "Machining Fundamentals" by Walker/Dixon is a good modern textbook aimed towards introductory professional training.

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    I guess that explains why nobody sells fly cutters in Taiwan. All cutter stores in Taiwan caters to professionals (they wouldn't be in business otherwise), and almost nobody machines for a hobby in Taiwan. It's also kinda hard for me to self instruct if I do not have a lathe myself... and no I don't want to buy a mini lathe or a cheap one, I rather spend the money on a Victory lathe (the best Taiwanese lathes on the market) than get a crap lathe that I will have to get rid of someday (and it costs me money to do that).

    But yes, I came to machining as a hobbyist and I'm trying to do this professionally which is a whole different kettle of fish. He's already taking the time to teach me the basics of CNC machining, something which I never really had much experience with because you know, those things are expensive.

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    '' How to operate any machine tools quickly but relatively safely... ''

    It's called practice and experience, manual machining is a skill, both manual a cerebral, that takes many years to learn (but seldom master) with many of the old hands (myself included) having to live on what they produced an hour, as opposed to being payed an hourly rate.

    Manual machining is NOT a video game / piece of simulator crap.

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    So you have a friend who let you use his machine and then could not stand to watch you figure it out? Thank him and ask him to teach you. Offer to pay him or trade something of value. Make him a present and ask him to take you on as a student.

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    Well, one thing you can do from home is plan your work. Pre-calculate your speeds/feeds, layout a good sketch with dims/notes, have selected your material/tools, etc.

    From there you can tweak your roughing passes to land at nice even values for finishing via the 3 pass method.

    Sent from my SM-G973U using Tapatalk

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    So I take it you did not have the luxury of "Etch-A- Sketch" when you were a child ? Same concept

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    Good, fast or cheap.


    YouTube

    "Far from good, good from far"

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    I'll be honest with you though, the guy did some stuff on the lathe that makes me scared.

    For example, he would face the cut (before the shaft) by REALLY PRESSING INTO THE WORK with the flat of the insert (It's a TNMG insert). The lathe makes horrible noise when you do this by the way. He told me how he ended up slipping the lathe tool (if he hadn't forced the tool into a face, it wouldn't have happened). Also, he's wearing a cotton work glove the whole time while operating the machine, and I was scared it'd catch on something. He also told me he can't seem to make threads that works, and told me that you could never disengage the half nut when making threads (he would thread, back up, turn the lathe in reverse, and advance it again hoping he remembered where he was before, the compound is there for a reason). I told him about the thread dials but on their lathe it is not working.. and you use the thread dials to get your thread back if you ever disengages the half nut.

    The fly cutter is finished. I did the rest of the work myself. Took me about 2 shop hours (mainly because of using HSS end mills for bulk of the material removal, if I have a better MRR end mills, I can cut this down by at least half). Carbide end mills cuts so much better (and faster) than HSS end mills too, and leaves a much better surface finish. Except the older end mills I buy cheap (obviously not sharp) didn't really work that well and the new 6mm end mill I bought, made in Taiwan, works fantastic and leaves a beautiful finish. I cut the slot into the thing for the tool bit and the fit is snug. Machine rigidity is good, not spectacular because it's a 1 ton mill but it's better than Bridgeport clones.

    img_0845.jpg

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    Default 3-pass finish technique

    Quote Originally Posted by Cole2534 View Post
    From there you can tweak your roughing passes to land at nice even values for finishing via the 3 pass method.
    This is the first I've heard of this method, and it seems my Google-fu is lacking, as I get 2 examples from Sandvik that aren't very clear to me.

    FWIW, this is the algorithm I got from the 2 examples I found with a Google search:
    F = desired finish diameter
    1. Measure diameter = M1
    2. Run first pass at D1 = M1 + (F - M1) / 3
    3. Measure diameter = M2
    4. Run second pass at D2 = D1 + (F - M2) / 2
    5. Measure diameter = M3
    6. Run last pass at D3 = F + D2 - M3


    Does this look correct?

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    Quote Originally Posted by mountie View Post
    Does this look correct?
    Leave it to Sandvik to complicate something.

    -Rough your part to some easy multiple of 3 away ie .09"
    -Take a .03 cut
    -Measure it and adjust DRO for actual removal
    -Take another cut at the next .03 reduction (is it on size?)
    -Take the last .030

    This assumes that your tool is cutting within a few thou but has usually worked for me for rigid work in the +/- .001 area.

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    I'm drunk in Greece, aint reading formulae.

    Basically this-

    land your last roughing pass at a nice number from your finish diameter. On a 2" shaft say .150" o/s.

    1st pass take .050 (1/3 of o/s amount), stop, measure, note results.

    2nd pass take .050, stop, measure, note results.

    3rd/final pass take required amount from shaft while observing results of previous passes.

    Done correctly, this >should< yield a very good finished size. Step 1 establishes machine output vs machine input (ie- cut size vs dial movement), step 2 proves it, step 3 allows you to adjust to hit your mark.


    Sent from my drunk ass on a boat in Greece

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    Thanks Hazzert and Cole, that's what I figured I should do but the Sandvik stuff just messed me up.

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    Nobody reads books anymore? Yeah, all the tired lines about needing real works experience, sure, of course you do.....but if you want to come a learning curve really really fast (and safely except for paper cuts), get the practical as well as the lifetime of experiences of a few good authors. Your position of knowledge and understanding of what is happening and needs to happen when you go to use the machine will be night and day.

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    It's not that I can't operate a lathe but I guess the guy had to be somewhere and didn't want me taking all day to do it. But the way he's really doing it is pushing the machine, and you have to know the machine really well to do that... not possible on someone else's machines.

    Reading books isn't going to help me operate a lathe and turn out parts faster.

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    Quote Originally Posted by taiwanluthiers View Post
    Reading books isn't going to help me operate a lathe and turn out parts faster.
    Neither is this discussion. There are no shortcuts.

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    Quote Originally Posted by taiwanluthiers View Post
    Reading books isn't going to help me operate a lathe and turn out parts faster.
    If you read, understand, and practice, maybe you would not have said " The HSS blank I ground flat out sucked" , its not that hard to do.

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