Thoughts on maching this bushing in a VMC
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  1. #1
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    Default Thoughts on maching this bushing in a VMC

    So our lathes are book for the foreseeable future and a good customer wants these bushings made (250 pieces) from 416SS.

    My thought is this;

    Cut the rods ~.300" long and hold them in soft jaws, drill the through hole, mill the OD and thread. Flip part in soft jaws and mill off the excess and cut the flat on the top.

    Seems this may be best to insure that we can machine de-burr most all the features.


    I think I have him talked out of the cone shape on the top and just keep it flat to make it easier.

    What your thoughts?

    threaded-bushing.jpg

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    Why not just farm it out, 250 of those weigh next to nothing postage wise?

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    Done it several times, no issues with your plan even if you want to keep that angled surface on the part. I'd still outsource it if I had a choice though. Let me know if you need a good screw machine shop reference.

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    I've used a longer piece in a 3jaw or collet up off the table. Pull out a bit, mill, slitting saw off.

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    A shop on eBay (fivecee) sells these really well made dead length 5C mill blocks. I did an offer for $300, he charged $21 in shipping and I had it in a week. Of course, I wanted the Boss Tool Works one, but this is mostly just an experiment to see if I can make screws efficiently in the Robodrill and I found the Boss pricing of $1075 for the same bit of kit a bit high.

    I expected this to be junk for less than 1/3rd the price, but it is really well made. I am sure the Boss is nicer, but not 3x nicer.

    Also, made by the seller- not some Chinesium junk. It's really a killer price and great quality.


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    Default Open to RFQ

    I'm open for quotes if anyone is interested.

    I forgot there is a RFQ section, sorry.

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    Quote Originally Posted by Captdave View Post
    I'm open for quotes if anyone is interested.
    United Machining | Swiss Turning/ Milling Machine Shop – United Machining LLC is excellent, the owner is a member here.

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    Hi Captdave:
    How long would the job take start to finish if you tore down one of the setups on a lathe and just bit the bitter pill and ran it one evening, then set the lathe back up to do what it was actually supposed to do?
    These look like 3 minute parts to me so one overnighter should have them all sitting in the chip pan if you can run them unattended.
    They're a doddle to set up and program on the lathe too.

    They look like 10 minute parts on the mill so you'd be screwing around for a week unless my estimates are way way off and they're also an operator job made from pre-cut blanks instead of just taking them off a bar.

    So you gotta pay the operator to cut them all up, debur one end so it'll go in the collet and hang around while Op one gets run.
    A second setup and the operator is hanging around again while Op 2 gets run.

    Unless you can gang up a plateful of these, so the operator can get away to do other useful things, this job is going to eat your shorts for you if you run it in the mill.
    A gang fixture will kill you with the overhead to make it on only 250 parts, so sadly no joy there unless you already have something modular that can quadruple your cycle times and you've got a mill idle to run them on.

    I'd be eyeing my lathes and looking at which one would be least painful to spring free for an overnighter, or sub out the job as others have suggested.

    Cheers

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

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    Hi Marcus,
    I couldn't agree more, already have a couple of folks interested in quoting so I'll wait for their replies then make a decision. Its spring time and every weekend is spent at the farm so no days off for the past few months, the thought of staying late one evening isn't too appealing either.

    Thanks for your reply, some times its good to here another perspective before you make a commitment to a customer.

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    Hi again Captdave:
    I wasn't advocating you standing there in front of the machine for a whole night...that would just be uncivilized!!
    I was hoping you have a live tooled lathe with a barfeeder so you can just load and go, and have a nice snooze while your machine makes you unassisted moola and you keep your good customer happy.

    Staying up all night for a job...that's a "Young People Thing", NOT an "Old and Wise People Thing".

    Cheers

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

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    We have one Mazak live tool bar feed machine but just the thought of staying late one extra evening stinks!

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    Marcus of implantmx makes a lot of sense.
    Like always - imo - he is really sharp.

    But a midsize vmc could run any nr of these at a go, gripped between a couple of slabs of steel bored suitably.
    250 might be a one-run job on multiple vices or hydraulics, 3 ops perhaps.

    Ideas - that may be all-wrong (hope to hear why !!):
    Thread-mill bored holes in a 2-part flat bar fixture, gripped in vices, to hold some/all of the parts after op1.

    The 2-part fixture needs about 5000 mm length for 2 part slabs or == 14 mm piece + 5 mm separation per part.
    About 5x1000 mm on a VF5 or similar, or equivalents on shorter tables.
    Any small VMC should do a 10 x 25 matrix.

    It looks like == 1 minute for op 1 to do sizing and external shape, drill, bore, thread.
    == 5 hours for 250 parts.
    (could be 2 minutes depending ..).
    Swap all parts into fixture. 1/2 hour.
    Do second op.
    Perhaps 1-2 min each for good cosmetics.
    == 5-10 hours.

    So it looks like 5+10 hours machine time, 1-2 hours operator time, 3-4 hours programming and proof on initial pieces and every x pieces.
    15 x 60
    + 4x200
    + 2x50
    == 2100 price on 250 pieces == 8.4$ each.
    == if the 50$/hr operator can do this, it is 1300 total at 5.2$ / piece.

    == if the ops can be done under 2 min total it is 500 min =8.4 hours machine time vs 15.
    9 x 60$ machine
    + 2x50 operator
    == 640 $.

    There is a wide variance between 2100$ and 640 $.

    An advanced lathe or mill-turn usually runs around 250$/hr.
    So a single all-nighter as Marcus said would be == 2200$.

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    Hi Hanermo:
    I seem to be looking at the cycle times a bit differently from you.
    I don't think I can mill the thread OD, threadmill it and drill and ream it in a minute and still get a decent finish or decent size control.
    I'm pretty sure I can do it quicker on the lathe since I can keep the tool cutting almost continuously and I can typically push it harder on the lathe without tearing up the tool.
    You may have a different experience...I don't know, but as a rule of thumb I've typically budgeted a third the price for turning over milling with operations like these and I've not had to cry about underbidding turning work very many times.

    A great example is the time difference to chamfer a round part in the lathe vs the mill.
    In the lathe the cutting time to do a separate op for a chamfer is around 0.04 seconds to make 2 revolutions of the part if it's spinning at 3000 RPM and you just touch it with a chamfering tool rather than running a turning tool along a path.
    On the mill, a toolchange and tool approach might be almost as fast as the lathe, but the path length is 1.5 inches (0.5" diameter part) so at 15 IPM is about 2 seconds just for the milling and if you have to do it in 3 places on the first operation it really adds up.
    You'd have to run the mill tool at 600 IPM to be as fast as the lathe is for chamfering.

    Also, the stock handling on 250 parts is significant if you've got to chop up the bar into 250 bitsy little blanks and debur one end of each.
    It's why I love bar feeders and bar pullers and cutoff blades.
    I can hit length perfectly, I can debur in the same op and I never have to touch the bar except when I load it and when I toss the remnant.
    I believe just the time saved on that preparatory op avoided, is significant and more than pays for the extra cost per hour of the turning center assuming it's true they actually cost more to run. (I bill both out at the same rate in my own shop but I do not have sophisticated turning).

    Another point to consider is that by turning them it's one chucking per part to drop a completed item, and it's a fast, bulletproof chucking.
    On the mill it's three if you count cutting up the bar into blanks, four if you include the deburring step.

    The last argument I can make for turning is that I don't have to build anything; just fire up the toy, load my tools and my bar, write a bit of code and push the big green button.

    So I just can't see any scenario where I can outrace my lathe with my mill on these parts or make more money on the mill, or for that matter even make acceptable money on the mill.

    Of course 250 piddly little parts is not much of a moneymaker on the lathe either; but the OP has a good customer who's needs he'd like to serve, so it's worth it just to keep the customer sweet.

    I'd still heave a sigh, tear down the lathe run the piddler job and set the lathe back up to do what it's supposed to be doing.
    I might even get lucky and not have to set up very many new tools or take out anything that's already in the turret.
    I'd be cursing a little bit until the cheque comes in, and then it'd all be OK again.

    Cheers

    Marcus
    Implant Mechanix • Design & Innovation > HOME
    Vancouver Wire EDM -- Wire EDM Machining
    Last edited by implmex; 05-17-2018 at 08:57 PM.


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