Wanted Looking for Machinests in Turning Aluminum

Discussion in 'Yard Sale / Wanted' started by SinfulDarkLord, Oct 4, 2019.

Help Support The Rocketry Forum by donating:

  1. Oct 4, 2019 #1

    SinfulDarkLord

    SinfulDarkLord

    SinfulDarkLord

    Well-Known Member

    Joined:
    Feb 21, 2012
    Messages:
    2,571
    Likes Received:
    8
    I didn’t know where to post this, but I hope the watering hole is okay, if not the moderators can move it to somewhere appropriate.

    I am looking for machinests who are experienced in turning down aluminum tubing. I need precison turned aluminum tubing to use as mandrels. They have to be within a 0.002” tolerance.

    The length at 72” and wall at 1/4” or 1/8”. If need be, I can order the tubing as I know where to get it for cheap. This is going to be 6061 aluminum.
     
  2. Oct 4, 2019 #2

    jderimig

    jderimig

    jderimig

    Sponsor TRF Sponsor

    Joined:
    Jan 23, 2009
    Messages:
    2,833
    Likes Received:
    288
    $$$$$$$$$
    I am curious on what response you get. That's a pretty tight tolerance for a long wet noodle.
     
    dhbarr likes this.
  3. Oct 4, 2019 #3

    timbucktoo

    timbucktoo

    timbucktoo

    Well-Known Member Staff Member Global Mod

    Joined:
    Jun 13, 2014
    Messages:
    5,896
    Likes Received:
    505
    Gender:
    Male
    Location:
    Cocoa Beach
    moved to yard sale
     
  4. Oct 4, 2019 #4

    SinfulDarkLord

    SinfulDarkLord

    SinfulDarkLord

    Well-Known Member

    Joined:
    Feb 21, 2012
    Messages:
    2,571
    Likes Received:
    8
    Thank you Tim
     
  5. Oct 4, 2019 #5

    dhbarr

    dhbarr

    dhbarr

    Amateur Professional TRF Supporter

    Joined:
    Jan 30, 2016
    Messages:
    5,521
    Likes Received:
    528
    Have you considered ground hydraulic piston and/or ground precision oilfield rod?

    NOTE: I'm not saying it'll work, it just seemed feasible on the surface when I looked at it and put it on the "not now" pile
     
  6. Oct 5, 2019 #6

    SinfulDarkLord

    SinfulDarkLord

    SinfulDarkLord

    Well-Known Member

    Joined:
    Feb 21, 2012
    Messages:
    2,571
    Likes Received:
    8
    It will work, but they are extremely heavy. The last thing I need is to be sent to the hospital with a broken back lol.
     
  7. Oct 5, 2019 #7

    wsume99

    wsume99

    wsume99

    Well-Known Member

    Joined:
    Feb 28, 2014
    Messages:
    80
    Likes Received:
    3
    My 2 cents .... I think you'd be better off having the tubing centerless ground. Not sure what it would cost. Turning something that long to that tolerance will not be easy.
     
    SwingWing, dhbarr and AeroAggie like this.
  8. Oct 5, 2019 #8

    AeroAggie

    AeroAggie

    AeroAggie

    Forum Supporter TRF Supporter

    Joined:
    Jan 21, 2017
    Messages:
    222
    Likes Received:
    47
    Gender:
    Male
    Location:
    Wichita, KS
    Are you going doing room temperature cures or are you putting them in an oven? The thermal expansion alone is likely greater by a factor of two or three than the tolerance you're asking for.

    Why does your tolerance "have" to be 0.002? Because it sounds cool? I'm not a machinist, but I am an aerospace engineer in the business of making really expensive composite parts for commercial and defense applications and I can tell you, 0.002 is a bit...sporty. It's not unheard of, but it's certainly not in the realm of "normal" in most aerospace applications. Tooling companies add a lot of zeros to tooling when you ask for that kind of precision. We use multi-million dollar Invar tools for some of our products and they're not that tight.
     
    Wallace, 0011001100 and dhbarr like this.
  9. Oct 5, 2019 #9

    Chris_H

    Chris_H

    Chris_H

    Well-Known Member

    Joined:
    Sep 13, 2017
    Messages:
    419
    Likes Received:
    55
    Refining and defining your tolerances will yield better response. Or, taking an approach of searching for a machinist who is set up for turning lengths of tubing, and then ask them what they can do. If their tooling is good, and they are skilled, they can probably do what you need. In thinking of all of the places that a tolerance of 0.002" could be applied, some are realistic, some are highly unlikely. Is that plus 0.002" or minus .002" or +/-.002"? and where? Sounds like some more research into learning what your needs really are, and how to ask for it is the next step. Good luck.
     
  10. Oct 5, 2019 #10

    Garyb

    Garyb

    Garyb

    New Member

    Joined:
    Oct 21, 2017
    Messages:
    4
    Likes Received:
    0
    Gender:
    Male
    Location:
    S.W. Illinois
    I would love to give you a quote. first what is the final finished diameter, second what kind of finish are you wanting.the second question will mean a lot to the price, along with a realistic tolerance.
    Thanks Gary
     
  11. Oct 5, 2019 #11

    SinfulDarkLord

    SinfulDarkLord

    SinfulDarkLord

    Well-Known Member

    Joined:
    Feb 21, 2012
    Messages:
    2,571
    Likes Received:
    8
    How close of a tolerance can you get? The annoying part about aluminum is its high thermal expansion compared to other metals, makes it have the need for some tolerance.

    I am looking for a 2.998” 3.498” and a 54mm at 2.148”. Let me know if this is do-able. I am not too crazy about the finish being polished or anything so no finish.
     
  12. Oct 5, 2019 #12

    SinfulDarkLord

    SinfulDarkLord

    SinfulDarkLord

    Well-Known Member

    Joined:
    Feb 21, 2012
    Messages:
    2,571
    Likes Received:
    8
    It is going in an oven. By saying it has to have a 0.002” tolerance, is due to the nature of how a tube is turned down on a lathe. Even machines are not perfect and so there can be a taper on one end. That taper needs to be very little or else the cured composite tube can be stuck. I don’t know why you imply that it sounds cool, but let me assure you that it is not, because if I don’t have a good tolerance I can kiss the cured composite tube and the expensive mandrel goodbye.
     
  13. Oct 5, 2019 #13

    OverTheTop

    OverTheTop

    OverTheTop

    Forum Supporter TRF Supporter

    Joined:
    Jul 10, 2007
    Messages:
    2,910
    Likes Received:
    547
    Gender:
    Male
    Location:
    Melbourne Australia
    0.002" is only 50um. That's not a particularly tight tolerance to get. Although confounding that is the fact it is aluminium and long, as others' have stated.

    We have some parts machined to around 5um tolerance, but they are the stainless rods in the quadrupole of our mass spectrometer.
     
  14. Oct 5, 2019 #14

    TimothyG

    TimothyG

    TimothyG

    Well-Known Member

    Joined:
    Nov 1, 2018
    Messages:
    200
    Likes Received:
    70
    Gender:
    Male
    Also at what temperature are you wanting your toleranced dimension? Seeing as how you’re oven curing these does it need to cure at this dimension? So at heated temperatures?
     
    OverTheTop likes this.
  15. Oct 5, 2019 #15

    thequick

    thequick

    thequick

    Well-Known Member

    Joined:
    Sep 8, 2015
    Messages:
    110
    Likes Received:
    7
    How about machining the cured tube to size rather than the mandrel? If you get it within a few thou then you can ream it (or bore it?) to the final dimension without removing too much material. And you eliminate the thermal expansion variable coming into play.
     
  16. Oct 6, 2019 #16

    SwingWing

    SwingWing

    SwingWing

    Well-Known Member

    Joined:
    Jan 18, 2009
    Messages:
    1,801
    Likes Received:
    16
    This is your answer. look for centerless grinding or bar grinding in your area
     
    AeroAggie likes this.
  17. Oct 6, 2019 #17

    patelldp

    patelldp

    patelldp

    Well-Known Member

    Joined:
    Jan 23, 2009
    Messages:
    5,454
    Likes Received:
    35
    You're probably best off sourcing DOM tubing in those dimensions. Seeing as they're common rocketry dimensions (aside from the 3.5"), odds are ALCOA is already making them or an email to Gary at AG71 machining (gar741a@hotmail.com) MAY turn up what you need, assuming he has material left.

    Ask yourself if you truly need that tight of tolerance. In hobby rocketry, the answer is likely a resounding "NO."
     
    Binder Design likes this.
  18. Oct 7, 2019 #18

    Mendal

    Mendal

    Mendal

    Well-Known Member

    Joined:
    Feb 5, 2016
    Messages:
    215
    Likes Received:
    11
    I agree with what others have stated that you should be looking for someone to centerless grind these tubes for you.
     
  19. Oct 7, 2019 #19

    jbr

    jbr

    jbr

    Well-Known Member

    Joined:
    Nov 22, 2017
    Messages:
    188
    Likes Received:
    73
    54mm tubing even at 36 inches is a real pain to lathe
    good luck in your quest
     
  20. Oct 7, 2019 #20

    heada

    heada

    heada

    Well-Known Member

    Joined:
    Jan 18, 2009
    Messages:
    2,583
    Likes Received:
    145
    Gender:
    Male
    Location:
    Indianapolis, Indiana
    I've seen video of some machinists that can get those tolerances on steel over an 8ft long, 4in diameter solid shaft but not in 6061 Al hollow tubing. You could find someone with a tool post grinder that might be able to come close.
     
  21. Oct 7, 2019 #21

    jsdemar

    jsdemar

    jsdemar

    Well-Known Member

    Joined:
    Dec 31, 2009
    Messages:
    2,177
    Likes Received:
    241
    I have made mandrels to those tolerances, but not from hollow tubing. My suggestion is to make it from solid aluminum with a slight overall taper, whatever you can tolerate in the final ID spec of the composite tube. The surface finish is also important to allow breaking the mold release bond.

    Another suggestion is to make the mandrel as two 36" pieces center-pinned together. The taper would be in both direction from the center (low at center, high at each end). Thread each end to crank in opposite direction to turn and pull the two-piece mandrel from both ends. The other advantage of two 36" pieces is that you'll find more people will lathes that can handle that length.
     
    dhbarr likes this.
  22. Oct 7, 2019 #22

    SDramstad

    SDramstad

    SDramstad

    Well-Known Member

    Joined:
    Jun 26, 2014
    Messages:
    246
    Likes Received:
    47
    You probably dont need that kind of absolute accuracy on the size what you need is a variance of +-.002. If the size is off 50 microns its not a problem as long as the diameter is consistent.
     
  23. Oct 8, 2019 #23

    alexzogh

    alexzogh

    alexzogh

    Well-Known Member

    Joined:
    Sep 30, 2010
    Messages:
    563
    Likes Received:
    20
    As a user of Mandrels in a filament winding machine, I appreciate the original poster’s request - very hard to get off if the tolerances vary too much.

    I really like John’s idea above. May give it a whirl.

    I've also used 3d printed mandrels - if you print using HIPs filament, you can just dissolve the mandrel post cure in D-limonene.
     
  24. Oct 9, 2019 #24

    Rocket501

    Rocket501

    Rocket501

    Member

    Joined:
    Feb 9, 2018
    Messages:
    23
    Likes Received:
    1
    First of all, my apologies, but I am unable to meet your request. I am not allowed to manufacture parts for sale on school machines.

    However, as someone who has machined aluminum for this same purpose, I can say I have serious doubts that this would work, especially with the tubing you supply. My experiments with 4" inch OD tubing (0.125 wall) went poorly. There was noticeable warping after just two curing cycles.

    If the parts are going into a curing oven, unless you use solid, stress-relieved aluminum rod (which is rather expensive), the mandrel is most likely going to warp way out of tolerance and soon become unusable.

    For you, I believe the real challenge will be to find someone with the equipment necessarily to machine something 72 inches long. Since we do all of our machining in house, I don't really know who to approach.

    I really like the tube I purchased from you and wish you luck with your business.
     
    0011001100 likes this.
  25. Oct 9, 2019 #25

    JohnCoker

    JohnCoker

    JohnCoker

    Well-Known Member

    Joined:
    Apr 13, 2013
    Messages:
    1,561
    Likes Received:
    181
    I have gotten quotes from eMachineShop before; you can submit a STEP file online.
    https://www.emachineshop.com/

    I spent about $5000 for a 50" long, 5" diameter Al mandrel back in 2000, so that's probably not relevant any longer. Widespread CnC machining should bring that price down quite a bit, but the length you're asking for will reduce the ease of making it.

    Note that if the mandrel is not tapered, you will have a very hard time getting the part off (at least the first part or two until the mandrel is seasoned). I had to pack in the inside of the tube with dry ice for hours then pound from the end to get the first part off.

    [​IMG]

    jcrocket.com/nike-asp.shtml#tubes
     
  26. Oct 9, 2019 #26

    SinfulDarkLord

    SinfulDarkLord

    SinfulDarkLord

    Well-Known Member

    Joined:
    Feb 21, 2012
    Messages:
    2,571
    Likes Received:
    8
    Thanks Rocket501,

    I’m curious what temperature did you heat it to? I never had an issue with warping thus far. Even with 1/16” walled aluminum tubing.

    Also do you happen to know what type of aluminum was it? I know some metals down work so well with heat at low temperatures.
     
  27. Oct 9, 2019 #27

    SinfulDarkLord

    SinfulDarkLord

    SinfulDarkLord

    Well-Known Member

    Joined:
    Feb 21, 2012
    Messages:
    2,571
    Likes Received:
    8
    $5,000 ouch, I for sure will not pay that price. I will be sure to have it tapered, I was told it is better that way and I can see why.

    Thank you John
     
  28. Oct 10, 2019 #28

    Rocket501

    Rocket501

    Rocket501

    Member

    Joined:
    Feb 9, 2018
    Messages:
    23
    Likes Received:
    1
    We cured the tubes at a maximum temperature of 300 degrees Fahrenheit for three hours.The alloy used was 6061 T6 aluminum. There wasn't all that much warping, but it was enough to prove troublesome.
     
  29. Oct 10, 2019 #29

    SinfulDarkLord

    SinfulDarkLord

    SinfulDarkLord

    Well-Known Member

    Joined:
    Feb 21, 2012
    Messages:
    2,571
    Likes Received:
    8
    Ouch, yeah I never liked having a cure shedule of more than an hour. I mostly cure mine at 180F or 200F for an hour and that is it.

    It is enough for the mandrel to expand and for the resin to cure rock solid. Once cooled the tubing would slip out.

    I had issues in the past due to the short pot life of most resin systems. The resin would become solid first, before the aluminum could expand. This caused a tight grip around the mandrel and I could not remove it without the aid of a pick up truck to yank it out. The result ended up damaging my mandrels.
     

Share This Page