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CNC Noob Fixture Plate Question

Discussion in 'CNC IN THE HOME SHOP' started by Jonathans, Jun 18, 2017.

  1. Jonathans

    Jonathans United States Professional Fish Killer H-M Supporter-Premium

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    I'm still waiting on delivery of my mill. The use of a fixture plate looks very appealing.
    My question is this: Why do folks who own a decent mill purchase ready made fixture plates?
    Aren't their own mills more than capable to make an acurate one themselves?
    Are commercially made ones more precise?
    Is the choice of steel or aluminum significantly different when choosing an appropriate material?
     
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  2. JimDawson

    JimDawson Global Moderator Staff Member Director

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    Of course you can make your own fixture plate. Some people would just rather buy than to take the time make their own. Aluminum is easier to work and less durable than steel, but should give years of service in a hobby environment. For a commercial application, tool steel would be a better choice.

    On the other hand, in 50 years of making chips I have never used one. But if I needed one, I would just build it.
     
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  3. shooter123456

    shooter123456 United States Active Member Active Member

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    If I were to guess the reasons others would buy instead of make them:
    Time. You could be talking 100 holes that need to be spot drilled, drilled, reamed, then tapped. If your mill doesn't do rigid tapping, that would sure take a while.
    Uncertainties about precision. Can't quite get that tram right to flycut perfectly flat? A little too much runout in your drill chuck to drill holes within the tolerance?
    Lack of travel. A lot of the plates I have seen are a good bit larger than the mills travels. Sure its possible to machine precisely while pausing to refixture a part, but that adds time, complexity, and regardless of how careful you are, error.
    Factory bought ones are relatively inexpensive. When compared to the time to design, fixture, and machine, a lot of the time it is "cheaper" to just buy one.
    Not everyone's cup of tea. Some people want to make parts and see the tools/fixtures they need as inconveniences to get around. There's nothing wrong with that, and to those people it might make the most sense to buy it.

    Personally, I love building the tools and fixtures I need to make the parts I want. It all just depends on what parts of the hobby bring you the most satisfaction and what means you have to get there. For me, designing the plate and machining it would be as satisfying as making the part I need the fixture for. I could probably afford to buy the tools I need, but that would take money away from buying the things I can't make.
     
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  4. Boswell

    Boswell United States Hobby Machinist since 2010 H-M Supporter-Premium

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    I think Shooter's summary is right on. I will only offer that I am at the other end of the spectrum where I would rather purchase the tooling that I need and use my time to make parts. It is a trade off between price to purchase and time and skill to make. Occasionally I will made a tool because the cost/time trade off is just so lopsided even I can't ignore it. Of course when you need a custom fixture, there is no choice. I have a ton of respect for those that make a lot of what they use, often starting with the machine. It is just not my thing. I am not retired so I have and income and limited hobby time. Once I retire, the equation may work out much different with more time than money. In the end, if it is hobby then the choice to build or buy is personal so do what makes you happy.

    - a different perspective -
     
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  5. Jonathans

    Jonathans United States Professional Fish Killer H-M Supporter-Premium

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    Good perspectives, all.
    If using aluminum, whether manufactured, or self made, is there a risk of electolosys between the plate and the table?
     
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  6. JimDawson

    JimDawson Global Moderator Staff Member Director

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    I suppose that if you were using a water based coolant, and left the plate permanently mounted, there could be a problem, but rust would be more likely. Oiled paper between the table and the plate would pretty much eliminate the possibility of either.
     
  7. Cheeseking

    Cheeseking United States Active User Active Member

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    Here is what I did for a tooling plate fixture...
    [​IMG][​IMG][​IMG][​IMG]
     
  8. Jonathans

    Jonathans United States Professional Fish Killer H-M Supporter-Premium

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    Am I the only one who can't see Cheeseking's photos?
     
  9. dlane

    dlane Active User H-M Supporter-Premium

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    No , it's probably a tapatalk thing, if you hit reply it might load the pics.
     
  10. Cheeseking

    Cheeseking United States Active User Active Member

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    Sorry guys. Every so often my phone settings get change and I inadvertently post the dreaded x boxes. Funny I never use my pc much anymore I'd be dead without tapatalk. Works very nice for me and soooo much easier to post pics and read forums. Anyhoo lets see if these post

    ImageUploadedByTapatalk1498084153.505104.jpg
    ImageUploadedByTapatalk1498084204.425196.jpg
    ImageUploadedByTapatalk1498084241.526337.jpg
    ImageUploadedByTapatalk1498084320.881405.jpg
    ImageUploadedByTapatalk1498084358.117458.jpg
     
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  11. Cheeseking

    Cheeseking United States Active User Active Member

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    My theory on the fixture plate is why drill ALL the holes ahead of time? Drilling and tapping hundreds of holes is a lot of unnecessary labor up front when most will go unused. I simply put a zero locating dowel in the center x,y so to add more holes I just need to drop it on the table, the dowels on the feet fit snug in t slots so just indicate center pin in table and drill new holes as req.
    I don't tap the holes. Instead I use F drill .257 and c-bore for standard press fit type bushings. 1/2"od x 1/4"id x 1/2"h. Bushings are a slip fit to the c-bores and serve to elevate the stock off the plate. Very inexpensive and I have about 8-10 but usually 4 is plenty to hold the work. Reason being is I make pattern cores from HDPE and modeling board and all the sides get tapered and machined down to the bottom. Rather than screw down to a wood or other spoil board I just elevate on the spacers.
    If 1/4-20 is too large a thread to tap in the part I have used 10-24/32 screws with washers. The spacers still work the same located in the c-bores.
    Now I know there are lots if ya but's about this way of doing it.
    Its not good for every situation. Not the most rigid/super accurate if re-locating the part becomes necessary.
    I cut stuff all in one and done.
    For hogging steel its not the way
    True, tapped holes in the bottom of the part may not always be acceptable.
    Being raised up off the table allows me to take it on and off without messing with my vise.
    If need be I can make taller standoff feet or space them farther or closer together.
    It sacrifices about 5" of Z height.
    If I need to clamp from the top, the .257 holes are conveniently the tap drill for 5/16-18.
    The only real purpose for the c-bores is to keep the spacers aligned with the tapped holes in the part. Lot less fiddling with my 6" scale fishing underneath moving them around to get them in line.
    Raised up and thru holes I never need to mess with clearing packed chips out of holes or using a jillion setscrews which still get chip packed in the hexes.
    I don't wear out/gall/strip threads in aluminum plate.
    Much less labor than threading all them holes.
    My table stays mint, no rust between plate etc since the table comes off when finished.
    Thats my story and I'm sticking with it....
     
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  12. Boswell

    Boswell United States Hobby Machinist since 2010 H-M Supporter-Premium

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    Cheeseking, I like the idea of the spacers you can mount your fixture plate without having to remove the vice.
     
  13. Jonathans

    Jonathans United States Professional Fish Killer H-M Supporter-Premium

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    Cheeseking,
    I like what you did for projects that don't require a lot of rigidity.
    If you don't want to remove the vice, and the fixture plate is small enough
    have you considered making a plate that clamps into the vise?
     
  14. Cheeseking

    Cheeseking United States Active User Active Member

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    Yes I do that occasionally. Have even screwed material down to a S4S pine board clamped in the vise. For one off light work it does the job.
    For ready made fixture plates check these out - http://www.baselabtools.com/Tables--Breadboards_c_11.html
    I stumbled on them awhile back. Looks like its for optics prototyping but pretty cool
     
  15. fretsman

    fretsman Active User Active Member

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    Thanks for posting that, any ideas of the flatness specs on those plates?

    Thanks,
    Dave
     
  16. Cheeseking

    Cheeseking United States Active User Active Member

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    I don't but there may be specs listed somewhere on their website. We have a laser marking machine at work and another engineer bought one to fixture parts. I thought it was cool and made note of their site. Prices arent bad a 3/4" 12 x 18 was about $200 iir.
    I think the way these are used (or at least how I do) the flatness really isn't relevant. My twist on the fixture plate is sort of a offshoot of the OP's original question. If folks are looking to laminate their tables with something larger, semi permanent where vises get mounted on top then I guess the super flat, million threaded hole plates are better.
    I added mine to the sprutcam fixture library...
    [​IMG]
     
  17. fretsman

    fretsman Active User Active Member

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    thanks for the info, I actually checked the sight closely and I don't see anything so I will shoot them an email.
     
  18. fretsman

    fretsman Active User Active Member

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    Just an update, those plates are only guaranteed to be within .015" which is not good at all for what I need.

    Just wanted to share in case anyone was serious about buying one.
     
  19. dlane

    dlane Active User H-M Supporter-Premium

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    I once got a 2x3' X 1-1/4" aluminum plate called MIC 6 that was flat , it's made for cnc fixturing plates
    Got it cheep , it has turned into smaller plates now
     
  20. MontanaAardvark

    MontanaAardvark United States H-M Supporter - Premium Content H-M Supporter-Premium

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    I really have to thank you for this link. I've been back and forth between making and buying a tooling plate since I posted on this back in April. They have a 6x18 plate, which is probably a good fit for my G0704 at a very reasonable price, and not that much more than plates half the size for Sherlines I see on eBay. To top it all, those eBay plates aren't anodized.

    Seems like a good compromise. Most of the time, the flatness is probably acceptable.


    Bob
     
  21. Jonathans

    Jonathans United States Professional Fish Killer H-M Supporter-Premium

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    Well, after all my prep to make my own plate I ended up buying a commercially made one.
    I decided I wanted a hardened steel plate that was blanchard ground. I soon found out that thes were quite expensive.
    Hover, I made a bid on a new from mfg Tosa TT1634C on Fleabay and I ended up being the only bidder. It was a fluke,
    but I got it for 60% off of the regular price. Not a whole lot more than the steel and grinding would have cost me if I had made my own.
     

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