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I want to be a metric purist

Discussion in 'General Talk' started by Lee Saferite, Jun 14, 2014.

  1. Lee Saferite

    Lee Saferite Journeyman
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    This is a bit of a ramble with a TLDR of "I would prefer to work solely in metric."

    The eccentric spacers from the OB store (and any other store I could find them at) are a mixture of metric and US. The I.D. is set for M5 screws and the length is 1/4". I cannot find M5x8mmx0.25" concentric spacers, they don't seem to exist unless maybe you can have them custom made ($$$).

    This would be partially ok if not for the cheap spacers the OB store has been using (no offence Mark). The I.D. of those spacers is much too large (7mm) and material is much too thin (0.5mm). This is causing my bearing bolts to skew just slightly when tightened. This in turn makes the bearing too tight or too loose depending on how the spacer is sitting. The eccentrics are only designed to tighten the carriage to the rail, not make up for mis-aligned bearings. If the spacers were the correct M5x8mm spacers, you'd have an I.D. of 5.0-5.2mm and an O.D. of 8mm with a material thickness of 1.4-1.5mm. Even better if we used M5x10mm spacers as then you get a solid 2.4-2.5mm material thickness and the spacer becomes much more stable. Of course, this again comes back around to the fact that the length we need is 1/4" due to the eccentrics using a mixture of sizes.

    So, since we have this mixture I thought maybe I would try to find a way to normalize the eccentrics to metric lengths. 1/4" in metric is 6.35mm and my idea was to find a M5x1.35mm shim but I've been unable to source that part.

    Since I cannot source a shim to normalize the eccentric spacer, the other option would be to source metric only eccentric spacers. I cannot seem to find those either, at least no in the sizes we need.

    My current solution is to loosen all the bolts, assemble the pieces and slowly tighten them back working top down in an attempt to let the weight pull them all into the same alignment. I've yet to get it perfect but it's a little better. If there is a better way, please let me know.

    Perhaps I'm totally misguided on the spacer issue causing the bearings to be misaligned. Please tell me if I am.

    Even if I am misguided there, the mismatch of US spacers on an otherwise metric machine cause another issue, at least on the OX. The Y carriage uses a 65mm bolt with 2 wheels to span the double width Y beam. The spacing of the slots is 100% metric, but it's impossible to get the wheel spacing correct using a US spacer and metric shims. You can get close, but if you look at where the wheels ride, they are not correct. The slot centers are 20mm apart, the wheel center to outer edge is 5.5mm. That's 20 - 5.5 - 5.5 = 9. You need exactly 9mm between the bearings on each wheel. Using a 1mm shim on each side you need a 7mm spacer, not a 1/4" spacer (6.35mm). Frustrating, but solvable by finding an M5x8mmx7mm spacer at another shop.

    I love working with the OB v-slot rail, but I wish that all the parts were 100% metric.

    Comments and suggestions are greatly welcome.
     
  2. GrayUK

    GrayUK Master
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    It was bound to happen. I don't know how the Yanks manage in a Metric World. I did not grow up a "Metric Person", but have had to adapt, and to be quite honest, I find talking and working in Metric a lot easier to understand and visualise, than I used to in Fractions. I guess we went over to it, mainly because "they" are so close to us, just across the water, but the USA is a long way from the Metric Zone.
    What you have written about, just about blew my mind, although I got the gist of it.
    I don't know what the answer is, but it certainly needs to go, one way, or the other.

    Cheers
    Gray
     
  3. Mark Carew

    Mark Carew OpenBuilds Team
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    Thank you for the feedback Lee, this is what helps us grow and create a better overall system that works for everyone.
    We agree that we should be 100% metric and the spacers are in the works to be changed over. :thumbsup:
    We understand about the thin wall spacers and have been testing many different versions to find the best solution. So far we are happy with the 10mm OD M5 ID keeping it more in line with the 10mm eccentric can and creating a much more stable platform for the wheels to be tightened down solid to the plates. We are also working on an alternate 6mm eccentric and with that OpenBuilds will also become metric purist! ;)
    Thank you again for your feedback and suggestions.
     
  4. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    If dual wheel configurations are going to continue to be developed, a 9mm spacer really needs to happen. I can work with the 1/4" spacers at the end as the offset to the plate is really not important but we need something to properly set the distance between the wheels fairly soon.
     
  5. Mark Carew

    Mark Carew OpenBuilds Team
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    Agreed Rick, Lee and I had just discussed this today they are also on the list along with 3mm spacers and 6mm :)
    Thank you for he feedback
     
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  6. JustinTime

    JustinTime Master
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    Actually the USA is jammed between two metric nations. Canada, which is officially metric but still uses some imperial in the private section, an Mexico.
     
  7. GrayUK

    GrayUK Master
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    Well, I never imagined Mexico as being Metric! Would have thought they would be wrapped up in the Dollar.

    Gray
     
  8. Lee Saferite

    Lee Saferite Journeyman
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    The US is one of the non-metric holdouts left in the world.
     
  9. GrayUK

    GrayUK Master
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    And yet, the Dollar is based upon the unit of ten. That is really odd, but interesting? :rolleyes: It's just the "Imperial" weights and measures you're all hanging on to. That must be due to our Colonial brothers bringing it over with them, those "few" years ago. :D Still, they hung onto our Language as well, so it's not all bad. They did better than us. :ROFL: :ROFL:

    Gray
     
  10. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Is there any currency out there that isn't?

    As for the US going metric, it won't happen. Too many highway signs would need changed.
     
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  11. GrayUK

    GrayUK Master
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    Well we weren't, we used 12's and 10's, till they got us. I must admit, for our kids of today, currency is real easy to understand and work out. I think our pounds, shillings and pence, was the most complicated form of currency there was! We still hang on to Miles, because as you say, it will cost a fortune to change the road signs.
    I don't think the US will go metric, but I think it will be used, more and more, until it quietly slides in there between the shoulder blades.
    Gray
     
  12. bit53b

    bit53b Well-Known
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    That's great analysis - I am also building a double width axis and have noticed that the wheels do not sit correctly, using the 1/4" spacer and various shim combinations.

    Can you say where you found your M5x8mmx7mm spacers?
     
  13. Lee Saferite

    Lee Saferite Journeyman
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    Well, I was apparently mistaken and 7mm isn't generally available.

    that being said, a 6mm and 3mm without shims will give the needed 9mm spacing.

    3mm and 6mm are common.
     
  14. bit53b

    bit53b Well-Known
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    After much googling, I find I cannot source the metric spacers that I need. However, experimentation yields a satisfactory span on the double width Y Axis using multiple 1mm precision shims. Couple of questions arise:
    1) is this acceptable? I recognise that it is not very elegant, but are there any technical reasons why it may be a bad idea to use this many shims?
    2) using the "Ox approach" 1/4" spacer and 2 precision shims solution - I just can't get the correct wheel spacing. Curious if anyone else is hitting this (other than @Lee Saferite who started this thread!) - I'm not sure why this hasn't been flagged up before buy all the Ox builders - unless the ~1mm play is within overall tolerance?

    DSCF0125.JPG
     
  15. GrayUK

    GrayUK Master
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    Although I haven't looked, isn't it possible to find some small diameter tube, with a suitable sized bore, to be cut to length? It doesn't have be a "Spacer". Anything will do really. There must be something in the plumbing game that would adapt. Someone on an earlier thread found some pipe and cut it to size.
    By the way, my nickname is McGuyver. I can usually find something which will adapt.
    How about micro-bore copper pipe? I think a store we have here, called B&Q, used to sell piping like that.
    Model shops must do something similar.
    If that is nine washers, and the black one is the wheel hub, why does it have to be round. It looks like a cube of something about 9mm in size, with a suitable sized hole drilled through it, would clear the actual wheel, sit on the hub, and meet the purpose. There seems to be loads of room there.

    Just a thought. Haven't hit that problem yet myself.

    Cheers
    Gray
     
  16. Lee Saferite

    Lee Saferite Journeyman
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    Oddly, using those 1mm shims is significantly better than the current spacers OB is selling. The shims have a 5mm ID and 10mm OD, do they provide excellent stability.

    You could source 3mm and 6mm spacers and drop the shims between the wheels.

    Using metric V-slot and those 0.25" (6.32mm) spacers you'll never get the wheel alignment perfect. You'll be 0.32mm too wide or 0.68mm to narrow.

    You need exactly 9mm between the wheels.

    EDIT: Stupid auto-correct
     
    #16 Lee Saferite, Jun 21, 2014
    Last edited: Jun 23, 2014
  17. Mark Carew

    Mark Carew OpenBuilds Team
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    bit53b Great solution and I see no reason would not work like a charm.
    Actually, we have since updated and are now selling new (still need to update the pics and drawings in the part store yet) better quality 1/4" spacers that are 3/8"~9.5mm OD wide. The wider stance to will help stability as well as match the up coming metric spacers/eccentrics ;)
    Having all metric part compatibility is going to be very nice indeed :thumbsup:
     
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  18. Lee Saferite

    Lee Saferite Journeyman
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    Woohoo, that's great news!
     
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  19. GrayUK

    GrayUK Master
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    All the parts are coming. All the parts are coming.
    All the parts are coming. All the parts are coming.
    (Sung to the Coca Cola Christmas advert)

    Gray
     
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  20. Tweakie

    Tweakie OpenBuilds Team
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    :)

    Tweakie.
     
  21. bit53b

    bit53b Well-Known
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    Thanks - I did try to cut a longer spacer to length, but it was a disaster. Got me thinking though with your plumbing references that I could have used a pipe cutter for a better cut. I think the pipe would be too thin for the stability, but top marks for ideas!
     
  22. bit53b

    bit53b Well-Known
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    thanks - sounds like the spacers might appear on OB soon !
     
  23. Mark Carew

    Mark Carew OpenBuilds Team
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    Hey guys just a heads ups to let you know the metric spacers are available on the Part Store and we think you will like them! We are thankful to everyone who offered feedback to help make these possible.
    We have fattened them up to 10mm OD to make a much more stable platform with an M5 ID to give a thicker wall to keep the screw snug and centered.
    They are available in 3mm - 6mm - 9mm - 20mm - 40mm
    (6mm eccentrics also coming soon :) )

    [​IMG] [​IMG]
    http://openbuildspartstore.com/aluminum-spacers/
    Thank you for your support!
    Mark
     
  24. GrayUK

    GrayUK Master
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    Cheers Mark.

    The trouble is, I can't really remember how this first came to light? (It's an age thing) :duh:
    I know it was to do with the wheels across the X axis, not quite being positioned right, I think.
    I know I didn't order the ones I needed until these metric ones became available.
    As I say though, I can't quite remember what they were for. If you could recap I would be very obliged.
    Plus what size bolts, one would need now, because of the new metric size.

    That would be using Roberts plates as well!

    Many Thanks
    Gray
     
    #24 GrayUK, Aug 30, 2014
    Last edited: Aug 31, 2014
  25. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Mark,

    Do these space out the gap properly in double wheel configurations?
     
  26. Lee Saferite

    Lee Saferite Journeyman
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    The double wheel spacing was the whole reason these were needed.

    Yay!!!

    Thanks Mark.

    Now I'm eagerly awaiting the metric eccentric spacers and the puzzle will be complete.
     
  27. Lee Saferite

    Lee Saferite Journeyman
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    Mark, is there any plan to update the Ox part list and sketch up files with the metric parts?
     
  28. Mark Carew

    Mark Carew OpenBuilds Team
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    Yes Rick they do.
     
  29. Mark Carew

    Mark Carew OpenBuilds Team
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    We have a few made up already :) Just need to be sure all is well and we can run with them very soon! :thumbsup:
    When I find some time I will update them (easier for the parts list as an option) to be correct.
    Thank you all for the kind works as well as sharing in on the excitement, it makes it all worthwhile.
    Mark
     
  30. David Gustavson

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    We changed many of the highway signs during the gas shortage about 40 years ago. The change was started by gas prices--the old pumps couldn't handle prices greater than $1 per unit, so they switched to liters, which all the pumps apparently were designed to handle. Then people figured it would be good to just change over to metric distances as well. By the way, last I checked, metric is the preferred system in the US--it's just that the general public prefers the complicated old systems. But it didn't take long before all gas pumps were upgraded to handle the higher prices, and the system started slipping back to gallons.

    If there's anything harder than converting a culture to metric, it's gotta be converting it to metric then converting back! And in some cases we've done that cycle more than once. It's really sad. You'd think now that cars are metric, everything else would switch over. And it has, and then back, and then...
     

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