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OpenBuilds Parts Store M5 x 20mm low profile screw dimensional problem

Discussion in 'CNC Mills/Routers' started by T762, Nov 14, 2017.

  1. T762

    T762 Well-Known
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    TL;DR- Openbuilds Parts Store M5 x 20Mmm low profile screws have a head dimension to large for the C-Beam aluminum end plates and may bind in the hole, preventing normal removal of the screw. Consider sourcing other screws or reducing the diameter of the provided screw head.

    During a recent build of a c-beam machine I found that the M5 20mm low profile screws I received had a significantly larger head diameter than the others. Other screws I measured were on average .011" smaller in head diameter of my 20mm screws. Unfortunately this means that the 20mm screws head is actually larger in diameter than the couterbored hole in the C-beam end mount plates. This causes the screws to bind around their perimeter when inserted as instructed. This binding may prevent the screws from being removed because it can lead to stripping of the hex socket.

    During my build I had to remove the plates to correct an error. I found that one screw on each plate was bound and could not be removed without stripping the socket. Interestingly enough you could actually see on the sides of the hole how the aluminum had been deformed by inserting the screw. (A slight crater like ridge that could be seen with the correct lighting). I was able to remove the plate by removing the lead screw an the other 3 screws in the plate, then rotating the plate the unthread the screw.

    I suggest that if you find the screws not seating properly in the aluminum plate, that you either get new screws or possibly attempt to reduce the diameter of the screw before using. I am not sure but its possible that a drill combined with a file or sand paper could remove enough to correct the fit. If you don't, you may find yourself in my shoes with a near permanent connection that can't be easily removed without damage.

    I should note that I contacted the Open Builds part store about the issue a week ago and they have thus far failed to provide any response except "We'll remind the person responsible to get back to you". Very disappointed with the lack of customer service in any shape or form.

    If there is this much variation in screw head diameter I suggest that the design be modified by increasing the size of the counterbored holes to account for variation in the screws.

    I ended up purchasing more screws to replace the damaged ones and will likely take a little off of the diameter using a lathe.

    Good luck! And hopefully you have a better CS experience with open builds than I did.

    P.S. This is my 3rd CNC router, the first being a Shapeoko 2, and the second CNC Router Parts 4x8 Pro. So far this thing seems WAY more robust than the Shapeoko 2, very excited to get it up and running.
     
  2. patdee

    patdee Journeyman
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    I am sad to say that this kind of "apathy" on most companies is getting worse with every passing day.

    I left a question (because they were closed that day) to "Open Builds Parts store" recently; and I received NO response for days. Finally it came; but it was much later than what I thought was good "customer relations".

    This bugs me to no end with MOST companies today. Yet NO one would know this by their websites and their bragging on themselves in various and sundry ways; of how wonderful they are.

    But the worst of all is MOST companies are opting of late to have NO telephone communications with their customers. This is dead WRONG; and a crime and should be punished as a felony IMHO.

    Oh well.
     
  3. Giarc

    Giarc Master
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    Hmmm... I haven't noticed bragging. Also, explain why the lack of a phone number should be a felony. No one is forcing anybody to do business with them, or any other businesses that choose email as their primary communication.
     
  4. Flash22

    Flash22 Veteran
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    This can happen with a change in suppliers, or a spec change, tbh if you got them from ooznest or the opensbuilds shop they usually sort out any issues

    Felony, is a bit of a ott reaction, if you don't like the way a company works eg. no phone support, vote with your feet and buy from another supplier

    What I have come across is imperial bolts being sold as metric

    As for the op's problem if it binds or gets tight, back it off, put all the bolts in loose (hand tight) and then nip them up if it 'feels' wrong it probably is), its always worth running a chase or tap down a thread to make sure its clean

    If you have a stuck screw soak the area with wd40 or release agent (GT85 or Plus Gas but I'm not sure if you can get them that side of the pond), if your in a cold shed/garage/workshop move the part in to a warmer environment for a few hours, failing that heat up the area with a hot air gun as the aluminium reacts to temperature differently than the harden steel (cold alloy will grip the steel bolt)

    If you have managed to damage the head on a metric bolt try a imperial hex key/bit - If its too far gone drill the head of the bolt with a Ti (titanium) drill bit

    Over time and with experience you will get the feel for these things
     
    Peter Van Der Walt likes this.
  5. TrishC

    TrishC OpenBuilds Team
    Staff Member Moderator Builder

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    Hello T762. Thank you for reaching out to us. We have a resolution to the situation you described and have contacted you directly through email. We appreciate your patience and understanding and helpful feedback. Please know that we are taking care of this right away.
     
    GrayUK likes this.
  6. T762

    T762 Well-Known
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    Recieved the replacement screws, Diameter is smaller on average but they still bind in the holes. The first batch averaged maybe 9.15mm on max measurement of the head, while the holes measure just under 9mm, the replacements averaged around 9.10mm(Maybe they won't bind so firmly, but I'm not eager to test it when the system still doesn't seem to be performing as intended).
     
    #6 T762, Nov 29, 2017
    Last edited: Nov 29, 2017
    Retrosmith likes this.
  7. T762

    T762 Well-Known
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    Just an update for everyone. Openbuilds did reply to me after a week and several emails. They sent a bag of replacement screws and I ordered a set separately. I received them the Saturday before thanksgiving and have now had my first chance to attempt to start a new build. Unfortunately both sets have an oversized screw head (which isn't present on other screws I have tested in the kit). The set they sent me did have a slightly smaller diameter on average, but they still do not fit properly.

    I'm shocked at how much of an ordeal this is to get resolved. I have been interested in open source hardware for quite some time and love the idea of it. I also understand that this is a kit and not intended for an inexperienced consumer. However I also can't see how these parts could be shipped together knowing the effect it has on the end user. My personal experience with Openbuilds has been pretty negative. I hope to continue the build on this to fully evaluate it, but will definitely take the part and customer service issues into account for any future purchasing decisions. (Although on principle I want to simply return the kit because my experience has been so frustrating, but the design seems to have a lot fo promise for a compact router.)

    Hopefully they reply to me and can provide proper parts.
     
    #7 T762, Nov 29, 2017
    Last edited: Nov 29, 2017
  8. T762

    T762 Well-Known
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    Thanks for the suggestions. In my case, the holes in the aluminum extrusion were tapped properly, the issue was the head diameter (You can actually see where the aluminum end plates deformed around he counterbored hole just slightly. The edges of the hole "cratered" up as the screw was inserted and displaced the aluminum. This caused the aluminum end plate to grip the screw head very tightly. I did use the proper metric hex keys, but they still stripped on one screw on each end plate. I attempted to drill and use a screw extractor, no luck. I had to remove 3 of the 4 screws and then unthread the final screw by rotating the entire end plate. Had another screw been stuck the entire assembly would have been permanently assembled, requiring drilling to disassemble.

    The frustrating things is that this seems like SUCH a preventable problem. For example, making the countebore larger in diameter or ensuring that the sources screws are appropriately sized.

    For reference, the 8mm screws in the kit have a head diameter (measured at its maximum since the heads are slightly out of round) of about 8.90 mm. They drop freely into the counterbored holes. However, the majority of the 20mm screws have a head diameter of 9.15mm or greater.

    I did go back and measure the bag of screws that they said were tested. Upon closer inspection it looks like they generally are smaller in size, Most around 9.10 mm diameter. (however they still do not fit freely in he counterbores)

    I am measuring the counterbore diameter of about 8.98mm (only with a pair of digital calipers, so that is not a perfect measurement).

    That still leaves ALL 20mm screws I have with an interference fit in the hole. Yet screws of other lengths fit fine.

    It seems that this may be caused by a combination of several problems. Out of spec screws, possibly slightly under sized holes (assuming the design called for 9mm holes), and a design that itself is not tolerant of the variation in screw head diameter from their suppliers. I would suggest to open builds that they modify the design to increase the size of the counterbores on the end plates at a minimum, but probably plate with counterbores should their screw supplier have issues.
     
  9. Rick 2.0

    Rick 2.0 OpenBuilds Team
    Staff Member Moderator Resident Builder Builder

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    It's not the screws, it's the plates. The recesses are 9.0mm in diameter when they should be 9.2mm according to the published drawings. And I have 3 sets just like yours. While it's not a problem for me as I plan to put the lead screws in tension which means reversing the plates and thus the recesses are not used, I understand the frustration that comes with something not fitting right. You basically have 2 options. You can contact the store and get the plates swapped out or you can spin up the screws with your drill and sand the edges of the head down ever so slightly to where they fit. If you're in a hurry, I'd go with the latter as the shop is generally swamped this time of year so the process may take a while. But if you're a perfectionist (which I totally understand) get them swapped out.

    Please note that while I am a moderator, I am strictly a volunteer with no connection to the business end of the company which means when it comes to parts I am a customer like everyone else. And in the nearly 4 years I have been on the forum I have never come across a situation where OpenBuilds didn't take care of the customer 100%.
     
    MaryD and T762 like this.
  10. T762

    T762 Well-Known
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    Thanks for the info, I didn't think to check the specs on the plates (very dumb of me since that is the entire point of an open source design!). I'm glad to see that the design seems to be correct. Hopefully this was just an issue with a single batch and won't effect others.
     

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