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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 at 9:01 PM.

  1. T762

    T762 New

    Nov 22, 2016
    Likes Received:
    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. Retrosmith

    Retrosmith Well-Known

    Oct 23, 2017
    Likes Received:
    Can confirm exactly this issue as well. In my case it wasn't every single screw, but probably 80% of them bound up in the motor plates as described.
  3. patdee

    patdee Well-Known

    Oct 31, 2017
    Likes Received:
    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.
  4. Giarc

    Giarc Master

    Jan 24, 2015
    Likes Received:
    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.
  5. Flash22

    Flash22 Veteran

    Sep 1, 2015
    Likes Received:
    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.
  6. TrishC

    TrishC OpenBuilds Team
    Staff Member Moderator Builder

    Mar 1, 2017
    Likes Received:
    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.

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