1. #1
    i am a newby to building a cnc and i am making the jgro cnc but the terminology of the nut and bolts IEhex head bolt 1/4-20x3/4 is confusing me how can i revert the term into metric as i live in england

  2. #2
    i2i's Avatar
    Lives in Cardiff, United Kingdom. Last Activity: 23-12-2016 Has been a member for 7-8 years. Has a total post count of 693. Received thanks 30 times, giving thanks to others 0 times.
    1/4 - 20 x 3/4

    Sounds complicated, but all you have to do is break it down into the three parts.

    1/4 = outside diameter of thread = 1/4" = 6.35mm
    20 = the pitch of the thread 20 threads per inch
    3/4 = the length of the thread = 3/4" = 19mm
    Hex head, that's the shape of the bolt head which in this case is a cylindrical head that has a hexagonal hole for an allen key

    If you're looking to replace the whole thing with metric, ie. if you're making it from scratch it would be 6mm x 20mm Hex head/cap head.

    The original bolt is probably 1/4 unf x 3/4"


    Edit, i've just noticed a few american sites are using "hex head" to describe a standard hexagonal bolt (six sided bolt head)
    Last edited by i2i; 29-06-2011 at 09:21 AM.

  3. #3
    Quote Originally Posted by i2i View Post
    Edit, i've just noticed a few american sites are using "hex head" to describe a standard hexagonal bolt (six sided bolt head)
    The type you use an allen key with is called socket head strictly speaking...

  4. #4
    Quote Originally Posted by Jonathan View Post
    The type you use an allen key with is called socket head strictly speaking...
    That's what i'm going to use, looks neater to me, more professional.

  5. #5
    Quote Originally Posted by deannos View Post
    That's what i'm going to use, looks neater to me, more professional.
    I agree, also the heads are stronger than phillips / slotted.

  6. #6
    Socket head screws are also called Cap screws as well. I find that the biggest benefit of using them is for access with tooling. You can get to them without the need for large spaces to fit a spanner and they can be counter sunk into your job as well. Just take care when tightening them up if you are using ball-end keys. I have snapped a few of them off inside the cap screw, particularly with cheaper tooling.

    Regards

    Ian

  7. #7
    Quote Originally Posted by Web Goblin View Post
    ...they can be counter sunk into your job as well. Just take care when tightening them up if you are using ball-end keys. I have snapped a few of them off inside the cap screw, particularly with cheaper tooling...
    Counterbored surely...:whistling:
    I've never snapped a ball-end key in one, but I have often had the key get rounded off and stop working. When that happens I just grind off the end of the key to make it into a standard key.
    I use socket head cap screws on everything, for the reasons you gave, except where the head is too high - then it has to be button head.

  8. #8
    Counterbored, ok I`ll give you that one. I had once snapped the ball end off a 12mm key trying to get a road wheel off a very old rusty shaft on a gas cutting machine. Ended up ordering a new wheel and shaft and cutting the shaft out with a gas torch. Right PITA it was too.

  9. #9
    many thanks for all the answers and for taking time out to look at the problem

Similar Threads

  1. Bolted Joints and Thread Fasteners
    By Lee Roberts in forum Gantry/Router Machines & Building
    Replies: 4
    Last Post: 01-04-2011, 09:53 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •