How to shorten screw?

Discussion in 'Gunsmithing' started by cinch, Oct 29, 2008.

  1. cinch

    cinch Well-Known Member

    Messages:
    542
    Joined:
    Jun 4, 2006
    I recently installed a Ken Farrel 20 moa base on a SA Remington 700 only to find the front screw was a little too long. What is the best way to shorten this screw without dammaging the threads? It doesn't need much, but it is not seating down against the base. Thanks for the advice in advance. Cinch
     
  2. specweldtom

    specweldtom Well-Known Member

    Messages:
    1,066
    Joined:
    Jun 7, 2004
    cinch, I use a tool from Brownell's called a screw gizzie. It holds the screw and helps you gage how much you're taking off. I use a 120 grit belt on a belt grinder to shorten if it's just a little; like 1/8" or less. If it's more, I just cut them a little long with dikes and finish them up square on the the belt grinder. When I've got it the length I want, just barely bevel the new end of the screw to help it start. After it fits, I cold blue the raw end and rub a little gun oil on it. Works every time.

    Tom
     

  3. eddybo

    eddybo Well-Known Member

    Messages:
    1,651
    Joined:
    Jan 5, 2007
    Thread a piece of sheetmetal for the screw. Thread the screw through the sheetmetal allowing only what you want removed the extend past the surface. Grind the screw flush with the sheetmetal.
     
  4. vintec

    vintec Well-Known Member

    Messages:
    148
    Joined:
    Jan 18, 2008
    I would scew a nut on the bolt, two if you have enough room. Then you can use one nut as a jam nut to control the amount you remove. The nut also will allow you to grip the bolt with out damageing the head. When you remove the nut, it will help remove he burrs left from cutting or grinding the bolt.
     
  5. Ridge Runner

    Ridge Runner Well-Known Member

    Messages:
    987
    Joined:
    Dec 13, 2002
    I just chuck them in a cordless drill, and hold against sandpaper or grinding wheel at a slight angle, keep them spinning and touch the disc, be careful makes small screws short fast.
    RR
     
  6. cinch

    cinch Well-Known Member

    Messages:
    542
    Joined:
    Jun 4, 2006
    Thanks for all the info. I'll have to try and do it this weekend.
     
  7. NesikaChad

    NesikaChad Well-Known Member

    Messages:
    753
    Joined:
    Jan 28, 2007
    This is how I do it.

    Two methods depending on the type of screw.

    Guard Screws.

    I have a plate drilled and tapped with various thread pitches for an assortment of actions. The screw is installed and snugged up to either the shoulder or to where the threads stop on the shaft.

    Throw it in a vice on a set of parrallels and touch off with a 1/2 inch endmill. Zero the DRO's Z axis and remove what ever is required. Then I give a quick spin against a Kratex wheel to knock off any burrs and to put the lead back into the initial thread.

    Now, a simple trick goes along with this that some might find handy. Say its a guard screw that cannot interfere with something else (like the bolt). Assemble the rifle as you normally would. Snug everything up in the stock. Insert the bolt and then start backing out the screw while counting the revs. When the bolt falls into battery you know you've gone far enough with the screw.

    Remington's, Nesika's, and many other actions use a 28 pitch on the thread. 28 threads per inch comes out to .036" per rev so if the screw took four 1/2 turns to allow the bolt to drop, then just multiply 4.5 X .036" and that's how far you plunge with your cutter.

    I generally do little screws (scope mounts) by grabbing the shaft with a pair of hemostats and giving a quick swipe with a belt sander followed by a Kratex wheel. Hemostats allow me to throw a caliper on the screw easy enough to keep track of the progress. If I ever get around to it, I'll modify my fixture plate to work with these as well.

    Hope this helps.