Moore & Wright 400 Series BS939 Engineers' Square 100mm (4)

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The blades of Moore & Wright 400 series BS939 Grade B 4" Engineers' squares are straight to a maximum total deviation of 8 microns, the working faces of the stock are ground to a unilateral (concave) tolerance of 6 microns and the two are square to each other (inside and outside) to a maximum total deviation of 16 microns.

Engineers squares have largely replaced conventional woodworking squares because of their superior ability to remain square.

A square is a tool for transferring squareness. They should be regularly checked against an inspection square (that is never used for anything else) and adjusted if necessary by judicious tapping of the corners against a soft but sturdy surface.

These Moore & Wright 400 series Engineers' squares are very accurately manufactured bits of kit indeed. I took a random selection of 15 of them in various sizes and systematically compared the inside and outside of each one with the outside and inside of every other one - spot on throughout!

  • 100mm / 4" (internal dimension)
  • BS939 Grade B
  • DIN875

6 Reviews Hide Reviews Show Reviews

  • 5

    Posted by Guest on 26th Jul 2022

    We use these squares here at Waters and Acland Furniture School and Fine Furniture Workshop. They are of high quality and are square. Thats pretty important. Well worth the investment.

  • 5

    Posted by Karen on 2nd Sep 2015

    Bought for my husband, he was very pleased. Said it pays to buy quality

  • 5
    A proper square

    Posted by Mike D on 8th Jan 2015

    Heavy but precise - quality through and through

  • 5
    Quality square, square!

    Posted by Kieron on 3rd Dec 2014

    We'll made and we'll proportioned, and all square. Don't bother with cheap ones just have these!!!

  • 5
    Square square's!

    Posted by K on 5th Nov 2014

    Very we'll made and most importantly they are square. Don't bother buying cheap non-square squares, just buy these Moore and Wright square's and you'll be very happy and square!

  • 5
    Quality Square

    Posted by Rick on 2nd Feb 2014

    This is a quality square for laying out joints and other detail work, echo the comments above