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TIE RODS AND SCREWS for Square Accessories
Tie Rods and Screws serve the same purpose as clamps for rectangular style blocks:  To hold
 combinations together.  The difference is that the combination is held together internally,
 through the center hole of the square blocks.
1. WHEN USING TIE RODS AND SCREWS, THE COMBINATION OF GAGE BLOCKS AND
    ACCESSORIES MUST BE WRUNG TOGETHER BEFORE INSERTING THE TIE RODS
    INTO THE HOLES OF THE COMBINATION.   
2. DO NOT RELY ON THE FORCE OF THE SCREWS TO SQUEEZE THE BLOCKS
    TOGETHER.  THIS IS UNRELIABLE AND MAY RESULT IN INACCURATE
    MEASUREMENTS.
3. IT IS IMPORTANT NOT TO OVER TIGHTEN THE SCREWS.  OVER TIGHTENING CAN
    ALTER THE DIMENSIONS OF THE GAGE BLOCKS.  NEVER USE MORE PRESSURE
    THAN IS COMFORTABLE WITH THE THUMB AND INDEX FINGER.
The force of the screws may compress the gage stack and change the length.  Because the amount 
of compression is unknown, the accuracy of measurement may be destroyed.   It is estimated that 
6 inch-pounds of torque on the screws will compress a 4 inch block by approximately 14 microinches.
Construction:
Tie rods and screws use 8-32 threads.  The countersink on the square blocks is angled at 72°.  This 
is less than the 82° angle of the screw head.  The screw head sets inside the countersink and only makes
line contact with the side of the hole.  The difference in the angles between the screw head and
 countersink prevents the screw from binding or becoming stuck in the countersink.  NOTE:  Only blocks
 .200 in. or 5.0mm and larger are countersunk on both faces.   Wear blocks .100 in. and 2.0mm thick
 have countersinks on one face only.
Finding the Length of Tie Rods to Use in Combinations:
1. Because of the length of the shortest accessory screw, .850 in. (21.5mm) is the minimum
    length combination that can be fastened  together.   (See diagram above.)
2. The total length of the tie rods must be between .250 in. (6mm) and 2-3/8 in. (60mm) smaller
    than the length of the combination.

Example 1:   A combination of square blocks 23-1/2 inches long.   What tie rods are needed?
The combination of tie rods must be between 23-1/4" and 21-1/8" long. (Between 1/4" and 
2-3/8" shorter than the combination.)
Length of SA 20 tie rod
Length of SA 14 tie rod
19.75
  2.25
22.00
These two tie rods together, will
 work as the combination of tie
 rods is between the Minimum and
 Maximum required lengths.
Between the SA 20 and SA 14 tie rods, they must be joined by an SA 8 stud which is
a double-ended screw.
Some tie rods are adjustable for greater flexibility.
SA 16.  Tie Rod is adjustable between 4-1/2 inches to 6 inches.  ( 114mm to 152mm)
SA 17.  Tie Rod is adjustable between 6 inches to 9 inches.  ( 152mm to 228mm)
Example 2:   A combination of square blocks 65 inches long.   What tie rods are needed?
The combination of tie rods must be between 64-3/4" and 62-5/8" long.  (This is, between
1/4" and 2-3/8" shorter than the combination.
19.75
19.75
19.75
  4.50
63.75
Length of SA 20 tie rod
Length of SA 20 tie rod
Length of SA 20 tie rod
Max. Length of SA 16 tie rod
19.75
19.75
19.75
  6.00
65.25
Length of SA 20 tie rod
Length of SA 20 tie rod
Length of SA 20 tie rod
Min. Length of SA 16 tie rod
The SA 16 tie rod is adjustable in 1/4" increments from 4-1/2" to 6 inches in length.  This gives a
 lot of flexibility when choosing tie rods if an adjustable length tie rod is included in the
 combination.

The combination also requires three SA 8 studs which must be between each of the four tie rods.
Tie Rods & Screws Available As:  (For Use with Square Style Only)
SA 7           Knurled Screws                   Tightens using fingers.
SA 8           Stud                                    Double ended screw.  Used to join tie rods together
SA 9           Flat Head screw                   1-1/4" long  (32mm)
SA 10         Flat Head screw                   5/8" long    (15mm)
SA 11         Slotted Nut                          Used in short combinations instead of screw at one end
SA 12         Tied Rod (solid)                    3/4"     (19mm)   
SA 13         Tied Rod (solid)                   1-1/2"   (38mm)
SA 14         Tied Rod (solid)                    2-1/4"  (57mm)
SA 15         Tied Rod (solid)                   3"         (76mm)
SA 16         Tied Rod (adjustable)          4-1/2" to 6" adjustable   (114mm to 152mm)
SA 17         Tied Rod (adjustable)          6" to 9" adjustable   (152mm to 228mm)
SA 18         Tied Rod (solid)                   11-3/4"  (298mm)
SA 19         Tied Rod (solid)                   15-3/4"  (400mm)
SA 20         Tied Rod (solid)                   19-3/4"  (502mm) 

				
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©2008, Webber Gage Division, The L. S. Starrett Co, Cleveland, Ohio , 44145
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