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391.37A/B – R429U boring bars​

  • Tool pre-setter


Fine boring head 391.37A/B

391.37A​ 391.37B​


Mounting of boring bar

  1. Fit sleeve to head (if sleeve is to be used).
  2. Align line on sleeve with line on head (if sleeve is to be used).
  3. Fit boring bar to head/sleeve.
  4. Align cutting edge with line on head.
  5. Make sure that the boring bar is not protruding more than indicated by scribed circle on shank in the picture  (valid for 16 mm (0.63 inch),
    20 mm (0.79 inch) and 25 mm (0.98 inch) bars).
  6. Tighten the clamping screw to recommended torque. Click on the table below to get the recommended tightening torque for the clamping screw.



Tool setting

  1. Mount insert.
  2. Set tool pre-setter to required diameter and place tool in tool pre-setter.
  3. Rotate tool to obtain largest diameter on display and unlock locking screw of setting mechanism.
  4. Retract boring bar by turning dial anti-clockwise to facilitate setting from smaller to larger diameter.
  5. Set diameter by turning dial clockwise. (Note: for 391.37B- also set the balanceweight. See information below).
  6. Tighten the locking screw(s) to recommended torque. Click on the table below to get the recommended tightening torque for the clamping screw.
  7. Check diameter and length of tool in the tool pre-setter. If possible, transfer tool data to machine control system.


Warning  – avoid damage to the tool!

Do not set the diameter without first unlocking the locking screw (1).
Make sure that the flat of the ball – not the sphere – is directed towards the cross-slide (2). Do not exceed the diameter setting limits (3).



Setting of balance weight

  1. Unlock locking screw of balance weight setting mechanism.
  2. Identify selected boring bar.
  3. Identify selected diameter to be machined.
  4. Find setting value, see section Mounting dimensions for T-Max U fine boring units .
  5. Turn setting dial until setting value lines up with datum line.
  6. Lock locking screw.

Example (see table for setting values below)
Boring bar R429.90-14-040-09-AC

  • DC = 18.1 mm
  • Balance value = 56



Minimum clamping length

Boring bars with shank diameter 16, 20 and 25 mm (0.63, 0.79 and 0.94 inch) have a scribed circle indicating minimum clamping length (max overhang). Boring bars with shank diameter 12 mm (0.47 inch) (have no scribed circle) are to be mounted as deep into the fine boring head as possible. For mounting and setting of fine boring head, see table for setting values

Min. clamping length

Clamping on sleeve

Hole through​
​Clamping on bar through hole on sleeve​



Datum line

Scale for balance setting


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