Brother b831 Service Manual page 21

ffi Feed Dog Position Adjustment
Procedures
1. Set the feed adjustment dial to 0. {This sets the feed amount to zero.)
Install throat plate O with screws O and O.
Install needle O in needle clamp 0 with screw 0.
Place presser bar 0 into jaw part of arm.
Turn the machine over.
Loosen four screws 0 and adjust with the horizontal feed shaft 0 so that feed dog 0 moves left and right in the
opening of throat plate O. (After adjusting, fasten securely with screws 0 so that there is no play in horizontal feed
shaft 0.)
When feed dog 0 is at its highest position, loosen screw 0 and adjust with feed bar 0 so that the distancefrom throat
plate 0 surface is 1 mm for medium-thick materials and 1—1.2 mm for thick materials. (Fasten screw 0 securely.)
Holding the distance of 13.5 mm between needle bar 0 and presser bar O. fasten horizontal feed arm screw0 at the
position where thetip of needle 0 enters thecenter offeed dog 0 needle hole. Afterwards, fasten screws 0 and 0 in
that order.
• Fasten screw 0 when the needle bar rocking crank 0 is at the center of its swing.
* Adjust to 14.2 mm in step 0 above with models B835 and B836
8
Si Rotary Hook Base Position Adjustment
ai
0.2 mm-
2 mm
Procedures
Rotary hook point
Rotary hook point
• 2.4 mm
0 05 mm
Center of needle
0j
\np-About 0.2 mm
Remove the throat plate.
After aligning the dot mark of spiral gear O and pinion 0, temporarily fasten screw 0 to the screw seat of the lower
shaft.
Adjust to a clearance of 0.05 mm between the rotary hook point and needle 0 by moving the rotary hook bases (Rand L)
when the needle rises 2.4 mm from the lowest position, and tighten screws 0 and 0.
Fasten screw 0 and two screws 0 so that a 0.2 mm space is between the rotary hook base and spiral gear 0.
Loosen screw 0 and then fasten with the rotary hook point at the center of needle 0.
The above adjustment is for thread cutter sewing machines. Figures for other models mayvary from those give here.
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