Usage:
D342 And D353 Engines
Some D342 and D353 Engines have spacer plate cylinder blocks. Precision counterbore depth is needed for the installation of stainless steel inserts in the cylinder block. The 6V2120 Spline Sprocket (Illustration 1) can be used for better depth control during counterbore operations. The sprocket is used on the 5P4175 Boring Tool Group (Illustration 2). The 56 reference marks along the outer edge of the sprocket permit fine adjustment to the cutting bit depth.
The adjustment nut directly controls the depth of the cutting bit. It uses the 6V2120 Spline Sprocket as a positive stop when the boring tool cuts into the cylinder block. For complete details refer to Special Instruction, Form GMG02442-01, "Using 5P4175 Boring Tool Group and 5P1618 Tool Arrangement."
Illustration 1. New 6V2120 Spline Sprocket with reference marks.
Illustration 2. The 5P4175 Boring Tool in position on the cylinder block.
After the initial counterbore cut is made, the depth is measured with a micrometer (Illustration 3), and the adjustment nut is turned counterclockwise to lower the bit for the final cut. Formerly, rotation of the nut for depth adjustment was made by estimate; there were no marks on the sprocket to give any indications of the amount of change as the adjustment nut was turned.
The reference marks on the 6V2120 Spline Sprocket permit the adjustment nut to be turned a measured amount (Illustration 4). This will also lower (or raise) the cutting bit a measured amount.
Illustration 3. Counterbore depth being measured with micrometer.
Illustration 4. Alignment of sprocket reference marks with adjustment nut scratch mark.
As the scratch mark on the adjustment nut is turned past the reference marks on the sprocket, the cutting bit will lower (or raise) .001" for each reference mark.
A small flat spot needs to be ground on the lower edge of the nut for the scratch mark.
Installation Of The 6V2120 Spline Sprocket
Use Illustrations 5 and 6 as a reference for these procedures.
1. Remove the drive chain guard from the 5P4175 Boring Tool.
2. Remove the drive chain and clean the area around the sprocket.
3. With the tool holder installed, hold the retaining nut between the jaws of a vise and loosen the splined shaft with a 1P2852 Spanner Wrench.
4. Install the new 6V2120 Sprocket, tighten the spline shaft, and reassemble the drive chain and guard.
Illustration 5. Location of splined shaft, adjustment nut, and drive chain on 5P4175 Boring Tool.
Illustration 6. Location of tool holder and retaining nut on 5P4175 Boring Tool.
NOTE: The plastic knob is a permanent fixture. Do not remove it during disassembly. Also, be careful not to get dirt in the boring tool housing.
The 6V2120 Spline Sprocket is adaptable to all 5P4175 Boring Tool Groups.