The set-up procedure for a line borer will vary, depending upon type of job, the size of the work piece and the machine’s manufacturer, but the fundamentals are pretty much the same. To give you an idea, we’ve summarised the set-up procedure of a Mirage Line Boring Machine assuming it’s to be used on a typical project such as a cantilever crane boom.
The example described here is a LB100-H line boring machine, which is a hydraulically operated line boring machine. The machine incorporates two hydraulic motors, one rotating the boring bar, the other feeding the tool post hub along the boring bar. The machine is fixed at both ends using ‘Self Aligning Bearing Support Plates’.
1. Fix bearing support plates to the work piece
Above: Self aligning bearing support plates
The first task is to fix the self-aligning bearing support plates to the work piece. This can be done in several different ways. Where permissible, sacrificial mount posts can be tack welded at each end of the job. These are then bolted to the self-aligning bearing plates. Alternative methods are to drill and tap into the work piece, or to mount or utilise existing securing points.
The self-aligning bearing plates should be fixed as accurately as possible, making sure they are aligned with the centre of the bores located within the work piece. This can be done with the boring bar inserted to act as a guide. Fine adjustment can be carried out at a later stage. It is important to note that the orientation of the boring bar will determine which end the drive motor and gearbox assemblies will be attached to.
2. Attach the split nut hub around the boring bar.
Above left: split nut hub. Above right: attaching the tool holder directly and on an arm.
The split nut is the component to which the cutting tool is fixed to. When machining bores less than 15” diameter, the tool holders can be mounted directly onto the split nut hub. For larger sizes of up to 36” the cutting tool is mounted onto an arm which is fixed to the split nut hub.
3. Attach the bar drive motor assembly.
The drive key on the motor needs to be engaged in the keyway slot in the end of the boring bar. A stud should pass through the hole in the end plate, but do not add the M22 nut just yet.
4. Attach the bearing end plates
Next, bearing end plates are fitted to both ends of the assembly.
5. Attach the feed gearbox
Install the ‘Feed Gearbox’ assembly by aligning the hex drive with the lead screw hex and installing the locating spigot into the boring bar.
6. Lock bearings into place
With both the Drive & Feed motors now in place, the bearings can be locked to the boring bar using the supplied, hinged C-Spanner.
Traditionally, the boring bar is set using dial test indicators, alternatively, it can also be aligned using a laser kit, which uses the two 58mm bores in the ends of the boring bar to locate the laser targets.
8. Fine Adjustment
This is done by moving the bearing housing relative to the end support plates. To do this you release 4 x M12 bolts approximately half a turn. Next use the 4 x centralising blocks to bring the boring bar into a central plane. When complete, tighten the adjustment locking nuts to secure the assembly in position.
9. Check for obstruction
Ensure the tool post cannot clash with the work piece when it is rotated.
10. Attach the hydraulic hoses to the drive and feed motors
11. Check the direction of rotation
Turn on the hydraulic feed to the drive motor and check the rotation is counter clockwise when viewed from the bar drive motor end of the machine. If the direction is incorrect simply swap the orientation of the hoses to reverse the direction.
12. Check the feed direction of the tool and hub assembly.
Turn on the hydraulic feed to the feed gearbox assembly to check the feed direction of the toll and hub assembly. Again, if this is incorrect, swap the orientation of the hoses.
As mentioned above, the set-up process can vary depending upon the project and additional operations can be carried out such as facing the outer surface of the bore. This is done using an optional facing arm with a striker wheel and post arrangement.
You can find out more about Mirage line boring machines by getting in touch with your regional Mirage contact here or by downloading the Line Boring Machine Buyers Guide.