Machining
Line Boring
Restore alignment of bearing housings in one continuous set-up. Line boring re-machines main bearing bores so every saddle shares one true axis with the crankshaft.
What this covers
- Alignment and housing-size measurement
- In-situ line boring of main bearing housings
- Verification of bore-to-bore concentricity and alignment
- Restoration of correct crank running axis
Overview
One axis, machined as one line
When main bearing housings are worn, distorted or out of alignment, a new set of bearings sits in saddles that do not share one true axis — and the crankshaft pays for it.
Line boring machines all the bearing housings in a single continuous set-up, so each bore is concentric and every saddle shares the same centre-line as the crank.
Reconditioned to measurement
Reconditioned to measurement. Not guesswork.
Decisions on line boring are made from recorded measurements against specification — never from how a part “looks”.
Symptoms
When is this work needed?
These are the problems and symptoms that typically point to the component needing reconditioning work.
- Repeated bearing failure across more than one journal
- Measured housing misalignment or out-of-round saddles
- Crank that binds or runs untrue after a rebuild
- Damage from a previously spun bearing
Inspection
Inspected and measured before machining
3 checks and measurements inform the decision to machine — nothing is cut until the component has been assessed.
- Main bore housing size, taper and out-of-round
- Alignment of all housings to a common axis
- Condition of saddles and bearing locating features
Measurement & quality
Alignment is the whole point
Line boring is specified on measurement — housings are checked for alignment before the decision to machine.
Verified after machining
- Bore-to-bore concentricity across the block
- Final housing size suitable for the bearing set
- Run-out of the machined axis verified
PRT process
How we carry out the work
- 01
Measure
Housing sizes and their alignment are recorded.
- 02
Set up
The line-boring bar is aligned to the crank axis of the block.
- 03
Machine
Housings are bored in one continuous line to the required size.
- 04
Verify
Concentricity and alignment across all bores are confirmed.
Machinery & stations
Performed at the right station, with the right tooling
Detailed equipment make, model and specification sheets are pending from PRT. The functional stations involved in this service are:
- Line boring set-up
- Precision measuring & gauging area
Gallery
From the PRT shop floor
Authentic PRT photography will appear here as it is captured and approved. No stock imagery.
Line Boring work in progress at the PRT facility.
Real photography of the operation will appear here when PRT approves imagery.
Before-and-after records of PRT jobs are published as real projects.
Related services
Work that belongs with this one
Cylinder Block Reconditioning
Strip, inspect, measure and machine the engine's foundation. We recondition cylinder blocks for rebuilds — cleaning, crack detection, boring and honing, deck surfacing and, where needed, line boring of the main bearing housings.
View serviceCrankshaft Grinding
Restore worn journals to size and true running geometry. Crankshaft grinding returns main and crankpin journals to specification for use with matching undersize bearings.
View serviceEngine Assembly
A controlled, clean, torque-accurate build. We assemble reconditioned engines from measured components — so the finished unit leaves the shop built to specification and ready to run.
View serviceFAQ
Common questions
Straight answers to the questions we expect about this service.
When is line boring needed?
When measurement shows the main bearing housings are no longer concentric or aligned to the crank axis — often the result of a spun bearing or prior damage.
Is line boring done with the block in the car?
Line boring is performed on the stripped block in our shop, machined in one continuous set-up for accuracy.
Does line boring change which bearings I need?
The housings are bored to the size the chosen bearing set requires. Bearing sizing is confirmed from measurement before machining.
Get a Quote
Discuss a line boring job
Tell us the engine or component, its condition and what the rebuild needs to achieve. We will confirm the scope from an actual assessment.