Boring Lathe: How to Make a Boring Bar

What You'll Need
1 inch diameter, 10 feet long cold rolled steel bar
Lubricant squirt oil
Electric drill
Cutter made from high carbon steel
Allen screw
Protective gear, eye goggles and nose mask

Large diameter holes that require precise and accurate alignment such as stern and rudder tubes can be best be cut using a boring lathe or boring bar. They are ideal for the job as it can be difficult to bore such holes. Usually, it is not easy to see the processing surface as the scraps are kept in the hole during cutting. This also prevents obtaining a surface with the correct roughness. Such problems are eliminated by a using a lathe.

Step 1 – Assemble Materials

It is advisable to get high quality material so as to make a strong and durable boring bar. Make sure to buy a cold rolled steel bar from a hardware or lumberyard supply store. If the boring bar is to be used for different jobs, buy a selection of bars which can be made using the steps described below. Buy only high carbon steel cutters. Select the bits needed as they can be interchanged to suite different applications.

Step 2 – Drill Hole

Use an extension drill to make a hole in the bar. The machine must be fitted with a conventional drill bit. It is advisable to start with a 3/4 inch diameter drill bit and increase the size of the hole with large sized bits.

To make the process easier, make the pilot hole in the deadwood while both ends can still be accessed easily before the boat is framed and planked. If there is a mismatch in the hole, clean it out later.

Clear the hole to make sufficient diameter in the bar by using a 6 foot long, 1 1/8 inch diameter extension drill.

Step 3 – Line Up Bar

Make sure that the hole is clear and insert the boring bar. Align it carefully and make sure it lies centrally in the drilled hole. Where it protrudes from the stern post, center it and wedge it in position.

Step 4 – Set Up Bearings

Bearings are used to hold the bar. They keep it well placed in the center and also hold it in correct alignment. Lubricate the bearings using squirt oil and position them at either ends of the deadwood. Ensure that they are fixed further out to ensure the bar works correctly.

Step 5 – Attach Cutters

Check the pilot hole is well aligned and the bar is set up on the shaft line. Insert the first cutter and use allen screws to fix it in position. Make sure it is secure and well fastened. Attach it to a slow turning electric drill. Check that it is firm and fixed firmly in position. The new boring bar can be used to make hole. Change the cutter or bit to suit a particular job.