The actual process is pretty straightforward and most folks should be able to tackle it if so motivated. To begin with I purchased a replacement bed for the lathe to be used as a donor. I cut the donor bed roughly in half and had an extension piece for my own bed that was 12" long. The extension was placed on a Clausing 8520 and faced. I sanded the paint off of the end of the recipient lathe, I suppose if you had access to a mill with a 25" capacity you could face the end, but for me I was satisfied using the factory end and just sanding it smooth.

 My next step was to mount both pieces onto a 36" length of 6x2 steel channel. I set both pieces where I wanted them and used a clamp to secure the 2 beds together. A transfer punch was used to mark the holes on the channel. I marked and drilled each hole one at a time, putting a bolt into each hole as it was completed to maintain the alignment.

As a sidebar on a related project. To help reduce chatter and to increase the rigidity of my mini-mill I mounted it to a 70lb plate of 5/9 steel. This made a dramatic effect and as you can see in the photo it allows the mill to handle heavy work pieces with ease. I plan to add an angle plate to the back of the mill and replace the Big Nut, this should yield additional gains in the fight against chatter.

With the two pieces secured to the channel iron it was time to join them together. With the pieces disassembled again I drilled 2 holes in the extension piece, everything was then bolted in place again and the locations of the holes was transferred to the lathe itself. Everything was taken apart again and the 2 new holes drilled in the lathe bed. I wanted both holes to be a bit loose and leave room for movement to align both beds when everything was tightened for the last time. I reassembled everything one more time and started with the rest of the details. To make full use of the stretch you need to add another rack to the front of the lathe so that the carriage will use the whole length of the bed. Adding the new one was as simple as clamping it in place, marking the holes and then drilling and tapping them. On the backside of the lathe I cut a piece of 1/8" aluminum to fit the contours of the joint between beds and then bolted it in place as a backing plate. The end bracket for the leadscrew was moved out to the very end of the bed and a small mounting plate was fabricated for the lower mounting bolt. Due to structural limitations of the casting what I wound up doing was using a .125" mounting plate and milling an equal amount off of the lower half of the pillow block so that the mounting would remain flush.

The next task in the project was to fabricate a 37" leadscrew for the stretched lathe. There are 3 ways to go with this part of the modification. You can buy a 5/8"-16 replacement leadscrew for a 9x20 lathe and adapt it to the project, you can join 2 leadscrews to obtain the length you need or you can cut the threads for a new leadscrew. For me the easiest solution was to make an extension and join it to my original leadscrew. I turned a 2-step spigot onto the end of the original leadscrew and then bored out an extension piece taken from another leadscrew to match. I used Loctite 290 to secure the joint and the carriage assembly & half-nuts were used as an assembly fixture to ensure that the threads matched up on both sides of the joint.

This photo shows how the 2 ends of the leadscrews were prepared.