BENSON LATHE RECONDITIONING

By Neil Baker


To resurrect a steam roller that had been in a scrap yard for 25 years many parts need to be made. I was looking around for a lathe, a Myford for preference, but as funds were short I couldn’t afford one! The opportunity to buy a small machine cropped up and I agreed to buy it, knowing it would not be in pristine condition. That was back in 1980.

On  getting it home, we found it looked as though it had been left out in the rain some time ago, despite a coating of black preservative ‘gunge’. It was also nearly impossible to move the saddle. On removing the saddle we found this was due to a gear in the feed train (in the saddle apron) being displaced, its pivot being loose. This gear, made of aluminium, was discarded along with its pivot.

The good news: there was a set of collets that fitted into the spindle nose, but the drawbar was missing. There was a 3-jaw chuck that was badly ‘bell mouthed’. This was (sort of) fixed by mounting an electric pistol drill with a small grinding wheel in its chuck on the saddle.

There was also a faceplate and about 30 change wheels. Amazingly the electric motor and starter worked, although the centrifugal contact for the starting winding was worn out. A modification of the starter connections eliminated the need for the contact. A Myford chasing dial, was added (the leadscrew is  8TPI) and better spindle lubricators.

We now had a usable machine, (Fig 1) although one that had suffered a lot of abuse in its life. It looked as if someone had been using the saddle feed and crashed it into the headstock, causing the damage to the gear train. The bed was also badly worn near the chuck such that if the adjusting wedge was tightened there you could not move the saddle more than an inch without loosening the wedge. However, despite all of this, and with the addition of a new 4-jaw chuck, a lot of pins and fittings were made enabling the Aveling to steam again.

Time rolled on, and I got a 71/2” Colchester Triumph lathe which was useful  for maintenance of the steam rollers. But the small lathe was still really handy for smaller jobs. Now an apprentice model engineer, I began to think about replacing the little lathe with a ‘proper’ Myford. I found http://www.lathes.co.uk/ on the net and emailed that I was interested in an ML or super7. By email Tony@lathes.co.uk  talked me out of this, as in his opinion the Benson is a very high class machine and was worth persevering with. (See also http://www.mpmengineering.co.uk/html/lathes_9.html). So I decided the much cheaper option of reconditioning the Benson was the way to go.

The first step was to make a drawbar for the collets (Fig 2). The Colchester was used for this job. Being able to use a collet with the saddle on a less worn part of the bed convinced me that getting the bed re-ground would be very worthwhile. I got a quote from the Birmingham Machine Tool Company which was very affordable, but I kept using the little lathe for odd jobs. When I was ready to get the job done they were no longer in business! Similarly Unislide!
Googling machine tool reconditioners was fruitless. Andy Richards, the maintenance engineer at Seetru recommended that I look in South Wales, and  I found Te-bar (http://www.te-bar.com). After a constructive ‘phone call I was ready to go. The machine was dismantled and the bed, saddle and adjusting wedge were loaded into the back of my Land Rover and taken to Port Talbot.
There was a large job on the slideway grinder (Fig 3) that would take at least two weeks to finish, so I would get a call when my job was done. After a few weeks the expected call came, but in the meantime the Land Rover had developed a spectacular knock climbing Rownham Hill and was out of action. I was eventually able to borrow a van and collect the refurbished and refitted parts.

While this was going on I decided to get all of the feeds working again. The cross feed worked OK, but due to the missing gear the saddle feed didn’t. The support casting at the rear of the apron assembly was also broken. This fitted so well that this problem was not noticed until it was cleaned. A repair bracket was made and fitted. A new gear and pivot were needed. All I knew about gears is that they mesh. 

After much measuring, CAD work and 3D printing of candidate gears, (Fig 4) and thanks to Phil Bridgway we eventually found the gear to be 14T, 20DP. I got one from the net. Incidentally, one of the few things FreeCAD is good at is designing gears. The pivot hole in the apron was tapped 3/8 BSW and a pivot made from a 3/8 bolt, to suit the centre hole in the new gear. The pivot and gear were machined in the Colchester. When the pivot was screwed into place it was keyed with an M6 grub screw. (Figs 5 & 6).
While the bits were away in South Wales, repainting of the parts left was done with rattle cans. While this  method gives quite a good finish, masking off takes a huge amount of time. Reassembly was straightforward, once the various parts were identified. The high standard of construction with all parts needing alignment, scraped and located by dowels made this task a pleasure. This machine is a tribute to British workmanship, both in its initial construction and the work done recently in Port Talbot.

I had bought a replacement 3-jaw chuck at our last Bristol Exhibition, so the first job was to machine the 3-jaw backplate to take the replacement one. This was done in situ and the ‘new’ chuck has already been used. (Fig 7).


Fig 8 is the change wheel chart riveted to the bed rear leg and Fig 9 is the maker’s plate, sadly damaged when removing the saddle the first time.

This article first appeared in the Bristol Model Engineer.
 
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