#6 The first year at the School of Jewellery.... (Part 3: Making a Mini Clock - Pillars, Screws, Washers and Nuts)
After completing the main plates it was time to join the components together. This post covers the making of the pillars, the screws, washers and nuts that holds everything together. Apologies for the lack of photographs, I didn't take that many as I went along, but future posts should have more step by step pictures!
I decided to choose a basic straight pillar design as I tend to favour more minimalistic designs and also this would make machining a lot easier. The majority of the work was completed on a Colchester lathe to the dimensions on my sketch sheet. Once the stepped shoulders had been machined, I spot drilled the ends of the screw pillars and drilled to the required size. As the work was set up and was now concentric, I used this opportunity to start a thread for the screws. I brought the tailstock up to the work and placed a tap in its wrench and lightly sandwiched it between the work and tailstock and started cutting the thread- this helped me to get a straight cut thread. This process was also used for the external thread but with a die instead.
The washers were fairly straightforward to manufacture as they were basic in design. Two washers were to be centre drilled 4mm (for the pillar shank under the nuts), and the other two were drilled 2.8mm for the screws. I faced off the end of a brass bar in the lathe, then lightly polished the circumference with finishing papers. I did this now as it is more difficult to polish when the washers are cut to size. I then spot drilled the end before drilling. Once drilled, I removed from the lathe and cut the bar just longer than the final washer thickness. As the washers are not thick enough to be held in a three jaw chuck, I used a step chuck mounted on a watchmakers lathe and faced the rough cut end of the washer and then polished the ends.
(Above) Drilling the washers in the lathe
To make the screws I faced off both ends of a piece of silver steel bar on the lathe. Using Dykem fluid I marked the length of the area to be turned down and then turned down each end to the appropriate diameter for a 6BA thread (2.8mm). Once I got close to the required diameter I used a micrometer after each cut to see how close I was- I could then adjust the tool post to cut less or more material until the desired thickness was achieved. Whilst the bar was mounted in the lathe, I chamfered the ends to allow for easy threading and a desirable finish to the end of the thread. The bar was then roughly cut with a hacksaw with a coarse blade at each end with enough material to create the screw head. At this point I chose to create a cheese head style screw as it would match the flat washer and straight cut pillars. After cutting each screw, I then mounted the metal back into the lathe and faced off the screw head down to the desired thickness. To cut the screw head slot, a piercing saw was used and then the slot filed with a slotting file. I found that the slot made was relatively accurate, however, I would have preferred it to be slightly wider and deeper to accommodate a more suitable screwdriver. If I was to make the screws again, I would mount them in a milling machine and cut the slot this way which would be more efficient and give a very accurate and uniform slot, however, for this task the use of a milling machine was not permitted. Before threading and bluing, I needed to polish the screw head to a mirror finish. I used varying grits of sandpaper, then micro finishing paper followed by liquid metal polish- these were all applied when the screw was fitted into a watchmaker's lathe. I then threaded the screw but found that this is where I had the most problems. I started the threading off with the screw mounted in a lathe to ensure the die was cutting straight. Once the thread had started to form, I transferred the screw to a bench vice and finished the threading there. To blue the screws, I thoroughly cleaned them to remove contaminants, then heated a small bowl of brass filings with a bunsen burner. Once the filings were warm, I laid the screw on top of the filings and gently heated until the colours started to change- first straw, then purple, then finally blue. I found that the colour change happens very quickly and I had little control over the temperature so it took a few attempts to get the hang of it. The final result wasn't as I had desired as it is blotchy with patches of purple- I think with the screw had become contaminated when I had previously polished off failed bluing attempts. This is a point for definite future practice. Since making these I have made my own bluing plate which allows screws to be heated to a constant temperature and a much better final result to be had.
(Above) My new hand made bluing plate
(Above) New bluing plate 2
(Above) A blued screw using my bluing plate
Lastly, before polishing and assembling the plates I made the nuts. These were created in a very similar way to the washers but with extra added steps. I firstly faced off a hexagonal brass bar, then polished it, then drilled it and then tapped it. I roughly cut each nut with a piercing saw, then individually mounted them on to a special carrier that I had made. This allowed me to face and polish the rough ends easily and also allowed me to add a slight chamfer to the corners. This was all completed on the watchmakers lathe.
Now that the construction had been completed, I polished the inside of each plate starting with coarse papers and gradually getting finer, then moved on to polishing papers and finally Brasso. The outer sides of the plates and their edges were finished with a straight grain style. I originally left the plates slightly oversized so that when I got rounded edges from polishing I could tactically use the straight grain on the plate edges to sand the rounded edges away. This worked perfectly and I do not have any rounded edges. I struggled to achieve a good grain in the step, but improvement can be made with further time, practice and patience.
(Above) Test fitting the pillars- The excess material is for riveting
(Above) Test fitting the pillars in the mainplates, this is the side that takes the screws, nuts and washers
Halfway through the finishing process, I riveted the pillars to one of the plates. The pillars were made with one shoulder slightly longer to enable riveting. The workpiece was mounted on a solid metal base and protected with sheets of paper, then using a hammer and punch I hit the ends of the shafts being careful not to slip- this causes the shaft to expand within the hole holding the pillar securely and permanently.
(Above) A picture showing the riveted pillars- the straight grain is applied and the riveting appears invisble!
Another part was to create an arbor and a collet to hold the pallets in a future part of the project. I decided I would make these entirely on a watchmakers lathe only using hand gravers. I started by facing off a brass bar, then measured the silver steel bar diameter. I then drilled the brass to the diameter of the steel. Using gravers I made a stepped collet and parted it off with a piercing saw. Then I made my first pivot on the steel. I worked slowly and carefully to ensure no bends or unwanted cuts were made and turned the pivot down to just under 1mm. I chamfered the shoulder to 45 degrees and slightly rounded the end of the pivot. This was repeated on the other end. Every so often the arbor was checked with the mainplates to ensure an appropriate amount of endshake was achieved. The collet was then soft soldered on to the arbor using multi-core solder and a bunsen burner.
(Above) The arbor and collet in place
The last job was to cut an oil sink. I used a Bergeon oil sink cutting tool and cut the sink so that the pivot was just showing out of the sink. Cutting the sink was the last job as it has to be cut to bespokely fit the arbor's pivot.
(Above) The oil sinks cut and everything assembled for the submission of part 1!
Thank you for reading, I hope that you enjoyed this part. I am hoping to upload some servicing work in the next few weeks so please keep your eyes peeled!