Having taken a few days to recover from the last workshop sessions; and since I get up early in the mornings, I decided to go into the workshop before my brother Steve came over to take me sea fishing in our boat.

The reason for my early start was the gear cutting request from Thomas, which at first sight was a simple task, but it turned into something both more complicated and a good learning experience. The main lessons for me were the lack of availability of reasonably priced cutters for the size required, and having to refresh my knowledge on gear cutting in general.

I did the sums in both imperial (DP) and for metric (MOD) since Thomas required metric finish sizes to enable me to find a cutter. I thought I had solved the problem when I found the right hobb for a very reasonable price. In the past I have used Tracy Tools based in Torquay (only a few miles from me) but they didn't have the sizes required. So Arc Eurotrade are certainly worth a visit for metric hobbs at very reasonable prices.

The Hobb purchased from Arc Eurotrade

However the hobb has a thread form so the blank to cut the gear on must be free to revolve, something the design would not allow for this project so it was back to square one. I decided therefore that it may well be easier to go back to the original plan and make a form tool of the tooth myself.  This was soon made and I decided to make a new tool holder for the milling machine since I found the one I was going to use had a 20 thou 'wobble' which obviously would not do.

New tool holder for gear cutting

The last workshop session saw me make the tool and holder but because I was unwell, I could not for the life of me do the basic calculations (my excuse)to use my Vertex dividing head. Unfortunately the tables that came with the Vertex have decided to hide themselves, so I have to work them out each time unless they are in the data tables books I have. So of course the 15 divisions Thomas want's doesn't appear anywher since the lowest given is for 20.

Now it is relatively simple and John Stevenson has written quite a bit on gear and gear cutting (search Google) and there is an excellent book available written by Ivan Law (Workshop Practice 17 Amazon link on my main website) and anyone new to cutting gears should consider buying a copy. So once I had sorted out the numbers for the Vertex I wanted to check that they were right, hence my early morning start. I have decided that I will put gear cutting for novice engineers as part of my main website, hopefully adding a novices perspective.

After finding a scrap piece of brass of the same approximate diameter I secured it in the chuck and started to cut using the specially ground tool. I didn't want to take too deep just enough to count the teeth. So after 15 cuts I checked the piece and was more than just pleased to see the correct results. Whilst the tooth shape is not correct because of the depth of cut, trying the unfinished scrap piece on the gears Thomas supplied and it all looks fine so as soon as I am well enough to go back to the workshop it shouldn't take to long to finish the job.

The scrap piece of brass used as a trial for checking it is 15 divisions

I have two outstanding projects that stand in the way of my resuming the Seal engines. One, making some simple gears, has become something of a marathon purely because I cannot source a gear cutter at a sensible price. I thought I had the answer when I bought a hobb at a reasonable price from Arc Eurotrade only to find I couldn’t get it to work properly. So I sent off an email to John Stevenson (very experienced engineer) and at the time of starting the session, was waiting for his reply .

The second is a set of adjustable handle bars for one of my brother in laws. This project is only held up because of the amount of material that has to be removed is causing me some discomfort issues with all the turning of the ‘Y’ axis on the milling machine. Since I didn’t feel up to resuming that work I thought I would have a go at a non critical project. A new bait board for the new (to us) fishing boat I share with one of my brothers (see http://.www.dartmouthfishing.co.uk ).

So having decided what to do I went to the marina and picked up a tube used to fit in a socket on the floor of the boat, the other end fits into a bracket attached to a table top. My idea was to simply make an oblong table that would use the tube, but instead of putting the table on it I would make a bracket that would allow the new bait table to sit on top of the tube.

A look into the stock room soon produced a piece of aluminum that had been ‘scrapped’ when I cut the wrong thread pattern for another project.  It would be ideal when bored out to suit the tube end. The design was simple really; just bore the centre to size then turn down the outside so four holes could be drilled and countersunk. These would be used to screw the bracket to the new wooden bait table made yesterday which already had its first coat of paint applied.

The first machining task was to mount the aluminum in the 4 Jaw chuck on my Myford ML7. Once the piece was centered and faced off a boring bar was used to bring the required diameter. I nearly made a mistake when taking the required diameter as I used the base of the tube for my measurement. When I had the bore close to size I picked up the tube and saw that the plastic insert that fits into the table, was about 100 thou wider than the base. So a little more metal was removed from the bore before cutting down the outside where the 4 holes for the screws would be located.

Initially I had the part flush with the chuck face when boring it out but then I had to reset it using parallels between it and the chuck face and of course had to center it again. Something that a little forethought would have overcome.  Still that job has now been completed so onwards and upwards as they say………………………..

Nearly completed- all that remains is to transfer the brass ruler made earlier

I haven't managed as much time as I would like in the workshop so I decided that since our boat has been repaired after onlly 270 hours use (be wary of mercruiser 1.7turbo diesels!) whe have bought a mercury (daft I know...)4HP as an emergency standby.  I thought about all sorts of engineered solutions to lock the engine to the outboard bracket but in the end a stainless steel padlock fitted exactly!

However we like to have the outboard secured safely as well. Not locking in place but a chain or cable that loops around the bracket of both the engine and boat.  So a visit to the local chandlers produced a short end of stainless steel wire which was mine for the princley sum of £1.50 I thought that I could make up a couple of ends myself so headed back to the workshop.

After doodling for a while I thought I would keep it simple so turned up some ends that were then milled with an overlap and a 4mm tapped hole on one side and a countersunk clearance hole on the other. After silver soldering the ends and cleaning up we have a simple but strong cable with only half of the original piece used.

The picture below shows the finished article. If you want to knwo more about our fishing antics or the trouble with the engine then click here for the website link.

Carbide tipped saws have been recommended for metal work in the past, especially when they are slitting saw size. In the UK I couldn’t find a supplier of small blades but a HMEM forum member (from Canada) sent me some blades to try. There are some really nice people in the model engineering fraternity. I am sending a traction engine book back to Canada (as soon as it comes back into Amazon stock!) but thanks are in order.

Instead of just trying the blade in my slitting saw arbor I thought I would bring forward an idea I had about building a saw table. The reason I wanted to trial the carbide tipped saws was to cut a round bar in half so I can make two crankshafts for the Seal build. Since the camshafts have now been made the next major item for the Seals is the crankshafts, so you can see all roads in fact led to the saw table.

Since I don’t sleep very well I often ponder designs during the night, scribbling down some drawings at my 0600ish breakfasts. I started by writing out the design criteria at one of these breakfasts, with the aim of making some CAD drawings, leading to a set of plans (Alibre) which could be made available on my website.  So this particular project covers many areas of interest for me. Such as making a workshop tool, using CAD, and helping with the Seal twin engine project. Not a bad result really.

The design criteria covered such things as having two blade sizes (the larger ones found in the UK as well as the smaller ones from Canada) so it would be useful to be able to use both blades on the same machine. The blade depth of cut should be adjustable and by a measured amount. The top should be as adaptable as possible, allowing the safe holding of materials. The blades should have some form of safety guard and make use of an existing electric motor I have.

Other ideas will no doubt come up as I progress, especially in the area of the work holding. I don’t feel confident enough yet to just draw the design out in 3D CAD. Rather it will be a bit of both, build and the use of Alibre CAD. The help in laying out the plan I used some foam rubber/plastic as a former to check the size of the saw arm and the quadrant. By using these materials in a mock up I discovered my initial quadrant lever would not work so a new shape was soon cut out and tried.

Since I have several ¼” (0.250” or 6.35mm) sheets of aluminum ‘recovered’ from my local scrap yard I wanted to use these to make a strong box shaped saw table (please see photo).The first task was to check the speed of the electric motor. I have a rev counter which measures revolutions from model aero engines and made up a temporary shaft to hold the Mills propeller. The measured speed was approximately 1200 rpm. The saw blades run at around a maximum 6000 rpm so I needed to increase the speed from the motor.

I had a look at the spare gears from the Myford and there were both 20 tooth and 65 tooth gears that can be used.  That should give me around 4,000 to 5,000 rpm at the blade. With these speeds I decided that all pulleys will have bearings and it was whilst searching for bearings I saw a diamond grinding wheel that would also fit the design. So I ordered the bearings and the diamond cutting wheel.

Now the project has turned into a versatile saw and grinding table which longer term I would also like to develop to grind camshafts in the future. Madness you may say (and you may well be right!) but if you take the saw table top as a base for holding various fixtures, then it should be an ongoing (maybe years) development for my own tool centre.

The rough design schematic is shown in the photo below to help you understand where I am going. To make the blade/grinding wheel adjustable I will use a quadrant with teeth cut into it, matching with teeth on the saw/grinding wheel arm. With the screw thread used for adjustments I should be able to make fine and measured cuts. Since this movement involves the arm then the pulleys will need to have a tensioning system to take up the difference.

Since I hope to have the tool for many years I will also be looking at the materials used, for example the saw arm needs to have a guide and clamp to secure it when any adjustment has been made. Just cutting through the aluminum wouldn’t really serve long term so I am letting into the plate a brass section (made from two lengths of square bar silver soldered together).

The drive belt I shall be using is circular in cross section and the two ends are ‘welded’ together (see photo), access to the belt as well as the gears (in case I need them on the Myford) and saw/grinding wheel needs be incorporated for change of belt, blades or now the additional grinding wheel.

Leaving design for a moment I made a start on the main pulley that will hold either the larger saw blade on one section or the smaller blade or the diamond grind wheel on another, since they have the same bore. The front of this pulley will have two diameters for the blades/wheel and the rear of the pulley will contain a sealed bearing.

So far the pulley has been turned to outside diameter and the belt groove done (photo). The bore has been drilled and reamed with a start made on the bearing housing but was put to one side whilst the bearings were ordered (arrived in just two days!). Hence a start being made on the saw arm using a ¼” (0.250 or 6.35mm) thick piece of flat steel.

I am happy using the DRO’s to co-ordinate the machining of parts but I still like to mark out the design to make sure I am in the right place as it were. So after marking out the arm, the rotary table was secured to the milling table and a start made in cutting the small end of the arm (photo). When it came to the larger end I had to make new clamps so the complete part of the diameter could be milled and that is where the project was left at the end of the latest session.

Tomorrow I hope to complete the arm profile and maybe the inserts and perhaps the saw head pulley. I don’t expect to spend too much time on the basic saw table, before switching to the Fowler Traction engine before going back to the pair of Seal 4 cylinder petrol engines.

I have finally decided that these are the three main projects I will concentrate on over the next couple of months and try to keep other engineering ‘distractions’ at bay. Again, time will tell……..