A Stuart Williamson build

[Sanjay F]

£35 .......get's you the drawings if you're lucky these days!

I have finished stage 1 and its looking okayish, the centres are bang on so it should fit fine, however, the big end slot is a little too near the rod, but I don't think it'll matter. I need to wait for the inifinitely small end mills to arrive before I and mill the slots. I was wondering about the best way to grind the files so they are smooth on the sides, should I use the grinding wheel.

[Jasonb]

You could leave the big end slot short of that hole that is a bit close to the turned section, it will be covered by the strap.

Bench grinder, belt sander/linisher or even an angle grinder would do.

[Sanjay F]

I made the slots, they are a bit bit near on the big end side and I got through quite a few of the tiny end mills in the process....

I'm not sure about the split bearing, I tried making one but it came apart when trying to part it off .......I may just leave it in one piece?

[Jo]

Hi Sanjay, this is coming on nicely 

Next time you may want to try the way I make my slots in rods:

Yes drill the holes, then using a woodruff cutter of the correct width (I make these out of silver steel  ) cut in from both sides to give a nice crisp rectangular slot - it will go in only a short distance but it reduces the remaining metal. Smaller diameter woodruff cutters cut deeper than larger diameters ones, but you need to make it with a thin shaft. Dig out an abrasaw file blade (or if that is too thick a jeweller's blade, ganged to widen if required) and use that to cut between the pilot holes. File to fit the cotter in the slot.

Those are tungsten end cutters you used so yes they will be prone to snapping and need much higher speeds than most of our milling machines are capable of. The old fashion HSS end mills like clarkson's will be more forgiving and happier at slower speeds.

Jo

[Jo]

Forgot to ask: how are you making your split bearing? Mine are normally snuggled inside a collet when I finish the second face so it cannot separate.

Jo

[Jasonb]

You can also keep them together with the rod & strap or if for a bearing the pedestal and cap.

The other method is as Jo mentions, form the central recess then saw off and hold in a collet to bring to length, drill and ream. If you don't have collets then a split bush from some scrap will do the same job.

But as you say on a crankpin like this it could be made solid provided you can assemble the engine but I should think that is possible.

[Chipswitheverything]

Some good and rapid progress under way here Sanjay!, your enthusiasm for getting stuck in is impressive.  The teeny, long series tungsten mills do look very fragile, as Jo says, need to be run at speeds unachievable by most of us. The Abrasaw type of blade if not too big dia. seems like a good way to go. Dave

[Jasonb]

The slots are only 3/64" 0.047" or 1.2mm so no way an abrasaw will fit.

ARC used to do the files with just teth on the edges but they would still need to have been thinned down as they are about 1.5mm thick.

A square or or warding shape with their tapered ends would be best once ground flat

Even HSS cutters would be hard to get upto speed at 1.2mm dia as they would need 8,000rpm. So may as well buy the cheaper and readily available Carbide and treat them as disposable. I've gone over to carbide now, can't remember the last time I bought HSS probably 2019 or earlier.

The plunge cutting method was one that Anthony Mount Suggests on a few of his engines and where I picked it up from when I did my Benson engine. You can see here that the slots have been formed by milling and only need the ends squaring up.

[Jo]

Lots of swarf there Jason. Not sure what your CNC mill is making but CNC machines tend to run much faster than manual machines and you can program the mill to move finer than most can move by hand.

I can't remember when I brought any HSS cutters either  Some of mine must be 40 years old now and I just keep resharpening them  .

Jo

[Jasonb]

Jo as I said that is my Benson engine built many years (2011) before the CNC so like 98% of my milling done on the X3 with it's 2000rpm top speed and feed by hand as I did not even have the power X feed then.

The other 2% is recent stuff done on the CNC but even that only goes upto 5000rpm. I'd need a high speed spindle to get the 24000rpm that 1.2mm carbide is said to need in the books but in practice you can still get good results at slower speeds.

Need to use them before they need resharpening, maybe I get a bit more done than you these days. I did the sums quite a few years ago when it tried out that EMG sharpening machine and I would need to be sharpening 100s more cutters than I buy to make it worth whikle. But that was back when I mostly used branded FC-3 type HSS cutters. Now I can buy Carbide at 20% of what an FC-3 would cost so not worth sharpening and they hold their edge for longer, I'd rather be making engines.

[Jasonb]

Commercial Tome file at the top and one I ground down below, it only needed a bit off so the valleys between what were the teeth can still be seen

[Jo]

Yes the prices vary a bit. Depending on the cutter size. (Scrap Carbide is paying a good price  )

My T&CG cost £50, 30+ years ago. Someone over here liked them: https://www.model-engineer.co.uk/forums/topic/emg-12-endmill-re-sharpening-module/page/4/  Personally I still think they are a fortune for a machine that does so little.

As I mentioned Jeweller blades are available quite small: 0.15mm if you so desire but they won't last long cutting steel. Once you can get a small hacksaw blade in that will last longer.

Jo

[Jasonb]

Sure a extended length 20mm cutter like that will cost that sort of money but not something that is needed much on our models. Any sizable area is best done with insert tools where you are only paying for a small amount of carbide. The larger head diameter has the bonus of getting the cutting speed up.

[Sanjay F]

Modified a file, not great, but it works. I started on one of the straps by drilling, milling and more filing. Then went onto make the first wedge & cotter......my goodness are these small fiddly little items, but the first one doesn't look too bad, I just don't want to drop it and lose it 

[Sanjay F]

Like my school report used to say 'could do better', but these are my 1st wedges and cotters....... I'll squeeze them tight on final assembly