So I dug up a little slab of 6mm ali plate and hacked off a piece approx the size I needed. Then came the 1st issue to overcome, as the biggest milling cutter I have at present is 6mm I felt it was unwise to size the frame piece in one pass. So I took off my milling vice and decided to clamp the frame to the top of a 3-2-1 block that was squared up to the table, and use the side of my 4 flute mill to size.
I then moved on to the cylinder. I had a piece of 19mm square brass bar. This presented a new challenge, I dont have a fly cutter or a milling cutter over 6mm. So how can I machine this 19mm square bar to 17mm x 15mm, and get a reasonable finish?
Up steps the 4 jaw chuck.
I remember reading somewhere about how to turn a cube using a lathe, and I just borrowed the idea, and what do you know, it worked!!
So I now have the cylinder blank sized and ready to bore, and that's as far as I got.
However, in the process of sizing on the lathe I found out that getting a nice finish relies on smooth advancement of the cross-slide. ( yea, I know that you all know this, but it was new to me ) I found a bit of a cheats way of taking the monotony out of winding it back and forth, and getting a better finish. I just attached my cordless drill to the capscrew holding the handle on the cross-slide and just ran it on a low speed. Got a far better finish than I could've got otherwise. You just have to be careful to keep the drill in line as best as poss.The center drilling went well, and even the drilling with progressively larger drills until the bore was 3/8" ( this time I had an imperial drill set, so no metric convertion needed )
It was at this point I realised that the 9.5mm and 10mm reamers I thought I had as a part of a set were not there, the set only went up to 8mm and all are hand reamers, not machine reamers, and so even if the set went up to the needed size they would be useless as the bore is blind and only just over 1" deep.
So this is where the newbie-ness gets a little more obvious, instead of thinking that I could get a correctly sized and type (machine) reamer in a few days time, this numpty decided to spend 2.5 hrs trying to make one.
Sense has finally prevailed after making the bore look rather rougher than when I had just drilled it, and so I called it a day before I totally wrecked the cylinder blank.
So a total of 3hrs to bore one hole, and even that's gonna need reaming out.
This is what it looks like,You wouldn't believe how much of a numpty I feel. When I read your post Bogs it hit me like a ton of bricks, "I have a boring bar set for my mill" :bang: ( looks around for the hole in the ground to appear ) But I will file your C-o-C for future reference thankyou very much
Anyway, when I finally got over my numptyness this is what I got done today. I mounted the cylinder blank into the 4jaw, centered it and then took a couple of light skimming cuts and then about 4 repeated cuts to eliminate any springing of the boring bar.Then to turn down the other end I wanted to chuck it in a ER32 collet to not leave markings on the pin, but I dont yet have a ER32 chuck for my lathe, but I do have a MT3 ER32 chuck for the mill, and the headstock on the lathe is also MT3. Not having a long enough drawbar I brought up the tailstock to ensure that I wasn't chased around the workshop.
Once the pivot pin was turned down to the right size to be tapped M3, I then cut the M3 thread. You probably noticed that the tailstock is removed for this, I ran the lathe at the lowest speed ( I thread at the lowest speed so I dont run into the chuck ) and as I found out when trying to remove the ER32 chuck it was well stuck in there.
I then chucked it the other way round in the ER32 collet but made the error of not tightening it enough and it came loose just as I was parting it off to length
So I added to my collection of spare "smaller than I wanted" pieces and hacked off another lump of brass, chucked it and turned it down as before. This time I also drilled and tapped M3I find this to be a good method of tapping on the lathe, to explain; The drill chuck is not jammed in the MT of the tailstock, it has some grip but is free to turn with light pressure. Also the tailstock is also free to move on the ways, and the tap in the chuck is also loose enough to turn if the tap jams in the work. I then run the lathe at a very low speed.
Here's the completed piston, cylinder and frame.
So that's all I got done today, just 2 pistons made, 1 junked and one that fits ok. If I put a M3 screw in the piston and slide it into the cylinder and turn it upside down the piston gently slides down and stops at the entrance of the cylinder, with out the screw it just falls out. I dont know if it's too loose, if I pull the piston out rapidly I get a satisfying "pop".
Things I've learnt today;
I learnt that my ER32 chuck has a runout of 0.02mm,
Always start off with a piece of metal that is longer than you need as it makes life easier.
I also tried making a con-rod out of 303 stainless, it didnt go quite as planned but I learnt that it really helps to use sharp carbide tooling and that it doesn't like my Hss threading tool.(prob was a bit dull, I must resharpen it) I'll try again the next time with some brass as per the plans.
Also learnt to think a few steps ahead to see what I can do while workpiece is still chucked and true before taking the piece out and then spending 15mins truing it up with the trusty dial indicator.
And finally, always remember to check that whatever chucking device is used is properly tightened up.Ok, managed to get a couple of hours in the workshop today. Started off by setting up and drilling the offset hole for the crank pin.
The more observant of you will have noticed that the Crank-disc is not properly seated on the 3-2-1 block and so did not drill square. I didnt notice that until I'd finished today and as I'll explain in a bit I may have to re-bore the pin-hole square.I managed to make a start on the flywheel, and got one side shaped (to a fashion :scratch:), and today I bored and reamed the 5mm hole for the crankshaft, then remounted to machine the other side, centred it using the 5mm hole as a reference and then shaped the 2nd side. ( I was so excited about getting so close to completion I forgot to take any pics of these parts )
I then turned a some 6mm brass rod to a close fit for the flywheel, and threaded the end M5, and mounted the flywheel to it to clean up the rim and make sure (hopefully) that I dont have a wobbly flywheel.
After that I drilled and tapped the flywheel for the setscrewI then made up a round base out of some ali bar I had, drilled it and counterbored for the mounting screws, and also drilled and tapped a center hole M6. The center tapped hole is for mounting the Ali base onto a wider turned wooden base that I plan to make. (if folk are interested I'll do a project log on that too)
Here's the little wobbler on its little base.I finally got round to finishing off this project by turning a wooden base for it. Now this is more familliar territory for me, and while I did this on my woodworking lathe, the techniques are the same on an engineering lathe equipped with a toolrest.
1st of all I got a chunk of oak that happened to be around my dad's workshop (that's where my woodturning lathe is residing), and that chunk of oak just happened to be quartersawn ( nice looking grain ).