PM Research Engine Number 1

[gary.a.ayres]

One thing's for sure, I'm not going to improve by not making parts - so I'll keep making parts!

That's a great attitude Stuart!

The engine in progress is starting to look handsome now, with he contrasting metals.

gary

[propforward]

Thanks Gary!

Haven’t made much progress this week. I’ve been investigating an issue with my mill - which I now think is just caused by using cheap cutters that are now worn. Another problem for the inexperienced machinist is knowing the signs of worn tooling.

Anyway, hopefully get down the shed today and turn some parts. Might just be some of the simpler bar stock parts - but I need those anyway, so all good fun.

[gary.a.ayres]

Yes indeed! I have that problem with cutters too... compounded by the fact that different metals have different requirements in terms of sharpness.

So much to learn in this field...!

[propforward]

Well, got a little shed time in today.

I started the crank shaft quite some time ago. This is as far as I got it.



I decided at the time that I would be better off making the base first, so that the crankshaft could be turned to fit the bearing journals, and that was a good decision.

I swapped over to my collet chuck to proceed. It bums me out that I have to true up my collet chuck every time I refit it - but I suppose expecting to rely on the large threads on the lathe to accurately locate a chuck in terms of concentricity was naive at best. It actually only takes me about 10 mins to align it now in any case. The collet chuck has a set of 4 adjustment screws for fine tuning.





I can get it set up and running true enough that I can't detect run out on this DTI, and the ER collets are a lot better to work with than the 3 jaw on diameters 1" and down.

So - bit of clean up on the face:



Drill center hole:



And clean the diameter.





Then I cleaned up the outer faces of the cranks a bit:



It is necessary now to turn the larger diameters next to the crank to an exact length, to locate the crank shaft centrally in the base casting. It was at this point I decided that it would really nice to have a fine adjustment carriage stop - or any carriage stop come to that. So I have paused work on the crankshaft to make one.

The plan is to get the larger diameters turned to length using the collet chuck to hold each side, then I will turn the 3/8" diameter shafts to size between centers to get best concentricity.

But first - carriage stop. Different thread. 

[gary.a.ayres]

My ER32 collet holder plugs straight into the Morse taper of the lathe spindle - no chuck/faceplate involved. There's still a little bit of runout but so far liveable with I think. Could be worth considering, but I know... always more tooling to buy...

Nice work on the crankshaft so far.

[propforward]

Unfortunately, although this lathe does have a morse taper in the spindle, it doesn't readily adapt to any available collet tooling. I do have an adapter, but then I'm starting to stack up tapers, with nothing actually locking them in place, just friction, which makes me uncomfortable. So I went this route. The more I use it, the quicker it is to true up, so while it was frustrating initially, it's not too big of a deal any more, and it's a really solid set up.

[gary.a.ayres]

Yeah, I'm sure it will be fine the more you get used to it.

My holder has a drawbar thread in the back end and could be used on a mill of the same taper. So far I have just used a length of threaded bar with a nut and washer at the back end as a 'temporary' solution... 

[propforward]

That’s exactly the set up I originally planned! I actually obtained an MT3 quick change collet set up, but no thread in the back. Just as I was starting to conjur some sort of Machiavellian solution, I discovered this rather clunky collet chuck, suitable for mounting to a threaded spindle type back plate, which ended up being the right solution.

Bonus is the MT quick change collet holder fits my tailstock, so I se it there. Win.

[propforward]

Back to the engine!

My 1/4" reamer arrived, so I decided to finish up the cross slide. Got it all set up, found the edges and positioned the center of the pin. Did a quick visual with a drill blank to make sure it looked centered in the casting boss.





Then spot and drill. I drilled to about .015" undersize, but drilled out half way to that first.





Then reamed to 1/4"



Checked with a pin gauge - got it spot on this time!



Then set up and milled the slot.



Finding hole center by using pin gauge and a feeler gauge.



I plunged the slot to get most of the material out.



Then cleaned up the sides and bottom of the slot. The end mill was just long enough. Worked well though.



Finished!



And it even fits and slides easily up and down the rails. Will wonders never cease?





Decided to finish off the valve. I had faced and pocketed this some time ago, but was not happy with the amount of error I was getting milling depths. I now have that resolved, and so......





I tickled out the slot until the material to be used for the nut just fit in.



And then the same for the other slot. Again - plunged most material out, leaving 0.01" on depth, then cleaned up.



Finished part - still needs some deburring.





Then I started thinking about some other components. I was enjoying milling so I moved on to making a collet to hold square bar stock, which will be used to make linkage components for the valve drive rod.



The overhang of this aluminum rod did cause some chattering at the end, but by making a finish pass it cleaned up fine.



After taking the shaft about 0.01" past centerline, I rotated the part 45°, positioned the cutter and milled a slot.





Chopped into two pieces, and being used to hold the sqaure stock in the lathe.



That's as far as I got today. Next stage is either the linkage components or go back to the crankshaft.

A good day in the shoppe today. 

[crueby]

Great results, and I like that square bar collet.

[mklotz]

Since they have no lip on the front edge they may slide into the collet that holds them; retrieval will waste some time.  A fix for this is to tap the front of the two halves for small screws which overlap the edge when seated.  Alternatively a bit of bent wire loctited into a hole will prevent them from hiding in the collet interior.

If you want to use the 4jaw when turning polygonal stock, you may want to think about making one of these...

https://www.homemadetools.net/forum/centering-aid-polygonal-stock-27183

to aid in centering.

[propforward]

Blast. I didn’t think of that. Thanks Marv, I’ll make an adjustment to the collet. Maybe I’ll even make another one. Most of the time taken was aligning the rotary table, and that is still set up.

I like your centering aid. I wanted to use the collet approach this time just because it is small size stock.

[gary.a.ayres]

Nice progress. 

The square bar collet looks like a very handy idea...

[propforward]

I wish I could claim it as my idea - but it isn’t. Anyway, I tried making another at the weekend, with a lip to stop the adapter disappearing into the collet, but the endeavour didn’t go so well, and now I have to try again. I think this adapter will be useful over time, so worth having one that is made properly.

[propforward]

OK - I made a new holder. Same idea as before, but turned the body down to 3/8", leaving a stock 1/2" lip to stop the adapter disappearing inside the collet, per Marv's recommendation. This has indeed turned out to be a good move.

New holder:



And using it to start making the linkage.



The little holder is not perfect - it is not quite centered. Off by about 0.002 I think, which is really not acceptable - I could center much better than that in a 4 jaw, but my 4 jaw is a bit big for this job. I may attempt another holder. It's actually quite a good exercise for tuning in my milling techniques.

Not much progress, but some.