PM Research Engine Number 1

[zeeprogrammer]

The flycutting looks great to me. I would be one happy fellow to achieve that.
I'll be interested to see what others say.

[propforward]

Thanks Zee, I'll be interested in feedback too. I did shim and tram my mill column in last year, so I was pleased to see cross hatching. I should check tram again and see how it looks lately. Job for tomorrow night maybe, although looking at these, not too much to worry about?

[Flyboy Jim]

Like Zee...........the cross hatching looks good to me. A fly cutter is really handy to have for situations like this.

Jim

[propforward]

It certainly is, made quick work of this. Really throws the chips around, too!

[gary.a.ayres]

I will be interested to hear what you and others think about collets as perhaps an earlier purchase than a smaller three jaw chuck.

MJM460

I have found my ER32 collets and collet chuck to be excellent for keeping things running true.

Nice work on the cylinder Stuart.

gary

[propforward]

I made a start on the crankshaft tonight for no particular reason. It's just what I felt like working on.







Not sure I'm entirely happy with that set up, so I'll look at that again before any more turning. Probably put on a cutting tool with a smaller radius for a start.

Also tonight, a little more flycutting to level out both sides of my jig plate.



My cross feed drive broke down, and is under investigation. I can probably repair it - better that than $450 for a new one.

[Flyboy Jim]

Bummer about your cross feed drive Prop. 

Please elaborate on your misgivings about your set up for turning your Crankshaft. I'm getting closer to turning the crank on my PMR #5 project and was thinking along the lines of what you're doing.   

Jim

[propforward]

Slightly annoying about the cross feed for sure, but I'll figure it out. Not the end of the world - a bit of research shows that these units are prone to failure, especially around the speed control potentiometer. Maybe I can make it an engineering opportunity and change things to be more robust. Could be fun. Or - maybe I'll buy the cheap one I found on ebay.

As for my misgivings, I feel better about them this morning. I have never set up my lathe tool in this way before, so I think I was just questioning my approach to be sure about it. It keeps the toolpost well clear of the chuck and part, and gives me access all round, so I think that makes it a win. I will change over to a sharper insert though (I mean smaller tip radius).

My plan is to turn the crankshaft around, clean up the other half, and then mount the shaft between centers to turn both halves of the shaft to size. That is what the drawings suggest, and it sounds like a decent approach, so I'll try it.

I have heard that the crankshaft can go out of true when removing the center support web, so I'm actually giving thought to taking that out before doing any more turning. Might have to make support clamps for the center journal maybe?

Just musing out loud (via the keyboard) now.

[steam guy willy]

Milled out the pocket anyway. Got the size of the cutout within 0.005" on all sides, within 0.002" on depth and centered on the part within .002" each direction. Always good to see how close you hit the mark.





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That finish looks like end grain growth rings on wood   as if it was cast from a patern  using end grain wood ??!!!  good work...

Thinking I'll polish up the main face on a surface plate before it goes in to service.

Then had a try at some flycutting. I have a piece of aluminum plate that I want to use for holding the chassis casting. I started sanding it flat a while ago, but it quickly became apparent that it was going to need a fair bit of material removal. So, I ground a tool according to the geometry I found on Toms Techniques website, and had a  try.







I don't know much about interpreting the cross hatch pattern, but I think this is not too bad. The casting no longer rocks on the plate, although I still have a bit more clean up to do on the underside of the casting to get it set down all around, but progress made anyway. Only problem being the cross feed motor died shortly after I started, which is a bit vexing, so I had to hand feed everything. Probably just a contact brush issue I think.

[propforward]

That finish looks like end grain growth rings on wood   as if it was cast from a patern  using end grain wood ??!!!  good work...

Thanks! Unfortunately those are endmill marks from where I machined it - but the photo does exaggerate them somewhat. Even so, I'll want to lightly polish those out before putting the part in to service. I think the machined pocket came out reasonably well though.

[crueby]

I like to give those surfaces a polish with a diamond coated steel lapping plate with oil, followed by finer grits of diamond paste - flattens out any tool marks and gives a nice tight seal. Just moving it back and forth by hand, pressing down on the center is all it takes.
 

[propforward]

Excellent yes, thank you. I was thinking fine grit emery, but what you describe will be a much better finish for sure.

More tinkerings. Replacement cross feed drive came today. It's wired incorrectly, such that it works in reverse. Will open it up and sort that at some point. Not a big deal, plus it was CHEEEEEP.



More importantly, I flattened the underside of the base casting. Levelled it first longitudinally along the regions I had given a light sanding on the surface plate. Crosswise it was about 0.007" off, which I figured was not enough to worry about, and in any cae with this set up I'm levelling the base relative to the (admittedly unfinished) slide rails. Seems like as good an approach as any.



Took off about 15 thou.



Still a couple of rough spots, but I don't think it's essential to take those out, I just want a good level surface around the whole perimeter.

Then set it up on my flattened aluminium fixture plate. Set it up so that it was as square as possible to the aluminium plate, using the slide rails and cylinder mounting face as references, as best as possible since they are not machined. Essentially "averaged" the position between the 3 surfaces, which should work well when I start cleaning material.



Yes, I did support under the extremes of the casting.



Then went around and drilled through the bosses, lightly spotting in to the plate below. Then removed the casting, tap drilled the plate, and tapped the holes to 4-40 thread.

Hey presto, base casting now on a holding plate and ready for machining.



I need to take a file to some of the flash first, but then I will look at setting up to machine the datum face where the cylinder mounts, once I have written out my operation sequence.

[propforward]

I decided to make a start on the base today.

I decided to start with cleaning up the end face. This is the datum surface everything is referenced from. My plan being to get this flat, then put all the holes in it, and use the center hole to locate the height of the slide rails, and also establish the center line for cleaning up the insides of the rails and the inner surfaces of the bearings for the crankshaft.



Although the drawing calls for spotfacing the end, that seems unnecessarily complicated to achieve - I suppose not much work with a boring head - but just milling it flat over a large enough area is simpler at this stage.





Then mounted it upright for the end face. I saw someone else mount one a bit like this, but I was concerned about how the plate would actually hold up. Thought I'd try it though.



I did mark up the end as a visual aid. I like to establish points from edges using an edge finder, and then center drill locations, rather than try center punching them. But I thought it might be a good sanity check to have this marked out to refer to.



Worked out OK. I actually found center by measuring the part, and then using an edge finder, and indexing from there, to keep the center point central, but my back up scribing was reassuring to have.



However, the plate did start to vibrate, so I decided to remount before going further.

I have this angle plate. I crudely set it up first





Then secured the fixture plate to the angle plate, and used the actual part face to get everything squared up, level and true.



I found center of the part again, using a co-axaial indicator, and then started spotting holes.



I used the geometry approach to establish the coordinates for the bolt circle pattern, which is very simple on a six hole pattern. My little Zeus book has these all predefined for easy reference.



Anyway, a bunch of counting of dial turns later, being sure to remember to take up backlash, and there we have it.



Test fit:





Which looks OK to me.

Then I spent a little time cleaning up the boss surface.





It seems to take me an exceptionally long time to set jobs up. For instance setting up the angle plate and getting the face of the base casting level and true was about 2 hours. But maybe that's just a matter of practice. At this stage I'm more interested in getting the set up right, than how long it takes to do it. I'm pleased with the last few workshop sessions results.

[crueby]

Great setup for the casting - well worth the time to get it all trued up. Thats the kind of stuff that practice helps with, after a while you wont notice that you are just setting it up without having to think it all through.
 

[propforward]

Thank you for the encouragement, that is appreciated and very well received. I got the fixture plate idea from Bill Lindsey in his PMR #1 build thread, and certainly I have seen others use the concept as well. I must say, it makes handling that casting an absolute breeze. Working on it the last couple of sessions was a real pleasure.