Chris' Built-up MEM-Corliss Build

[crueby]

After watching along on the other threads building the MEM-Corliss engine, I got inspired by thier wonderful work to attempt one myself.

One drawback was figuring out how to do the facing and cylinder bore on the large block on a Sherline lathe and mill. The largest stock it will hold in the chuck with the jaws forward (without adding the riser blocks) is 1.5" diameter. Reversing the jaws allow it to go larger, but then it would not fit in the steady rest, plus the steps on the back side of the jaws are pretty small, meaning there is not a lot holding a pretty heavy chunk of steel.

After some great ideas from others, including some key advice from Captain Jerry, decided to do a built-up engine block more like a lot of the real ones were done. As Jerry pointed out, the large rectangular block is with the insulation and covers all in place, the actual core was usually made up from other castings, like the first picture below shows. Once I started thinking along those lines, everything fell into place - start with a 1.5" diameter rod for the cylinder core, and add plates on the ends for the cross valves plus side/top pieces to fill in the steam chests and the central valve disk. A sketch of that is photo 2, note that it is a work in progress and is still being tweaked, but it let me work out enough to get a start on things. One difference in my engine from the original MEM plans is that the valves will be slightly farther away fromt the cylinder bore - that let me leave the thinner area at the end of the cylinder a reasonable thickness. Should not impact the performance at all, the finished engine block will just be a little taller. The floor plates it mounts on will be adjusted to keep the centerlines out to the crank the correct height.

So, on to the shop! 

Starting with a length of 1.5" 303 stainless steel bar, got it centered up in the 4-jaw chuck using a dial indicator, then added the steady rest to help support it. (photo 3) With that bar in the chuck, there is just clearance for the outer ends of the jaws above the ways. Drilled a 3/8" starter hole through the bore (largest the drill chuck will hold), and was ready to bore out the cylinder.

Since I would be boring all the way through the piece, and the bore would be larger than the center hole in the chuck, I left the part 1/8" long and cut a recess in the face that was slightly larger diamter than the finished bore. Then reversed the part, centered all up again, with the recessed end up against the chuck, and started boring using my smaller boring bar (photo 4). When making a pass, I could tell when the bar got to that recess and would stop cranking. I had the bar set in the holder so it would not quite be able to reach the chuck face.

Once I got partway out, switched to the larger boring bar to finish things up (photo 5 and 6). Everything went great till I got to about 1" diameter on the bore, then had to stop frequently and experiment with different cutter heights and speeds since it started chattering - sounded like the part reached a thickness where it started ringing like a bell. Up to that point it was all going smooth (too smooth!). After a bunch of fiddling, hit on a combination that let me finish the boring with a decent surface. Just in time too, the experiments were eating up the last of the material.

With the bore done, switched back to the turning tool and cut in the recesses at both ends that will take the end plates. Photo 7. While doing the second end, also trimmed back the material that formed the edges of the recess, taking the part to the finished length.

Now, as you can see (I hope!) in the final photo, there are two cylinders. While cutting out the stock for the cylinder and the end plates, I decided to make a spare set in case anything went wrong along the way and I ruined a part. It is much quicker and easier to make a second part once a setup is figured out than to go back and do another one later. So, I'll either have a spare for disaster recovery, or this will turn out to be a two-cylinder engine! Here's hoping!

Next week I'll get a start on the end plates, for now am getting ready for the sea trials on my new RC sub tomorrow, it is a Great White shark - should be a good way to get the last swimmers out of the pool! Will include some pics of that next time too...

Chris

[zeeprogrammer]

  More opportunity for fun!

 

I appreciate the description you gave on boring and the 'troubles' you had. That kind of stuff really helps newbies like me to a) recognize when it happens and b) know what to do to overcome.

Hope you have enough cookies to last the project.

[crueby]

More opportunity for fun!

 

I appreciate the description you gave on boring and the 'troubles' you had. That kind of stuff really helps newbies like me to a) recognize when it happens and b) know what to do to overcome.

Hope you have enough cookies to last the project.

It was really obvious when it happened - loud screeching noise, finish on the bore looked like corduroy cloth. Near as I can tell, either it was hitting the resonance of the cylinder tube, and/or as I got farther out the cutter was now on a slightly different angle of the part, so I had to keep raising the cutter height and fiddling with the lathe speed. Never really got it totally smooth again, but good enough that I could take some light final passes to get a good finish. It will get lapped with the piston later on as well.

For the size/complexity of parts, I think that getting past the engine block construction and the flywheel (which will have to be built up as well) will be the two biggest milestones on getting this engine out of a small lathe.

Still a few bags of cookies in the freezer, can always make more! Glad you are watching along and keeping the banter flow going! Don is going to be a little depressed, dont think there will be a lot of brass parts in this one. Have to add some details in brass just for him.

[Bluechip]

If your '303' is the same as our EN58 ( I think it is close, without checking ) it work hardens. So, your last cut needs to be over some 0.002" otherwise it just tend to push the tool off.

There used to be a variant of EN58 ( with a 'J' suffix IIRC    ) which wasn't so intractable.

You might find it cuts better with a HSS tool for the last skim. It needs to be newly ground and honed and you'll only get one pass. 

Dave

[crueby]

If your '303' is the same as our EN58 ( I think it is close, without checking ) it work hardens. So, your last cut needs to be over some 0.002" otherwise it just tend to push the tool off.

There used to be a variant of EN58 ( with a 'J' suffix IIRC    ) which wasn't so intractable.

You might find it cuts better with a HSS tool for the last skim. It needs to be newly ground and honed and you'll only get one pass. 

Dave

Hi Dave,

Nearest I can find is a chart that shows the 303 is simaler to the EN58-AM version, some of the other EN58 versions are like the 302 or 304 steel here. Gotta love standards, everyone has them, and nobody shares!

I have used a lot of 303, never had any work hardening issues with it while machining so far. For this bore I went from a 3/8" starting hole, all the way out to about 1" with multiple passes with the boring bars before having any issues. I am using carbide inserts on the boring bars, and cobalt alloy drills. changing the cutter position and speed seemed to help a lot as the hole got larger. When cutting in the shoulder on the outside (also with carbide insert cutter), had no trouble there at all, it cuts very easily.

[Bluechip]

If your '303' is the same as our EN58 ( I think it is close, without checking ) it work hardens. So, your last cut needs to be over some 0.002" otherwise it just tend to push the tool off.

There used to be a variant of EN58 ( with a 'J' suffix IIRC    ) which wasn't so intractable.

You might find it cuts better with a HSS tool for the last skim. It needs to be newly ground and honed and you'll only get one pass. 

Dave

Hi Dave,

Nearest I can find is a chart that shows the 303 is simaler to the EN58-AM version, some of the other EN58 versions are like the 302 or 304 steel here. Gotta love standards, everyone has them, and nobody shares!

I have used a lot of 303, never had any work hardening issues with it while machining so far. For this bore I went from a 3/8" starting hole, all the way out to about 1" with multiple passes with the boring bars before having any issues. I am using carbide inserts on the boring bars, and cobalt alloy drills. changing the cutter position and speed seemed to help a lot as the hole got larger. When cutting in the shoulder on the outside (also with carbide insert cutter), had no trouble there at all, it cuts very easily.

I've had a poke around, and it may have been EN58BM that was the better material.
As you say, there may be no direct equivalent from AISI to EN Series.

Found a bit of inf.o from the Vincent Owners Club magazine , MPH, which may give some of insight without going too deep.

http://www.voc.uk.com/net/docs/14/14-246-16.pdf

Page 2 on this actually says '58BM to be excellent machining with '58A is fair .. ??

http://www.voc.uk.com/net/docs/14/14-241-8.pdf

I might add I did little or no boring of 303 / EN58 / whatever  , usually just plain tuning.

Dave

[steam guy willy]

I have heard that the EN prefix for steels refer to Emergency Number    this was brought ab out in the first world war to clarify the different steels used for the weapons industry etc , Please correct me if i am wrong
thanks
Willy.

[crueby]

Dave, I took a look at the documents, and I think the 303 is equivalent to the en58am, where the m suffix denotes the free machining versions. Ive found it to be great to machine, using it on everything from trains to rc models. Thanks for the links, did not realize that there was such a difference between the countries in alloy specs, knew that there was in thread specs. I take it you work on old Vincent's?

[crueby]

I have heard that the EN prefix for steels refer to Emergency Number    this was brought ab out in the first world war to clarify the different steels used for the weapons industry etc , Please correct me if i am wrong
thanks
Willy.

Interesting!  I found this history of it:

EN steel specifications stockholders and suppliers, delivering to the whole of the UK. The EN range of steel specifications was first introduced in 1941 as the War Emergency, British Standard Schedule BS970. With the assistance of the Technical Advisory Committee of the Special & Alloy Steels Committee the British Standards Institute published 58 specifications (EN1 to EN58). These steels covered a variety of types including carbon steels, alloy steels, case hardening steels, spring steels and stainless steels. The grades were arranged sequentially according to the chemical composition, starting with low carbon grades EN1, EN2 and EN3 working up to stainless steel grades EN56, EN57 and EN58. IN 1955 the BS970 EN range of steel specifications was revised to add further steel grades.
 
No allowance had been made in the 1941 edition for a possible insertion of further steel grades and the British Standards Institution considered that to have applied a high EN number would have divorced the grades completely from steels of similar types. Therefore with numerous grades suffix letters were added (for example EN19 became EN19A, EN19B and EN19C). The BS970 1955 revision of the standard increased the number of specifications to nearly 200.

[Flyboy Jim]

Chris,

This is great to be able to start following along right at the start of your build.  I've learned a lot from your build threads, seeing how you deal with making various parts on your Sherlines.

Jim

[crueby]

Chris,

This is great to be able to start following along right at the start of your build.  I've learned a lot from your build threads, seeing how you deal with making various parts on your Sherlines.

Jim

Thanks! Pull up a comfy chair and some popcorn, we'll see if this is a tutorial, a mystery, or a horror show! With Zee along, there is bound to be some comedy too, which is good.

[crueby]

While waiting for batteries to charge on the radios, went in to do some setup for taking the endplates to size from their current rough sawn state (recip saw with metal cutting blade). Had to turn the mill vise sideways and add the headstock raiser block to get the reach needed in both directions.

For picking the end mill, have questions for you guys: for milling down the side of the plates (1/2+ thick) with the side of the mill, does it matter which diameter mill that I use? Any difference in the finish I will get from a 1/4" vs a 3/8" mill on 303 stainless steel? Are there rules of thumb for this, like there are for picking tooth count on a saw for different thicknesses of stock?

[zeeprogrammer]

For picking the end mill, have questions for you guys: for milling down the side of the plates (1/2+ thick) with the side of the mill, does it matter which diameter mill that I use? Any difference in the finish I will get from a 1/4" vs a 3/8" mill on 303 stainless steel? Are there rules of thumb for this, like there are for picking tooth count on a saw for different thicknesses of stock?

Oo! Good question! I've wondered many times about what end mill to pick for any material when doing basic operations. I've always thought bigger is better...mainly for stiffness. But it just seems that the finish is different. I suspect though...that there's so many variables that come into play...feed rate, depth of cut, etc. Still, it would be interesting to get some rules of thumb. But I kind of think it always comes down to experience. This worked...so I'll use that. The danger, for me, is getting stuck in a rut and not trying something different to see if it's better.

[Captain Jerry]

Chris

That is an interesting design.  It looks exactly like some of the old design sketches in my archives.  I am going to enjoy watching this proceed, especially with that magick boring bar that creates a 1" bore without a huge pile of swarf.   OK, I know you clean up as you go but I wanted to see what the chips looked like.  Little curly chunks or long winding strings that can take a finger off.

As to the end mill question, when bringing stock to size, I like to use the biggest end mill that I have.  Fewer passes and more consistent finish.  Where possible, I like to use a fly cutter.  You can't beat the finish.  I use brazed carbide tool bits in my flycutter on cast iron and I think they would work on your SS.  My smallest has a radius of just under an inch.  You can't take the same depth with a flycutter as you can with a 3/8" but since the path is so wide it can actually mean fewer passes and a better finish.  I also prefer to use a flycutter where possible because they are really easy to sharpen and sharpness is always the key to a good finish.  I have no way to sharpen a two flute or four flute end mill.

Jerry

[crueby]

Jerry, its easy to make swarf disappear, just stir in a shop vac with a cyclone separator, and whoosh! Its gone! Easier to see the parts in the pictures with the light background than the part-colored one too.

The chips from the boring bar were mainly short tightly curled ones, sometimes longer when the speed and diameter hit a sweet spot. With such a long bore I have to stop every couple passes and clear the bore of chips.

I usually use a fly cutter for putting flats on a surface, but like side milling for narrow stuff like the end plate edges - less vibration plus it makes a whole lot less mess, the fly cutters throw chips a long way. On other projects when making round bar into square sections the fly cutter was perfect.

Thanks for the tips on the end cutters, keep em coming!