A raw beginner attempts an Elmer's 25

[clivel]

It didn't take long for reality to set in before I put aside my plans to build a 5" gauge loco in favour of something more suited to my limited equipment and even more limited experience.
A rummage through the storeroom-cum-garage-cum-workshop soon unearthed a box containing two sets of rusty castings; one set each for a Stuart 10V & 10H that I had been given a few years back. Heading over to the lathe I whiled away a pleasant few hours experimenting with holding the castings in the lathe chuck or on the milling table in various configurations, but I just couldn't work up the courage to actually attack those expensive and now hard to obtain castings with a cutting tool. So the castings were once again packed away and a decision was made to attempt a relatively simple engine that I could possibly complete successfully which could also be constructed from easily replaceable stock material. A perusal of the web turned up a wealth of possibilities of which I eventually decided on a little oscillating engine - Elmer's #25.

My "workshop" consists of: a workbench in the corner of the garage, a Unimat PC Basic lathe/mill, and the miscellaneous hand tools, measuring instruments and other odds and ends that I have managed to accumulate over the years.

The wooden rectangle in the middle of the bench on which can be seen the embryonic bits of my budding engine, is a cover for a 9 x12" granite surface plate. There is nothing too remarkable about the cover other than the brass screws I first tried assembling it with. These were bought at one of the big-box DIY stores, no country of origin on the label, just marked imported, three guesses as to where they were made?

And that was after I had pre-drilled the holes in the soft wood used for the sides!

-------------------

Actual engine construction started with a piece of 1/4" thick aluminium that was soon destined to become both the frame and the base. I initially planned on using the mill to machine the frame to shape, but never having used a mill before I instead opted for a hacksaw and some files. On the whole I am happy with how it turned out, but the inner curved corner does have a slight kink where it joins the straight.

The frame was then followed by the rectangular base. This time I threw caution to the wind, mounted the milling vice on the mill table and milled it to size ... eventually ... on the third try. What was not immediately apparent to this novice, is that when the table is traversed, that unless both vice and table are scrupulously aligned to the lathe axis, nothing comes out parallel.

Next puzzle to solve was how to align the frame and base for drilling the fixing holes. After marking out and drilling the two holes in the base to tapping size, I eventually hit on clamping the frame to the base, aligning it correctly, turning over and then clamping the clamp in the drilling vice.

For some reason figuring this out (and I am sure there is probably a better way), something that is probably trivially simple to an experienced machinist, gave me an enormous amount of satisfaction.

After drilling the crankshaft bearing and pivot pin holes in the frame, the port drilling jig was made up out of a strip of steel with three carefully placed holes. The next item, was my first real turning job - the 'locating pin'. This is used in combination with the port drilling jig to place the port holes in the frame as can be seen from the next picture.
Prior to this I had only really experimented with the lathe i.e reducing scraps of metal to swarf. Now I was faced with turning something a close fit. On my first attempt I completely overshot the mark, but my second attempt was much more successful. This probably had something to do with the realisation that those markings on the hand-wheels are actually useful and accurate!

That's it for today, so far it has been fun But what came as the biggest surprise to me is just how little time is spent actually machining in comparison to marking out and setting up.

The other thing that surprised me is just how much arithmetic is involved in machining a part to size. The plans are in fractions of an inch, the digital vernier in decimals both inch and metric (which also makes it a handy tool for converting between the two) and the lathe dials are metric. I don't want to get into a metric versus imperial debate, but as someone who is comfortable with both systems, I found metric with its consistent use of decimals so much simpler to use as a beginner when compared to the dual format fractions/decimals used with inches.

Clive

 

[90LX_Notch]

Clive-

Welcome to the madness! You're off to a great start.

-Bob

 

[AlanHaisley]

Clive,
If you want to use those brass screws (regardless of planet of origin), try two thing. First, after drilling the pilot hole, insert a steel screw of the same size as the brass one. Second, before inserting the brass screw, apply a little bee's wax (never soap) to the threads.
In fact, if the wood is a hard wood, you will probably want to wax the steel screw to put it in.

(If you have trouble finding bee's wax, you might have luck with a :toilet: bowl wax seal, although they are compounded a bit softer than the straight wax.)

Alan

 

[mklotz]

Clive,

Congratulations on opting to work up to castings and locomotives gradually. You'll relish the wisdom of that decision in the future.

If you're buying brass items at the big box stores, be sure to carry a magnet with you. Don't buy any of the magnetic brass. You'll be surprised at how many items are nothing but brass plated steel.

As you learned, aligning the vise to the mill traverse is critical. Most of us use a tool called a DTI (Dial Test Indicator) to do this job and many other alignment tasks common in the shop.

I started out with a Unimat. I had no DTI nor was there headroom under the spindle to use one. I made a T-shaped strip of aluminum and bolted it to the mill table doing an eyeball alignment. I then took a cut across the end of the T crossbar and, voila, I had a reference edge parallel to the table motion. Using this I could align accessories by butting them against the rail. Later I added another T-rail so I could align in both directions of the table movement.

Your observation about the ratio of setup time to machining time is right on the mark. While the novice might take slightly longer setting up, even experienced practitioners spend far more time on preparation than cutting metal.

Despite living in the last holdout of the Inferial system, I have to agree that the metric system is far superior, and not just for machining.

 

[b.lindsey]

Nice choice for a first engine Clive and a great little set-up you have there too...wish mine was as neat and orderly :big:

Bill

 

[Sshire]

Welcome Clive
I find that the most interesting aspect of this whole madness is devising ways to setup and hold parts. It's a wonderful mental exercise.
Keep at it. I made my first engine entirely on a mill since I didn't have a lathe at the time. Ask questions. You'll get responses from folks with years of experience who are anxious to help.
If you haven't found them yet, you might enjoy mrpete222 (aka Tubalcain) videos on Youtube. I believe there are more than 150 at this point.
Also the MIT machine shop videos have loads of useful tips.
Best
Stan

 

[arnoldb]

Nice start on Elmer's wobbler Clive Thm:

On the Elmer's engines I've built so far, I just took the plans and converted all measurements to metric and jotted down the values on the plans. I noticed you also converted threads to metric; that's just dandy. I just look up the closest metric thread and substitute it. Rounding off to 0.02mm for the measurements are just fine in most cases, but I tend to round them to 0.01mm and try and machine to that.

Looking forward to your progress

Kind regards, Arnold

 

[purpleknif]

The fun is definitely in figuring out how to do it. The actual cutting is kind of a let down.

 

[Blogwitch]

Clive,

A wonderful start into your journey of trials and tribulations. I just hope that you really catch the bug and carry on.

As you have most probably found out yourself, finding ways to actually get the shape you want is 90% of the exercise, and of course, if you do hit a problem, don't be afraid to ask, as I am sure there are many people on here that will have hit the same problem, and they will willingly share their knowledge with you.

Just keep up the good work, and don't rush things. Don't forget, make one good part at a time and you can't go far wrong.


John

 

[lazylathe]

A great start Clive!!! ;D

Like you the problems i am having is how to hold/clamp things and the order of operation.
Having never done this before i can visualize the finished part and the steps required
to get there, just the order gets me everytime! ???

It is a slow process but as long as you are having a good time that is all that counts!!!

Looking forward to following you on your journey!

Andrew

 

[clivel]

Thanks everyone for the great advice and words of encouragement
If anything this forum illustrates what a wonderful sense of camaraderie and general helpfulness there is amongst this community.

@Alan, thanks for the beeswax tip definitely something to keep in mind for the future.

@Marv, the T-shaped guide for the milling table is an excellent idea. Although I do have a little indicator I had some difficulty in using the round bar lathe bed as a reference surface for the magnetic stand. I think in the end me getting the milling vice traverse parallel was more luck than skill. From looking at other builds it would seem that a better way to go would be to mount the indicator on rod held in the mill chuck. But as none of the attachments that came with my indicator seemed suitable I will have to try and rig up a better arrangement next time

 

[clivel]

Once the frame and base were completed I decided to make the crankshaft bearing. Made from brass this proved to be fairly straightforward. This was successful at first attempt and although drilled, not reamed, it is a nice sliding fit on the 3/16" drill rod to be used for the crankshaft.

Emboldened by my success I expected the next part which was to be the crankshaft to go off without a hitch. But as they say pride goes before a fall.
Having previously decided that I could avoid learning the black art of tool grinding by sticking to indexable tipped tools, I mounted a RH tool in the toolpost, carefully checked it for centre height and then chucked up a short length of 3/4" cold rolled steel which was to form the crank disc.
A light skim off the face was met with disappointment. The surface was horrible - as rough as barbed wire. A skim along the length was no better, no matter how slowly I traversed the carriage or how light the cut, I just couldn't get a smooth surface.

I double checked everything was tight, I tried a straight tool, I tried faster, I tried slower, I tried with and without cutting fluid, but to no avail I just couldn't achieve a satisfactory finish:

Eventually after taking the lightest cuts possible, very slowly and then followed up with a file I managed to achieve a barely acceptable finish.

The bar was then transferred to the bench vice so that a slice could be sawn off. The plan was to reverse the chuck jaws to hold the machined side while the sawn face was faced to the correct thickness followed by drilling a central hole for the crankshaft.
But what I hadn't realised was that with the jaws reversed the chuck couldn't close down enough to grasp the disc. With the disc now too thin to grasp securely any other way I could see no other alternative than to remake it, but this time with the crankshaft hole drilled at the first turning.

However I didn't want to remake something and still be unhappy with it. There had to be a better way, so after a little research I decided to order a diamond tool holder.
When the tool arrived a few days ago I mounted the bit in the supplied grinding jig, turned on the newly purchased bench grinder and 30 seconds later had what appeared to be a correctly sharpened tool bit. I mounted the tool holder and bit on the lathe and using the same material as before proceeded to turn a new crank disc. I was stunned at the result. The finish was excellent. After turning to size, and drilling the crankshaft hole, the disc was fitted to the end the crankshaft with a dab of loctite.

Twenty four hours later, once I was sure that the loctite had set the crankshaft was grasped in a collet chuck so that the disc could be faced to the correct thickness:

Last night I fitted the crank pin, again with a drop of loctite to keep it in place, and this is the result:

Having it sitting on my desk all day I have been hard pressed not to give it the occasional twirl. Actually I have twirled it so many times, it's touch and go as to whether my thumb and forefinger or the bearing will wear out first

Tonight I plan on starting work on the cylinder - a rectangular block of brass with a 3/8" bore. I still haven't figured out how I am going to bore it out, but a thought did cross my mind, and there is probably a very good reason why not to, but couldn't a two fluted 3/8" endmill be held in a tailstock chuck and used to plunge "bore" the cylinder?

 

[ProdEng]

A two flute milling cutter is usually called a slot drill. The difference between a slot drill and an end mill is that the slot drill has a cutting edge on its face that goes all the way to the centre so it can drill; an end mill will not drill. Either way the result of using a milling cutter will be similar to using a drill, a hole that is not very circular and not particularly straight. For a cylinder bore we would like a hole that is parallel to the port face else the engine will probably lock up as the crank goes around. One answer is to use a boring bar to get within a few thou of size and then ream or lap to get a parallel bore with a nice finish. I usually drill close to size and then bore and lap.

 

[thayer]

Hello Clive,

Welcome to the wonderful world of Elmer's Engines. I started the same as you, with his #25. My results are my avatar at left. Keep picking away and you will be done soon. I don't recall, but think I might have done as you suggest and used a 3/8 end mill for the final cut after drilling out most of the cylinder stock.

Here is mine in action.
[ame]http://www.youtube.com/watch?v=AcOpUwI-v70[/ame]

and the follow on, which honestly, I think took less time to build.
[ame]http://www.youtube.com/watch?v=NLKUff-7xZo[/ame]

Thayer

 

[arnoldb]

Good going Clive Thm:

I'd advise against just plunging in only with slot mill held in the tailstock chuck. The brass will want to grab it and will easily pull the chuck out of the tailstock.

First prize would be to make up a boring tool, and drill and bore the cylinder to size.
You can also make up a D-bit reamer; it's not difficult. The problem with the reamer is getting the last bit in the cylinder done, as there will be a cone left from drilling. You could simply drill and ream right through the cylinder, and then turn up a cylinder head and solder it in. If you're only going to run the engine on air (not steam) you can even Loctite the cylinder head on.

What you can also do is to drill the cylinder out to depth just under size with a normal drill. Then with the slot mill clean it out to size; run at high speed and feed in very slowly; take care on the last bit where the slot mill has to remove the cone left by the drill. Also when retracting, do it very slowly; that should leave you with a bore with a finish plenty good enough for this engine and no need to lap afterward.

Kind regards, Arnold

 

[clivel]

Oh what lovely engines Thayer, and what a high standard to aim for

Arnold & ProdEng, thanks for the advice. It seems that I really should try boring the cylinder the correct way - using a boring tool. And as I intend making the flywheel with a deep recess on the front, that will probably need to be bored as well.

I do have an indexable tip boring bar, but as it has a minimum hole size of about 12mm I will probably have to bite the bullet and try and make something smaller. In the book "Model Engineers Workshop Manual" George Thomas describes some small hole boring tools that don't look too difficult to make so I think that I will give one of his a try unless someone has a better suggestion.

When I get to making the flywheel I can picture how one would use a boring tool to turn the bottom and outer edge of the recess, but how would one normally turn the inner edge, a left-hand boring tool?

Thanks,
Clive

 

[thayer]

Clive,

Thanks for the kind words. It was a lot of fun to build those engines and I am looking forward to doing another soon. As for the flywheel question, if there is room, I would just come into the hub area with a conventional RH cutting tool once you establish the inner face.

Thayer

 

[clivel]

I spent the evening attempting a boring bar as per Geo Thomas's description.

I chucked a length of 1/4" drill rod in the four jaw chuck, offset by about it's diameter. I then turned down the middle bit for about and inch. Initially I found the eccentric turning quite alarming. I was convinced something would break, but I gritted my teeth and persevered:

(Sorry about the quality of the pictures, the camera just wouldn't cooperate tonight).

After removing the bar from the chuck I filed the tip flat to a fraction over half its diameter followed up by filing front and side clearance. I expected it to be a difficult job but it went surprisingly quickly. The filed surfaces were then finished off with emery cloth wrapped around the file.

At this point, it was far too late to start playing with fire, so tomorrow evening evening I will try hardening and tempering the bar. I just have to figure out what "cherry red" actually looks like.

 

[clivel]

As for the flywheel question, if there is room, I would just come into the hub area with a conventional RH cutting tool once you establish the inner face.

Oh of course thanks Thayer.

 

[Maryak]

I just have to figure out what "cherry red" actually looks like.

Like a red cherry ;D

Seriously the above is pretty accurate but the colours are normally stated as being those you would see in daylight in a well naturally lit room. Not outside in the sunshine or in a dark dingy corner.

Hope this helps.

Best Regards
Bob