P.M. Research #5 Steam Engine

[Sarah]

My next project is the P.M. Research #5 Steam Engine. The picture below is the #5 from the P.M. Research website. It has a mixture of cast material, including aluminium, brass and iron. First impresions are very good, the cast parts look excellent and the drawings very clear and precise. A lot of the smaller cast pieces are all joined together on a Sprue, this should make it easier to hold whilst machining. A lot of the specified threads are UNC, I will buy a set of 2-56 taps as there are a lot of 2-56 screws included in the kit. For the other threads I will use the BA taps and dies I already have.

The first bit to be tackled was the cast aluminium, or as it's an American product cast aluminum, Base The casting is very good with just a little filing to remove the sprue bit. The base and top were lightly sanded against some abrasive paper on a sheet of glass. This removed a few odd lumps and gave a nice flat surface to work from. The tapping drill size was 1.85mm for the four 2-56 internal threads in the top of the casting. I used the nearest I had at 1.8mm, even though it was smaller than specified it was very easy to run the tap through. I might try a smaller drill bit size next time.

Next will be the Standard and a chance to use my nice new Faceplate

 

[trlvn]

The tapping drill size was 1.85mm for the four 2-56 internal threads in the top of the casting. I used the nearest I had at 1.8mm, even though it was smaller than specified it was very easy to run the tap through. I might try a smaller drill bit size next time.

The reference I use says a 1.75mm drill gives 74% thread penetration. A #50 drill (0.070 inches or 1.778mm) gives 69% thread penetration. Using a 1.85mm would give a very low penetration IMHO.

Craig
(From "Handyman in Your Pocket" by Young & Glover, 2008.)

 

[Sarah]

The reference I use says a 1.75mm drill gives 74% thread penetration. A #50 drill (0.070 inches or 1.778mm) gives 69% thread penetration. Using a 1.85mm would give a very low penetration IMHO.

Craig
(From "Handyman in Your Pocket" by Young & Glover, 2008.)

Thanks Craig, you are correct about the thread, it was very shallow.

The book that I have been using is:

Screwcutting (Crowood Metalworking Guides) by Marcus Bowman (Author)​

That book has been really useful. I have since checked other sources and they specified a #50 or 1.8mm drill bit. When I assemble it all on completion I might use slightly longer 2-56 screws and nuts to be sure. I have ordered some #50 drill bits for the rest of my project

 

[Sarah]

The Standard was tackled next.

The top and bottom of the Standard were uneven, so I took some time to file the top until it was nice and flat. I also checked it stood up vertically with an engineers square.

I needed a way of holding the Standard and I discovered that there is a shelf like form at the bottom of the crosshead guide. A T-nut, wrapped in aluminium sheet, fitted against the shelf perfectly. I could then attach the Standard to a nice flat sheet of aluminum, which can be fixed to a faceplate or mill table.

 

[Sarah]

With the Standard fixed to the aluminium plate, and appearing reasonably flat and level, it was machined in my milling machine. The aluminium plate was placed on two steel parallels in my milling vice and tapped down on top of the parallels. This gave me a nice base to machine from, but it was the top of the Standard which would be my reference for other machining.

 

[Sarah]

The Standard was fixed to my shiny new Faceplate by clamping onto the lower bearing hub each side. My guesstimation with getting a flat base with the engineers square can't have been too bad. The Standard only needed a thin strip of aluminum, from a drinks can, to get the top of the Standard nice and centered with a DTI. The top of the Standard was machined to the drawing, including 2 1/2" into the top of the Standard. To finish the machining a reamer was used to finish off the crosshead guide inside.

 

[Sarah]

The upper bearing hubs were machined together initially, this made it a lot easier to hold and align for machining. They were then separated, finished off machining and drilled and tapped for oil cups.

 

[trlvn]

The Standard was fixed to my shiny new Faceplate by clamping onto the lower bearing hub each side. My guesstimation with getting a flat base with the engineers square can't have been too bad. The Standard only needed a thin strip of aluminum, from a drinks can, to get the top of the Standard nice and centered with a DTI. The top of the Standard was machined to the drawing, including 2 1/2" into the top of the Standard. To finish the machining a reamer was used to finish off the crosshead guide inside.

View attachment 159883

Any consternation when you first spun up the lathe?

It actually looks like it would be reasonably well balanced. Did the lathe want to hop around much?

Craig

 

[Sarah]

Any consternation when you first spun up the lathe?

It actually looks like it would be reasonably well balanced. Did the lathe want to hop around much?

Craig

Hi Craig,

I was quite anxious when I was about to start, then I checked it again and again

It was actually really smooth when running, I was surprised how smooth it was. I did keep checking everything was tight, the thought of something coming loose and flying around was constantly in my thoughts!

Sarah

 

[Tug40]

Sarah, I built the PMR#5 couple yrs ago.
It looked easy to build at the time.
Looks can often be deceiving as some of the setups involved some serious head scratching for me.
I’m enjoying your build!
And I agree, things flying out of the chuck are never good.
Don’t ask how I know.

 

[Sarah]

Sarah, I built the PMR#5 couple yrs ago.
It looked easy to build at the time.
Looks can often be deceiving as some of the setups involved some serious head scratching for me.
I’m enjoying your build!
And I agree, things flying out of the chuck are never good.
Don’t ask how I know.

I did have a problem trying to drill/tap the bearing hubs, I ended up having to make some really long drill bits. I'll post pictures of them tomorrow.

Any advice, hints or tips would be appreciated

 

[Sarah]

The Standard was mounted on its side and the lower bearing blocks were machined to get a nice flat surface.

Drilling the lower bearing blocks was not straight forward, I couldn't get a Chuck or collet to take a standard length drill bit because the Standard frame was in the way. It required an extra long drill bit to clear the collet above the Standard. To complicate matters I had already drilled the top bearing blocks for a clearance fit of the #2-56 screws. I ended up using some brass tubing in the upper bearing blocks, to centre a 1.5mm drill bit and made an extension from some brass tubing. The 1.5mm drill bit was cyno'ed into the tube and a length of 1.5mm brass rod in the other end so it would not get crushed in the collet. This worked very well, but I had to be very delicate putting pressure through the tube.







I then had to drill out the holes in the bearing blocks to take a #2-56 tap. With no more brass tubing, I used a piece of solid brass rod drilled in one end to take the drill bit. The rod had then to be taken down in diameter to clear the Standard frame.

 

[Sarah]

With the bearing blocks threaded, they were clamped together and thin cyno applied to the joints. I didnt want to trust must the 2-56 screws to keep evrythjng in place whilst drilling/reaming to the crankshaft size. The 2-56 screws were fitted, before fixing the Standard to a 90 degree block.

I drilled both sides to 6mm diameter, then went through one side into the other. I was initially pleased with the process, but later realised I had not taken the lower bearing blocks to the plan dimensions. I am not going to do anything about it yet, but wait to see how other components will be effected by the slightly higher bearing centre (1mm).

 

[Sarah]

I blunted my only #50 number drill bit on the bearing blocks, so whilst waiting for a couple more I started to machine the Cylinder. I used a file to lightly take down a few high spots then fitted it to my shiny new four jaw chuck. It didn't take to long to get it centered, I centered it left/right first, then up/down. Yes I have been spending, not only a new 4 jaw chuck, but a faceplate as well .

I got a really good finish with one of the polished inserts, they are meant for non-ferrous metals. The cylinder was then reversed in the chuck and the other side faced off.

 

[Sarah]

With a couple of new #50 drill bits I set the Standard on its side again and started drilling the four holes which will be tapped 2-56 for the slide valve shaft. The first was a bit tough, second and third were a little easier, but the last one would not drill, even though I was using a cutting liquid. It was trying to drill through diamond! I swapped for a new drill bit and eventually managed to get through. I doubted that I could tap the hole and after reading a couple of previous builds decided not to try with such a small tap. I drilled all the holes out to an 1/8" and fitted small lengths of brass rod. A skim with a milling cutter left them all nice flat and level. Then it was an easy job to drill/tap them all for 2-56.

After getting a good reference with machining the top of the Standard, I have used this to set up for all the other machining. The front of the base was flat and on the same plane as the four mounting points for the slide valve shaft, so that was used as a second reference to machine the bearing blocks and the four mounting points.

 

[Sarah]

So far......

 

[Sarah]

With the bottom of the Standard just a tad out of true, I thought it would be worthwhile truing it up.

Whilst the Standard was upside down I also drilled the 2-56 clearance holes in the base.

 

[Sarah]

With the base now nice and true I clamped the Standard down and drilled the four #50 holes in the top. When I was tapping the last hole the tap struggled to get through, I took it out a couple of times to clean it and the hole but it snapped . After a lot of panicking and various pointy tools, I managed to get the broken tap out. Unfortunately it left a hole that was too big for a 2-56 thread. So it was time to do another brass insert. I left it overnight for the loctite to cure, then it was tapped to 2-56.