Bolton No.2 Mill Engine

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jcreasey

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Time to start a new engine, so I thought I would try and show the progress here.
It is a Bolton No. 2 Mill Engine. I found the castings amongst all the tools and other junk I got when I purchased my lathe from a man clearing out his Dad's garage. I'm pretty sure these castings date from around 1968. The price written on the sole plate is $1.20! I think they were probably made by the original Burnaby Bolton. Luckily I was able to get a new set of plans from EJ Winter so this should be a fun little project.

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jcreasey

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First job was to clean up the base. I ground it flat on my surface grinder. I supported it upside down on some parallels in a grinding vise. Then flipped it over to clean up the flat spots on the top. I have just cleaned them up at this stage. I can easily tweak the heights later when I know where things need to be relative to the cylinder.

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jcreasey

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Next job was to make the bearings.
I started out by cleaning them up in the mill.
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Then I drilled and tapped them so I could fit the 8ba bolts that hold the two halves together.
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Once that was done I split them using a slitting saw. The saw I have is a solid carbide one and it works amazingly well!
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Here they are reassembled and bolted together.
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After separating them I bolted them in place on the sole plate so that I could drill and ream them in position.
I mounted the sole plate in my mill using an angle plate. I used the two studs to get things horizontal before tightening up the strap shown and another clamp which is out of frame.
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Last job was to set them up on a small fixture in the 4-jaw so I could clean up the sides. I was able to center it up on the through hole to make sure everything was concentric.
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The ends of the bearings were tidied up on the belt sander before bolting everything back down on the sole plate.
The crankshaft rod was tested and all runs freely.
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I did clean up those burrs a little while after taking this photo.
 

deeferdog

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Pretty sure this is all going to end well. Looking good, liked the way you set up both bearings and then reamed. Cheers, Peter
 

jcreasey

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This weekend's goal was to get the cylinder built.
I started by boring out the casting. I left it .001" undersized so I would be able to lap it in later.
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To make sure that everything else was consistent with the bore I decided to spend a bit of time and make a nice expanding mandrel. My plan was to use it both as a fixture to hold the cylinder in the lathe and the mill. I also plan to use it for lapping the bore. I used the taper turning attachment that I made a few months ago for my Myford Super 7 to create the matching tapers on the mandrel.

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This worked really well allowing me to clean up the ends in the lathe by turning between centres.
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Next step was to mount the mandrel in a collet block so that I could easily machine the two faces flat and orthogonal. I could also mill the valve ports.

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After some careful measing and calculations I setup the cylinder in the sine vise to connect the ports to the cylinder.
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I drilled three holes for each port and later opened them up to form a single slot using a diamond burr in the dremel.

I still have to complete the cylinder lapping and the exhaust port but that will have to wait till next weekend! After a trial fit this engine is starting to look the part!

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jcreasey

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This weekend I spent a bit of time remaking my tapered mandrel. I improved on the first version by adding a thread at both ends. This allowed me to accurately adjust the position of the tapered sleeve while still holding it firmly in place. It also made it easier to get the tapered sleeve off when I needed to.

The first sleeve I made ended up splitting into two parts because of slitting saw operator error so I remade that also. This time out of brass. Brass turned out to be quite a bit softer than the bronze used for the cylinder so I think that worked out well.

Quite a fun challenge as the thread used on the thicker portion was nothing standard so I had to cut the thread for that on the lathe. It worked quite well and I now have what appears to be a very parallel and smooth bore.

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jcreasey

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Next job was the slide bar assembly.
I have no castings for this so I machined it from a piece of 1/2" bronze rod.
I don't know why it ended up with the interesting pattern but it's quite nice.
First I turned it down to correct width and then I used a ball nose end mill to thin down the center section.
I used my sine vise to machine it to a 10 degree angle flipping it to get everything nice and central.
A bit of drilling and other messing around and I have another part to the puzzle.
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jcreasey

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The next step for the little mill engine was to clean up the flywheel.
Unfortunately this was not a great casting and I had quite a lot of trouble trying to figure out where the middle was.
I didn't really do a super job in the end but at least it runs true and hopefully with a bit of paint it won't look too bad.

I started with the 4 jaw and an indicator and did my best to set it up true.
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After I cleaned up one side and drilled and reamed out the bore I flipped it and used the outside jaws on the 3 jaw chuck to finish things off.

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jcreasey

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The next part to build was the cylinder end cap.
Initially I started cleaning up the bronze casting for it but I quickly worked out that it really wasn't big enough to do the job.
Not to worry as I have a nice lump of bronze sitting on the shelf so I sliced off a chunck off of that.

First step was to turn to required diameter and then make a tenon on the end sized to be a nice tight fit in the cylinder bore. You can't quite see it in this photo unfortunately but it's there on the end.
Once that was done I parted off enough to make my end cap.
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Now I used the remaining stock to machine a mating mortice to hold my newly made tenon.
I didn't want to waste too much bronze so I used an end mill to make a nice shallow hole which I opened up to size with the boring bar.
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At this point I used some superglue to attach my cylinder cap parted off earlier to the newly created mortice.
I was a bit wary of the glue getting too hot especially while I was roughing things down so I used a bit of tailstock support to absorb heat and hold things firm. I also used a bit of freeze spray from time to time to keep everything nice and cool.

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Now the fun part!
Earlier in the day I spent quite a bit of time making a form tool to create a nice dome shape on the end of my cap.
I took things very slowly here and gradually worked my way down to the some shape I was looking for.

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Pretty chips!
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Last step was to break out some wet and dry to even out any tool marks before final finishing with some paper towel and diamond paste.
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Here we are with all the parts so far. It's slowly but surely coming together.
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jcreasey

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I don't know if anyone is following this but here is this weeks progress.
I spent a lot of time on the cylinder end caps. I decided it would look nicer with 8 x 8ba studs instead of the 4 x 7ba bolts specified in the plan. This involved shortening 16 8ba bolts which I did using a little threaded bushing and a lock nut. I used the DRO to measure from the end of the bolt head so they all came out the same size.
Once I had those done I decided that the washers I had perchased really didn't look very good so I decided to make my own. This was quite an easy job and I don't think I will ever buy them again from now on as the result was much better.
Final photo shows the current progress. The steam chest is next and I have started by squaring that up on the mill.

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Drilling and tapping the cylinder.

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Shortening the tiny 8ba bolts to make studs. I loctited the nuts on the end so they will actually still be bolts but they will look like studs.

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I used the DRO bolt circle function to layout the 8 holes. To transfer them to the end caps I drilled one hole and then bolted it down before spotting and drilling the remaining 7 holes. I set the mill depth stop so that the drill stopped at exactly the right depth.

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Making my own washers. This wasn't too difficult at all. I just used the DRO to measure the correct distance from the end.

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Current progress shot. It's getting there slowly. One weekend at a time!
 

deeferdog

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JC, that is really lovely work, I wish that my standard was as high. Thank you for the time and effort you have gone to in recording this build, sadly, comments are often hard to come by. Cheers, Peter.
 

jcreasey

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JC, that is really lovely work, I wish that my standard was as high. Thank you for the time and effort you have gone to in recording this build, sadly, comments are often hard to come by. Cheers, Peter.
Thanks Deefer!
 

larryg

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I'm following this. Your doing a great job. A bit more detail on your lap would be appreciated as I have to do some lapping on the valve bore of my PM#4 documented in the castings builds.
lg
no neat sig line
 

jcreasey

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I'm following this. Your doing a great job. A bit more detail on your lap would be appreciated as I have to do some lapping on the valve bore of my PM#4 documented in the castings builds.
lg
no neat sig line
I think there are plenty of photos but if there is something specific you would like to see I can take some more.

The lap works like an adjustable reamer. It has a tapered mandrel and a matching tapered collet. This is held between two collars which sit on the threaded sections of the mandrel. So by adjusting the position of the two collars you can widen the lap by moving it further along the tapered mandrel.

Because I couldn't slit the collet part without damaging the mandrel I made a sacrificial one to hold things just for the slitting process.
The first time I did it I tried aluminium but I got things wrong and ended up making my slits too long. The second one I used brass and it worked out ok.

I used diamond paste as an abrasive. I bought a whole bunch of this in different grades very cheaply from China. It's very useful stuff and I use it all the time for polishing and lapping.

The result wasn't the mirror finish I was hoping for. I'm not sure why. Maybe brass was too hard to lap bronze. It is nice and parallel though and I think it will be ok.
 

jcreasey

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This weekend I had a crack at the steam chest.
I cleaned up the casting on the mill and then set it up on the 4-jaw. I used a form tool to get a nice fillet on the corner of the gland and drilled and tapped it.
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Then there was some drilling and some tapping.
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The little casting for the steam chest cover wasn't really big enough, so I sliced off a bit of bronze that I had lying around and made something from scratch.
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Finally I had a go at the cross head which seemed somehow to defy all measurement. I kept taking .001 off of both sides for many many passes till eventually it seemed to fit fairly well. No doubt this will require more fitting and tweaking as I think it's going to be the really tricky part to get right.
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Anyway it's another step closer
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