Alright, I'm down to the last few parts! Hopefully we'll get to initial assembly and an initial test run quickly!
First is the eccentric hub. I'm using the mill as an over the top marking out machine. I centered up the stock and then from center moved over the spec'd .1875" to get the center of the offset. I drilled a shallow center hole in order to facilitate the setup on the lathe. I used the supplied material from the PMR kit, which seems to be free free cutting, possibly 12L14 or maybe 1215. I can't tell for sure.
Then over to the lathe with the 4J chuck installed. I offset the stock until the just created center hole was running true. I used my home-made spring-loaded centering rod for this. This actually works quite well and I find it fast to get to a given offset.
Then on to turning the eccentric. Shown is the point where the cut is just about continuous.
Then drilling and reaming the thru-hole.
I turned the strap area using the 3 mm carbide insert parting tool you see in the pix. This works well as it's extremely sharp and it can be moved sideways if the cut being taken isn't terribly deep. I think that this is properly called a 'groove/turn' insert. I'm about to part the finished piece off.
I didn't show the operation but I drilled and tapped the 5-40 hole using the mill. The part is shown as completed laid on the print.
And finally the eccentric hub is shown loosely installed on the crankshaft.
Next part to be done is the eccentric cap. It's shown in the condition as supplied from PMR. One important point to note is that the hole in the cap as cast, is fairly oblong along the axis of the casting. This gives allowance fo the part to be split. Note that this allowance is .125" shown on the print.
The first thing I did was to drill thru with a tapping size drill for the 5-40 screw and then drill to 1/2 the depth with a clearance drill. Finally the 'bottom' of the hole was tapped thru 5-40. Since this was a thru hole and the material cut well, I just chucked up the tap and put the mill in neutral and hand rotated the chuck to create the threads. This is about a a tap as I'd use with this technique. In any other circumstances, I'd install a tap follower and use a very small tap handle.
Then I turned the cap sideways and cleaned up the oiler location with an EM prior to drilling and tapping.
I failed to take any pix of drilling/tapping this hole or the hole for the valve eccentric rod, but here's the cap with the valve eccentric rod rod loosely installed in the cap.
Here's a pix of the part as I'm installing it back into the mill. I blued it up and scribed where the top of the initial cut should be at, more or less! To align this, I used a 3/8" rod chucked up and just compared each side of the part by eye. I couldn't come up with any better way to do this as there's really no known flat reference surface to work from, at least the way that I was thinking about it.
Then I installed a .045" slitting saw and gently touched the part with the saw slowly rotating and moved the table down until the top of the cut just intersected the reference line that I had put on the part.
Next was cutting thru the part, manually feeding the saw thru and rotating the saw fairly slowly, somewhere around 300 rpm or so.
Then, since I had to remove a total of approximately .125" of material, and I had just taken out .045, I moved the table up another .080 and made another cut. You can see the thin waste material after the 2nd cut was made. I'm always extremely impressed at how smoothly these slitting saws cut. The finish is almost perfect.
Showing the cap after being split laid out on top of the print.
Just a pix to show what I think is a good practice. I put small matching punch marks on the bottom of the cap. The marks won't be seen when the part is installed, but I don't think you can necessarily count on these halfs being capable of being installed 'backwards' without running into fitment issues. Certainly making match-up marks on big engines and assemblies is a common practice.
Next i clamped the cap down to a bit of scrap AL on my small tooling plate. I used a DTI to get centered as well as possible under the spindle. This is a bit of an art as the casting definitely isn't smooth, but as near as I could tell the hole was within about .010" between x and y so it appears that the print was really close when they suggested removing .125" of material when cutting the cap apart.
Next shown is boring the center hole to size using a boring head. I used the power downfeed and the stop to kick-out the feed at the bottom of the part. This to me, is one of the best features of the Bridgeport as it takes away any concern about working toward a closed bottom. Plus the finish that this process creates is usually very good. The first pass was just taken and you can see that the material being removed is quite even in both x and y.
After the hole was finished, I used a 1/4" carbide EM to take each side of the part to the spec'd thickness. Since centering isn't critical at this point, I had the luxury of being about to easily remove the part for measurement as I went along.
And finally the cap is shown installed on the hub. Success on this part!
And now we're down to the last part! This is the connecting rod and while there are some tricky bits, there's also a couple of features on the casting that make this part a slightly easier. The first thing I noticed is that the con rod body is almost exactly the same thickness along it's length, after I just very lightly smoothed it with a file. Shown is the part held on top of a bit of flat 1/4" AL scrap and further held by small toe clamps on my small tooling plate. I found the center of the small end of the con rod visually using a 1/4" rod held in the chuck and then touched each side of the big end with the same rod in the chuck and moved the end of the part until the DRO was equal on each side of the big end. I made sure that the top end of the rod remained in its initial position and rechecked both ends several times during this process. The pix also shows the 1/4" drilled and reamed hole at rod's small end and 2 small center marks representing the top and bottom of the material to be removed. This is the same deal as the eccentric cap. There's about .125" of material that can be and needs to be removed when cutting the big end apart.
Then for reference for the TBD sawing operation, I blued the big end up, drilled the center holes just a bit deeper and then scratched a line in Y across the part.
I then took the tooling plate from the mill vise and clamped it onto the 90 degree plate. I ended up edge finding for x and then moving over as necessary but for Y I just used a rod held in the chuck and visually aligned it. Shown is somewhere in the middle of the drilling and tapping operation.
Then the part was sawn apart using a slitting saw. I had a reference from the flat at the end of the con rod, but I also was careful to check the saw position against the lines drawn earlier.
Then the tooling plate was moved back to the mill vise and the newly created big end rod cap was fastened back to the con rod body using some 5-40 screws. One point to note is that the single line and single center mark are actually 1/2 each of the 2 lines and center holes from the previous marking. This at least confirmed that the sawing operation was correct and the amount of material removed with the slitting saw was spot on! I was fairly exciting to some this come out as expected!!
The hole was drilled thru and then reamed to the print's spec.
Each end of the rod was milled to the spec'd width. I used a 1/4" carbide EM for this. This was pretty stress free for me as the part can be removed, measured and re-clamped down as the alignment is not critical at this point, only the width is.
The hole for the big end rod oiler is drilled and tapped so as to intersect the hole previously drilled from the inside of the rod bearing surface. Shown is my standard method for small holes, that is a spring tap follower and a very small tap handle.
The small end of the con rod needs a few more operations in order to create the clamping mechanism for retaining the pin that attaches to the cross slide. Shown is visually setting the con rod to 45 degrees between the hole centers.
I didn't take pix of all the operations, but I milled a small flat area and then drilled thru with a tapping size drill, then 1/2 way thru with a clearance drill then tapped the bottom of the hole, all as per the print. Shown is moving the con rod and a bit of scrap material ot the 90 degree angle plate and visually aligning the screw boss area vertically. The only critical thing is to make sure that the slot to be created is close to the center of the screw boss area.
Then I put a 1/4" ground pin thru the rod small end and moved the table up just until the bottom of the saw blade was touching the top of the pin. Since I had the saw blade thickness and the pin diameter I moved the table up until the saw was on center with the rod small end hole and made the cut.
This is the completed connecting rod laid on the print.
And lastly is the assembled 'bottom end' of the engine with the connecting rod, cross head and eccentric assembly all installed and much to my surprise and pleasure, everything at this point, rotated fairly smoothly!!
So now, I'm caught up with posting pix. Everything from this point is pretty much as its now happening.
Next up will be the initial assembly, followed by a (hopefully) initial run without all the proper fasteners or gaskets installed, just to check for proper operation and to find and fix any mistakes.
All for today.
Enjoy!!
Mike
