Hi Everyone
I took the base casting back over to my buddy?s shop so I could use his shaper to machine the locating reliefs in the main bearing saddles.
Here it is set up on the shaper; when he did his it was decided that it would be best to do the saddles one at a time instead of trying to get a bar long enough and a set up that would allow both of them to be cut at the same time. The shaper could do it but it would have required some tooling to mount the base beyond the block on the shaper. As the bearings are going to be bored anyway it really didn’t matter.
Getting started; there is no DRO or edge finder on a shaper; so it is pretty much working to your layout lines. I did set up a 1? travel indicator on a mag base so that I could stop at the same point at each end of the cut.
Action shot!
An adjustable parallel and mic were used to measure the dimension of the cut. The target was .875?. I got one spot on and the other a couple of thou over. The caps are cut to fit so the finial dimension isn’t super critical.
All finished and ready for the next operation.
This is the first time for me on the shaper; it is a fun tool and I can see how one could be a great addition to the home shop.
Next is the machining and fitting of the main bearing caps.
Here are the caps as received cast as a pair.
I decided the best way for me to deal with them would be to saw them apart and work on them individually.
The caps were set up so the bolt bosses were aligned vertically by eye with a precision square; then a very light cut taken to give a reference surface. The cap then flipped over and the same done to create two parallel surfaces. Due the thickness of the caps these surfaces will be mostly removed in later operations.
Not shown; a skim cut was taken off the bottom on the caps using the newly machined surfaces to hold on to and a parallel to sit it on; referencing the top of the cap.
This operation made the top and bottom parallel; checking here with a square.
Now having 3 machined surfaces the holes were located, drilled and spot faced.
Using the drilled holes each end of the caps were brought to length; the outboard ends left .005 long so that a skim cut could be taken after they are mounted.
Again using the holes as a datum and locating the cap on parallels using the spot faced bolt holes; the final thickness and the locating boss is machined.
The main cap mounting holes on this engine present a problem due to the bottle frame it is impossible to drill and tap them from straight above. This operation required a little special tooling. So here is how I chose to tackle this problem.
A pair of drill fixtures that fit in the main cap reliefs were machined from CRS. If these were going to be used more than once they should be hardened; but for a one shot deal I decided to leave them soft.
Here is a close up of the drill and driver; the drill was made using a new 135 deg. split point screw machine drill which had most of the shank cut off. The drive portion was made from a 5/16 socket head cap screw (SHCS) with the threads removed and the drill bit silver soldered into a hole drilled through the length of the screw. The bit was held with a pair of aluminum soft jaws in my bench vise for soldering. The driver was made from a Bondhus ball driver cut down and pressed into a piece of 3/8” stock.
I had originally planned on just chucking up the hex driver in the drill chuck but the run out was awful; so I went to plan B which was to shorten up the ball driver and press it into the 3/8” stock.
Here is the drilling operation; the fixture is clamped into position with a parallel machinist clamp. Using my battery powered drill this operation was done by hand. With the new split point drill it was very easy to drill the 4 mounting holes.
Here is a close up shot of drill and the driver. The ball hex and the bit were lubricated with some machine oil to make things run a little smoother.
Here are the holes drilled and ready to be taped.
Here is the hi-tech tapping set up; using a tap guide the holes were tapped first with a spiral point tap and then finished up with a new bottoming tap.
Holes have been drilled and tapped and the bearing caps secured with temporary socket head cap screws.
Here is a closer view.
Next operation is to set up and drill the clearance holes to pour the Babbitt bearings. The Babbitt will be drilled and bored similar to the previous operation.
Thanks for checking in.
Dave
