A JIG for Machining the columns of the triple expansion marine engine
by John
At last!
A day on the steam engine. SWMBO went to Melbourne to choose marble so I was free!!
After discussing my problems with machining the triple expansion engine columns with the senior members of the GSMEE (Geelong Society of Model and Experimental Engineers), I have machined a JIG to assist with this issue.
The JIG thickness is precisely the width between the columns (30.05mm). It is made in 2 halves so I can bolt the columns from their critical surfaces which are the con rod slides.
I will use the CNC mill to drill the holes in the jig, and the matching columns, then finish milling the columns which are attached to the JIG.
The jig for machining the columns. Not yet finished.
Bottom left is X=0, Y=0. The photo shows the 4 countersunk M4 screws.
The holes will be centre drilled then through drilled 4mm. The columns will be drilled 3.3mm then m4 tapped.
Hopefully that will happen tomorrow if the workshop is not too hot.
You will see what I am intending with the next post.
johnsmachines 
John,
why do you not using a wide jig for the three colums together so you get a straight line over the crankshaft as well. Even for the distants between the colums in the leght side.?
Huib Hoogendoorn
Netherlands
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Hello Huib
Yes, it is long enough to to hold all 6 columns in their correct position.
I will post a picture tomorrow
John V
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If you had had strips on the jig on the left side and along the bottom the jig could have been used to drill the holes in casting so all would be the same.
john f
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