Machining the columns on the Titanic Engine Model
by John
Deep drilling using CNC. The last hole was drilled manually, with problems. CNC rules OK!
A warm day today. Too hot to wear a shirt in the workshop. But no metal splinters from machining the brass and aluminium, and only one hiccup, which will be described.
The jig which I started yesterday, needed 9 more accurately positioned holes drilled and tapped M4.
So I programmed the CNC mill, only to discover that there is a limit of 8 holes able to be programmed. So the final hole would have to be separately positioned, and that was the cause of my problem.
Firstly, the 8 holes were deep drilled (30mm deep, 4mm diameter) after centre drilling. All done with the CNC.
All went beautifully. 2mm pecks, some cutting fluid brushed on.
Then I used the CNC to position the last hole, and centre drilled it manually, AND BROKE THE CENTRE DRILL IN THE JIG!!!
I did not want to remove the jig from the vice, because it was all accurately set up. But I could not see the broken high speed steel tip, so I removed the jig, and tried to dig out the broken tip. Unsuccesfully.
So the next method was to use an old carbide end mill, 4.5mm diameter, to drill into the hole and to break up the high speed steel fragment. That method worked, but at the cost of enlarging the accurately placed but incompletely drilled hole. Next step was to reposition the jig in the milling vice, then deeply countersink the hole, then complete the 4mm drilling operation. It seemed OK, but it later became obvious that the hole had moved about 0.5mm from where it was intended. I eventually used a carbide end mill to enlarge the entire hole, in the correct position, at 4.5mm diameter. All a bit messy, but not fatal.
The jig halves opened up, and the drilling positions which were entered into the CNC instructions.
Then the columns were drilled and tapped. 2 attachment points per column, so with 3 holes per column in the jig, there are 2 possible positions for each column in the jig.
The columns to be attached to the jig.
A column on the wedge in the milling vice, ready to be drilled and tapped.
The columns screwed to the jig.
2 columns are integrated with the condensing unit.
Re “Titanic” engine heading… I get a lot more hits on this blog if I include the word Titanic. OK?
Now that all columns are attached in their final position on the jig, I can start hacking into them to produce some flat surfaces
The columns sitting on the base in their correct position, using the jig.
LP is the column for the low pressure, biggest cylinder. HP is the column for the high pressure, smallest cylinder. IP is intermediate. C is for the steam condenser.
