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View Full Version : Making a fitting as a mock casting



Michael G
15th Nov 2015, 08:06 PM
I bought a small milling head a month or so back with the plan of fitting it to my mill so that I could use the quill when necessary (possibly the one feature that my mill lacks that would be really handy).
Bob identified it as a Centec vertical head but looking at other pictures of these heads, the arm for the quill was missing. The arm itself with typical Brit bare functionality is easy as it is just a bent bit of rod with a ball knob on the end but to connect it to the shaft it requires a cast tee piece.The casting is nothing special but to have one cast would probably cost $50 or so, and that does not include making the pattern.
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The piece itself is not complex but the T shape precludes it being turned in the lathe. Trouble is, the typical cast shape makes it complex to make in the mill, but it was about the only way I could think of to get the necessary shape. As I would have had to do something similar to make a casting pattern, it was in for a penny, in for a pound.
I started with a piece of steel in the lathe and shaped the leg of the T.
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Once that was done, the blank was mounted on a piece of threaded rod in preparation for some 5 axis machining. In the photo below the mill is set up as a horizontal spindle machine and sitting on the table is a 8" rotary table. Bolted to that is a scrap steel frame and then on top of that is a small Ellis dividing head*. In this case the dividing head is used to index (5 degree increments), while the rotary table is imparting the barreled shape. I used a 1/4" ball nose cutter for this, although standard procedure is to use a flat ended cutter for convex surfaces. (I could not be bothered trying to work out the offsets needed). A tailstock would have been nice for this set up but mounting it - urgh!
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The shape was scaled off the photograph shown above, so one of the big questions was size was everything. All I could say for certain was that the shaft coming out of the head was 17.9mm in diameter and the width of the part was no more than 1". Everything else was estimated based on that known size. Comparing the model picture and what I produced, I didn't get it quite right but I may have another go another day...
The next pic shows the barreling , along with the progress around half way along.
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At the end of the passes, I had this
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A bit of clean up with a grinder and then a light dressing with the linisher and the result was
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Next I need to bore the tapered hole down the middle and tap the T leg for a rod, but that bit should be easy (by comparison). A coat of paint and it should look sufficiently casting like (I hope)

*The Ellis came to me as a bargain looking for a job although there were lots of bits missing. it is a standard 40:1 DH but as well as rotating in the normal axis it will also rotate around the base. One day I'll think of a special use for that feature...

Michael

YBAF
15th Nov 2015, 10:53 PM
"...A coat of paint and it should look sufficiently casting like (I hope)..."

Lay the paint on thick and no one will know.... except us here :U

DSEL74
16th Nov 2015, 08:00 AM
That is quite the impressive work around.

steve.rsa
16th Nov 2015, 01:05 PM
Far more elegant than just welding the rod onto a large nut. Looks great.

KBs PensNmore
16th Nov 2015, 01:22 PM
What size black knob do you need Michael??? If, I have one the size required, will be down Saturday morning with it.
If you have access to a sand/grit blaster, blast the outside to give it the cast look.
Kryn

Michael G
16th Nov 2015, 06:44 PM
What size black knob do you need Michael?
If you have access to a sand/grit blaster, blast the outside to give it the cast look.

I'm estimating that the knob is 1" or perhaps 1 1/4", but I have something around that size
Thanks for the offer though. Work has a small sandblaster so I can rough up the surface a little after I've done the tapered bore (no point in putting jaw marks on a nicely as cast surface)

Michael