No Spotting bit...what to do

Small hole, just spot with a center drill and have at it with the pre-ream size drill in one shot.

This Thursday a 30.25" Dia. X 3/4" thick plasma cut disk, 304-304L stainless clamped to an aluminum faceplate
Center drill, had to use a taper extension to get across the gap which I had to remove followed by a 1/2" drill thru.


Drill thru with a 3" drill, this is not a pleasant operation with the tail stock.


Bore 5" thru, counterbore 9.83" X .550 deep, turn OD 30.00" and face entire part, it turned out reasonably well.

So have at what you are trying to do, if you worry about every possible detail it will never get done, if you bugger it up so what, make another one. Above all other considerations have fun and you will also learn a good deal in the process.
 
Wreck: what's holding the SS plate on the aluminum face plate in the last pic ?
 
dlane said:
Wreck: what's holding the SS plate on the aluminum face plate in the last pic ?
Click to expand...
You can just see 1/2-13 tapped holes on a 14" bolt circle, studs went through the face plate with nuts on the back to hold the part, I rough cut through them so that the finish cut had "less" interruptions.

The last operation is drilling out the threads to .562" and countersinking for flat head screws which the part requires. Another step I realize yet the simplest way to hold it, also an interrupted cut often produces a poor surface finish around the holes so cutting through the 316 SS threaded rod studs works better then having the tool bounce over the empty holes.

The set up is far from ideal, with the gap removed the toolpost is 8" away from the part face so I used a 2 1/2" Dia. boring bar held upside down with the spindle in reverse for the OD and facing OP's. The part also extends outside of the apron as well so the tool post is rotated and the holder is on the operator side of the cross slide with the compound fully extended. A sheet metal coolant pan keeps a fair mount of it off of the floor, it is a mess however.

The aluminum face plate is bolted to a regular faceplate with 5" long spacers in order to get the part 1/2 way across the gap, the gap is on the blue cart in the background. When turning/facing near the limits of travel there is always the DANGER of running past the ends of the DRO linear scales with the expected result of making the Boss shed a tear or 10.

When installing a DRO it is excellent practice to use scales that are as long as possible or build physical stops. This particular lathe is 110" between centers, in the past someone (not me) removed the tail stock to turn the end of a part held in the chuck and a steady, this machine has an electric motor in the apron that will rapid the carriage and cross slide. As you can probably imagine they ran the carriage all the way back and destroyed a 100" Heidenhain glass scale causing the owner to shed 8000 $1.00 tears, one at a time. Don't do this (-:

 
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