Rebarreling and Home-Shop Machining

Finished Fifth Column

Photo 1 and 2 show the front and back side of the finished fifth column including the painted Slotted Plate that was prepared in the topics below. Photo 3,4 and 5 shows the heavy duty bench below the lathe. I am pleased with the results.

Alignment Of the Lathe to the Fifth Column

I installed the slotted plate on the new cross arm with the lathe loose on the bench. I used a feeler gauge to determine the rough alignment of the plate to the 1 inch bars that secure it. I shimmed the right side of the lathe up about .050 inch so that the plate was more parrallel to the 1 inch bars on the vertical. This will help with the problem described below. The bench on my table has rather large factory holes to mount the lathe. The holes are not quite on the same center as the lathe, though. This means that there is not much adjustment room of the lathe left and right and front and back in spite of the large holes. I lifted the lathe upwith a come along and rotated it and filed the left side holes a little longer with the long axis of the table. I put the lathe back. Now I could adjust it left and right a bit. I put .010 inch shims between the slotted plate and the securing bars and tightened the socket head capscrews and the speed ball Handle which tightens the slotted plate to the cross arm; all this with the lathe slightly suspended. I lowered the lathe with the quadralift. I had good vertical alignment of the slotted plate and good placement of the left side of the lathe so that the cross arm face was parallel to the slotted plate on the faces horizontal axis. I retrammed the mill head as I had the lathe suspended by the milling arm. Now I removed the .010 shims and used a feeler gauge to determine the proper shims to but at each corner of the slotted plate.

Plate Flex

I found that shims above or below the bolt would cause even this 3/4 inch thick plate to flex and become not flat. I prepared some U-shaped shims by putting a big stack of one inch square shims in the vise and using the cutoff wheel on the angle grinder to cut a U in the shim to accept a ½ inch bolt. This can be smoothed with the dremel. I did not. I did rehone the shims that I used flat on the cut edge using a small course stone. My round arbor shims with a ½ inch hole in the center have not arrived yet. Using the U-shaped shims worked much better than shims above the bolts. I could remove and replace them with a dentist pick by loosening the four bolts just a bit. They stick out just a little.

Final Shimming and Tramming Test

I first shimed the plate until it had a .002 gap on each corner of the cross-arm. This made the plate parralel to the cross-arm face on two axis. Then, I added  .003 inch to each shim stack leaving a slight preload between the slotted plate and the cross-arm face. Tightening the speed ball handle will move the indicator set up to tram the mill a little less than .001 inch. The mill head is trammed to about .001 inch across a 4 inch distance at three points after tightening. The fourth point is at about .002 inch off due to a slight twist in the milling table. I don’t think it can be made better than this. This is very suitable to all the milling tasks that I have attempted.

Note on the Paint

The Rustoleum Stone Creations Grey Stone Paint covered with clear acrylic enamel has proved to be durable as well asnice looking. It has no tendency to Chip. You have to gouge it pretty hard to remove any.

Milling Arm Rigidity Test (NEW)

I expected the milling head to be much stiffer than before. My .150 deep cut with a 3/4 inch mill described below already proved this to me. I also tested the milling head rigidity before and after adding the fifth column with the setup in photo 6. Before the fifth column when I added a 100 foot-pound torque on the milling arm with the torque wrench it flexed downward .0180 inches. ( I used a steel block with a ½ inch bolt installed in it to apply the torque) With the new heavy duty fifth column bolted up to the slotted plate this was reduced to .0025 inch. This is an 86 % reduction in flex and resulted in a cut that could be 20 times deeper than before without the rattling that shows you are reaching the limit of the machine. I have not tested the new model Eldorado mill.

Milling Table Rigidity

I tested the rigidity of the milling table by applying a 100 foot-pound torque to it with a setup like in photo 7. The bed flexed up .0015 inch. The rigidity of the mill arm with the new fifth column at .0025 inch is now more in line with the stiffness of the milling table.

Lathe Spindle Rigidity

            I also expected that the headstock would be stiffer than before due to the added support from above which will prevent it twisting on the headstock’s vertical axis. I tested this with the setup in photo 8 before and after the fifth column. The flex was the same, at .0015 inch deflection at the spindle flange with a torque of 100 foot pounds trying to bend the spindle and headstock using the setup in photo 8. The flex is probably in the tapered roller bearings or spindle itself as I know the fifth column should improve the rigidity of the headstock. The rollers in the tapered roller bearing will compress slightly in response to a bending load on the spindle. I also tested the rigidity of my receiver truing jig which is detailed in the CD for my book Precision Rebarreling. It has a stiff draw bar that goes through the spindle. Although the rigidity of the jig was improved 100 % by adding the drawbar, the rigidity of the improved jig was the same after adding the fifth column. This leads me to believe that most of the flex is probably in the tapered roller bearings.

|  Add to del.icio.us |  digg this