In the pursuit of doing more with what you have, this month’s article explores a unique method of “piggy-backing” with the sub spindle to produce two holes at the same time.
This method uses the time and motion of the turret as it drills in the main spindle to drill simultaneously with a part semi completed that is already in the sub spindle. This gives you two drilled holes in the time it takes to drill one hole. Since drilling is often the longest single operation in a cycle, any way to reduce it or benefit by doing something else is a bonus. (More money in your pocket) Those of us who used to work on manual turret lathes know the value of “piggy-backing” or using “trees” and “nests” to put more than one tool into the cut at one time with some good old ingenuity. The difference here is we are using the machine and it’s programming to get creative instead of a complete manual solution.
The easiest application or drilling two holes at once is where your holes are the same size and the same length. Let’s say you have a 4” long part that has a 1” hole all the way through with a 1.25 counter bore on each end. Instead of drilling the 1” hole all the way through from one side, you could drill half way with each spindle and save time and money by doing it.
When there are odd diameter holes to be drilled there are a few items to contemplate before deciding whether this method will work satisfactory.
Size of the holes
Depth of the holes
Type of material
If the diameter of each hole is too far off from each other, the surface footage may be too unmatched to make this work well. As an example, if the first hole in the main spindle is 1.000 inch diameter and the 2nd hole on the sub spindle side is .125 diameter, the difference between the two diameters is .875 creating a problem in most materials.
However, even with a big difference in diameter and surface speed, a situation like this could be resolved by using a carbide drill for the 1.000 diameter on the main spindle and a high speed drill for the .125 drill.
An example of this:
A carbide 1.00 insert drill in 316 SS=400 SFM at .003 IPR
Main Spindle RPM= 1528
Subspindle RPM= 1528
The machine I used for the article example was done on the Eurotech 735SLY, a dual spindle, single turret machine.
I hope you’ll be able to take away something of value from this month’s article and as always, keep on turning!
Oh! And by the way if you are reading this before September 14th, check out my up and coming movie star (we pray) daughter on the AMC channel at 8PM and September 15th at 3AM (if you are an insomniac). She is hosting “Dinner and a Date” during the breaks of the movie “Pretty in Pink”. Her name is Mary Greenawalt and I hope you will watch and be able to say you saw her when she was just starting out. Wishing you all great success and Mary, “break a leg”!
For any comments, questions, or additional information, email me at larryg@eurotechelite.com
