Thread: Help ~ criteria when selecting a Pedestal Drill!

With regard to accuracy there are a few things to start with.

Look at the general construction and rigidity of the base, column and table. It is essential that there is no movement under the loads that you will place on the unit. If you are likely to be working with unbalanced loads, some tables will rotate out of square to the spindle because thay are flimsy and poorly designed, lacking metal in the casting to ensure rigidity. With most Chinese machines with a tilting table facility, the table will rotate around the tilt pivot despite being clamped as firmly as possible. I have also seen the front edge of tables on these machines sag a couple of degrees due to loading.

The next item is spindle run out. This is the wobble that a bit might develop when the spindle is rotated with the feed arm up, and is caused by poor bearings, bearing alignment, and machining of the shaft, quill, chuck and arbour. If a problem exists, it will never go away.

The next issue is quill machining. Grasp the chuck and wind the feed arm to it's lowest point, and raise a couple of mils. Then try to wobble the chuck that you are grasping. Poo grade machine will have a load of movement at this point,, 2-3 mm is common, and is caused by poor machining of the drill head casting.
This will severely affect the accuracy of the machine if you use jigs, or fences and stops to accurately drill, and also drill pilot holes before drilling the finished hole. Because of the normal length diference in drills, if you set up for this type of work, you normally use a lot of feed movement for the the shorter pilot drill to ensure that the longer finish drill has sufficient room without adjusting the setup. The pilot drill position can then be out by a mil easily, causing grief through the rest of the job.

malb

Many thanks for your sage words,

SB,

there are heaps of threads about this on the forums - just do a search.

here's a couple of good ones.
http://www.woodworkforums.ubeaut.com...ad.php?t=43632
http://www.woodworkforums.ubeaut.com...ad.php?t=44272