Can my pillar drill be improved

Bit of a long shot, does anyone have the above mentioned article please? My old nu-Tool has done me well and deserves a bit of TLC!

Just curious has anyone trammed with a dial indicator how square the table is to the spindle on these cheapo machines,? though these drills should be much better what can one expect when only paying £39 23 years ago! I just wonder do the orientals make a batch of drill parts,then apply selective assembly to the drills to obtain say 80% reasonably accurate, then assemble the remaining parts quickly and sell them off cheap,its more profitable to sell cheap rubbish assembled drills rather than scrap the defective parts.

Yes, my Chinese-made Craftmaster is a large, heavy bench mounted drill press that has a 16mm chuck and is very heavily made but a "low cost" brand. Does not flex noticeably under normal home shop drilling forces, as you would expect for a lump that large. But when I trammed the table with a clock, it was 40 thou out of square across the 14" or so diameter table. Bit of shim in the joint where the table can pivot side-to-side, which feature I never use, and it is all good now. But clearly was never checked at the factory and obviously was machined crooked by a small amount, magnified by the distance from column to outer edge of table.

That and new bearings all through it and it is a decent machine now. Plus I put an extra bronze bush in the top pulley to stop the quill rattling around in the loose splines there and making a noise that annoyed me.

But still, if I am doing anything special and want to be sure my holes are dead nuts square etc, I do it in the lathe using the vertical slide. EG con rod in a model engine etc.

Comment first. The tram of a pillar drill isn't as critical as the tram of a mill. The uncorrected error in Hopper's Craftsmaster means a hole 30mm deep will be off centre by 0.08mm at the bottom. For most ordinary purposes the error wouldn't matter, and it's less than the wander caused by a poorly ground drill tip.

By 'ordinary purposes', I mean the sort of drilling I mostly do, which is holes to take nuts and bolts. They're usually less than 5 or 6 diameters deep and deliberately oversized to avoid alignment problems. I don't drill several matching 10mm holes in two objects and expect them to line up so perfectly that 10mm bolts will fit through them all without bother!

This website suggests these 'tight tolerances' for various location methods used in manufacturing. By 'tight' they mean more care is taken than normal. Unless something extra special is done, 'tight tolerances' mean manufacturers should assume holes will be placed no better than:

Centre Punch and Drill - 0.5mm
Bushed Drill Fixture - 0.2mm
Precision Mill/CNC - 0.2mm
Precision Mill/CNC with optical or other precision location - 0.076mm
Jig Boring with optical or other precision location - 0.013mm

Although home workshops can and do achieve better, it suggests our expectations may be too high! Possibly too much is expected of pillar drills in general, and far too much of the cheaper ones. They're a quick way of drilling holes with moderate accuracy, not tool-room jig borers! And not worth spending big money on unless lots of tightly toleranced holes are needed. In my workshop the pillar drill is used for relatively low accuracy work, and I switch to the mill or lathe when better is needed.

My pillar drill is a cheap bench type badged 'Clarke'. No measurable up-down movement in the chuck but the run-out is 0.45mm 100mm below the chuck. In practice this doesn't matter unless the drill is poorly aligned with a centre pop: when the drill is spinning it balances along the spindle axis, and stays straight on that unless mechanically forced off course. The machine is inaccurate when the job is firmly clamped, but works well when the job is floated gently into alignment with the spinning drill tip. The technique is totally different from milling where rigidity is vital, and floating makes it possible to get reasonable results out of indifferently made hobby drills and badly worn pro-kit.

On a 160mm diameter the table is tilted high on the right, and is slightly high at the back. From 6O'clock: 0.00mm, -0.15, -0.30, -0.30, 0.05, 0.20, 0.35, 0.28 : much worse than Hopper's!

The right-left tilt is adjustable, but I haven't bothered to level it because it's not awful compared with a set-square with a bright torch light behind. I can see the gap is a bit wider at the bottom and could be improved, but it's not enough to worry me unless I were to start drilling really deep holes:

Two ways of looking at this small inexpensive pillar drill:

• Grossly inferior compared with an expensive industrial drill costing ten times as much
• Despite warts, a worthwhile tool that been doing a fully acceptable job in my workshop for nearly 10 years.

Best drill ever made? No!!! China-bashers will plenty to criticise, but only if they ignore the price. Value for money and Fit for Purpose in my workshop? Yes. If I'd paid for a better drill than this one, I'd have wasted my money.

However, what other folk do in their workshops and what makes them happy makes all the difference. I choose not to chase accuracy or other qualities in tools unless I need them to do a job. Although I don't need a better pillar drill, I'm sure plenty of others do.

Dave

If the drilling machine has a hollow spindle for using a drawbar to hold milling tools, it could be used for small scale milling, otherwise not, it would be dangerous.

Here's a drill that could do with improvement.

But if you drill and ream a dowel hole in one end of a 14" length of flat bar, when you mount that bar to another piece of metal with a dowel pin, the far end of the flat bar will be out of alignment by the 40 thou error on the drill press table. The error in the hole itself is small, but not so when multiplied by the length of the job.fth

Even on something as small as the crankshaft of the Potty mill engine, that small amount of error was enough when drilling and reaming the holes in the flanks to make the result useless, requiring the mainshafts to be skimmed in the lathe after assembly to make them run true. That's how I discovered my drill press table was out of whack.

Edited By Hopper on 11/07/2022 00:58:02