Perpendicular Drilling

Hello,

I am having awful trouble achieving a reasonably perpendicular hole, through any real depth.

Forgetting round stock for the moment; I had the same problem, this afternoon, on a piece of rectangular aluminium (25 mm depth).

Does anyone have any pointers on this ?

I would say I have a reasonable drill press, with sharp bits.

Hope someone can help;

regards

How are you clamping the workpiece down?

A photo would be useful to see what the problem is.

Michael

It's a bit strange that it would behave like this if what you say is true, then we're dealing with a drill press with a reasonably good "squareness" to the table, a fairly low depth.

How are you centering this drill? sometimes a lead at an off angle can take the drill askew.

With round stock its better to use an endmill to make a flat first before using a center drill.

Michael W

Edited By Michael Walters on 28/03/2016 18:08:05

Lubrication ? What diameter drill ? Have you checked the squareness of the table to the drill bit. Put a bit of straight rod in the chuck and then an engineers square between the table and the rod. Some poor quality drill points are off centre.
BobH

If your drill press has angle adjustments for the table, regardless of what any angle scales and pointers on the machine say, check perpendicularity of the table to a known straight rod mounted in the chuck. Check front to back and side to side. Use the longest square that will fit between table and chuck to help magnify any angle errors. If it is like any drill press I've seen made in the last 20 years chances are it will be significantly out of square right from the factory, when all scales/pointers read zero degrees. While you've got the known straight rod in the chuck unplug/remove the power cord and rotate the chuck by hand. Is the rod running concentric with no wobble/runout? If you have a dial test indicator or can borrow one that is a good way to check runout and also to check for table deflection under load. Have a friend watch the indicator fitted under the table edge furthest from the column while you drill a deep hole.

On a small drill press I had, the table fastenings were so light and material thickness was so thin it would deflect downward a few degrees when drilling steel. it took a while for me to notice that, as I didn't expect it in an all cast iron machine. An improvised screw jack with a piece of all thread rod and a long hex nut fixed that issue by supporting the front of the table against deflection. On that machine, it wasn't that one part was too light or fitted badly, ALL the parts were a little light and a little loose! Cumulative tolerance stackup and overly economical use of metal in the castings added up to bad precision in drilling.

The other thing to consider is the grind of your drills. If they are good quality HSS drills from Dormer or Cleveland or Precision, and brand new, this factor may not be an issue. But if your drills are from China or someone's been at them with a bench grinder and wasn't careful, the lips may be unequal lengths or angles and drills like that will wander off axis frequently in deeper holes. Money spent on really good drills is money well spent, in my opinion. It will save you time and your work will be better if you use good drills (and/or grind them correctly).

With the spindle fully extended (chuck as low as it can go) is there any side to side or front to back wobble/runout of the chuck? If so this can be a major cause for the drill to go off perpendicular. When I bought my present drill press I looked any many in stores doing this test until I found a particular one with almost zero detectable play.

Just some food for thought and ideas for testing. Lots of factors can cause wandering holes. Good luck. JD

Thank's everyone for such quick feedback.

Plenty of food for thought. Mainly find myself reassessing the "reasonableness" of the drill press itself.

I will carry out the various checks as suggested.

It was only a 3.5 mm hole and was clamped in a vice (same source as the drill ).

The drills themselves are from a reputable source.

Some photos of the scene;

I will probably be shot down for saying this and dont really want to criticise your equipment, but in my opinion those X-Y cross vices are horrible things. I once had one in the early days but soon got rid of it.

I think you would do better to use a simple hand held drilling vice as near to the surface of the table as possible, it might also be the fact that you have your vice bolted down that is forcing the drill to go off line, if you have a simple hand held vice it will find its optimum position on the table and under the spindle automatically once the drill has started the hole.

Phil

Check that cross vice for square under drill pressure, it might be going out

which is pretty much what Phil P said above.

Edited By Dave Halford on 28/03/2016 20:46:29

Hi Daniel, been there done that!

I agree with Phil P. I have the same cross-vice as you and it doesn't do a good job for me either. It's particularly bad when going straight in with a twist drill.

The method I settled on is to hold the work in a machine vice that's relatively loosely clamped to the drill table. The vice is held sufficient to stop it jumping upwards but it can still move sideways.

A Centre Drill is used to make a pilot hole before switching to the twist drill. Then the point of the twist drill is carefully positioned over the pilot hole. When drilling starts, I allow the loosely clamped vice to centre the work under the drill. It may not be the best method but it works well enough for me.

I think the problem with cross-vices is that they are too rigid to let the work centre, but not rigid enough to keep the drill perpendicular.

Cheers,

Dave

If the job is firmly clamped in a vice which is fixed to the drill table prior to using a centre drill it should be in perfect alignment when you change it to a twist drill. No need to position over the pilot hole because it is already there.

+1 on S.O.D. and Phil's comments - the cheapie XY vices are big trouble. It seemed a great solution when I bought one years ago but I soon found out as others have there are many many problems with them. There are exceptions - some very expensive ones made in USA are OK- but the cheapies are to be avoided at all costs.

For a drill press vise - I recommend the square bodied ground cast iron ones from Palmgren in USA. They are MUCH better than the usual Chinese 'flat' style with the shallow but wide unguided jaw and side slots, for many reasons.

Do clamp your work, always, with a good vise, as others have said, things are ultimately easier that way, and your work will be better. JD

.

But what make are they and where are they getting them from.?

I have given up on 'chances' and only buy Dormer now. - I find them cheaper in the long run.

A quality branded bit should last us hobbyists ages. I have in the past bought drills from so called reputable suppliers only to find they are not ground evenly and have the lifespan of a Mayfly.

Nick

Daniel, I had a drill press similar to yours(swivel and tilt table), it was supposed to be heavy duty but the table was anything but solid and could be seen to deflect as pressure was put onto the drill. A support from the front of the table to the base helps. Some attention to the flange the table bolts to may solve the problem but the casting really needs to be twice the size. I replaced the machine with a model with a one piece table, much better! I have not used the new machine much, I do all my drilling on the Bridgeport. I understand the ram bends up and the knee bends down but this hasn't been a problem so far.

Dave

Model engineers ( and apprentice training instructors!) seem to be obsessed with clamping drill vices down. When I worked on the tools unless it is a job which is likely to grab we didn't bother, for a big drill we'd arrange the vice to abut the pillar or a bolt sticking out of the table. Unless it's a precision job (and I'd probably do that in the milling machine), just whack a big centre pop so that the chisel edge of the drill is located and get stuck in. The drill will pull the centre pop into line.p

Jeff Dayman mentioned very good xy vises made in the US. The only US brand that comes to mind is Palmgren. I do not have much respect for their products.

Hi Daniel,

Assuming all right angles are truly square, perhaps there are accumulating deflections due to the `separating’ force between the drill tip and the work-piece.

Following the path of drilling forces (downwards through the workpiece, vice assembly and table, across and up the drill column, then down to the drill tip), your setup suggests the forces have a considerable distance to travel. Each component will contribute some level of deflection. Access to a dial indicator (and magnetic block) could determine the deflection when suitably placed.

As has been intimated by the chaps above, a rigid prop under the table will all but eliminate any table deflection.

Regards,

Sam

Daniel,

If you want to produce a truly perpendicular hole in a block of material such you illustrate I do not think you will ever be able to do it with the type of drill press that you have for all the reasons stated by others about table deflection.

I would mount the block on the lathe faceplate, centre pop the hole position then using a wiggler and DTI to get it aligned with the lathe axis. Drill the hole from the tailstock. Start the hole with a modern spotting drill (rather than the traditional centre drill who's centre could break off) and open the hole with progressively larger drills.

Of course if you have a Bridgeport then use that!

Hi Daniel

The Drill press looks a little like my Rexon a Taiwanese made drill I have had for maybe 20 years, It has given good service within its capabilities. Yes I have scraped the swivel bearing face to make the table a true right angle. With smaller drills I like it for the light and sensitive touch. For heavier work I use the milling machine but the quill is a lot heavier and less sensitive.

There will be some deflection of your drill table with heavier drills say over 10mm particularly if you bear down on them trying to push them into a piece of tough steel or grabby Brass. The drilling pressure can be significantly eased by drilling a smaller pilot hole first, to drill through 25mm steel you will need to peck drill to clear the chips or you may get a jam. It is important that drills are kept sharp. The smaller drill will also find the centre of your centre punch marks more easily, the web of a 12mm drill may miss unless you punch heavily. So the smaller drill is acting as a spotting drill as well, it should result in more accurate work.

Regards
John

Ah, i already know what this is now, i have a tilting vice with the same time of jaw and you do get an ungodly amount of jaw lift with them.

Michael W