Acceptable runout on drill chuck

Together with my mill, I ordered a drill chuck from Warco.

I went to have a go at drilling for the first time yesterday and noticed a visible wobble on the chuck itself. I took it off the arbor, gave everything a very thorough clean and re-seated everything, but to no avail.

I put a DI against a 6mm drill in the chuck and measured a runout of ~0.4 mm. I then re-tried with a bigger (12mm) drill, which made matters a little better. I took a series of measurements, taking the drill out and re-chucking it in between which gave me a average of 0.315mm over 4 readings (0.24-0.37). I also tested the arbor which had about 0.005mm runout, so pretty good.

Another chuck I got from the same supplier had a much better runout of 0.11 mm using the same technique.

I've put some videos up on my drive of the actual measurements in case I did something strange. But the wobble is visible.

Measuring the arbor

Measuring the drill (6mm drill)

Now I will be returning the chuck with the big run-out, but I'm not sure about the other one. If I need to drill very precisely I'll use a collet. Which leads me to the question: what is acceptable runout for a drill chuck?

Here you find the maximum concentricity deviation that Rohm gives for its drill chucks, **LINK**

Niko.

Yes that is way too much. My good Rohm drill chuck has about .002" runout, so about 0.05mm

My cheap chucks have about .003" or .07mm.

Anything more than that and I don't use that chuck.

Runout up next to the chuck is one thing, but then if you put a piece of straight ground bar in the chuck you can sometimes find that a few thou runout at the chuck is half a millimeter at the end of the bar, where the tip of the drill would be. That is not much use for drilling any kind of precision holes. Maybe ok for carpenters but not for me.

If you pay the big money for an Albrecht chuck you might get close to zero runout. I dont know. It's beyond my bank account.

Niko, interesting link, thanks for that. Not as good on the runout as expected on those chucks.

Hopper, thanks for confirming, just trying to get a feel for what's acceptable as I lack the experience.

Rohm Supra chucks come in several "flavours" (L, S,...) with different concentricities:

**LINK**

Top of Rohm line is the Spiro series (0,05 mm):

**LINK**

while Albrecht is given for 0.04 mm.

Massimo

Whichever chuck you have will only be as good as the arbor it's mounted on, sometimes I think the arbor is the cause of runout some people experience.

Emgee

Wow those Rohm chucks look nice, but range from 80 to 150 quid.

Emgee, I did measure the arbor which barely wiggles my needle at ~0.005mm. It's definitely the chuck.

It depends on the accuracy required of the hole!

From the video it looks as if the 0.4mm run-out chuck is too far out, but even so it would still be reasonably accurate at the cutting end if started by a centre-pop, and the hole wasn't too deep (less than a diameter). The reason is drills tend to cut around the spinning axis at the tip and the spring of the drill takes up much of the chuck wobble. A wobbly chuck would be good enough for most woodwork, but probably annoying drilling metal.

A few other points:

• Three jaw chucks, even expensive ones, aren't noted for high-accuracy. Collets are much better.
• Twist drills aren't good either! The shank may not be round, or be bent. Drills won't cut straight unless the cutting edges are ground equally : symmetric angles, lengths, and sharpness. Twist drills can wander if not perfectly perpendicular, if swarf gets in the way, they hit a hard or soft spot, or the lubrication is uneven. Under cutting pressure, the flutes open up, which will cause wandering if one flute is slightly stiffer or weaker than the others. Twist-drills cut straighter if the work rotates rather than the drill - a lathe does better than a mill.

I find twist-drills pretty good for ordinary purposes, but it pays not to rely on them for real accuracy, especially on deep holes. Designs usually adapt to twist-drill short-comings, for example, it's usual for bolt holes to be drilled oversize to leave the bolts room to align with whatever is underneath without binding. Common to see a few bolt holes in a group to be slotted to give even more room.

Accuracy is improved by reaming or boring out drilled holes. Reaming corrects diameter errors, but not bending. Boring fixes both and is the best way of making high-accuracy holes.

I feel it's unwise to chase high accuracy unless specifically needed because ±0.02mm / 1 thou is fairly easily achieved with ordinary tools and methods and is plenty good enough for most jobs. Doing better is hard, needing close attention to technique and better tooling throughout. Might find:

1. Moderately priced twist-drills aren't good-enough, must buy £best
2. £best twist-drills don't perform well in a moderately priced drill chuck, so buy a £best chuck
3. £best chucks don't perform well in a value for money milling machine, so upgrade that as well.
4. And so on. If high-accuracy holes are essential, then the answer might be a Jig Borer, not a milling machine. Not an elderly worn jig-borer either, but one is good condition that's been set-up correctly.

The danger of chasing accuracy for it's own sake is of the whole workshop turning into a tool-room, which is great for accuracy, but dreadful for productivity. Not good if making or repairing typical mechanical engineering stuff is the goal. No problem if achieving ultra-accuracy is the hobby interest, but don't end up buying a tool-room by accident!

Dave

George Thomas in his book "The Model Engineers Workshop Manual" reported on measurements of run-out he did on drill chucks he owned (page 114). The US made Jacobs chucks he measured varied from (inches) 0.0012 to 0.0003 close to the jaws to 0.0022 to 0.0003 at 1 inch away. Pretty good !

That's why I use collet chuck only on my mill ....

Yes, they're a good choice for round number sizes, but using a 3.3mm or 4.2mm drill, as I commonly do, isn't too good with the standard collets. Even though I have a 3.5mm ER32 collet, I still typically reach for (or more often just can't be bothered to change it) my drill chuck when using a 3.3mm drill.

If you are coordinate drilling on your mill then it gets important. You should make a high accuracy holder, not collet blah blah system to hold a spotting drill dead true.

The old fashioned system of marking out on a surface plate, centre popping by feel at the intersection of the microgrooved lines produced, then drilling in stages could get things as accurate as your height gauge. (and skill). A wobbly chuck mattered less, within reason. It also makes sense to have a small chuck for a small drill to start things off. edit - by which I mean a 0-1/4" not a 0-3/8"

Edited By Bazyle on 22/03/2022 13:50:17

I have just returned two 100mm 3 jaw Warco chucks with MT2 backplates for my Warco HV6 rotary table, which by the way was superb in all respects. this was due to the first chuck being so poor that it required two hands to rotate the chuck key, The second one showed 0.4mm concentric run out. The body run out was very slight but the jaws were the problem and did not even come fully together on one pair. These were made in India. The price of these chucks has just risen by a whopping amount.

We do need to return anything which isn't 'fit for purpose' even if it is cheap or now not so cheap. A lot of things from the east has now gone up by a fair amount, I suppose they will keep pushing until it's as cheap to make it here.

Tony

I agree with Emgee, check the arbor runout before blaming the chuck. They are made with a soft centre and are easily bent. You have measured this and it runs fine so the next thing is to measure the chuck off the arbor to see if is the process of putting the chuck on the arbor that is causing the problem. I would grip a suitable rod in a collet and grip the other end with the chuck to check its taper is running true or not. Try a few different positions around the rod to see if there is a runout that follows one position on the chuck.

Martin C

Edited By Martin Connelly on 22/03/2022 15:29:48

Wow, so much information. I'm already learning lots on here, thanks for the input everyone.

Martin, I don't think that would really make any difference with my measurement. I've measure the arbor which is (as good as) colinear with my spindle. That means the runout will either be caused by there being an angle, or lateral shift between the axes of rotation of the chuck and spindle. If I turn the chuck upside down and clamp it to a bar in a collet I'd be measuring the exact same thing, but with the added error of the collet introduced. Or am I missing something here?

I think I can draw the following conclusions:
- The chuck should be returned as the runout is unacceptably large
- Drilling with a chuck is not terribly accurate, although a pricier chuck is a little better.
- Drilling with a collet should be better still, but limited in drill sizes
- Turning a holder to the exact size of the drill will get you the best accuracy, but will probably hit the point of diminishing returns.
- Drilling is not that accurate due to inherent limitations of the process, if you want an accurate hole you should bore/ream/lap.

All being said and done, this is already a massive step up from my cheap silverline pillar drill that tries to walk off every time I turn it on above ~500RPM!

And those were considered "normal" chucks in the day. Even old pistol drills came standard with Jacobs chucks. You can drill very accurate holes with good drill bits and good chucks like that -- within the constraints of a drill bit as a bit of a "roughing" tool that needs to be followed by a reamer for accurate sizing for dowels etc. But even a drilled hole can be made pretty accurate to size if you round off the outer tips of the cutting edges with a slip stone into a tiny radius and use a pilot drill just a small bit less than the finished size.

Todays cheap hobby grade chucks are obviously a different story though. But 0.3 or .4mm out is pure and simple grounds for return to sender for sure.

Collets are probably better than turning your own holders because manufacturers have better kit and Quality Assurance than we do! Unless you go too cheap or get a defective one.

Collets usually have excellent concentricity but only a tiny grip range. In many systems you need a 6mm collet for a 6mm drill, and the number of collets needed to cover all the common imperial and metric sizes is scary.

Good news! A relatively new collet system, ER, has collets that squeeze down a full millimetre much reducing the number of collets needed. The picture below is from ArcEuroTrade, other suppliers available. There's a collet chuck which plugs into the mill (be sure to get the right taper for the machine R8, MT etc), and then a set of individual collets. The most popular hobby size is ER32, covering 1mm to 20mm. ER40 does larger sizes, ER25 smaller. ER collets are used to hold drills and milling cutters (including threaded shanks), plus wobblers, in a mill, and are also suitable for holding work accurately in a lathe. (For which another chuck may be needed.) Have a look at Warco's offerings for prices and what's available.

When buying collet chucks, prefer the type with ball-bearing nuts which are easier to tighten than the plain type. (They like to be tight!) Ball bearing nuts can be bought separately and retrofitted.

I only fit a drill chuck to my mill when drilling lots of different sized holes all in one session, which is rate. The drill chuck allows faster tool changing, which is worth it when drills are being constantly swapped. Otherwise collets are somewhat slower but you get lower run-out and much better resetability.

ArcEuro sell Stevenson Collet Blocks, which are a handy work-holding accessory, if you already have ER:

Dave

What you are seeing on the arbour taper is probably what the inner spindle run out is. Chasing precision on cheap equipment is very hard work indeed. In your video, I can see that the run out is in the pressed outer assembly of the chuck. It looks like the part with the taper is OK. That chuck is junk and should be returned. I would expect better than 0.05mm TIR from a good chuck. It can be keyed or keyless. There is a new keyless chuck that comes with a spanner to undo the chuck. These can be used for LH drilling etc To get the best out of a chuck is sometimes to grip the chuck with a piece of round stock at close to the max size with the jaws just about flush with the body. And then check the taper run out. Try different ways to get the true as possible. Sometimes the rear taper needs to be reground. When this is done, the chuck will be very accurate.

You could rule out any mounting error by clamping the drill chuck onto a piece turned/held in the lathe and then clock the drill chuck mounting hole. I have that same chuck as Dan showed and the runout is nowhere near as bad. Factory rejects are getting put into regular circulation.

Mike