Common issue with Hand Powered Drills

[Rhyolith]

I own around 30+ Hand powered drills and have been seeking the "best" ever, for no reason other than a fairly easy and cheap hobby.

After testing a load of these via drilling holes in a small log, I clicked that the most common reason for underperformance was wear inside the various spindles, mainly that connecting the main wheel to the body. This wear is not that obvious to look for as its present in many otherwise good drills and in such a high proportions (approx 50% of all decent drills in have seen or bought have significant play in the crank wheel) that its easy to not know it as being wear at all. It is also easy to miss as it can spin round lovely and smooth until under load (drilling) only then does the mechanism become rough and stiff.

The core point is that there should be virtually no play in the main crank wheel of a hand powered drill, even if it has an equaliser (thrust bearing) or second pinion (though this does allow for a little more play than simpler single pinion models). Further I don't think there is a solution to it short of making a load of new parts, as I have seen limited success with the washer method outside of a handful of specific models (mainly simpler English made ones). So those looking to buy nice second hand hand drills for using, this is something really worth checking.

I am a bit unsure what causes such disparities in this wear, with drills that appear to have been equally abused (or not) judging by remain decals etc, displaying radically different levels of wear... maybe insufficient lubrication? Grit getting in?

 

[Eric The Viking]

I think it's lubrication. Oil and woodwork don't go well together, so people (me!) tend to leave it too long. And if you overdo it, oil goes everywhere.

You might drill out and bush the main wheel or relevant pinion, but it wouldn't be easy, as you say. You'd n0eed a well set up lathe, and I have no idea how you could do anything about the stub shaft for the handwheel - it would be very hard to remove and replace.

FWIW, my dad's war-finish drill (USA Stanley, IIRC) was just like that - jammed up under load. As a child I couldn't understand what I was doing wrong, but it turns out I really wasn't.

 

[AndyT]

Interesting question. I can think of several possible explanations.

1) Sloppy fit as originally designed - if you design in plenty of slop the parts will always go together and spin round when not loaded and you won't need to reject many.

2) Designed to fit nicely but production accepted parts beyond what should have been used (ie with shafts too thin or holes too big) so as to avoid the cost of rejects.

3) As above plus lack of lubrication.

4) Big quality difference between drills with gears made by casting iron and those made by machining steel. (Bit of a guess this - I don't have any information about how these things were made.)

Looking at old catalogues, there were many choices available, covering a wide range of price points.

Are your poor examples mostly at the cheaper end of the range? Even with a big name manufacturer there must have been corners cut at the lowest price models.

 

[Phil Pascoe]

I wonder whether the machining tolerances were on the large side? I'm clearing out and I've come across seven or eight 803s - none of then feel quite the same.

 

[Cheshirechappie]

I'd say it was down to manufacturing tolerances, too. Generally speaking, the higher the value of the item being manufactured, and the greater the consequences of it's failure in service, the tighter the manufacturing tolerances are set. The tighter the tolerances, the higher the manufacturing costs, too.

Thus, for something like a hand drill, where the consequences of a 'rough one' are that the manufacturer might have to stump up for a replacement drill if a customer is disgruntled enough to complain, tolerances would be quite wide to keep cost of manufacture down. It could well be that Rhyolith's rougher-running examples have been like that since they left the factory.

Just as a side note - it's quite surprising how much difference to 'fit' even very tiny differences in size can make. During my engineering training, we had to do a machining exercise, making a ring bored to a set size, and a shaft with three bands on it, one loose running fit on the ring bore, one a very close 'transitional' fit, and one a light interference fit. The difference between the three bands on a nominal diameter of 1 1/4" is just two thousands of an inch. My 'transitional' band allows the ring to fit with a gentle push all the way in one direction, but is too tight to fit all the way in the other because of a worn lathe producing a very slight taper on both components - one that can barely be detected by a micrometer reading to 0.001", but can be felt easily. A higher-resolution mike would detect a diametrical difference of a couple of tenths or so. The difference between the 'transitional' and the 'running' is stark - one rattles and one is a push fit - the difference in diameter is only a thou.

On smaller components, the effect is more pronounced because a difference of one thou is proportionally greater relative to the diameter.

It would be possible to make hand-drills such that they all ran sweetly when leaving the factory gate. However, nobody would buy them - they'd cost several times the usual catalogue price. Think of the difference between a modern Stanley sweetheart and a Holtey (or even a LN and a Holtey) and you get the idea. It's all about acceptable fit and finish for the price the market will bear.

 

[AndyT]

Agreeing with what CC described, one answer is presumably to use ball bearings instead of a plain pin in a hole.
Do some of the top end hand drills have ball bearings?

 

[Rhyolith]

Are your poor examples mostly at the cheaper end of the range? Even with a big name manufacturer there must have been corners cut at the lowest price models.

Most of my drills are big names such as Millers Falls, Goodell Pratt and North Bros, so all realtively good quality. Indeed one of the best examples of the issue is between a Millers Falls 87 & 97, two identical premium models where one performs perfectly (the 87) and one not so much (the 97); there is consiberable play in the crank of the 97 despite it looking like its in prestine condition.

 

[Rhyolith]

Agreeing with what CC described, one answer is presumably to use ball bearings instead of a plain pin in a hole.
Do some of the top end hand drills have ball bearings?

Many breast drills have one large one at the front, to take the combination of pushing and rotational driving load. I have never seen a more exetensive use of them than that in these tools.

 

[ED65]

It would be possible to make hand-drills such that they all ran sweetly when leaving the factory gate. However, nobody would buy them - they'd cost several times the usual catalogue price.

I'd be very surprised if this were not right. Which forcibly brings to mind one of these:

This is a Bridge City Tool Works CT-6, which when in production was a great deal more than 'several times' the price most would be willing to pay for a hand drill (original full retail was above $400, they go for more now).

From the maker:

ABOUT THE DESIGN
Most past hand drills suffer from manufacturing inadequacies, almost always related to the bevel gear train. here's why...

Bevel gears provide non-linear rotary motion transmissions. In a hand drill, the gear train transforms the handle rotation to the chuck shaft-a ninety-degree axis shift. Properly engineered, bevel gears have a very low threshold for manufacturing errors. There is only one spot between the drive gear and the pinion(s) where the mesh allows maximum power transmission with minimum "grind". The most common way to "design around" these tolerances in the mass produced hand drills of yesterday was to "float" the pinion(s). This means the pinion gear was purposely "sloppy". Upon rotation, they would "float" and find "the spot" where the train appeared to work. Unfortunately, the driven pinion is connected directly to the chuck shaft, so by default, this shaft had to "float" as well. Consequently, the entire chuck/shaft/pinion assembly was always loose int he body of the tool. This is just an awful way to build a drilling tool, and it is why many of these drills performed very poorly at low rpm's-which is exactly where they were to perform best!

Many manufacturers disguised this loose assembly with springs or other methods, but this mechanical flaw is only cured with precisely located and properly cut gears.

What's galling is that almost every one of these superbly made drills (ditto all Bridge City's other tools) are never used in anger, at least not by the current generation of owners.

 

[AndyT]

That's a fascinating insight Ed. I suppose that when small hand drills were common, bearings were not cheap. Now that they are, the demand for a mass produced product has disappeared.

 

[JohnPW]

This is a Bridge City Tool Works CT-6, which when in production was a great deal more than 'several times' the price most would be willing to pay for a hand drill (original full retail was above $400, they go for more now).

From the maker:

ABOUT THE DESIGN
Most past hand drills suffer from manufacturing inadequacies, almost always related to the bevel gear train. here's why...

Bevel gears provide non-linear rotary motion transmissions. In a hand drill, the gear train transforms the handle rotation to the chuck shaft-a ninety-degree axis shift. Properly engineered, bevel gears have a very low threshold for manufacturing errors. There is only one spot between the drive gear and the pinion(s) where the mesh allows maximum power transmission with minimum "grind". The most common way to "design around" these tolerances in the mass produced hand drills of yesterday was to "float" the pinion(s). This means the pinion gear was purposely "sloppy". Upon rotation, they would "float" and find "the spot" where the train appeared to work. Unfortunately, the driven pinion is connected directly to the chuck shaft, so by default, this shaft had to "float" as well. Consequently, the entire chuck/shaft/pinion assembly was always loose int he body of the tool. This is just an awful way to build a drilling tool, and it is why many of these drills performed very poorly at low rpm's-which is exactly where they were to perform best!

Many manufacturers disguised this loose assembly with springs or other methods, but this mechanical flaw is only cured with precisely located and properly cut gears.

Why float the pinion and not the drive gear? If only the drive gear was sloppy/floating and not the chuck/shaft/pinion assembly then maybe performance wouldn't be affected.

As mentioned, I think lack of lubrication and bearings has a lot to do with it.

I think a bigger problem is the keyless chuck!

 

[woodbrains]

Why float the pinion and not the drive gear? If only the drive gear was sloppy/floating and not the chuck/shaft/pinion assembly then maybe performance wouldn't be affected.

As mentioned, I think lack of lubrication and bearings has a lot to do with it.

I think a bigger problem is the keyless chuck!

Hello,

The drive gear is connected to the operator, who would not let it float, certainly not continuosly, to find the sweet spots of the mating pinion gear teeth. To be fair, although there are the odd rough ones, in the main the sloppy nature of these tools work well enough. That said, I love the precision of that Bridge City drill and if I had one, I would definitely use it. It would be pleasurable every hole drilled.

Mike.

 

[Cheshirechappie]

I agree that a Bridge City drill would be a pleasure to use. However, would the resulting holes be any more round, accurate to diameter and depth, more precisely positioned than if they were drilled with a reasonable Stanley 803? I doubt it. The Stanley 803 is good enough for the job - and remains good enough for many years of use (it would be even better with a keyed chuck - but that's another matter!).

Just because you can make something to a very high standard of precision doesn't always mean that you have to. Roughly speaking, the more precision, the higher the cost, as described above. A perfectly acceptable compromise is a level of precision that gives a tool that does it's job, for a reasonable price. Horses for courses, as so often.

 

[Vann]

I'm clearing out and I've come across seven or eight 803s...

So it's not just me then. I gave away four No.805s (single pinion model) to a local kindergarten last month (after swapping a few 5/16" chucks for 1/4" chucks off my 803s). I still have too many 803s, and various other eggbeaters

I haven't found any eggbeaters with ball bearings either (except for thrust from the spindle).

Cheers, Vann.

 

[ED65]

I agree that a Bridge City drill would be a pleasure to use. However, would the resulting holes be any more round, accurate to diameter and depth, more precisely positioned than if they were drilled with a reasonable Stanley 803?

Nope!

I was dismayed by the amount of slop on my 803 at the chuck after I first got it home and tried it out, but I eventually found out that the slop is almost completely taken away by the bit engaging with the wood. So in short, it drills round holes and does it well enough that I'm happy to reach for this in preference to either of the two power drills I own when making clearance or pilot holes so I've become a very happy owner.

 

[Rhyolith]

Interesting to read about the CT-6 as well as being the first new premium model hand drill I have seen, the description about the importance of a precision pinion was particularly useful. What would really be useful is a design/manufacturing method that allowed the sweet spot to be held without the enormous expense. I assume this allows all the gears to have absolutely no play?

Ignoring the drills with wear or manufacturing inadequacies, the better tools I own (of which there is still quite a few!) are pleasurable to use and very effective tools. I don't think a design improvement is necessary for these ones, just manufacturing consistency; if every Millers Falls 87 (oppose to the 97 :evil: ) turned out like mine, I don't think there would be much left to be desired.

Further, more precision often results in more delicate items; for example the German WW2 pistols that would not work with even the tiniest amount of dirt in them. I see the chances of a precision made had drill withstanding a drop without loosing performance significantly lower than a drill that was not made so precisely... this might be a moot point as a lot of these tools are made from castings that would both shatter in that instance, but I am referring to small drops such as on to the bench from standing height.