I recently got an old bench drill in bad need of care. It is a relatively small ASEA made bench drill with a 6mm (1/4″) chuck, a 300W two-speed motor and a two speed gearbox, givig a total of four speeds.

The seller said it weighed about 40-50kg, but it was actually a good 72….

It was left for a few days, soaked in 5-56 and kerosene and after that, came apart quite nicely.

The motor on the top lifts up while the housing is split vertically in two halves, held together by some screws and two conical aligning pins.

Here we see the two halves of the housing and the spindle in the center. You also see the motor spindle and the motor windings.

The little quadratic cover plate was actually a glass window for a built in lamp.

The once white interior sections of the housing is a light reflecor for the built in lamp.

I disassembled the whole machine, washed the parts.

The ball bearings, 8 of them, all had a mix of grease and metal grit and need a thorough cleaning or replacement. Is there ant good reason not to use sealed ball bearings? Pieces of string hold parts together so that it will be easier to keep track of them.

To be continued

The situation

Some time ago I gave up on using a Dremel mini drilling machine. It’s one of those that take 3.18mm (1/8″) tools and has collets to hold the bits. I should have returned it when it was bought it because it was really quite bad right from the start. I do not know how many drill bits I broke with this machine. Finally, I opened it up to replace the bearings and guess what; I could not find any! As far as I could disassemble it, I really did not see any. Add to that the drill stand which is mostly plastic on a metal column, would easily move a millimeter, probably two sideways. But what could one expect at that price? Well maybe a bit more….. So out it went.

I have chosen the best dewalt drill, the best makita drill

Time for something better

Now I got something-something that looks a bit more robust, a Proxxon IB/E. It has the front end of the house in some metal alloy while the back end is plastic. Not quite built like a machine spindle but it is not intended to be, and not priced as one either. I knew it had a proper ball bearing near the spindle end so there was hope. The Proxxon is priced about twice the price of a Dremel, while machine spindles start from at least twice more again and go as high as you can afford.

Next, I slowly turned the drill around with my fingers, taking readings here and there. The dial was swinging about 40µm end to end, that is plus-minus 20µm peak to peak.

The Proxxon is definitely much more robust than the Dremel was. Much lower noise, vibration, and definitely lower runout than the Dremel even if I never did any measurements to compare. I did, however, make measurements on the Proxxon, after it had a few hours of use.

I measured with a 1µm (one micrometer) resolution micrometer dial and the machine fixed to the table, with a 3.18mm drill bit and the meter right outside the collet.

First I measured the radial lag. by pushing the drill with my fingers to one side, letting go, taking a reading, pushing it the one way, taking another reading. There was a lag of around 15µm end to end.

Next the axial lag; placing the meter along the axis of the drill. Pulling the drill bit out with my fingers and letting go. To my surprise, there was a 300µm axial lag, just by the spring force in the micrometer, which is really not much. Actually, one can easily feel this axial lag it with the fingers. 

Summary of spindle measurements:

Radial movement is quite acceptable to me while the axial movement is not.

Can we improve on that?

I was quite convinced could be better than the measured lags and run-out. After all, I am a tool geek!

Looking at the drawings of the machine, (attached) one can see that there is one bearing on the spindle shaft end and other bearings are inside the motor, probably not accessible. The front bearing size is 8x14x4mm, a fairly available size, quite easy to get so I ordered a new ceramic precision ball bearing to replace the original one.

One nice ting with quality tools, and basically all older machines and tools, is that you can repair them, refurbish, fix them. Usually, the newer and cheaper things are, the less possibility do you have to take them apart and repair.

Disassembling

So now we disassemble. Void the warranty!

The whole unit is held together by four long screws.

They are Torx size 10 

type, so do not try with hex / Allen key. The machine comes apart nicely; a back end with the electronics, a center body with the motor, and the front end metal house with the spindle.

A dead end

I assumed the hub was threaded on the shaft. However, it would require a special tool to remove it. So I greased the hub, filled it half full with epoxy and stuck a 6mm hex wrench in there. I let it cure for a day and then tried to unscrew the hub. It did not move even he slightest, despite heating the hub with hot air and applying as more force than I should. The conclusion was that the hub was not removable and the fan must come off.

Removing the spindle

The spindle is mounted with a circlip holding the bearing in place. The problem is that the fan a shaft coupling is blocking access to the circlip. There is no way one can get a tool in there to reach the circlip, without first removing the coupling and fan. Well removing the fan should be enough.

Looking in the parts list at Proxxon, the fan and spindle are available as a spare part if something breaks. So I tried as gently as possible to turn the fan on the shaft and again, with some force, yes, it moved.

So I the hob oiled it with a thin penetrating oil left it for a while and tried again. It would turn but was obviously not threaded, not coming out. So time to try to lift and pry it out. Hmmm, what tool? Finally I found that two teaspoons, the thinnest ones I had, could slide in between two of the cooling slots, just under the fan.. I had to bend the spoons a bit to curve them around the hub. Then, gently prying, the fan came of nicely! Now the circlip was accessible with a narrow long nose pliers or, in my case, a narrow medical needle holder, and the circlip could be removed!

After that, with a light tap on the spindle end, spindle and bearings come out.

Fitting the new bearing

Now it was becoming obvious that the problem with the lag was probably not the bearing itself, but the mounting of the bearing. In the parts list there is a spring washer that was not there on my spindle. That would explain the axial lag. The bearing itself was also neither tightly pressed into the housing or onto the shaft, which would probably explain the 10 mil or so lag in radial movement. So what to do? The proper way would be to get a ball bearing with a tighter fit or to add some plating to the shaft and housing, but both are really out of the question here.

So I went for a simpler option; locking the bearing to the shaft and housing by some epoxy. I could not use thread locking fluid or superglue, as I would need some minutes to assemble the whole thing before the liquid cured.

I used a semi-fast epoxy which allows 30 minutes of aligning, and I used about half of the time assembling. Most of the time was used to get the circlip back in place. The little epoxy used to fill the axial movement was probably a little too much. And when pushing the spindle in, that excess epoxy really has no place to go. It took some quite hard pushing with a thin screw driver to get that locking ring into place.

It was at once obvious that the axial movement was gone. The original 0.3mm movement was easily felt with the fingers. After the modification, there was no obvious axial movement felt.

After assembly, the front-end housing and spindle were warmed with a hair dryer to speed up the epoxy curing, while at the same turning the machine on for short periods to make sure the spindle shaft was centered.

Already now, the machine was obviously running quieter than it had been. Most noise is from the motors carbon brushes.

Preliminary results

The machine is quieter and has fewer vibrations. Axial lag has gone down from 300µm to about 10µm, radial lag has been reduced while run-out is virtually unchanged, so it could be due to movement in the upper spindle coupling.

But now, overall movement is within about two 100ts of a millimeter which is good enough for me. And just knowing the bearing will withstand hundreds of hours is good.

In addition, we can consider looking to buy Best Drill Presses

I will now give it some hour of use before doing measurements again.

Any comments appreciated!

The problem

In the 17:th and 18:th century, when Great Britain was building the empire and European colonialists where competing to conquer the world, there was one major problem in navigating ships; the lack of a method to find the longitude (east-west) position at sea. This led to uncertainties in navigation and cause the loss of many ships, thousands of lives and big fortunes.

While a method to determine the latitude, north-south position was well known for centuries, the problem of determining the longitude was so important that the British parliament offered a prize of Ā£20.000 in 1714, a huge fortune at that time, to anyone that succeeded finding a method to determining it at sea.

It was one of the great scientific problems of its time, despite efforts by many geniuses, including Newton, the top astronomers and mathematicians of the world. The main focus was to try to use measurements of the movements of the moon, planet and stars, perform advanced calculations and compare to calculated tabled values but no-one came up with a usable method.

What they all knew was that if one could measure the time accurately enough, the problem would be easy to solve. However they all agreed that it was impossible to construct a clock that was accurate enough when subjected to the movements of a ship at sea.

John Harrison

One carpenter, turned clock maker, John Harrison, thought otherwise, and spent much of his life trying to perfect different types of clocks and finally built the first usable ships chronometer.

The book The Illustrated Longitude by Dava Sobel and William J. H. Andrewes have dug into the story with all its twists and turns and intrigues that went right up to interventions by king George III. The book describes Harrisons struggles, efforts and a large number of inventions that he made, including temperature compensated pendulums, counter-rotating balances etc. It is very well written, has many excellent illustrations.

The Legacy

Many of his clocks still exist, he only built a handful, and the most famous ones are now housed at the Greenwich maritime museum, and are still after more than 200 years in working condition, including the critical original wooden parts.

In the beginning of the 19:th century most ocean sailing ships in the world carried chronometers based on John Harrison’s design and it had a huge impact on the shipping and world trade.

The book is highly recommended for anyone interested in handicrafts, history or simply for the intriguing story.

(Draft, in progress) Collets and tool sizes for routers, drilling machines are a bit confusing at first but in reality there are not tat many to consider for the small workshop or DIY, unless you have specialized needs.

Lets start with the small and work upwards.

Cylindrical collets

Dentists size; 2mm

Dentist tools and dental tech tools usually usually 2mm diameter shanks. While there may be imperial sizes, to my knowledge they are not much used.

1/8″ of an inch (3.175mm)

For “Dremel” size tools, the 1/8″ dominate totally. While there are metric equivalents in 3mm and 4mm these are not used much. Hand held machines this size are usually supplied with collets in several sizes but 1/8″ is used more than any other. This size is also used in engraving machines but above all, in the electronics industry for PCB manufacturing. The PCB industry use drill bits this size by the thousands.

6mm, 1/4″ and 8mm

This size is used much for hand held routers of the intermediate size. The 1/4″ (6.35mm) totally dominate in the US and UK. In Europe, the larger 8mm is quite common. Many machine spindles that that take 1/4″ usually take 8mm too, and the 8mm have significantly stiffer shanks. Try to get collets for both 1/4″ and 8mm. The 6mm is a size you can omit as it, to my knowledge, is hardly used at all. It is too close to 1/4″. Unfortunately some European manufacturers make 6mm machines that do not take 1/4″ collets and you will be very limited in the selection of bits for these machines.

12mm, and 1/2″(12.7mm)

This size is used for compact hand held machines, where the larger conical fixes would make the machine too big. The size is used for large hand held routers. Again, the imperial size 1/2″ dominates, but 12mm is quite common in Europe.

Other sizes

There are machines that use other collet sizes, especially lathes, but this is typically to hold a workpiece directly, not really made to hold a tool shank.

One note about the collets is that the collets themselves, the exterior, the nut etc are available in a large number of types. For hand tools these are essentially different for each manufacturer, even if the inner diameter is the same.

Conical

Cylindrical sizes above 1/2″ are seldom seen and adjustable chucks are typically limited to 13mm. Above this size, the conical mounts dominate.

Machine cones, Morse taper, MT

The next size up found in workshops is the “Morse” cones in a few sizes. The geometries are specified in ISO 296, also known as MT-sizes. While there are 8 sizes, zero to seven, you will mostly find size 2 and 3 in smaller workshop.

Other, larger conical mounts

In larger machines, there is a large number of standards and alternatives; Brown & Sharpe, R8, Jacobs, Jarno, NMTB, BT, ISO Tapers. I will not go into these here as it is a fairly large subject.

Summary

…..

It had to be done.

This site was something I just had to create, to acknowledge my inner tool nerd.

As a mechanical engineer, ex research engineer, ex welder, ex carpenter and house builder, ex kid from the countryside, there has always been tools around; hand tools, power tools, electronic measurement equipment of all kinds.

Now it was time to make a web site about it all, to connect with fellow tool nerds!

I am still working on getting the parts together, blog, forum, user management and of course the layout. I am really trying to make it simple and clear, staying KISS as far as possible.

My gut feeling is that the site should really be running well at around new year 2011, ie in about two weeks. Until then, there is some polishing and surface finish to be done. But it is really already usable so fell free to register and start posting.

I hope you will enjoy the site and the company of fellow tool nerds.