Set up and use of an automatic inkline.

This is one of a series of articles that will describe how to set up and use various Japanese woodworking tools in an effort to show you how they work and how you might be able to include them in your own workshop. If you already own some of the tools included in these articles, then you may find new ways in which you can use them.

When it comes to Japanese tools, there is rarely one ‘right’ way to make them work. While it is often said that you must use xyz tool in a particular, proscribed manner it is more likely a case of that way being one of several ways to use the tool. This is not a hard and fast rule, and if you find that you wish to use a tool in a way that ‘goes against the grain’, then you should go ahead and do it, provided that the method is safe and will not harm the tool.

The Tajima ‘Perfect’ compact automatic (retract) inkline.

auto inkline

In Japan, ink lines are used for marking straight lines on a variety of materials in a similar way to a chalk line. Chalk lines are available and popular, but the ink line shows no signs of becoming obsolete.

Traditionally these were one of the few tools that were elaborately decorated, and an especially beautiful sumitsubo reflected upon the craftsman using it, as these tools were most often made by the craftsman who used them. Carved from a solid piece of Mulberry or Japanese Elm, they were a tool where extravagance was expected, unusual in the world of the no nonsense, all business world of Japanese tools.

Today, inklines are still available in their tradtional sumitsubo form, but most common are modern incarnations of the tool designed to be cleaner, faster and easier to use for the tradesman on the job.

This Tajima brand ‘Perfect’ compact automatic inkline includes the main tool and a 35ml bottle of salt free ink, a small safety sheet (in Japanese) and an instruction sheet/backing card (also in Japanese).

The inkline itself is a compact model, being small enough to fit into a pocket easily and is often seen in the tool belt of many a tradesman in Japan. It is one of the most popular models on the market because of it’s compact size, economical price and ease of use. This model is made in Japan and Tajima also markets an identical tool at a reduced price that is made in Taiwan, signified with an ‘X’ in it’s name. The Japanese made model remains popular even with this direct competition.

The features are a special karuko (pin) that is specific to this model that includes a hole for suspending the line as a plumb bob (note the point on the non-business end of the tool) and a built in cushioning spring, a nose piece with multiple grooves for holding the line in place, a sealed ink reservoir and body to prevent ink leaks, an easily accessed 13ml. ink reservoir (more on this later), spring powered automatic line retraction and 15m of high quality synthetic ink line, 7.5m of which can be retracted in automatic mode.

It fits in the hand very nicely due to it’s compact size and there is little surprise in why it is so popular. It is a very nice tool with a quality feel and smooth operation.

To show how this tool works, we will place a couple of lines on this hinoki (Japanese cypress) board.

hinoki board

A few safety points first.

The automatic retract is not very powerful, maybe 1/4 as strong as a tape measure’s but it has to retract a very lightweight string and a light weight karuko, which as you may have guessed has a small, sharp hardened steel spike in it. It goes without saying (but I will say it anyway) that the karuko must be controlled at all times. If it comes loose, it will retract very quickly, and because you are holding the inkline, it is coming back at you. If the karuko hits you, it is going to hurt and will easily puncture an eye or do other serious damage. Letting the line retract unrestricted is asking for trouble, so don’t do it, even for fun. Luckily, the large wheel on the front of the tool is the reel the line retracts to, so in the case of a loose karuko you can slow or stop it very easily. Best to set the karuko, run out your line, mark and then take the main body back to the karuko letting the line wind itself in at a leisurely pace.

The ink should be kept away from anything you do not wish to be permanently marked such as clothing, materials or other items. While it is water soluble and considered non-permanent it is also very very black and it may leave a stain that is difficult or impossible to remove. Keep it away from children or animals. While it is considered non-toxic, I would not suggest sampling it even if you are on a low sodium diet. The salt has been removed from the ink to avoid corrosion of metal parts in automatic ink lines, liquid ink for traditional sumitsubo still has salt in it, as there is little metal to be harmed by the corrosive chemical. It will wash off skin easily with soap and water.

The line is very fine and very strong, consider it in the same way you would fishing line, and handle it in a like manner. If drawn across the skin, there is a very good chance that it will cut you, and leave a nice ink filled groove to remind you to not do it again.

Aside from these safety points, in general these tools are quite safe, but the potential for disaster is always present, so do be vigilant and you should have no harm befall you.

Getting started.

The set up for this tool is very simple. Simply take it out of it’s cardboard and plastic package, fill it with ink and off you go!

Well, maybe not quite that simple.

On the back of the tool there is a round disc where the reel is located and on this disc is a finger sized dimple and a small plastic button. These are part of the retract mechanism and tension the spring in the unit, and should not need to be touched at first. If you run out more line than the automatic retract can handle (approx. 7.5m) then there is a catch inside the unit that should release spring tension and allow you to draw out more line. If the line does not run out easily, stop and see where the problem is as excessive force will likely damage the tool and could place you in a dangerous situation. If you do find that the spring tension is insufficient then rotating the disc should add tension to the desired amount. The small button is a catch, as well as a handy crank handle for adding tension quickly. This is a case where familiarity will show you how it is done, so go ahead and try it.

Adding ink to the tool is very simple, simply push the small door on the top of the tool toward the nose of the tool, and flick it open to add ink. Before the first use, you should remove the small warning leaflet inside. As the reservoir is only 13ml., take care to not overfill the tool because if you add too much, it is going to come back out again, sealed unit or not.

auto inkline open auto inkline filling

The sponge inside is in two parts, a red lower and blue upper part, and the line runs between them. Once you add ink, they are both very much black.

When replacing line, it is a good idea to replace the sponge too. These parts are specific to this tool, and are not expensive. As the line runs through the sponge, is it subject to abrasion and as the line is wet and exposed to dust and debris, it will also wear and may fray. You should expect a reasonably long life from both the line and sponge, but they will not last forever. Only use genuine parts, as they are designed specifically to withstand the wear and tear anticipated from the tool.

The sponge goes in the same way it comes out, through that small rectangular opening. It may take a few tries to get the sponge to sit well, but a little persuasion from your sumisashi (ink brush) should set it right.

An interesting point about the ink reservoir that is rarely mentioned (usually assumed to be already known) is that it is an ink reservoir and is not restricted to just inking the line. If you have a sumisashi, then it should be able to collect ink from the sponge. If your sumisashi does not fit, simply reduce it’s size until it does.

auto inkline brush

Another point before we go further, and one that is again, rarely mentioned is the small rubber button on the ink reservoir’s door.

auto inkline button

This is to charge the line with ink as it runs out. In a traditional line you would use the sumisashi or a finger. As the reservoir is sealed, a button is added to allow the line to be charged with ink as required. This is an important point, as you will see later.

How to use the inkline.

Firstly, you will need to mark two end points you would like to join with a straight line. I used a simple steel ruler and a sumisashi bamboo ink brush to make a small mark 100mm from the edge of my board at each end.

auto inkline brush markauto inkline brush mark 2

Then, push the karuko into the board near one of your marks. I suggest end grain as the pulling force of the line under tension will be less likely to pull the karuko out. While I did use softwood here, the karuko can be easily pushed into hardwood end grain so that it won’t come loose under tension.

auto inkline karuko

If you are off by a little bit, don’t worry as the line can be moved across the end grain by a small amount and will stay put provided it is under tension. With practise, you will be able to adjust it from afar to good effect too.

Next is to draw out the line to your other mark, this is easily achieved one handed and you should keep a finger or thumb on the reel handle on top of the tool to keep steady tension on the line and to act as a brake if the karuko does come loose and the line begins to retract quickly with it’s little dart in tow. Also remember to push down on the little rubber button in the ink reservoir door to make sure the line is adequately charged with ink. It sounds like a bit of a juggling act, but you should be able to find a hold that is functional and comfortable for you. No contortions required.

Here is where the nose of the tool comes into it’s own. Stop the line running out before you hit your mark, and use one of the small grooves in the nose to hold the line, and place it on your mark and your line should be across both of your marks. The trick here is to use your free hand to hold the line off the surface of your board (or whatever you are marking) before setting it down. It takes a little familiarity to remember to hold the line before setting the line in place, but it should be a natural act with practise.

auto inkline stretched

Note that I have made little mention of how hard to push the button, how much tension on the line or from how high to ‘flick’ the line. This is something I cannot explain, and you will need to practise yourself to gain a working knowledge of how much is “just right”. Too much ink, too hard a ‘flick’ and too much tension will result in ink splatter around your very heavily inked line.

auto inkline line close up

Too little ink or too light a ‘flick’ will give you a much lighter but easier to lose track of inked line.

auto inkline line close up 2

With a little experience, you will learn how much or little of each of these variables you need to get ‘Perfect’ results.

auto inkline finished

And that’s about all there is to it.

Do take care to ‘flick’ the line as close to directly above your proposed line as possible as an offset flick may result in a curved line. If you are aiming for a straight line, curved isn’t going to work. It is possible to mark graceful curves with an inkline, but I cannot admit to knowing how this is done reliably and accurately. I do know that a smooth line release and a judged amount of offset it required, as is plenty of practise and a line that has less tension that is required to mark straight lines.

If you find yourself needing to mark lines often, then there are plenty of alternatives out there to make your mark. Few of them are as fast as an automatic inkline, nor as reliably accurate.

The inkline featured in this article is available from the toolsfromjapan online store here.

Thank you for reading, and until next time stay on the straight and narrow.


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