As I mentioned in an earlier post, I have found that the air pins on my caster are somewhat sluggish, and in some cases stuck completely.

To diagnose this and get the pins on the rear pin block moving freely, I disassembled the block, cleaned and lubricated everything, and reassembled it.

These are the parts I had to remove before I could lift the pin block cover: On the right, the pin jaws still attached to their tongs, and on the left, the rack, matrix jaws, and their tongs.

These are the parts I wanted to service: The pin springs, air pins, pin block cover, and guide rod for the pin jaws. One of the air pins (for selecting the O column of the mat case) is held up permanently by its spring but the pin itself is identical to the other pins which are raised by air pressure.

I tested the system airflow into the cylinders and found no problems other than a bit of dirty oil to blow out. After cleaning, the pistons slid freely in the cylinders, but they were binding in their cover holes, which had a layer of dried oil gunk in them.

The 8mm size from this brush set (from Princess Auto) was ideal for cleaning the pin holes in the top cover. In and out twice and the pins slid freely in their cover holes. Perhaps a gun cleaning brush of the correct size would have worked but these are not so readily available here as they are in some countries.

Now it was time for reassembly.

The rear pin block when stripped of its parts but still mounted on the caster.

All the pins are in place. The O (rightmost here) pin is held proud by the spring under it.

All the hold-down springs for the other air pins have been dropped into place.

At this point, I replaced the cover with just two of its screws and tested the pins under air power. All worked fine except for the A and D pins which seemed quite stuck. Turning these pins with an Allen key (the pins have a hex socket in the top for exactly this purpose) revealed that these two pins were not moving freely. I removed the cover again, swapped some other pin for the A pin and replaced the cover but the A pin continued to stick, implying that the hole in the cover had a problem. I removed the cover (again) and took a close look at the A and D pin holes and found a tiny dent on the edge of each, as if something hard had hit the top of the cover plate.

This dent (at the 6 o’clock position here) on the top of the pin block cover peened a small bump on the inner circumference of the hole, causing the pin to stick. You could really only see it by getting the light just right to see the shiny surface worn onto the bump.

I used an adjustable reamer to carefully remove the bumps inside the two holes, and a pin manually inserted into these holes now moved as freely as it did in the other holes. I replaced the pins and cover and tested with air again and all the pins worked (except for NI and NL which I could not test by injecting air into a single line, but they turned easily and could almost be raised using the Allen key). But I managed to miss the photo for this stage of assembly.

Although I had managed to remove the cover, I was finding that reinstalling the cover, the two matrix jaws, and the rack, which all interlock somewhat, was turning into a bit of a juggling act. As it turns out, removing the buffer and properly orienting the washer on the mould blade rod allows the jaws and rack to be slipped into place after the cover is installed.

The cover is now all screwed and dowelled in place, and the matrix jaws and rack have been slid into their track. The caster must be cycled to the point where the rack dogs are retracted before the rack can be inserted. Note the position of the flat side on the washer (red arrow) on the mould blade rod allowing the insertion of these parts. Rather than removing the buffer entirely, I left it connected to the spring pulling on the mould sizing slide and just moved it aside a bit.

The rear buffer has been re-installed. Note the nut (red arrow) and washer (hidden from view) that are used to compress the buffer spring to allow its removal and installation.

The matrix jaw tongs are now in place and locked onto the jaws.

Everything is now back in place, and the temporary nut and washer have been removed from the buffer spring and returned to the tool kit.

Now a similar procedure awaits the front pin block, but it will be a bit more work because I will remove the bridge to give me more open access, and the buffer is trickier to remove, being held down in part by a small bolt hidden under a cover and with only enough access to turn it ⅙^th of a turn at a time. As well, the taper pins for the cover can only be punched out by reaching up almost blind inside the base with an 18″-long punch.

What with helping to get our daughter’s Hallowe’en costume finished in time, and trying to clean our store for the studio tour coming up this weekend, I have had little time to work on my Monotype. The current tasks are to get the air pins moving freely, and to fix the air leak where the air supply enters the paper tower.

It looks like I will be making my own connector to replace the ball-shaped one currently on the caster, with the replacement part having grooves to hold O-rings to make a proper seal. The top of the pipe rising from the caster table is threaded with a ¼″-32 straight thread—another non-standard combination—so I will probably replace the pipe as well rather than trying to match that thread.

The pipe is ¼″ outside diameter, so I should be able to use ¼″ soft copper tubing to replace it. The connection in the table has a rubber seal and a nut to compress it around the pipe, and I can make the connection of my choice where the pipe meets the connector at the top. I may put an S-bend in the pipe instead of the straight original one, to give allowance for a bit of positional adjustment (by bending) when I install it.

I was planning to use a flared connection from the pipe to the tower connector, but the smallest fitting I could find for ¼″ flare joints converted to ⅛″ male pipe thread. On adding the matching female thread to the drawing of my connector made it clear that there would not be much metal left in some spots, making for a weak part.

So, what I think I will try instead is to make the part out of brass, with a ¼″ diameter hole in the side, where I can solder the copper pipe into place. I don’t have much experience with machining brass so I will have to see how it turns out.

Maybe I’ll have time for it Sunday.

Last but not least of the control valves to be serviced on my Monotype caster is what I refer to as the Mould Signalling control valve. Depending on what options the caster is fitted with, this valve might be used for casting low quads (rather than having the bridge detect the special quad mats which have a shallow cone hole for the centering pin), or for controlling one part of the mould blade when using a duplex or triplex mould. Some features require additional pneumatic mould control, so if you have a triplex mould or want low quads from a duplex mould, your caster would have a second (essentially identical except for choices of air lines) mould control valve beside this one, and for the triplex mould and the high-quad shutter used in mathematical setting, the Unit Adding control valve is also co-opted.

This valve (and its twin if secondary mould control is installed) are quite simple: Signalling the N air line not only raises the N air pin, but also diverts the 0075 signal from the 0075 air pin to the mould signalling line (secondary mould control uses 0005). A rod screwed into the top of the valve prevents it from moving if this operation is not wanted (in which case the N+0005 and N+0075 would act just like 0005 and 0075, causing the justification wedges to be set, turning off the pump, and/or causing the galley to operate, as appropriate).

At least, that is according to the ‘Monotype’ Composition Caster Manual. On my caster, the H and J lines are used instead of N and 0075, respectively, and I still don’t understand why. As a result of this, signalling the mould also raises the H air pin. If the signalling is used to select low quads, it doesn’t really matter which air pin pops up in the rear pin block, and it could be argued that H centers the matcase, producing on average a minuscule reduction in wear and noise when the matcase is positioned for the next character. But for use with a duplex or triplex mould, this limits casting to columns NI through H of the matcase when the mould is signaled (either regular or secondary).

In any case, I have reassembled this valve, putting the bent end of the spring inside the piston so it can’t jam when the piston moves, and reinstalled it on the caster. With all the control valves back in place I have to solve my other pneumatic woes: air leaks and stuck air pins.

Mould Signalling Control Valve re-installed with the top screw all the way down, disabling it.

After a short side trip to test and trace the individual air lines on my caster I have returned to the task of refurbishing the various pneumatic control valves.

The next one to do is the Quadding and Centering control valve. It actually consists of two valves stacked on each other. The outer one (on the right in the photo) is actuated by either A or B air from the paper tower, and its purpose is to prevent air from the C line of the paper tower from reaching the C air pin if either A or B is also selected. The inner one is actuated by the C air from the paper tower, and its purpose is to divert the air coming from the A and B paper tower lines to the Quadding and Centering actuators (rather than the A and B air pins) via the manifold that forms part of the mounting plate for the Unit Shift control valve. From this description it is pretty clear that none of the A, B, or C air pins can be raised for a character being cast for quadding or centering. This is not considered a shortcoming since this feature is intended for casting spaces, in fact, em quads specifically, and such spaces are typically located in the right-hand columns of the matcase, often in column O (which requires no air pins to select).

Rather than risk damaging more of the under-table copper pipes, I opted to clean the mounting plate for this valve in place, so it is not quite as sparkling clean as the plates for the Unit Shift and Unit Adding, but at least it is steel-coloured rather than gunk-coloured. I reassembled the valve using a light oil on the pistons and a heavier oil on the mating surfaces. I left the bottom plate screws just snug until I had snugged the mounting screws to hold the two valve bodies tight together, then I tightened all 8 screws.

The only control valve left to service is the mould signalling control valve.

The Quadding and Centering control valve, re-assembled and re-installed.

On removing the dummy plate on my Unit Adding valve base and testing individual air lines, I have determined that:

1. This valve uses lines I, K, N, 0005, and 0075 (not J, K, N, 0005, and 0075 as my manual states).
2. I had swapped two of the lines coming to this plate, causing my I and 0005 lines to be interchanged.

To fix problem number 2 I had to remove the mounting plate, disconnecting all the air lines, and re-mount it with the lines coming to the correct ports. I had tried just removing the two swapped lines but because of the way they were crossed I was unable to reposition them with all the other lines still in place.

Fortunately I found installing the plate much easier this time, perhaps because I inadvertently used a slightly different procedure.

On tracing all the lines I also found that my previous statement about the mould signalling (that it uses G and H) was incorrect; it actually uses H and J, which still does not match what the manual says.

I now have the rear pin block cover off and all the pins out for cleaning; once this is all reassembled and the remaining control valves are reinstalled I should find that all these airpins operate properly.

Using a sports inflator needle to apply compressed air to each air line individually, I am finding several oddities.

The first is certainly not unexpected: Several of the airpins are sticking. I think my best bet for these is to remove the two pinblock cover plates, blow gunk out of the lines, and clean and lubricate everything. Although the airpins have a hex socket in their top so they can be twisted to unstick them, every third airpin is obstructed by the rods that guide the pin jaws. I might try a ball-tip Allen key to turn these, but it is a pretty tight fit.

The next is that the I and 0005 pins appear to be swapped: applying air to one of these holes in the paper tower actuates the other airpin.

Finally, the mould signalling valve seems to use H and G together to signal the mould (and raising the H pin), but the documentation I have (the 2-binder ‘Monotype’ Composition Caster Manual) says it uses N and 0075.

I’m considering the possibility that I got some lines mixed up when I removed and replaced the bases for the Unit Adding or Unit Shift, but neither of these mechanisms uses G, H, or I (Unit Shift uses D, E, and F, and Unit Adding uses 0.005, 0.0075, J, K, and N according to the manual).

I will remove the Unit Adding dummy valve to identify exactly which lines lead where. Hopefully I can solve these mysteries.

It seems to me that the design choices of which lines control certain options never accounted for combinations of options that could have been useful in the future. For instance, the quadding and centering cannot be used to cast repeated characters from the A, B, or C columns of the matcase (it was only intended for quads, which are generally in the O column). The mould signalling uses N (at least, as my documentation states) and so cannot be used with 15×17 matcases because columns I and L would be inaccessible when signalling the mould (the N+I or N+L combinations would instead select column NI or NL). This is fine when it is used to select low quads but not when used to signal the side blade for a duplex or triplex mould; probably mats for duplex or triplex mould usage were only produced in 15×15 arrangements. Only the Unit Shift is designed in a manner that has no adverse impact on other functionality, but there is no reason why other options could not have been designed the same way.