problem with rails and trucks on a tabletop press

hello, I got what it seems to be a replica of an American n° 8 tabletop press, and I have a couple of problems with the rollers and rails. the rails are very far from being type high, they are about 19,5 mm, so, almost 4 mm lower than type high. in my head, the easiest way to solve this would be getting trucks with a radius 4 mm bigger than the radius of the rollers, but all the info about letterpress rollers that I have found says that the trucks have to be the same diameter than the rollers. what is the reason for this, and why my solution wouldn’t work?.
Another thing is that I think that the roller and trucks are the wrong size for the press. there is a lot of horizontal play, with the trucks almost falling of the rails after a couple of prints. the trucks are a little less wide than the rails, and I suspect that this must be the reason. is there a formula to get the dimension of the roller and trucks after measurements from the press? or a ratio between the rail and the truck width?. thanks

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cristianze -

I make rollers and trucks - often for presses with no rollers and trucks to begin with. I deal with this issue regularly.

Before I give you the formula I use to size rollers to a press, here’s an important basic issue to consider:

No matter what press, rail height, roller and/or truck diameter you are dealing with, the one important factor is the amount of contact between the rollers and the form.

All of those other items you mentioned *contribute* to the solution by adjustment, but the only thing that is important is that your rollers contact the form just enough to transfer ink to it.

So, to begin with, your rollers should be slightly less than .918” from the bed of your press. I say “less than” because we generally want to allow for some depression of the rubber on the roller - enough to leave a 12-18 point stripe on a solid block.

Most of the time, the trucks will be the same diameter as the rubber of the rollers - but not always. In fact, C&P used to supply sets of two different diameters of trucks with their presses and Adana made a truck that was reversible - with two different diameters.

Around 1900, a fellow named Morgan invented an “expansion truck” that used a rubber tire mounted between what essentially is a nut and a short bolt. As the nut was tightened, the rubber would be compressed and expand in diameter, offering a nearly unlimited amount of adjustment, quickly and easily.

In those days, one of the reasons adjustable trucks were needed is that composition of the ink rollers of that time allowed expansion and contraction depending on weather and humidity. They used what were known as “summer rollers” and “winter rollers”.

Today, we are not so concerned about expansion or contraction of the rubber rollers we use these days, but do need to pay attention to roller pressure as we switch between traditional printing with metal type and the far-more sensitive roller heights required for printing with the relatively shallow photo-polymer plates that have become so popular.

The important thing is the the trucks raise the roller shafts off of the bed rails just enough that the rollers make the contact we seek. Most often, that is the same size as the rollers, but not always. That’s why I calculate it as explained above.

To achieve this optimal height, the rails are indeed less than type high - they need to be - but not 4mm less… just a few thousands.

I just measured 5 table top presses in the shop here - just now. Rail height varied from .90-.91” or 22.6-8 mm. At 19,5 mm, your rails are indeed lower than average.

We compensate for this with the trucks - but not so much that we raise the rollers too high. That’s a subjective height - remember, we are seeking a 12-18 point stripe of ink on a solid form - less if you are printing from photo-polymer plates.

I do believe you will need to use some oversize trucks - grossly over-sized, although I’m not sure why your press was made with such low rails - but a lot of the popular amateur presses circa 1900 were also “experimental” in their engineering.

Now, to answer to your question:

Next, to calculate the size of rollers for a particular press, I measure the distance between the outside edges of the roller hooks to get the width of the shaft. I measure the diameter of the ink disk and the width of the chase to get the width of the rubber. I measure the distance between the adjacent hooks to get the diameter of the rubber - allowing, of course some space between the two rollers.

The trucks can - and should be - as wide as the rails and hooks allow. Remember that the chase takes up some space, too, but rubber should cover the entire chase - so that roller bearers could be used if needed.

So, truck width should match or exceed rail width - as long as there is clearance of the roller arm. Truck diameter should be sufficient to raise the ink rollers to just below .918”. (23,3 mm). I’d suggest aiming for .905 or so.

But in any case, these measurements are only starting-point guidlines. What must be measured - and the *only* thing that is really important in all of this is the success of the rollers transferring ink to the form.

Final adjustments
Once the parts you assemble - rollers, trucks, etc are installed, you can do fine adjustment as well.

1) If, the rollers are too high for the form, you can add shims behind it to raise the form up to the rollers. I use oiled tympan paper - no soft paper or cardboard, it could cause the press to bind up when closed.

As you add packing behind the form, you bring the type closer to the rollers. This is a very precise adjustment and easily controlled. Of course, you will have to consider the effect this shimming will have on your packing, but if you remove a sheet from the tympan packing and put it behind the form, the only thing that changes is the height of the form relative to the surface of the roller… or vice-versa.

2) To raise the rollers away from the form, you can either tape the rails to raise them, or tape the trucks to adjust their diameter. Taping the narrow rails of most table top presses is difficult. I prefer taping the trucks using black electrical tape. It works quite well and I describe the process at

So. Here’s a bit of a primer on roller and truck diameters and roller height - with a little possibly boring history thrown in as well. I hope you find it helpful.

- Alan


A 4mm difference is a great amount to increase your truck radius. I think this case would require you to increase the height of the rails (perhaps with some fine adjustment of the roller trucks to finish the adjustment). That great a difference between roller and truck (if you didn’t raise the rail height) would no doubt in my mind cause slurring of the roller on the form, slipping by at a rate different than that of the trucks on the rails.

I have use strips of sheet metal taped to the rails to make such a significant raise. This has been successful for me, but I do know that some presses were manufactured with low rails with the expectation that strips of leather would be stretched over the rails to bring them up, and at the same time allow for quieter operation.

John Henry

As for the horizontal play issue, it is common for rollers cores to have ears or lugs crimped into them, and for the trucks to have a keyway that is slid over the crimp. That keeps the truck from spinning or moving too far inward. And many trucks have an outer section of smaller diameter which may almost touch the roller saddle, and that keeps the truck from moving out.
I have seen Kelsey rollers and trucks without these features, and my fix was to drill, tap, and insert set screws.

All - well, in this case - with extremely larger trucks than rollers, my solution *requires* use of free-wheeling trucks. If the trucks were locked to the shaft, it certainly would cause slurring as JHenry suggests.

Raising the rails using a strip of leather is an interesting approach. I would be concerned about keeping the travel smooth and level, but the idea of leather on the rails is indeed intriguing. I’d never heard of that before….

Pins to hold the trucks stable left-to-right would be fine, but should not be needed. I have used thick washers as spacers at times, but prefer wider trucks.

Spring tension could also be an issue. Without sufficient spring tension on the rollers, they can wander and the trucks can indeed fall off the rails.

I would only recommend locking trucks when the roller and truck diameter is really, really close - like just a few thousandths of an ink.

If the rails can be modified to come closer to the .905+/- I found on these 5 of the table top presses in my shop, then locking trucks would be okay, and the issue of the difference in circumference of the rollers and trucks would not be such a problem.

But before stumbling around in the dark any further, I think we should ask cristianze to post some photos of his press - with particular attention to the rails.

As I thought about this further, it semed really weird that anyone would actually design a general-use press with such a low rail height.

I’d like to see just what we’re dealing with here.


- AR

Hi, thanks everybody for the help, now I have a better understanding about roller set up. I am also intrigued about the issue with the rail height, at first I assumed they were lower from the wear, but I don’t think that they could get that low. I think that for now I am going to print in photopolymer only, with a lower base. adding something to the rails to be able to switch between metal type and photopolymer seems to need a more experienced printer. I’ll try to post some pictures of the press tomorrow