Tension Mast Assembly:

Device that feeds the yarn to the carriage and controls the rate that the yarn flows to the knitting carriage

Visit the Classroom: Swatching is NOT Optional

1 Tension Mast Observations

by Angela Scarola (used with permission)

Not much has been written about the tension masts of knitting machines.

Comparing swatches knit at different tension mast settings reveals the how important this device is to successful machine knitting.

In attempting to do research for this article and having amassed a large collection of machines, manuals, how to books, patterns, magazines, and general books on machine use, I was unable to find much information. Following is what I have learned during my years of machine knitting.

2 Passap vs. Japanese Machines

  • The Passap manual does a better job of describing the yarn tension unit than the Japanese style manuals, but all are brief.
  • Neither manual made any effort to describe the effects of the tension mast units in regard to stitch size.
  • Both give specific instructions on how to thread the unit and a short description of how to set the tension for different weight yarns along with which is the tightest tension and loosest tension.
Passap has 13 tension mast settings (numbered 1-7 with half spaces included and 1 being the loosest).

Passap tells the reader that if the edge stitches are too tight or even not knitted, the knitter is to lower the setting on the tension disk.

Passap patterns routinely give tensions for both the lock stitch size regulator and for the tension mast tension disk.
Japanese Machines
Japanese style machines have five tension mast settings (- to + with the - sign being the loosest)

Japanese machine patterns routinely ignore the mast tension.

3 What Controls the Stitch Size?

The general consensus of opinion seems to be that the carriage/lock tension dial affects the stitches per inch while the mast tension controls the rows per inch.
While that may be generally true, over the years I have seen and experienced exceptions.

My only sure conclusion is that BOTH the mast tension and the carriage tension DO influence the gauge.

Following are some of my thoughts on what might be causing the variations that I've observed.

4 Stitch to Row Factor

My first conclusion was that part of the stitch to row factor is the slipperiness of the yarn and how it moves in the swatch once it is off the machine.

How the swatch is treated also has impact:

Measuring a swatch before and after "dressing" can get different results

5 The Lint Factor

Unless your machine is brand new, assume your tension dial is full of lint.
The first thing to check is the mast tension dial itself. Check it frequently for lint and clean it on a regular basis.

Small pieces of yarn can wrap around between the tension disks. Lint and fluff can build up inside the mechanism where the spring in located and prevent free movement of the tension dial parts.

When cleaning the units, only take one apart at a time; if you lose track of what goes where, then you can dismantle the second one.
  • You can do a partial check by pulling the spring portion apart to look for lint and check that the spring mechanism moves freely and springs back and that both sides of the tension unit move freely.

  • Keep in mind that the only way to get a full view is to take the end screw out and open the mechanism.

  • An amazing amount of lint will build up under the spring and in its case and can only be seen and cleaned by dismantling the tension dial unit.

  • If the spring is clipped in rather than loose, use a sharp point to help remove the lint.

  • To reassemble, line either the first or last number/mark with the setting line on the cup; adjust the piece next to the screw (in this case the metal "washer" with the red arrow) and tighten screw. Check that dial turns correctly; readjust if needed.

6 Assembly Health

Another factor is the individual tension mast and its relative health.
Suddenly after nearly nine years of use, I was getting loops on one side of my knitting. I checked the usual culprits:
  • The distance the carriage was traveling past the knitting
  • That the knitting was centered on the machine
  • That the yarn was in the mast tension disk properly (behind the little metal tab that holds the yarn in the tension dial mechanism)
  • That the mast tension was properly adjusted for the yarn I was using.
Nothing was apparently wrong.

I called Alles Hutchison, the late publisher of Knitting Machine News & Views and a twenty-five year dealer of knitting machines.
Her response was that the thin upper yarn guide had probably lost its "spring" and that I needed to replace that part of the mast.

You can test the thin upper yarn guides by threading them with the same yarn and the tension dials at the same setting. Pull the yarn backwards through the mechanism and release. The ends of the yarn guides should bounce up to about the same height.
Sure enough when the new arm was installed, I no longer got loops on that edge of my knitting. She felt that you should never leave the machine with the thin guide arm down holding yarn; you should release the pressure if you intend to be away for even a short while.
Yet I have seen knitters who always leave the yarn through the guide, and the guide bowed down and they have not experienced a problem.

You can test the thin upper yarn guides by threading them with the same yarn and the tension dials at the same setting. Pull the yarn backwards through the mechanism and release. The ends of the yarn guides should bounce up to about the same height. (I still have the "no spring" old guide and it does not bounce back up in this test; it is at least 3" lower than the adjacent guide.)

My Passap dealer says that the Passap thin yarn guides should also bounce back to about the same height; this means that one of my E6000 guides is no longer functioning as it should and I need to replace it.

7 Tension Mast Styles

Because the Passap always has two beds, there is only one style of tension mast.
Japanese Machines

  • Mast for the color changer: it utilizes a heavier gauge metal for the thin upper yarn guides as well as slightly stronger springs.
    This is necessary because a color may sit in hold for many rows and more pressure is needed to keep the yarn under the proper tension. Without the heavier gauge metal and stronger springs, the yarn that is waiting to be used would slacken and loops along the selvedges would result.

  • Regular mast
    The mast that came with your machine is different than the one provided with the color changer

If you have several masts, you should note which mast you have used for a swatch so that your garment knits to size.


Don't ignore the Mast tension dial on your machine. It DOES impact your gauge!

TIP: mark the center point of the dial to make it easier to see.

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carolyn s
 Mar 15, 2022
Carolyn S. I only knew that the mast fine tunes the tension. It is not easy learning these machines from the manual. Thanks for this info.

Greg B
 Mar 13, 2022
Interesting read. I noticed 2 things about the tension mast on my Taitexma TH160, the first being that the main rod fits loosely in the base. A little piece of blue painters tape helped to snug that up. The upper apparatus that holds the yarn is always twisting to the right, no matter what I do. I can knit, but it looks awkward and I keep thinking that a disaster is going to occur at some point. With all of the issues that I had had in re-learning how to machine knit, I sometimes think that I am better off sticking to hand knitting!

Karen K
 Feb 24, 2022
Great information! Thanks

Sara Jane W
 Feb 22, 2022
Thanks , I often wondered about that tension mast, Sara