How to Convert an Overshot Treadling Sequence into Shaft Lifts for a Four-Shaft Table Loom

Keep the threading, tie-up, treadling, and written weaving instructions together. A treadle number identifies a column in the tie-up; that column identifies the shafts operated by the treadle. The number alone does not tell you which shafts to lift. Weaver’s Craft explains these relationships in its guide to reading weaving drafts.

Before copying any rows, establish four things:

• Shed convention: Do the tie-up marks mean shafts rise or shafts sink?
• Starting point: Which treadling row is woven first, and in which direction do you read subsequent rows?
• Repeat instructions: Which rows are repeated, and how many times?
• Tabby notation: Are the plain-weave picks drawn explicitly, or supplied through an instruction such as “use tabby”?

Follow the draft’s reading direction rather than assuming every treadling runs downward. Weaver’s Craft, for example, explains that its treadlings are read upward, while some other drafts run downward. Its guide also distinguishes rising and sinking tie-up symbols; check your particular publication’s legend before interpreting the marks. Source: Weaver’s Craft, “Weaving Hints & Tips.”

If you have only a sequence such as 1, 1, 2, 3, obtain its matching tie-up before proceeding. Several different tie-ups could give those same treadle numbers different meanings. Likewise, a block or profile notation needs its structural interpretation before it becomes an executable shaft-lift sequence.

For a rising-shed table loom, write every instruction as the shafts that will be up during the shuttle pass. A rising-shed tie-up can be transcribed directly. A sinking-shed tie-up must be complemented: from shafts 1, 2, 3, and 4, select those absent from the marked sinking set. The Overshot Pattern Generator’s technical explanation shows this relationship for four-shaft overshot.

For example, if a treadle lowers shafts 1 and 2, your table loom must raise shafts 3 and 4 to reproduce that shed. If a treadle already raises shafts 1 and 2, lift 1 and 2. These instructions describe different sheds, so determine the convention before building your key.

The following is an illustrative sinking-shed tie-up, consistent with the four pattern combinations shown in the generator’s explanation. Its treadle numbering is an example, not a replacement for the numbering in your own draft. Source: “How it works.”

Pattern treadle	Shafts marked to sink in this example	Actual shafts to lift
1	1, 2	3, 4
2	2, 3	1, 4
3	3, 4	1, 2
4	1, 4	2, 3

Make this lookup table once, then use it for every occurrence of each treadle. Record shaft numbers rather than the visual positions of marks: a tie-up may place shaft 1 at the bottom of its grid. For this example, treadle 2 always becomes the lift set 1 + 4.

Traditional overshot alternates a pattern-weft pick with a plain-weave, or tabby, pick. Schacht’s explanation describes the finer tabby weft as the ground cloth and the heavier pattern weft as forming the design; it also explains the use of separate shuttles for the two wefts. These tabby passes are part of the weaving sequence, including between repeated pattern picks. Source: Schacht, “Reupholstering a Chair with Overshot Fabric.”

For a conventional four-shaft overshot threading that alternates odd and even shaft numbers, the two plain-weave sheds are 1 + 3 and 2 + 4. The odd/even threading requirement is explained by Janet Dawson in “Namedrafts and how to create them”; the corresponding tabby lifts are stated in the Overshot Pattern Generator explanation.

Label these sheds on your working sheet. Here, tabby a = lift 1 + 3 and tabby b = lift 2 + 4. Those labels are our working convention; if your project defines a and b differently, retain its definitions. For a renumbered or otherwise modified threading, verify which shaft groups actually produce plain weave.

If the draft says “use tabby” while showing only pattern rows, expand it into alternating pattern and tabby picks. If tabby rows are already drawn, retain them without inserting another set. Weaver’s Craft explicitly explains that “use tabby” notation omits the tabby rows from the displayed treadling. Source: “Weaving Hints & Tips.”

Keep the two tabby sheds alternating across pattern-block boundaries. Repeating one pattern treadle three times means weaving that pattern shed three times, with alternating tabby passes between them; it does not mean sending the pattern shuttle through the unchanged shed three times consecutively.

Here is an original worked conversion using the illustrative sinking-shed key above. Assume the project calls for one tabby pick after each pattern pick, with the first tabby being a. The example pattern-only treadling is 1, 1, 2, 3, 3, 4, 1. This is a conversion exercise for use with a matching overshot threading, rather than a complete project draft.

There are seven pattern picks. Replacing each treadle with its lift set gives 3+4; 3+4; 1+4; 1+2; 1+2; 2+3; 3+4. Adding seven tabby picks produces the following fourteen actual shuttle passes.

Actual pick	Weft	Original instruction	Lift these shafts
1	Pattern	Treadle 1	3, 4
2	Tabby	a	1, 3
3	Pattern	Treadle 1	3, 4
4	Tabby	b	2, 4
5	Pattern	Treadle 2	1, 4
6	Tabby	a	1, 3
7	Pattern	Treadle 3	1, 2
8	Tabby	b	2, 4
9	Pattern	Treadle 3	1, 2
10	Tabby	a	1, 3
11	Pattern	Treadle 4	2, 3
12	Tabby	b	2, 4
13	Pattern	Treadle 1	3, 4
14	Tabby	a	1, 3

The repeat boundary needs attention. This repeat contains seven tabby passes, so it ends on a. When the pattern restarts, pick 15 is the first pattern shed again, but pick 16 must be tabby b. Restarting the entire fourteen-row table unchanged would repeat tabby a at the next tabby opportunity.

For this example, either write two pattern repeats with tabby continuing throughout, or maintain separate markers for pattern position and next tabby. Two pattern repeats contain fourteen tabby picks, restoring the original tabby phase. This odd/even check follows from the example’s pick count; it is useful whenever you expand an abbreviated repeat.

Confirm which lever operates each numbered shaft before weaving. Ashford’s “Learn to weave on the Table Loom” manual identifies shaft 1 as the shaft nearest the weaver and explains its lifting notation through numbered lever operation. Use your own loom’s documentation and observe the shafts to establish its control mapping.

Treat each row as the complete required raised set, rather than a list of extra shafts to add to the previous shed. For pick 3 in the example, only shafts 3 and 4 should be raised. Leaving shafts 1 and 3 raised from the preceding tabby and simply adding shaft 4 would produce the wrong shed.

A practical sequence for each row is:

1. Read the pick number, weft type, and complete lift set.
2. Lower any shafts that should no longer be raised and raise the required shafts, using your loom’s mechanism.
3. Check that the open shed matches the written set.
4. Pass the indicated shuttle, beat according to the project instructions, and mark that pick complete.

For an early sample, returning all shafts to their resting position before selecting the next set can make the instructions easier to follow. Once the sequence is familiar, you can change directly between sets while still checking the final shed. Keep the row marker on the last completed pick so a pause does not leave its status ambiguous.

Use a short sample to separate errors in the written conversion from errors in operating the loom. Janet Dawson’s explanation shows why lowered warp ends receive pattern-weft floats on the upper face: when deriving a pattern shed, she lifts the other two shafts. This gives you a useful way to compare an intended pattern area with the actual shed. Source: “Namedrafts and how to create them.”

Check the sample in this order:

• Verify tabby alone. On the conventional odd/even threading described above, alternate 1 + 3 with 2 + 4 and inspect the over-one, under-one interlacement. If it fails, check the threading and shaft mapping before changing pattern instructions.
• Trace one pattern pick. Locate its original treadle column, identify whether the marks mean up or down, and compare the resulting lift set with the shafts actually raised.
• Check both wefts. Confirm that pattern and tabby passes alternate as instructed and that successive tabby passes use opposite sheds.
• Check a repeated block. Retain every specified pattern repetition and its intervening tabby.
• Check the repeat boundary. Continue tabby alternation when the pattern restarts, especially after an odd number of pattern picks.

If the sample differs from the draft, correct the earliest identifiable mismatch. Recheck the tie-up convention for an apparent exchange of pattern and background, the shaft mapping for consistently wrong sheds, and the row record for an isolated interruption. Changing several things at once makes it harder to identify which correction worked.

Your finished working sheet should name the tie-up convention, define each treadle’s actual lift set, include every required tabby pass, and show how repeats continue. Once those details are explicit, the overshot treadling becomes a pick-by-pick instruction list: select the shafts, use the indicated weft, and advance one completed row at a time.

• Learn to weave on the Table Loom — Ashford
• Weaving Hints & Tips — Weaver’s Craft
• How it works — Overshot Pattern Generator
• Namedrafts and how to create them — The Handweaving Academy
• Reupholstering a Chair with Overshot Fabric — Schacht Spindle Company