A tank undershirt armhole that gapes may have too much opening for the wearer, insufficient edge recovery or a distorted attachment seam. An armhole that cuts in may be too high or narrow, or have a binding that resists movement. Diagnose shape and finishing separately before asking the factory to “make it tighter.”
Record where the problem occurs
Mark front, back and underarm positions on a fit photograph. Note whether the problem exists at rest, appears while reaching or remains after movement. Check both sides, before and after laundering. A gap at the front edge and pressure at the underarm can occur in the same garment, so reducing the whole opening may improve one symptom while worsening the other.
Keep wearer and size references with the record. Shoulder slope, chest shape and posture influence the fit; one dress form cannot establish comfort for the full range. Test representative wearers at the smallest, base and largest sizes, including any size with an unusual grade change.
Use measurements that describe the opening
| Point of measure | Definition to put on the drawing |
|---|---|
| Armhole depth | Vertical distance from a named shoulder datum to the finished underarm opening level |
| Front and back opening shape | Separate curves with reference points; a single depth does not describe both |
| Opening length | State whether measured along the finished edge or attachment seam, and whether flat or as a full perimeter |
| Strap width and placement | Finished width at a named position, plus shoulder and neckline reference points |
| Binding width | Finished visible width, including the method at the underarm join |
Measure relaxed finished samples, not just paper patterns. Keep tolerances separate from grade increments. Record washed dimensions using the same endpoints. Changing strap width or its location can move the armhole edge even when the nominal armhole depth is unchanged.
Separate the pattern trial from the binding trial
First compare the actual cut and sewn opening against the approved pattern, including seam allowances. If the geometry is wrong before the edge finish is applied, correct that discrepancy. If the shape is correct but the finished opening distorts, examine binding material, cut direction, feed and attachment settings.
For a binding trial, hold the body pattern constant and vary one finishing factor at a time. Record cut binding length and the neckline or armhole seam length using an agreed convention that accounts for joins and allowances. The ratio is a process setting for that construction, not a universal target. Too much contraction may dig into the skin or pucker the body; too little may leave a loose edge.
Rib and self-fabric binding can both be candidates, but approval depends on their actual stretch and recovery. Check seam bulk and join placement because a stiff underarm section can cause discomfort even when the dimensions pass. Keep the approved setup by size; change it only with documented fit evidence.
A stretch-and-recovery record for the finished edge
Ask the factory or laboratory to agree how the check will be performed. Define the marked length, extension or load, direction, hold time, repetitions, rest time and care state. An unrecorded hand pull is not a repeatable test, and a fabric test report does not automatically establish the performance of the sewn binding.
| Stage | Record | Decision |
|---|---|---|
| Before extension | Relaxed marked length, edge flatness and sample condition | Matches the approved starting reference? |
| During agreed extension | Opening behavior, seam restriction and any stitch failure | Moves without unacceptable restraint or damage? |
| After the stated rest | Marked length, residual growth, waviness and rolled edge | Returns within the buyer’s agreed limit? |
| After laundering | Same measurements and procedure, with wash/dry details | Still meets both recovery and fit requirements? |
For an internal calculation, residual growth is the rested marked length minus the original marked length, divided by the original and multiplied by 100. Agree the acceptable limit with the product team and relevant test specialist. Do not borrow an unrelated elastic-fabric limit and assume it suits the sewn garment.
Approve movement and coverage together
Have wearers lower their arms, reach forward, raise them and return to rest. Record gaping, pressure and exposed area at the same positions. A sleeveless style provides different underarm coverage from a sleeved undershirt; binding adjustments cannot create the missing sleeve coverage.
If the armhole fails only on one size, revise that size’s shape or finishing as justified, then recheck adjacent sizes for a smooth grade progression. Retain the fit sample for each approved size or the documented size coverage agreed with the buyer.
Transfer the result to inspection
Issue the finished measurement chart, curve reference, binding specification and recovery check alongside the approved new and washed samples. Specify inspection coverage by size and colour explicitly; an AQL-based sampling plan alone does not guarantee measurement of every size. Check early units before the process repeats through bulk.
For the whole range, use the undershirt development brief. Broader outerwear tank construction is covered in the tank-top specification guide. Send the affected sample photographs, measurement records and desired correction through Knitwear Base, and confirm the proposed finish is feasible for the actual material before approval.
