ignition scratch

[Mestin]

это со сваркой связано

Ignition scratches shall be ground away carefully

[Lavrin]

Ignition scratches shall be ground away carefully. Each welder shall stamp his own identification mark beside the seam. Only TIG welding is approved. Certification must be presented prior to work for Buyers approval.
***
А это не "схемы розжига" в TIG-welding (дуговой сварке в среде инертного газа)
Схемы розжига следует внимательно проштудировать.

Или все-таки "ignition scratches" - это какие-то "скретчи" розжига (той же дуговой сварки).
"Скретчи" розжига следует тщательно заземлить.

[tumanov]

А может наждаком стесать...

[Lavrin]

- Ignition scratches - азы разжигания (дуги), основы разжигания (в дуговой сварке)
Ignition scratches shall be ground away carefully. - Азы разжигания следует хорошенько выучить.
***

Зажигание электрической дуги является первым приемом, которому должен научиться начинающий сварщик. Перед зажиганием дуги следует еще раз предупредить учащихся о необходимости защиты глаз. (из Рунета)

[tumanov]

Из Коллинза:

grind [] grinds, grinding, ground
1) to reduce or be reduced to small particles by pounding or abrading to grind corn to grind flour
2) () to smooth, sharpen, or polish by friction or abrasion to grind a knife
3) to scrape or grate together (two things, esp the teeth) with a harsh rasping sound or (of such objects) to be scraped together
4) (; foll by out) to speak or say (something) in a rough voice
5) (; often foll by down) to hold down; oppress; tyrannize
6) () to operate (a machine) by turning a handle
7) (; foll by out) to produce in a routine or uninspired manner he ground out his weekly article for the paper
8) (; foll by out) to continue to play in a dull or insipid manner the band only ground out old tunes all evening
9) (; often foll by into) to instil (facts, information, etc.) by persistent effort they ground into the recruits the need for vigilance
10) () informal to study or work laboriously
11) () chiefly to dance erotically by rotating the pelvis (esp in the phrase bump and grind)
12) informal laborious or routine work or study
13) slang chiefly a person, esp a student, who works excessively hard
14) a specific grade of pulverization, as of coffee beans coarse grind
15) slang the act of sexual intercourse
16) chiefly a dance movement involving an erotic rotation of the pelvis
17) the act or sound of grinding • See also grind in , grind on

[Alex Nord]

места возбуждения дуги следует тщательно обработать шлиф-машинкой