DIFFERENTIAL FEED
The differential feed has two independent feed dogs, one front (A) and one rear (B).
Each feed dog has an individual feed mechanism which enables fabric to feed at different ratios.
POSITIVE DIFFERENTIAL FEED
WHEN SET FOR POSITIVE DIFFERENTIAL FEED, the front feed dog (A) makes a longer stroke
than the rear feed dog (B).
This has the effect of accumulating fabric under the presser foot to prevent the fabric from
stretching.
NEGATIVE DIFFERENTIAL FEED
WHEN SET FOR NEGATIVE DIFFERENTIAL FEED, the front feed dog (A) makes a shorter stroke
than the rear feed dog (B).
This has the effect of stretching the fabric under the presser foot to offset puckering.
I
Illustration
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: Differential feed dogs
II
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: Positive differential feed
III
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: Negative differential feed
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(B)
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I
(B)
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II
(B)
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III
(A)
(A)
(A)