The man has already served time for both convictions but continues to protest his innocence.
He unsuccessfully appealed the assault conviction and sentence in the Court of Appeal last year, saying he did not injure the woman and the prosecution case was a police invention to disguise her assault upon him.
He also failed in a Court of Appeal bid against the threatening to kill conviction, but was granted a reduction in sentence to four months, despite having already served the sentence.
The man appealed both convictions in the Supreme Court, which today dismissed both appeals.
The court said the appeals were long out of time and would not meet the criteria, given he was trying to "re-litigate the particular facts'' of his previous appeals.
For the 2008 conviction, the man also argued the court transcript did not show the jury actually delivered a verdict - an argument the court said was without merit and had no prospect of success.
The court also dismissed appeals against sentence because both had been served.