White-supremacist Martyn Gilleard, 48, of Armley, Leeds, was jailed in 2008 for 12 years for terrorism offences and having indecent images, and was released in 2023.
On Friday, he appeared at the Old Bailey and pleaded guilty to a single count of collection of material likely to be of use to a terrorist.
The charge said that on or before May 28, the defendant, who also goes by the name Martyn Stone, collected information on the manufacture of explosive black powder, known as gunpowder.
The grey-haired and bearded defendant entered his plea by video-link from Leeds jail.
Mrs Justice Cheema-Grubb set a sentencing date at Leeds Crown Court for August 22 and remanded Gilleard into custody.
The former forklift truck driver Gilleard was previously found guilty of engaging in conduct in preparation of terrorist acts and collecting information for terrorist purposes having admitted having indecent images.
Police found four nail bombs, bladed weapons, bullets, documents about terrorism and extreme right-wing literature when they searched his flat for indecent images of children in October 2007.
Officers uncovered significant volumes of extreme right-wing literature and propaganda from far-right group Combat 18, as well as ammunition, weapons and homemade bombs.
A further search by detectives and forensic teams from the Counter Terrorism Unit (CTU) in Leeds uncovered more explosive material, camouflage clothing, balaclavas, a bomb-making manual and outdoor survival guides.
Humberside Police had also discovered around 39,000 indecent images of children including film and photographs.
A search of his workplace found a high-visibility jacket which had been modified with a hand-drawn swastika and Combat 18 lettering, and colleagues told police that he had expressed racist views.
Detectives launched a manhunt when the father of one failed to return home after the original search of his flat.
He was found three days later 300 miles away in Dundee, Tayside.
Gilleard was a member of a number of far-right groups, including the National Front, the British People’s Party and the White Nationalist Party.
In police interviews, he admitted sympathising with white supremacists and accepted he was racist, but said he had become less racist in recent times.
He admitted 10 specimen counts of possessing indecent images of children, and also pleaded guilty to possessing 34 cartridges of ammunition without holding a firearms certificate.
In his trial, Gilleard claimed the nail bombs were not intended for serious violence and said he made them when he was bored after drinking “a couple of cans”.
But the prosecution said he intended to use the weapons and documents found in his flat in terrorist acts to further his political cause.
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