i get SSDI & still worked but they lowered the amount accordingly. as for Social Security i don't know. all i know is in order to get SS you have to have 40 credits from working over your lifetime. my job came to an end several months ago, i'll never have another & yet all i have is 37 credits. can i get SS on that is debatable.
@fffred is correct - IF you are on SSDI rather than SSI then that means you have a SS benefit and at FRA it just converts from SSDI to SS retirement - same amount cause under SSDI you are getting your full benefit.
However, your "work" could be a problem depending on how much you can and do work - your work if you are paying into the SS system via payroll deduction could increase your benefit slightly. But on the other hand, if you can work it could also stop your SSDI benefits for a period or forever depending upon the amount and nature of the work - only you and SSA know your situation. This pamphlet from SSA explains it.
Not a SSDI expert here but my understanding is that if you are approved for SSDI (disability) this then converts automatically to the Social Security old age (retirement) benefit, even if you haven't met the usual "10 years". In this case your retirement benefit stays the same as your disability benefit.
I have read this in the past and this morning my brief Google search led me to these three publications from the SSA, they all seem to indicate the treatment I described. The last doc (10153) states "When you reach full retirement age If you’re receiving Social Security disability benefits, your disability benefits automatically convert to retirement benefits, but the amount remains the same."