I have 2 hard disks(2.5") 1 TB and 320GB.
ReadWrite head of 1TB Hdd is damaged.. so I am trying to put the platters of 1 TB hdd to 320 GB hdd..

I don't have exact screwdrivers to open it. Could any one please help me to specify the required type and size of screwdriver ?

Judging by what's written above I would say, it's gonna end up with a disaster, and you are gonna destroy your data for good, without the possibility of recovering.
I strongly recommend - if the data is valuable to you - stop what you doing and send it to a data recovery PRO
I know its not the answer you hoped for, but its the most honest reply I could have think off

if despite what I have said you insist to proceed then you need a torx screwdriver

Oh oh... I can see tears from down here...

Seriously, if you have to ask these questions, DON'T DO IT.
This is wrong in so many levels, it will only end up one way.

You DON'T move the platters when the heads go bad.

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WD Trusted Partners
http://www.northwind.gr
SandForce SSD Recovery
Ransomware Reverse Engineering - NoMoreRansom! partners

+1

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Data Recovery Pakistan

As already mentioned...this will not work. Your only option is to seek professional assistance before you completely kill any chance of recovery.

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Luke
RAID Data Recovery

+1 to every response above.

Sadly though, threads like this only lead to more people coming to the conclusion that we in the data recovery business are just keeping secrets to hoard mass amounts of money from people.

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Data Medics - Hard Drive, SSD, and RAID Data Recovery Service Company

i think this is some guy who just wants to spam the section of the forum

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HddSurgery - Professional Data Recovery Tools

Makes sense, he haven't logged in ever since to read the answers

Ask your client to supply the original screwdriver that came with the drive..

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Digitalsupport Data Recovery
https://digitalsupport.dk

Hello,
Send Me Your Address ,I will send you a Screwdriver Free ,Then You Can Transfer The Platters From 1TB To 320Gb Or Do Whatever .Are You Planning To Start Data Recovery As Business Or This is Your Personal Drive .

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Regards
Amarbir S Dhillon , Chandigarh Data Recovery Labs
Logical,Semi Physical And Physical Data Recovery
Website-> http://www.chandigarhdatarecovery.com