ITC for a Machine purchased for oil Mill

Yes, if it's for business purposes than you can take ITC on same...

Yes you can claim ITC of GST paid on purchase of machinery ( a Capital Goods ) since it is being used in the course or furtherance of business.

As per the Provision of Section 16(1) of the CGST Act 2017, ITC on Inputs, Input Services and Capital Goods "used in the course or furtherance of business" can be claimed ( subject to blocked credit under Section 17(5) of the CGST Act 2017 ).

Can we claim the entire credit in the same month or credit to be within 6 months. PL clarify with notification if any

You can claim entire ITC of Capital Goods in same month in which you purchased that Goods.

Can you please share the notification, if any

Refer Section 16 of CGST Act, 2017 read with section. 2(59) input and 2(19) Capital Goods definitions.