Machine Activty Log Table Design Issues

I have a number of checklists for my machinery

i have attached a couple of check sheets I have attached my table structure and an example of my check list in XLS format

i need to track which of these checks are being carried out each week..

I have created 3 tables so far, 1 called tLine and 1 called tMachine and 1 called tActivity

tLine
LineID (PK) - Autonumber
LineDescription - Text

Not sure if my use of PK is right, should it be the MachineDescription that i make the Key?

tMachine
MachineID (PK) - Autonumber
MachineDescription - Text

Not sure if my use of PK is right, should it be the MachineDescription that i make the Key?

tActivity

ActivityID - (PK) - Autonumber
Activity - Text
StdTime - Number

Not sure if my use of PK is right, should it be the MachineDescription that i make the Key?

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I am having a few issues i could really do with some help with please

Line 1 has a Filler and Capper
Line 2 has a Filler
Line 3 Has a Filler and a Capper

if i focus on the filler:

I have 5 checks to do on this however the Stdtime on activity 5 is different on Line 1 and Line 3 but the activity is the same.

if i focus on the capper:
this has 2 differnet activities and 1 activity which has the same description as the filler activity.

Problem 1:
Table Setup - not sure i am using the PK correctly etc, have read a few reference guides etc, but am struggling with this..

Problem 2:
how do i link the activitys to the machines and the machines to the Lines

Problem3:
how do i account for the same activity but different std times.

Problem 4:
I need to track these checks but i will try to get the table structure right first

I really would appreciate your help here please