Combining Two Tables with Date & Time

I suggest (starting with coilNumber/OrderNumber/Date & Time

• add a custom column that has a List of each Time at one minute interval during your time frame (1 hour before to 1 hour after)
• Do an innerJoin between the manual and the machine generated table

M Code

let

//Read in the two tables and set the data types
    Source = Excel.CurrentWorkbook(){[Name="machineTable"]}[Content],
    machineTable = Table.TransformColumnTypes(Source,{{"Date & Time", type datetime}, {"Swapped", type text}, {"Material", type text}},"en-DE"),

    Source2 = Excel.CurrentWorkbook(){[Name="manualTable"]}[Content],
    manualTable = Table.TransformColumnTypes(Source2,
        List.Zip({Table.ColumnNames(Source2),{Int64.Type,Int64.Type,DateTime.Type}}),"en-DE"),

//add a custom column with a list of the hour before to hour after at one minute intervals
// (if times are recorded to the second, could round the times first to the nearest minute,
//  or make the list at one second intervals)
    #"Added Custom" = Table.AddColumn(manualTable, "machineTime", 
        each List.DateTimes([#"Date & Time"]-#duration(0,1,0,0),
        120,
        #duration(0,0,1,0))),

//expand the list of minutes to rows
    #"Expanded allMinutes" = Table.ExpandListColumn(#"Added Custom", "machineTime"),

//Do an inner join with the machine generated table
    #"Join with Machine Table" = Table.NestedJoin(
        #"Expanded allMinutes","machineTime",machineTable,"Date & Time","joined",JoinKind.Inner),

//expand the Swapped and Material Rows from the joined table
//  and delete the machineTime Column
    #"Expanded joined" = Table.ExpandTableColumn(#"Join with Machine Table", "joined", {"Swapped", "Material"}, {"Swapped", "Material"}),
    #"Removed Columns" = Table.RemoveColumns(#"Expanded joined",{"machineTime"})
in
    #"Removed Columns"

Instead of a Join, you could instead add a filtered table in a custom column, where the filter is set to return anything from the machine table that is in the range of +/- one hour, but I suspect the join method will be faster.  If it is slow, then we can try the filter method

Filter Method Code

let

//Read in the two tables and set the data types
    Source = Excel.CurrentWorkbook(){[Name="machineTable"]}[Content],
    machineTable = Table.TransformColumnTypes(Source,{{"Date & Time", type datetime}, {"Swapped", type text}, {"Material", type text}},"en-DE"),

    Source2 = Excel.CurrentWorkbook(){[Name="manualTable"]}[Content],
    manualTable = Table.TransformColumnTypes(Source2,
        List.Zip({Table.ColumnNames(Source2),{Int64.Type,Int64.Type,DateTime.Type}}),"en-DE"),
    
    #"Added Custom" = Table.AddColumn(manualTable, "Custom", each 
        let 
            tStart = [#"Date & Time"]-#duration(0,1,0,0),
            tEnd = [#"Date & Time"] + #duration(0,1,0,0),
            mt = Table.SelectRows(machineTable, each 
                        ([#"Date & Time"]>=tStart) and ([#"Date & Time"]<=tEnd))
        in 
            mt),
    
    #"Expanded Custom" = Table.ExpandTableColumn(#"Added Custom", "Custom", 
        {"Swapped", "Material"}, {"Custom.Swapped", "Custom.Material"})
in
    #"Expanded Custom"