lining up screw holes accurately and building a box?

[purpleroad]

How do you line up four screw holes like the example of this pump on the board so one doesn't go off to the side and pull the other off where it should go? Also how do make sure it isn't on 'the ****'?

If I was going to box all this gear in. Is it worth running some baton or 2 by 1 all the way around the inside then screw the ply sides to that?

 

[Tigercubrider]

The wood in the picture doesn't look straight although it could be just the wa lens?

Normally if you used 18mm ply for the base, you could do without battens to build four sides around it.
Easier if you use b&q or somebody with a bench/wall saw to get accurate cuts if you don't have the kit.

Just draw lines to ensure straight fixing and fit the screws slowly and diagonal , tightening up a bit at a time alternately , so you can correct any pulling to the side

 

[Deleted member 174758]

And pilot drill hole for the screws - that way they won't move

 

[purpleroad]

And pilot drill hole for the screws - that way they won't move

if it was masonry could you pilot hole this as well?

 

[Deleted member 174758]

In terms of timber a pilot hole means a hole which is big enough to accommodate the core part of the screw, i.e. the non-threaded bit, so for a 5.0mm screw I'd pilot something like 3.5 to 4mm in softwood and 3.8 to 4.2mm in hardwood. Masonry is a slightly different prospect because with masoinry yo are often drilling something like a 7mm hole to take a 7mm (brown) masonry plug and using a 5mm screw to fix with. In that case if you already have a piece of timber drilled with clearance holes for your fixings (a clearance hole is one the same size or slightly bigger thn your screw - for a 5mm screw that would mean something like a 6.0mm hole to give a bit of "wriggle room", but not so big that the head of the screw can pull through) the timber would be offered up to the wall, levelled or plumbed with a spirit level and the drill holes "spotted" through the hanging holes in the wood into the wall using a tool such as an awl. The timber is then removed from the wall and a drill with a masonry bit is used to drill the wall and the plugs are inserted. When your timber is offered up again it should be possible to push screws through the holes into the plugs and tighten up