Wood Size / Strength

[DoubleDutch1962]

Apologies for maybe a very basic question but started my woodworking hobby and for the time being, focussed on storage / rough woodworking projects for the garage until I gain more confidence. My question: how do you determine the size/strength of wood to use?

E.g. I'm making a workbench from plywood/pine timber which has two plywood sides. 18mm ply seems too thick, but is 12mm strong enough? What thickness to use for my drawer (sides) and what size of pine shall I use (22x75mm??) for the corner posts and how many wheels does it need to avoid sagging?

Also made a trolley for my wood with some swivel wheels but given the size of the trolley (1220 x 660 x 18mm) should I put the swivel wheels closer to the centre to avoid the trolley base sagging?
Is there (easy) science to this or is it just guesswork?

 

[Terry - Somerset]

There is a science to it, but I suspect most forum members would have some sort of intuitive grasp of size and type of timber for different applications.

From the above I would make a few observations:

• make the workbench on the tough side - it will get stressed with hammers and weight. I would go with 18mm sides, legs ideally 75x50 minimum. Make sure it is braced so that it remains "square" - the joints between side and top need more than just screw and glue.
• drawer sides can be 9mm - alternatively use something like this Metal drawer sides. They make construction quick and accurate it you have had little practice
• the trolley it will be more stable with the wheels at the corners. To avoid sag it would be worth reinforcing the base with a (say) two lengths of 50x25 softwood screwed and glued below the base for the full length.

 

[Dee J]

Apologies for maybe a very basic question but started my woodworking hobby and for the time being, focussed on storage / rough woodworking projects for the garage until I gain more confidence. My question: how do you determine the size/strength of wood to use?

E.g. I'm making a workbench from plywood/pine timber which has two plywood sides. 18mm ply seems too thick, but is 12mm strong enough? What thickness to use for my drawer (sides) and what size of pine shall I use (22x75mm??) for the corner posts and how many wheels does it need to avoid sagging?

Also made a trolley for my wood with some swivel wheels but given the size of the trolley (1220 x 660 x 18mm) should I put the swivel wheels closer to the centre to avoid the trolley base sagging?
Is there (easy) science to this or is it just guesswork?

It's not so much guesswork, it's observation and experience. We're surrounded by furniture, buildings, structures etc all the time. Look at the scale and proportions. Observe how design choices can strengthen a structure. It's all learning.

 

[DoubleDutch1962]

There is a science to it, but I suspect most forum members would have some sort of intuitive grasp of size and type of timber for different applications.

From the above I would make a few observations:

• make the workbench on the tough side - it will get stressed with hammers and weight. I would go with 18mm sides, legs ideally 75x50 minimum. Make sure it is braced so that it remains "square" - the joints between side and top need more than just screw and glue.
• drawer sides can be 9mm - alternatively use something like this Metal drawer sides. They make construction quick and accurate it you have had little practice
• the trolley it will be more stable with the wheels at the corners. To avoid sag it would be worth reinforcing the base with a (say) two lengths of 50x25 softwood screwed and glued below the base for the full length.

Thank you!

 

[Fitzroy]

I've often noticed many woodworkers go through a 'Fred Flintstone phase', I certainly did! My first garden furniture had a 70mm thick top, it has warped incredibly over the last 5/6 years and pulled the whole frame out of alignment. Thankfully thick enough that in the next few years I plan to disassemble and remake.

As per @Dee J a lot of my design comes from observation and copying items around me, combined with a bit of engineering understanding, eg thin stuff used in tension is effective,drawer bottoms as an example. I've found I'm also now quite focused on making things as 'light' as possible, and some testing/prototyping is often useful.

I've a couple of old woodworking books that have some drawings in them of typical furniture items which are also a useful starting point.

Fitz.

 

[Jameshow]

It's not so much guesswork, it's observation and experience. We're surrounded by furniture, buildings, structures etc all the time. Look at the scale and proportions. Observe how design choices can strengthen a structure. It's all learning.

When I got back into making stuff I looked a other people's designs on the post a pic of last thing you have made.
Also look at the likes of Paul sellars projects.
Anna white has loads of DIY designs which you will probably make you think I can do better than that!

Finally good woodworking books, like those of fine woodworking, on furniture design / cabinet making.

 

[Bingy man]

A lot of what I make is over engineered or as @Fitzroy say ( fred flinstone ) but I look at it simply- will it break if I stand on it ..posted pics of a bed I made for my son on ( post a pick of the last thing you made thread ) and I used mainly 2 x 4 . My son is a big Ladd . When I’d completed it and worse carried it to his moms house 5 mins away I did think that 2 x 2 would have probably been ok but I don’t want to make another . Also the 2 x 4 was on offer ..the unsupported sections of my kitchen worktop sit on 2 x 2 but 2 x 1 would have been ok .. you will get a feel for it but it all depends on what you are making, it’s intended purpose, the look , and where it will be displayed. I quite like the industrial look , others will prefer something a little more contemporary . For myself as long as it’s fit for purpose then its all good..