Good/Reliable straight edge?

[promhandicam]

Using my 2800mm straight edge yesterday to align the rollers with my planer bed :wink:

. . . .there are few, if not any, straight edges in nature...bosshogg

I found this out first hand working in a village in Zaire (as was) over 20 years ago. The majority of people, including those I employed doing maintenance work, were unconcerned if things were straight or square as long as they (sort of) fitted. As a mechanical engineer by training it was very frustrating at times until I read an article that pointed out that from birth, western babies constantly see straight lines and right angles - the suspended ceiling tiles in the delivery room in many cases! However children in rural parts of developing countries saw nothing, naturally, that was either straight or square unless living on the coast where they could see the horizon. Once I realised this it became a little bit less frustrating - but not much!

Steve

 

[bosshogg]

Steve, the horizon is anything but straight, this has been known way back to Pythagoras's days...bosshogg :!:

The most incomprehensible thing about the world is that it is at all comprehensible. 8)

 

[xy mosian]

I think steve must be 'flat earther' . (Insert amused grin here.)

xy

 

[promhandicam]

Steve, the horizon is anything but straight, this has been known way back to Pythagoras's days...bosshogg :!:

Straight enough for a carpenter :wink: and a lot straighter than a palm tree or a mud hut.

 

[imageel]

Hi,
An interesting thread - how straight is straight?, part of the answer depends on whether it is fit for purpose, however when it comes to say adjusting planer outfeed tables, the end purpose is undefined or unknown, so in that case a higher level of accuracy is probably required.
I've been making a woodwork bench, and decided to use the sledge method with a router to flatten it.
I already had a set of cheapo Screwfix levels, one of which was 1.8m long, and so bought another single 1.8m for around £30 and to check placed these together and could not see any discernable (to my eyes) light between them - so for my purposes over that length they were straight enough.
After clamping these either side of the worktop and sledge routing it, the worktop is now the same contour as the level(s) again measured by laying both levels along the length of the top and looking for any light gaps.

Now I haven't finished scraping the table, but to my eyes it is flat - perhaps not flat enough if I was floating glass across it to make mirrors, but for the joinery work I intend using it for it is 'fit for purpose'.
Of course in 6 months time the wood may well move slightly.... ;-)
Cheers

 

[Jacob]

......
After clamping these either side of the worktop .....

Oh dear! Quickest way to bend them, even if the bench was flat to start with!
In any case the need for a very flat bench is somewhat over rated IMHO. Sufficient to lay your levels over to roughly highlight any high points/areas and remove them, if you can be bothered. Not necessary to get down to all the low points (within reason) as most workpieces will span them anyway.

 

[bugbear]

In any case the need for a very flat bench is somewhat over rated IMHO.

Only needed for planing thin stock, and if you ever use your bench a reference surface.

if you only plane small, thin stock, and don't want to flatten your entire bench, you can get by with a "planing board"

But a flat bench top is a nice thing to have.

BugBear