Straight edges.

[garywayne]

Can someone tell me what the excepted tolerance is for a straight edge.

I have just seen some on the D&M site, (the maker is Maun). The tolerance is .001 to the length of the straight edge.

These particular ones sound iffy to me, due to the fact that the .001 is to the length, which varies. eg, .001 to the length of a 12" straight edge, and also to the length of a 48" one. I am assuming that the .001 is thousandths of an inch.

If all is well I shall go ahead and order a couple. Unless you can recommend somewhere else.

Waiting for your answers with baited breath.

 

[RogerS]

Certainly look the biz. What are you looking to use it for? If setting up infeed/outfeed tables on your planer then have you thought about how you're going to keep it standing up on edge while hands two and three are adjusting the tables?

If so then believe it or not you can get that sort of accuracy with common-or-garden spirit levels which is what I use for setting up my planer. It's not used for anything else but it does stand on edge by itself :lol:

 

[Paul Chapman]

I have one of the Veritas aluminium straight edges and that stands up on its own very well without toppling over http://www.brimarc.com/home.php3?page=p ... c=C_106_42 It's accurate enough for what I want it for.

Cheers :wink:

Paul

 

[woodbloke]

Gary - the Maun straight edge I use is accurate to 0.01% of the length, not 0.001 :? - Rob

 

[garywayne]

Thank you all for your replies.

Roger said:-

What are you looking to use it for?

I thought I would use it as a straight edge to see if things where straight. :lol: :wink:
I was thinking of using it to check anything that needed to be straight or flat. Including Table saw table, and to check the planner/thicknesser when I have decided which one to get.

Roger said:-

you can get that sort of accuracy with common-or-garden spirit levels which is what I use for setting up my planer.

How do you know the accuracy of the spirit level?

Rob said:-

Gary - the Maun straight edge I use is accurate to 0.01% of the length, not 0.001

Rob, I could only repeat what was stated on the D&M web site. Which is, .001 to the length.
They do not state, weather percentage, thousandths of an inch, or whatever.

 

[woodbloke]

Gary - I've had a quick trawl thru' the D&M site and had a look at the Maun straight edges. I have a pair of the 1701 straight edges and the tolerance stamped onto the rule is ...'0.01% of length', so my guess is that there's a mistake in the D&M info. Fwiw, they're respectable straight edges for general workshop use at a reasonable price - Rob

 

[garywayne]

Cheers Rob. In that case I'll get a couple.

 

[Anonymous]

Straight edges are graded to BS5204-2

Generally, the cheaper ones i.e. less than £50 are not manufactured to any british standard as far as I am aware.

BS5204-2 Grade A are pretty expensive. Moore and Wright are recognized as one of the top manufacturers

Mine (or more accurately, the one I borrow from work) came from Farnell and is 24" M&W grade A. These are pretty expensive though and many engineering companies will use grade B.

Farnell also sell Grade B edges made by Roebuck for reasonable suns

Go to http://www.farnell.co.uk and do a search for straight edge


The following is from Moore and Wright and shows the tolerances which for a 24" are 1/4 thou for grade A and half a thou for grade B over the full length

 

[garywayne]

Thanks Tony. Thats real handy.

 

[RogerS]

Gary

I took my feeler gauges with me and went through the stock. Laid one on top of another and tried to get my thinnest feeler gauges into the gap. I couldn't. Swapped the level round the other way just to be sure and agin couldn't get the feeler gauge in.

 

[garywayne]

Thanks Roger. Good advice.

 

[Anonymous]

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[ivan]

I'd wondered where to get a decent straight edge, the Roebuck ones are made to DIN874, either /2 general purpose or /1 grade B.

Had a google round but the best info I can find on the DIN standard gives the 'tolerance' for a 1m st. edge as either 33 (gp), or 21 (gradeB) micrometres. The grade B item is also stiffer. I presume 33 um is 0.000033m or 0.033mm. Tony, or anyone, do you know if this is the total error, or is it +/- 0.033mm ?

Presumably the Maun has a 'tolerance' of 0.0048", ie about +/- 2and a half thou

I had the same trouble trying to identify the right DIN standard when buying gogggles to use at the grinder; you'd think the info was a state secret!

 

[Chris Knight]

Making your own straightedge is described here http://home.comcast.net/~jaswensen/mach ... _edge.html

 

[Anonymous]

Making your own straightedge is described here http://home.comcast.net/~jaswensen/mach ... _edge.html

That's more or less what I was trying to describe above. You only need to make 2 however if you check side by side, which Swensen misses. 2 for woodworking purposes at any rate.
Otherwise the process is the same - eliminating the differences, or as he calls it "averaging".
cheers
Jacob