Straight edge question

[Tom Walz]

Thank you all for the kind words.

I appreciate them but they are more than a bit embarrassing particularly since woodpeckers wants to donate the straight edge.

I sort of feel unfairly singled out since many of you also do a great deal to make the world a better place. In my estimation, many of you do a great deal more than I ever could. I hope this is not out of line, but it seems to me that a great number of you under-appreciate the good you do by your participation here. There is a huge amount of knowledge freely shared here. What is more is that it is a great portion of it seems to be very well written, deeply thought out and presented in a very dignified, well mannered way.

Tom

[hank dekeyser]

plus one on using a level - They're tough and durable, don't bend (easily) and you probably already have at least one. I dont understand why anyone would "need" to have a "good" straight edge for woodworking if you have a good quality level on hand. I have a corral of Stabila"s and a handful of the aluminum I-beam style. Aside from setting up my endmill, I have yet to have the "need" for anything else. A good level and a set of feeler gauges is all I ever use. For a T-square I have a sheetrock square I modified that is every bit as accurate as anything you can buy -period- Pretty sweet offer on the freebie , cant pass that up. as usual -my 2 cents

[Jerome Hanby]

I've got a 4' Stanley fatmax level. It has "machined" edges. maybe I'm just a snob, but I can't imagine that it's as perfectly flat as a quality straight edge. If I'm checking the edge of a board or the face of a piece of plywood, then no worries on my part using the level. But in this case, I'm looking for something to setup shop equipment.

The T-Squares are really more of a want than a need. They look cool, have "Incra" style holes to fit mechanical pencil tips for drawing lines, and they are red! My wife bought me a drywall square for Christmas one year. I finally remembered it, found it, and wouldn't you know the darn thing isn't quite long (deep?) enough to reach across a four foot sheet of plywood! That seems pretty stupid to me, seems like that's the whole reason for having the thing! I suspect that there are other models/brands out there that are a bit longer. I'm thinking 50" would be about perfect. That would cover the entire width of a sheet of MDF with a little to spare.

[Gary Kman]

I was picking up some metal at a metal fab shop and asked just how straight their 10' shear cut. Shop foreman said really straight for strips at least 3" wide. He sheared me a piece of 12 ga 3" wide and about 7' long. I drilled a hole in one end to hang it up and shot a coat of urethane on it the next time I was spraying and have an excellent strait edge for a few bucks to add to my 24" and 48" store boughts.

[Jerome Hanby]

If that were a little thicker it's stand up by itself no problem. Sounds like a good solution.

[Rick Moyer]

I was picking up some metal at a metal fab shop and asked just how straight their 10' shear cut. Shop foreman said really straight for strips at least 3" wide. He sheared me a piece of 12 ga 3" wide and about 7' long. I drilled a hole in one end to hang it up and shot a coat of urethane on it the next time I was spraying and have an excellent strait edge for a few bucks to add to my 24" and 48" store boughts.

But what does "really straight" REALLY mean? May or may not be within whatever tollerance you expect. I think that's the point of these straight edges, a reference.

On another note, I may be totally wrong here and I don't wish to speak for Tom Walz, but I took his statement of "pick one and we will send it to you. No obligation." to mean 'we'll send you whatever you want and you can try it out, pay for it if you like it or send it back'. maybe it WAS offered as a freebie but I didn't take it that way, as some of you did.

[Van Huskey]

But what does "really straight" REALLY mean? May or may not be within whatever tollerance you expect. I think that's the point of these straight edges, a reference.

On another note, I may be totally wrong here and I don't wish to speak for Tom Walz, but I took his statement of "pick one and we will send it to you. No obligation." to mean 'we'll send you whatever you want and you can try it out, pay for it if you like it or send it back'. maybe it WAS offered as a freebie but I didn't take it that way, as some of you did.

I thought the same thing until I read Tom's last post and the word "donate".

[Mort Stevens]

I've got a 4' Stanley fatmax level. It has "machined" edges. maybe I'm just a snob, but I can't imagine that it's as perfectly flat as a quality straight edge.

A quick test; put it on a flat surface and draw a line end to end, then flip it end for end and draw a second line with a hairs separation between them- if the two lines are parallel then you can be assured that it's reasonably straight.

[Guy Belleman]

I have several straight edges, a couple in the tool box drawer and several hanging on the wall. For what I do, it seems that I most often use the 24". I just don't use the 32", 48" and 6" that often, not that they are useful when needed.

[Gary Kman]

But what does "really straight" REALLY mean? May or may not be within whatever tollerance you expect. I think that's the point of these straight edges, a reference.

Easy to compare edge to edge with the 4' (However straight they made it). It's easily straight within the width of the narrowest pencil line I can draw or I wouldn't call it a straight edge. What kind of tolerance do we need working with a material that is guaranteed to change dimensions with a slight change in humidity overnight? At the other end of the scale a visible movement in the bubble in my machinist level indicates a change in angle of about 3/8" in a mile. I sure don't want to waste my time trying to use it woodworking. Precision needs to match the work. More is not better.

[James White]

I thought the op wanted the strait edge for setting up and tuning machines. Tuning machines and woodworking are two different things. So If you use a strait edge of unknown straightness (a level) and are trying to tune your jointer. Then for some reason you are not getting things to work properly. You need to ask yourself. Is there something wrong with the machine? Is it me? Maybe my straightedge is off? With a known straightedge you eliminate one possibility.

Back to woodworking. How much snipe is acceptable .005". Then you join those two edges and now you have a .010" gap. That is visible. Possibly can lead to a failed glue joint. How about a miter. How many thousands gap is acceptable? A table saw fence .002" out of parallel toward the blade. Leads to burnt wood and increased chance of a kick back. Yes wood moves. But that doesn't mean that you can have a tolerance equal to the amount that wood moves. Having precision tools only allows you to get to those tolerances easier. They are not needed. You can do it the old way of trial and error. Or you can use modern tools to get there that much faster and eliminate variables.

James

[ian maybury]

I'm only getting into machine set up now, but have a feeling that a long 'precision' straight edge is a contradiction in terms - that unless it's got a very large section a long edge is going to flex so much as to make talk of a few thou straightness fairly irrelevant. Thermal and manufacturing caused stresses may play a part too.

There's maybe differences between needing a straight(ish) edge for marking out (accuracy to the thickness of a pencil line), and the sort of precision item one might use for checking machine tables, alignments and the like. (accuracy to maybe a thou) A precision level can be useful too.

I bought a shortish steel precision straight edge from Woodpeckers a few years ago which i use for machines, and a long aluminium spirit level which gets used for marking out along with a couple of Festool saw rails and a 10ft length of straight hardwood which i've had for years.

The steel straight edge could probably be a bit longer, but the thinking is that it covers most of the average machine table, and that longer surfaces can be handled by packing one or more ends until it's level (i've used brass shim stock) and measuring the gap underneath with feeler gauges, and then bridging on by another 24in or as required. The level can be useful to check for sagging in e.g. the long level in situations where that may happen.

I sometimes pull a fine line to confirm a straight line when marking out long cuts on sheet material....

ian

[Jerome Hanby]

While reading up on straight edges, I saw that the longer Starrett models have two points marked on them that must be supported to prevent sag from introducing inaccuracy, so the point about long and precision seems to be recognized by what I think it's safe to call the gold standard of precision. Buy have you seen that Woodpecker model? Man, it's pretty <g>

[ian maybury]

I've just had a look Jerome, very bling. Bear in mind though that there's a lot of different worlds where precision is concerned. High precision stuff used in toolmaking and the like gets incredibly precise and expensive - these guys do treated cast iron reference edges accurate to .0005in over the full 36in length. The Starret ground steel edges claim about .0002in per ft - pretty similar. Against that the Woodpecker items are aluminium and claim only .001/ft - five times less accurate and subject to wear - but fine for the purpose they are intended for.

Lee Valley against that do some nice heat treated and ground steel items of apparently very similar quality to the Starrett for pretty similar money to the Woodpeckers: http://www.leevalley.com/us/wood/pag...at=1,240,45313

ian

[Jerome Hanby]

I'm not ruling out buying one of those steel edges from LV. If they had them longer than 36", I might have done that from the get go. For now, I'm going to check out what I've got coming and make any additional decisions from there. Realistically I need something straighter than my long yellow rule from the Borg but can't imagine I need anywhere Starrett levels of precision to setup my 5 or 6 decade old cast iron saw and jointer and other slightly newer gizmos...