Hey, anyone got a suggestion for a 16 foot long straightedge? I'd like to be able to use it for template routing, rather than jointing, the edges of long panels and boards. I'm thinking an aluminum extrusion would be the way to go. JP
Yup. Extrusions usually come in 20 ft lengths. I use a 1/4" x 6" x 12' for roughing. It is sold by the pound. Any industrial alloy place will have those. Usually made in Brazil. Get the 6" wide one, because you'll need to leave room for the saw motor to go by your clamps.
rHi Jay,
It all depends > Hey, anyone got a suggestion for a 16 foot long straightedge? I'd like
You can't get there from here.
You could fabricate a rigid weldment, then have it machined to get a straight edge, but then you would have to keep it in a controlled environment to maintain it.
About 15-20K will get you started.
Lew
In the world of TS Alignment tools, you're right, that isn't straight. As a saw guide, 1/32nd over a 16 foot length is probably sufficient... even 1/16th.
[snip]I use two. One is a run-of-the mill 6" x 1/4 x 12' extrusion and is within 1/32nd. Pinske (
Again, not to pick at nits, but straight is a relative term.
Also, because extrusions are under tension, if you machine one side, it'll warp like crazy...like reaction wood grown on the side of a hill. A local machine shop, which turns propellor shafts for ships, tuned mine to .002. Not that I needed it, but the guy was obsessional. What is more important, IMHO, is that the sides are parallel so when you flip the _fence_, you lose the error.
I could probably live with a 32nd over 16 feet. If I did get a 3/8 x 6 x 192" piece of aluminum that was staight, or had it milled straight, would it stay that way? I'm guessing it would be pretty whippy to move around. Maybe I could loosely mount a wooden reinforcement to it or something. Maybe coupling a pair of 8 footers together, and then having the whole thing milled would be the way to go. I dunno. I'm not too confident in the accuracy of manhandling a 16 foot, 24" wide plank over a jointer! JP
Oh ... now you want durability too? ;-)
When you carry / store that aluminum, never let the 'straight' edge face either up or down without support under it. All straightness will be but a memory the next time you try to use it.
You might consider getting a section of box channel iron and having it surface ground square in a machine shop with a big surface grinder. But I wouldn't. How would I get it back home and down into my basement sop without losing all that expensive straightness?
Me? If I was going this route I'd probably rip a couple widths off some
3/4" plywood and lap joint / dowel them, using a third section to line up the joint.But I'm new here so what do I know?
Bill
Thank you. Even a blind dog finds a bone once in a while.
There's one in Troy, MI (used it to grind robot platforms) and another in Farmington, MI. Bound to be others somewhere. Table moves, head is stationary. BIG BUCKS for a surface grinder that needed roughly 40 feet just to cycle back and forth. ;-)
I want the contract to scrape it back to true when the bedways wear. ;-)
We welded up the pads, machined, keyed and assembled them then had them ground as an assembly.
The place in Farmington was an 89 day shop I made 87 days in. They fired three mill hands, hired me, let me work for 87 days and then told me that I was incompetent.
They're probably right. If I had known how to handle that part of the trade I'd have recognized them for the type of shop they are and never have tried to stick it out there.
Franklin Forge, ISTR.
Bill
You would need to do your own research on the degree of accuracy, but these must be fairly accurate as they are used for highway department and high f-number concrete work. They go up to 24 feet.
True, but my quick test wasn't very rigorous. I don't know if the two pieces bent in oposite directions or the same direction (one less than the other). At 65 lbs each I was too lazy to try all the various combinations.
Very interesting! I never knew that these existed. I wonder how well that 0.005" spec holds up over time. Probably only good lying flat. Such a long piece would sag quite a bit on edge.
Absolutely. And, it's quite refreshing to hear someone say that. There are only degrees of accuracy, nothing is perfect.
Very true. Extrusions do have a lot of internal stress. Machining the thin edge of a wide piece isn't likely to cause nearly as much trouble as facing one of the broad sides. Still, it would need to be checked after machining. Anybody with a mill that can handle pieces 144" (or even 150"!) won't have any trouble doing the job right.
The local rate for raw aluminum extrusions is $3.99/lb. My 3/4" x 6" x
144" pieces cost me nearly $260 each at the local metals supply. I would expect a 3/8" piece to cost about $130, a 1/4" piece should be around $87. Given the machine work, the Pinske straight edges look like quite a bargain to me. It sounds like just the thing for the OP if he doesn't want to take his chances with a raw extrusion.Ed Bennett snipped-for-privacy@ts-aligner.com
You would need to handle it pretty carefully. It would have a tendency to sag if you stood it on edge. If you left it that way for too long it would definitely lose its shape. Best to store it lying flat. And, you'll need to be careful not to ding the edges. Aluminum is pretty soft. And, it would be best if it were kept in an environment with relatively stable temperatures.
Jo> I could probably live with a 32nd over 16 feet. If I did get a 3/8 x 6
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