"Composite" straight edges?

DMS said:
The Busch Precision site is interesting. If you want a laugh (or fright?), take a look at the prices on their camel backs. The small one is about 3x what I paid for my first car ;)

I also want to add that both the previous posters have good points. Aluminum will move more than cast iron (coefficent of thermal expansion for aluminum is about double that for CI), but cast iron will move too. The thing you need to avoid in use is differential heating (getting one side at a different temp than the other) as this will cause the item to warp. Camelbacks have additional structure to prevent this, so if you can integrate ribbing into your design, that would probably help keep things flat.

Personally I am a little skeptical of the Busch design with cast iron facing. It looks like the design is balanced (cast iron on both sides) which will help, but it seems like a bad idea in general to mix materials like that. Maybe that line of straightedges is not meant for machine restoration?
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I expect the secret sauce for their ironclad aluminum straightedges is either very precisely balanced thicknesses, or the glue has very specific quality’s (it allows the iron to slide a bit on the aluminum, maybe), or a combination of both to give consistent performance. I also expect a lot of attention is paid to process, i.e. making sure that the glue on both sides is laid down very consistently and to a uniform thickness. I also expect for the price and the fact that these come hand scraped that they are intended to be every bit as accurate and consistent as their cast iron predecessors. It's actualy a great idea, considering how heavy a long straightedge can be. I don't think this would work well on a camelback design, at least not without some serous engineering going into the shape and composition of the backplane.
 
The cats Meow is the ceramic ones that weigh next to nothing and are not as affected by temp gradients. They come in a variety of sizes and shapes and are not as expensive as the granite/Cast iron ones. Tim
 
I haven't runin to ceramic ones.... do you have a link by chance? I'm definitely curious!
 
Re: "Composite" straight edges?

The Mazak installation guy was telling me about them, they have one that they use for installations. I have not done any research beyond that yet. So I don't have a link. Tim

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The Mazak installation guy was telling me about them, they have one that they use for installations. I have not done any research beyond that yet. So I don't have a link. Tim
 
I got a chance to give this a try this weekend. Results were actually pretty promising overall. I cut out the basic shape and glued it up using JB Weld marine epoxy. (No particular reason, it was just what I had.) The tile saw I used was ones of those super cheap ones I got years ago, a simple plastic tub and a motor that spins a 4" diamond disc. I think it was $40-ish.

Overall it's 24x2" (Surface plate is 18x12)

So, after cooking overnight I got to playing around with it.... it didn't spot well at first, just the two ends. It was bowed.... but not by much as a .001 gauge wouldn't slip in under the middle.

I decided to go after it with a diamond hone and it actually cleaned up pretty quickly. I have some areas that "light spot" still, but for less then 2 hours total time investment and less than $20 (Way less for me as the granite tiles were leftovers.) I think this little venture will end up a winner. I may try minimize the light areas but really they are missing by tenths.

Pics attached, some showing the pattern I am at now. One problem is that it wrings to the surface plate and "sucks down" even with a very transparent layer of canode on there. That's a problem I can take, LOL. I may try Prussian blue next time, thinned with WD40.

Anyway..... only time will tell on stability. I'll post back next time I get a shot at it.

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This seems like an interesting idea, although I have no familiarity with marble or marble counter-tops. Is it easy to obtain pieces of this size? What is the weight? I didn't understand the earlier idea of using something like JB Weld against a surface plate -- if you were going to do that wouldn't you simply apply a layer of it to something like this?

I suppose granite counter-top edging or door threshold or window sill would probably be closer to our desired dimensions.

http://www.lowes.com/pd_484570-25497-G024BTHR436_0__?productId=50157548
(apparently Lowes doesn't really have these)
 
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davej said:
This seems like an interesting idea, although I have no familiarity with marble or marble counter-tops. Is it easy to obtain pieces of this size? What is the weight? I didn't understand the earlier idea of using something like JB Weld against a surface plate -- if you were going to do that wouldn't you simply apply a layer of it to something like this?

I suppose granite counter-top edging or door threshold or window sill would probably be closer to our desired dimensions.

http://www.lowes.com/pd_484570-25497-G024BTHR436_0__?productId=50157548
(apparently Lowes doesn't really have these)
Click to expand...
What you ought to try working with is a granite bathroom door lintel- in tile dept. glue a pair of
elegant drawer handles on the back. Diamond will let you touch up as necessary. ....BLJHB
 
I definitely would NOT use diamond on a straight edge that is made of material that can readily absorb some of them. Diamonds are FOREVER. I keep them strictly away from my machine ways.
 
Has anyone done any machining on an as cast camelback straightedge? I have one 18" long and another coming that is 24" long. Before I screwed them up I thought I would ask if any of you had Machined them and then scraped them or were they Blanchard ground? Any ideas of what the cost for Blanchard grind would run. I checked with one place here in Houston and they said $600.
Any thoughts would be appreciated.
 
I machined and started scraping a square, but have not completed it yet. It was already annealed, and I rung it a few times with a rubber mallet as I was scraping it to help relive and stress and promote movement. It seemed to be settling down pretty well before I wound up moving to another project. The 600 quote sounds like a "we're not interested in the job" quote. I would think you should be able to get that done for 200 or so. Why are you set on Blanchard grinding? Surface grinding would likely be cheaper and easier to find someone to do it. If I were going to scrape it, I wouldn't bother with the grinding.
 
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