Need to Make a Vise

I have been bouncing around an idea for a specialty screw less vise. I've got the shape and design figured out, and I think I have the machine
processes to make it figured out. I'm still struggling with the exact best way to drill the pin holes, but that's not my hold up. I'm trying to decided what material to make it out of. The cheap steel that the Harbor freight vises are cast from machines nicely, but I don't know what it is, and I'm not sure it would be rigid enough. I could do it with aluminum easily enough, but I really don't think that would work very well. If the design works I can see myself using this vise for many many years, and even custom designing it for other machines. It doesn't have to withstand tons of holding force, but it should be able to handle upto 100 lbs of holding force with minimal distortion. I know, make it heavy, but the idea is really geared towards mini machines, so heavy really is not an option. I suspect a 75 lb vise would cause or contribute to motor stalling on some of these machines.
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Bob La Londe wrote:

7075-T6 AL perhaps?
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I thought about 7075, but was thinking a little harder than T6. You think T6 would do the trick?
I know they use 7075 for stabilizer links and all kinds of stuff on serious off road jeeps and rock crawlers. Its strong and machines well I have heard, but what about elasticity? Isn't the flex part of what makes it so strong for those applications?
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Bob La Londe wrote:

You might have flex in a foot long piece under 1,000# loads, but I don't think you will have any measurable flex in a small 100# load vise application.
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Ok... I'll start shopping around for some suitable pieces of 7075 for this project then.
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The Harbor Freight vises are made of cast iron. Not as rigid as steel. Look at Youngs modulus.
http://www.engineeringtoolbox.com/young-modulus-d_773.html
Steel is about three times more rigid than aluminum. Cast iron is a bit more rigid than aluminum, but less than half as rigid as steel.
Dan
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wrote:

Puzzled! Why do they make lathes out of cast iron? When I was in the market for a wood lathe I was definitely advised to avoid steel construction and look for cast iron body because of better rigidity.
--
Michael Koblic,
Campbell River, BC
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Michael Koblic wrote:

My understanding is that it's not the regidity but the vibration-damping properties of CI that make it more desirable for lathe and other machinery beds/frames .
--
Snag
Wannabe Machinist
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How much steel vs how much cast iron?
jsw
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wrote:

Cast iron is, or was, a lot cheaper than steel and lends itself to casting. Steel is a bugger to cast in detailed shapes.
Cast iron damps vibration -- the cheaper and weaker the cast iron, the better it damps. Steel rings like a bell.
Cast iron is easier to scrape.
Cast iron makes better bearing surfaces with simple lubrication.
It's true that steel is around 20% - 50% more rigid for a given section, but that's easily overcome with cast iron machine tool construction by the use of ribs, fillets, varying section thicknesses, etc.
--
Ed Huntress



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wrote:

I learn something every day, thanks.
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    [ ... ]

    Steel rings.
    Cast iron damps vibration.
    When you're turning, you don't want the vibration building up to chatter.
    If they used steel, they probably used less metal as well (steel costs more than cast iron, and steel would likely be built up rather than cast to near final shape and just the bearing surfaces and such machined smooth.
    Enjoy,         DoN.
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Good answer, Don. There is no specific superiority between steel and CI any more than there is between other metals. Each has its place within complex and highly variable sets of design parameters. In terms of evolution, CI became the dominant material of choice for machine tools at the dawn of the Industrial age. Now, composites of iron, steel and others are economically feasible but CI is still the machine tool choice considering all factors.
Bob Swinney
[ ... ]

Steel rings.
Cast iron damps vibration.
When you're turning, you don't want the vibration building up to chatter.
If they used steel, they probably used less metal as well (steel costs more than cast iron, and steel would likely be built up rather than cast to near final shape and just the bearing surfaces and such machined smooth.
Enjoy, DoN.
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In the 70's I assembled custom machinery for the auto industry. When they needed a difficult shape like a large rotating table they had it cast in aluminum, but I never saw any iron castings. All framework was welded from steel with any linear bearings bolted on, ie Thompson rod. It wasn't for lack of foundries either, NH had Hitchiner, Pine Tree Castings and plenty of small specialty ones.
jsw
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DoN. Nichols wrote:

Hmm. Good point. The natural frequency of vibration depends on both the spring constant and the mass. Cast iron has lower rigidity (lower spring constant) and if they use more of it, the resulting frequency will be lower. This is in addition to the damping.
Something to think about.
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On Sun, 05 Sep 2010 11:13:04 -0700, Bob La Londe wrote:

A36 steel for the fundamental structure, and hardened O1 for the jaw inserts.
Have Fun! Rich
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Rich Grise wrote:

Or interchangeable inserts of brass, rubber, plastic, etc.
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Hmmm... I thought various tool steels to begin with, but weight is a killer on mini machines.
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On Wed, 08 Sep 2010 21:04:35 -0700, Bob La Londe wrote:

Composite? ;-)
Cheers! Rich
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wrote in message

Titanium? ;^)
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