Need to Make a Vise

7075-T6 AL perhaps?

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?

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.

The Harbor Freight vises are made of cast iron. Not as rigid as steel. Look at Youngs modulus.

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

Ok... I'll start shopping around for some suitable pieces of 7075 for this project then.

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.

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 .

How much steel vs how much cast iron?

jsw

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.

I learn something every day, thanks.

[ ... ]

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.

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.

[ ... ]

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.

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.

I any more than there is

iable sets of design

choice for machine tools at

ers are economically feasible

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

A36 steel for the fundamental structure, and hardened O1 for the jaw inserts.

Have Fun! Rich

Or interchangeable inserts of brass, rubber, plastic, etc.

Hmmm... I thought various tool steels to begin with, but weight is a killer on mini machines.

Composite? ;-)

Cheers! Rich

Titanium? ;^)