Jaw Lift Description

[TechWriter]

Hey Everyone and thank you for your help in advance,

I'm trying to write a manual for our vises. I've run into a problem of explaining jaw lift. Every vise has jaw lift, but I want to accurately define it to help explain why we take the steps that we do to counter act it in the shop. I've tried to explain it scientifically, but it does not quite read the right way. Does anybody know where I can find a textbook definition of jaw lift? Everybody knows jaw lift happens, but it seems to be an abstract idea. Other than home grown knowledge of it, how do they teach it classically or in school?

Thank you in advance

 

[DDoug]

Please provide website linky to your customer.

 

[TechWriter]

website link to who? This is for training inside the shop with new machinist to start a apprenticeship program

 

[Insert]

Jaw has a small amount of clearance so that it can slide, when you squeeze something above the centerline of the jaw, the jaw rocks back, and since you are tightening it forward, it pushes the part up.

If you are trying to teach it, and they don't understand that:
1. Place a part on parallels, tighten jaw and show how the parallel becomes loose.
2. Put an indicator on a jaw while tightening it, and watch it move.

 

[TechWriter]

We are making a video in conjunction with this description. Would you happen to have a link to a book or training manual that has a description of this? The aim for it here is to have a college level textbook description that introduces the idea and defines the problem.

 

[TechWriter]

and thank you, that is a pretty good description

 

[Larry Dickman]

a college level textbook that explains jaw lift? WTF

 

[litlerob1]

"something, something Mechanical displacement something, something Unit of equal or greater Mass, something, something squishy happens, something, something lack of Inertia something."

If you look, I'm sure there's a video showing jaw lift. Or just do it real time. You are taking more time posting on this board than it would take to stick an Indicator with a Mag Base and tighten something, something.

 

[DDoug]

"something, something Mechanical displacement something, something Unit of equal or greater Mass, something, something squishy happens, something, something lack of Inertia something."

If you look, I'm sure there's a video showing jaw lift. Or just do it real time. You are taking more time posting on this board than it would take to stick an Indicator with a Mag Base and tighten something, something.

Op is writing "Ad Copy" literature for chinese copy of Kurt vice.

Why not just copy the literature as well ?

 

[litlerob1]

Ohhh. Gotta find "content". Got it.

 

[TeachMePlease]

Op is writing "Ad Copy" literature for chinese copy of Kurt vice.

Why not just copy the literature as well ?

Doug... Seriously, get your meds adjusted... He said he's trying to start an apprenticeship program in house. Nowhere is there even a hint of him knocking off a vise, or spamming, or collecting content from us.

Your "spammer" attacks have been getting worse and worse lately. Is it still cold up there? Not enough sun? Seasonal Affective Disorder?

 

[DDoug]

Doug... Seriously, get your meds adjusted... He said he's trying to start an apprenticeship program in house. Nowhere is there even a hint of him knocking off a vise, or spamming, or collecting content from us.

Your "spammer" attacks have been getting worse and worse lately. Is it still cold up there? Not enough sun? Seasonal Affective Disorder?

He has to re-write the book ?

Teachers are getting paid to write text books now ?

Don't believe everything that is written and locations.

Also, I don't see you attacking "Machtool".....

so please, try using the "ignore" function....it works nicely.

 

[TeachMePlease]

He has to re-write the book ?

Teachers are getting paid to write text books now ?

Don't believe everything that is written and locations.

Also, I don't see you attacking "Machtool".....

so please, try using the "ignore" function....it works nicely.

I don't want to ignore you. I generally like your posts, and you share a lot of stuff that I can learn from. I just think you're a bit quick on the "SPAM" button lately... Like, worse than usual.

 

[Winterfalke]

Everybody knows jaw lift happens, but it seems to be an abstract idea.

It's a lever, the most basic machine known to science. You apply force through the screw to one point (the input force), you have a load at the workpiece you are machining (the load), and it pivots around the screw or the lower ways connection (the fulcrum). It only differs depending on the position of the workpiece and the type of vice.

 

[jhruska]

Start with how to mill a part. If you leave this out anything you say is a waste of time.
Finished requirements are parallel faces that are perpendicular to the top and bottom.

Rough stock and any material without parallel faces will never seat on parallels(four points) in a vise.
One face will generally be parallel to a vise jaw face and the second face will be at an angle to the second jaw.
Usually but not always, only one parallel will be snug. And this depends on the type of vise and how loose it is.
Kurt vises and the knock-offs have a slight adjustment to reduce float of the moveable jaw.

Best test of a part that is square and parallel:
Place the part on parallels in a clean vise. Cut paper tabs and place them at four points between the part and the parallels.
Snug the vise.
Use the deadblow to seat the part. That means only enough force to seat the part. Hit it hard and the part will rebound up off the parallels.
Check the four tabs. If each one is tight the part is seated correctly.

That's the bare bones of it.
Factors;
The vise jaws need to be ground parallel.
The height of the part and how deep into the vise it is placed.
Clamping pressure is critical. Often the vise is over tightened. Put an indicator against the back of the vise(fixed jaw) and watch it move!
Using one or two hold-downs.
Substitute a bar of tpg instead of a hold-down.

All of the above is gibberish if the proper sequence for milling a square part is not performed.
Seating a part, "vise lift" is just part of knowing what proper vise work is.
John

 

[TechWriter]

John,
Alrite I think I'll go with that or at least a combination of that and some input between our machinist. What are the paper tabs for? Basically the explanation I got for milling soft jaws was that you seat a shim in between the jaws, tighten to operating torque, mill out the profile of the part, take out the shim, then with the same torque seat your part in the soft jaws profile. Doing this will ensure that the parallelism and the jaw lift is constant and a low variation between parts. I don't see where the paper tabs come into play?

 

[TechWriter]

Winter,
I know its a lever and I tried to break it into mechanical engineering terms, but like I said it didnt read right and when we did a test on students they didn't capture the actual idea of it. That's why I was looking for a book in use that explains it, to see where they split from mechanical engineering explanations to simpler terms.

 

[litlerob1]

Winter,
I know its a lever and I tried to break it into mechanical engineering terms, but like I said it didnt read right and when we did a test on students they didn't capture the actual idea of it. That's why I was looking for a book in use that explains it, to see where they split from mechanical engineering explanations to simpler terms.

Good Lord, just make them Mill some parts. Make a PB&J sandwich and smash it, then ask them why they can't taste the PB&J.

R

 

[jhruska]

I don't see where the paper tabs come into play?

ex:
Stock dimensions 2" x 3" x 5"
The stock rests on two precision parallels ground and hardened with dimensions 1/8" x 1" x 6"
Stock has been pre-machined and deburred and is ready for second operation.

How do you know when the stock sits flat on the parallels? Without knowing the thickness of the part or using an indicator?
finger it out

 

[TechWriter]

*Update*
I found a pretty good explanation in a physics book from the 50's. I will post the answer when I have it all typed out and polished for anybody that is following it for an answer. Thank you for your help, mostly John.