minimum amount of material in vise

[charlie_luna]

i have a program where i am running the mill at 1200 rpm and 33.6 inches per minute. what would you recommend the minimum amount of material to be clamped by the vise at this speed/feed rate? this is a cnc mill.

[br1]

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[Delw]

you left too much stuff out the question,it can never be answered with anything other than " Just enough to hold it securely"

[charlie_luna]

what else do i need to provide? the material is 6061 aluminum. it's being ran on a mini haas mill. max RPM is 7500. i will be using a 1" HSS 4 flute endmill. i mean, you didn't ask any questions either. if you know more than me, you have to ask me questions so you can give me an answer. i'm looking for an answer from someone who has done this for a long time. my textbooks don't give me a general rule of thumb for how much material should be in the vise. i'm planning on having a 1/4" in the vise. i just want to know if this is enough to keep the mill from kicking the part out of the vise.

the whole piece of material is 2" thick and i am contour milling it down to 3/4" or a -1.25" since the top of the stock is at Z0. then i am face milling it down to -3/4" and then doing some drilling and tapping. is that enough now? and yes, the RPMs and IPMs have been calculated with standard formulas found in a machinery's handbook that we use. i have charts to use in order to calculate those.

you know what, i just had an idea. forget asking this forum for anything.. the project i am doing is motorcycle related and i will go ask someone who knows what i am talking about. his name is Fabricator Kevin.

[Geof]

No need to get quite so snippy; here are the pertinent questions:

What is your depth of cut?

What is the radial engagement of the cutter?

What are of metal is gripped in the vise?

How high up from the vise is the part you are cutting?

These combined with the feed you give allow for an estimate of how much force the cutter is exerting on the metal.

You are working with a 1" cutter so if you had this cutting around 1/2" deep with half the cutter engaged you would be applying considerable force and the part would probably tend to move in the vise even if it was only an inch or so high. But your machine would probably not be able to drive the cutter under these conditions so it is a moot point whether the part will move.

Next time you pose a question give all the information you have in the first post: cutter size, material size, type of vise, plain jaws or stepped jaws, depth of cut, etc.

Have a look around this forum you will find many people, who do know what they are talking about, spend a lot of time answering questions for novices.

[KIMFAB]

Wrong side of the bed this morning Charlie?
Check out Geofs post above.

With proper support and fixturing you can get away with just about anything.
Given proper info I'm sure Geof can help. Myself, I just do what looks good and take it slow. If that doesn't work try another setup.
Unfortunately, experience is the key here. Remembering how you screwed up gives the experience.

[Cruiser]

Puzzles like this can get a bit complex. The first thing I'd consider is who is clamping the vise ? The vise exerts lots of pressure, enough to deform the aluminum to the point it is ready to spit out of the jaws.
The primary rule is to look for the weakest link in your chain, and stay within its limitations. Trying to compute the energy applied to a part is difficult at best, and the answer will change with tool wear. Don't forget abusive little problems that arise from nowhere.
Best bet is to test the situation with hammer and then put up a shield and test run and see. Then every run expect something to be different.