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Author Topic: changing out bits but keeping bit length...  (Read 3289 times)

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Offline BarryB

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changing out bits but keeping bit length...
« on: January 25, 2010, 12:56:41 PM »
Hey folks, I'd like to do a rough pass with a larger bit, and a finishing pass with a smaller one.  To do this, I need to switch out the bits mid job.  I'm sure this is a newbie question, but I'm a little dumbfounded.  How do I ensure that I have the same length of the bit for the finishing pass.  That way I can switch it out and continue immediately.

Barry

Offline Hood

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Re: changing out bits but keeping bit length...
« Reply #1 on: January 25, 2010, 02:44:14 PM »
All depends on how you set things up and what kind of machine you have. If you have several collet holders you can set up tools in them prior to starting and have tool numbers called and the offsets set for these tools.
If you just have a single collet such as a router may have or maybe R8 collets on a mill you can do a couple of things. First is you can zero your Z DRO on the top of your work with the first tool, then when your next tool is called you can jog away, change the tool, jog it down to the surface and zero the Z DRO again. Similarly if you have a knee mill you could manually wind the knee down, press GoToZ and then wind the knee up so the tool touches the surface of the work.
Some people also have collars that fit on their tools so they will only go into the collet so far and that way they can set tools all to the same length and repeatably.

Lots of other ways to do it, even automatic ways with a touch pad but all will depend on the type of work you do and the machine you have etc.

Hood
« Last Edit: January 25, 2010, 02:46:05 PM by Hood »

Offline BarryB

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Re: changing out bits but keeping bit length...
« Reply #2 on: January 25, 2010, 03:10:20 PM »
As this machine is 5 axis, I can't really just zero the Z again, it's gotta be the same.  However, I can do the multiple collet's and set up tools.  For this though, can't the bit slide in the collet till you tighten it onto the machine?  How is that locked into place?

Also, do you need two collets, and two collet nuts?  Or can you slip one collet out an the other in, without disrupting the spacing.

Barry

Offline Hood

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Re: changing out bits but keeping bit length...
« Reply #3 on: January 25, 2010, 03:39:16 PM »
When I was talking about collet holders I was meaning like a milling machine would use, for example a 40taper ER32 holder. From what I think you are saying is your spindle is the collet holder, if so then probably your only real option would be to have collars fixed to the tools so they can only be put so far into the collet and thus you can repeatably place each tool even if they are different lengths and you can set them up in the tooltable.
Hood

Offline BarryB

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Re: changing out bits but keeping bit length...
« Reply #4 on: January 25, 2010, 03:46:36 PM »
Interesting idea, thanks!

Offline BarryB

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Re: changing out bits but keeping bit length...
« Reply #5 on: January 26, 2010, 01:32:38 AM »
Kind of ghetto, but I sanded down a bit holder tube so I can but it on the bit and push it into the collect, and it'll rest on the surface of the collet at 35mm length for the bit.  I tested it with several different bits and they all end up being 35mm, or very close to it.  Is that the kind of thing people do to change things out?  I think I should probably machine a real tube/holder for this using aluminum, but this was damn easy to do as a test.

Barry

Offline Hood

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Re: changing out bits but keeping bit length...
« Reply #6 on: January 26, 2010, 03:13:01 AM »
Whatever works for you is good :)
Hood
Re: changing out bits but keeping bit length...
« Reply #7 on: January 28, 2010, 11:37:30 PM »
Kind of ghetto, but I sanded down a bit holder tube so I can but it on the bit and push it into the collect, and it'll rest on the surface of the collet at 35mm length for the bit.  I tested it with several different bits and they all end up being 35mm, or very close to it.  Is that the kind of thing people do to change things out?  I think I should probably machine a real tube/holder for this using aluminum, but this was damn easy to do as a test.

Barry

That's what I am planning on doing.

Is this 5 axis a wood machine or metal?  What CAM you using?

 Post some pics, I'm building a 5 axis metal with a trunion and like to see what others are doing.

Offline BarryB

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Re: changing out bits but keeping bit length...
« Reply #8 on: January 28, 2010, 11:40:59 PM »
It's made of metal, but for cutting wood mainly.  Sometimes it'll be metal, but sparingly.  You can see the progress of it in this link:

http://www.machsupport.com/forum/index.php/topic,13174.0.html