Thread: mill bit lengths
In Sketchup I have a kress spindle, I'm trying to work out how high the gantry has to be above the bed.
so with a mill bit installed into a spindle like a kress, how long would the bit showing be?
How long is a piece of string?
Edit: Tempting though that reply was I guess I should be more helpful ... you need to leave enough to change the tool so I'd say about 50mm. The shorter the tool is the better as it will deflect less. Clearly if you put a vice on the bed you'll need more ... this is why I made the height of my bed adjustable (CNC router bed that is!), and made a long Z-axis. Avoid doing the latter though as it's difficult to make it strong enough.
Last edited by Jonathan; 26-07-2011 at 10:30 PM.
I would think it is better to have extrusion as your gantry support as you can change or make it a bit longer and just move it up as required ??
I will be leaving a extra 50 mm on the total hight at the bottom of the support rail for this reason
even adding two to three more sheets of MDF to the bed would add extra hight if you remove two for a 4 axis ??
Last edited by luke11cnc; 27-07-2011 at 05:28 AM.
could it be made with a thread adjustment with stops on the gantry supports or just extra deep bed sides with block stops to put bed at different levels
If you just have two positions - one low down for sheet material and one high up for whatever, then you can use blocks. Put a block on both sides to rest on for the low position and two blocks that make contact with the top to align it for the high position.
To get it level you can put a DTI in the spindle / z-axis, touching the bed and move the Y-axis. If the bed is not actually flat you'll still need to skim it but that should get it close.
I'm making the height of the bed on my machine adjustible with two jacking screws, and bolts into the 6 supports on the main frame.
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