Quote Originally Posted by ngundtoft View Post
Can you please tell me what these profiles are called and where you can buy them. It looks like they are approx. 100mm high in the first of your pictures. I have searched the net, but I have not found the same profiles.
In the first picture It's an equivalent to ITEM profile size 120x80 with 8mm slot. Called Profile 40 I-Type Slot8 from Motedis in Germany.
http://www.motedis.co.uk/shop/Slot-p...60bnk0tfjmi0i0
You will need spacers with this profile for the BK/BF12 blocks as the slot hole spacing doesn't match.

The smaller narrower machines use 45x90 Profile B slot 10 and they do match the BK/BF12 blocks.

Other option is don't use BK/BF blocks and machine the bearings directly into the gantry sides and buy slightly longer screws.

Quote Originally Posted by ngundtoft View Post
One more question - what distance approximately should you aim for between the tip of the spindle and the bed (steel frame), in the down position?
Hard to answer because it depends on several factors like longest tool length and Max material size your likely to want to cut. Best way is to make a call on the max material thickness and the longest tool your likely to need and Add together plus 10-20mm extra.

For the amount of Z axis travel then I wouldn't go past 200mm with 150-160 giving a good balance of range and strength. The longer it has to extend the more it flexs so keeping short will be stronger but could limit you at some point with longer tools.
Too long and your weakening the machine. No point having 150-200mm travel when your only ever using tools that extend from spindle 50mm and cutting material less than 50mm. All your doing in this case is introducing risk of higher resonance which affects surface finish and accurecy.

This is why people who want a wider material cutting range opt for the adjustable bed because they can keep the strength and still have option of cutting thicker material with longer tools. The machine in Post#9 has this feature so can accept 150mm thick material and cut thru it with 150mm length for making mortice and tenions in 6" Oak beams or V-carve/relief the face of 310mm thick beams.

In normal day to day use the bed mostly stays in one middle of the road position.