Originally Posted by
mactec54
No spindles that are of the same type you are using are suitable for milling steel, the spindle bearing arrangement that is designed for these high speed spindle is where the problem is, apart from a cartridge type spindle and a independent drive motor I don't think there are any of this type of spindle that is made for low speed use just for steel or any type of metal cutting
If you take light cuts with what you have and have plenty of time for the job to be done you can use what you have, engraving should not be a problem, it's when using a Endmill it pulls down on the spindle releasing the preload on the bearings once this happens then you have a mess and it does not take much for this to happen
With the sand mixture unless it can bond to the steel or aluminum it is not going to make it anymore rigid, rigidity starts with the design of the machine adding pieces can help sometimes but it is always best designed for your needs at the start before you build your machine