Quote Originally Posted by njhussey View Post
Hi Dave,

I think what most people are going on about here is that you've used flat and angle without any sort of machining (not that I've seen mention of in your thread?) to make the surfaces true to either themselves or mating surfaces. Angle (as I'm sure you knowand have found out) is nearly always under or over 90° and the surface is never flat, certainly not the inner surface where you've mounted your Z axis bearings. This will lead to binding (your video unfortunately shows or proves nothing about how smooth the Z axis is just that you can turn the ballscrew and it moves, sorry) and premature wear of the bearings which will lead to a sloppy Z axis and inaccuracy. Jazz is being harsh (but perfectly fair) in his remarks, it's the way he is and he tells it like it is without any BS, he is one of (if not the) the most helpful and knowledgeable people on this forum and his comments are worth listening to, even if you don't like them.

If you'd welded your Z axis and then had it machined so the bearing blocks could sit square, flat and true, and had the ballscrew mounting section machined flat/square and where the spindle is going to mount machined square to everything else then all this would be immaterial, but there's no way in hell that all this is going to be square with just plain welded steel. Yes you'll be able to use the machine but at what accuracy (you may not need much accuracy so this is all immaterial) and how long before the bearings wear and it all become loose and sloppy? The spindle will require lots of shimming to get it perpendicular but if your rails aren't straight/parallel and true then it'll still not cut accurately. How have you trammed the rails so they're parallel to each other, what equipment do you have (DTI's, levels, straight edges etc.) to check for straightness, parallelness etc?

Whatever the outcome good luck with your build and I'm looking forward to seeing the first chips coming off this
Hi mate,

Thanks for the feedback. My measuring equipment consists of various levels, squares, straight edges rulers and a vernier caliper.

I had considered the wear on the bearings and have endeavoured to set them as true as practical. Initially I screwed the middles in one spot of the rails then used the ballscrew brackets motion to guide it back and forward and held each side of the rails in place with rare earth magnets to get my parralell edges. Also the magnets edges set the line for squareness.

I did need to reweld the old screwholes on 1 side and redrill new ones parralell to the other fully fastened side as it was quite a 'tough' fit and felt like there was more pressure towards the lower end when extending it. I've actually never spent this much time on one welding job ever. With more than 40 hours just in the Z axis alone. There is infact a tapering 0.8mm shim on the right side to get it so slick it wants to skate off in a breeze.

As far as accuracy goes. If I can cut a rifle stock to my 3D design and all it needs is light sanding then I'm happy. I've been doing them by hand so far and getting one side the same as the other is near impossible. Also, spending 6 hours with a dremel digging the action channel is not fun.

I don't have an issue with negative feedback, I just find it pointless and offensive when I see random posts that say "lucky you used round rail, profile rail wouldn't let you do that.". As I myself are not into BS, The pointless comparison between round rail and profile rail is unnecessary and not helpful.


P.S I am taking full advantage of my round rails. I'm well aware that I can use the radial axes for giving me some room to play. :)

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