Shark Pro lead screw nuts

Discussion specifically about the Shark's bigger brother, the CNC Shark Pro

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Shark Pro lead screw nuts

Postby mpinet » Mon Oct 08, 2018 3:34 pm

New to the board here, just picked up a used shark pro and want to replace the t nuts because of slop/ wear. The part set of three from nextwave is $99 for the set of three, but they are not the antibacklash type. Has anyone converted / updated this model? Just trying to see whats out there. Its a black model with MDF table top approximately 24''x24''.
X axis is a 3/8 size, Y axis is a 1/2, and Z axis is 1/2 ACME thread. Anyone have this model or any helpful hints are appreciated. Thanks.
mpinet
 
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Re: Shark Pro lead screw nuts

Postby rungemach » Thu Oct 11, 2018 6:12 am

New solid lead screw nuts will have a thousandth or so of fixed backlash. It is easy to feel the backlash as no springs are used to mask it. They will maintain that same backlash under high loads as well as light loads. Over time they will wear and get a bit looser, and can be replaced.

The anti-backlash styles will generally be rated for lighter loads, and under very light cutting force will have less backlash. However, the anti-backlash lead nuts will have greater variance under loads as the cutting force works against the spring that holds the two threaded halves together. This sort of backlash does not show up as a step in the cut, but rather a slower deviation from the true cut path as the cutting force increases. Because these are not ball screws, the pressure holding the nut halves together can not be great, due to friction. This lighter pressure can be overcome by cutting force as the machine moves, and you get a "gradual backlash".

IMHO, If you do only light carving with V bits or small diameter bits, and run slow speeds, the anti-backlash system may give you slightly better results. If you do any medium to heavy cuts, the anti-backlash nuts may give you greater deviation from your desired tool path.

The Sharks in general are not super rigid machines, and will show cut problems due to loose tolerances and flex anyway. Anti-Backlash lead screw nuts will not solve those issues and are not a magic bullet for accuracy..

Hope this helps

Bob
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Re: Shark Pro lead screw nuts

Postby mpinet » Thu Oct 11, 2018 4:27 pm

Thanks Bob, sounds like I'll just get the replacements and have a little better control....next machine will have ball screw drives.
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