alperin,

   I specify a surface finish of 500/250 microinches (12/6 microns).  Who cares what the thread profile is.  

   If you do not have a surface roughness gauge, get one.  Maybe, you want to go rougher.

    

               JHG

I typically use a pitch of 0.5mm.

I've also played with some different profiles but once you go away from a standard shape you might as well make them circular grooves instead of a helical. In that particular case it worked really well but if you want to go this route you'll need a non-sequential optics program to play with the shapes and see the effectiveness.

Bead blasting the surface has worked in the past but you need to be careful because that may create a lot of 'glare spots'. I normally try to avoid that but it's worked before.

HTH,
Dan

We have good success with this:

http://pioneermetal.com/optical_black

 

Harold
SW2011 SP2.0 OPW2011 SP2.0 Win 7 Ultimate
BOXX 8550 Xtreme Dual Xeon 5680 @4.2Ghz
nVidia Quadro 4000
www.lumenflow.com

Thank you for the feedback. For the first article I've specified a .5mm pitch and we'll see how it turns out. The optical black finish looks very interesting and I'll keep it in mind for future applciations. This one, however, is medical, and if we change any materials we will have to do disinfection and sterilization validations.  

Update: Prototype units with a 0.5mm thread pitch and sharp pointed thread crests came out very well. Significant glare reduction from the non-threaded model.  

Glare reduction from edges is actually quite non-trivial.  If you are particularly sensitive to it, you might need to do some thorough testing by varying the angle of the detector and source relative to the threads.  With high-intensity source at low grazing angles relative to the threads, you might still get glints from the edges of the threads.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies
Chinese prisoner wins Nobel Peace Prize

Didn't finish my thought.  

We used razor blades in one application to minimize the glint.  Your comment about the sharp crests is spot on.  Just make sure that your manufacturer doesn't start to get lazy and wind up with duller crests.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies
Chinese prisoner wins Nobel Peace Prize