Quote:
Originally Posted by AndrewJ
Gday Mark
Sounds simple in practice, but to drill "a perfectly concentric" hole into the end of an existing worm, without any runout is not a simple exercise. And i make this comment based on the tolerances we are talking about.
At the precision we are talking about, getting the encoder mounted without any eccentricity is a critical requirement to getting repeatable results.
My lathe, even with a collet fixing probably isnt up to this 
Andrew |
Andrew, the tolerance you have stated is fine for the worm and worm wheel but are not necessary when mounting encoders. For example when I run the EM200 at full slew you can plainly see the encoders oscillating around the central axis as a result of them being fixed to the worm by grub screws. My EM 200 delivers +/- 2arc sec PE without PEC (you don't have a choice on the PEC, there isn't any nor does it need it) and when properly polar aligned drops the target smack bang in the middle. I build miniature engines with my lathe and mill and my latest project, a V8 required me to drill the camshaft hole 100mm long with a max tolerance of 1 thou run out over the length. With careful setup and patient drilling with a sharp drill and lots of coolant I got the job done. Mounting an encoder would not require anywhere near this accuracy and the hole would at most only need to be 5mm deep. I base this statement on using similar encoders to those found on the EM200 which are basically glorified volume pots. You may have a different system in mind.
Mark