I generally only suck down until the resin goes green.
Two things --plummet-- ,why the $50 is worth it for the adjustable switch; not
counting the idea that now your part stays under vacuum till the resin is cured
& the pump only runs 5 minutes every Hour :
** different type core materials Really want different Hg settings.
if using bamboo or wood core,in lu of foam the setting will be WAY higher.
That re-fridge pump Ya got will suck 20Hg; i have one near the same on top of my beer-keg.
** you can pre make 50K carbon uni for board stiffeners by placing a .5oz plain weave Glass
with peel-ply, on either side of then sucking down. when cured just trim the sides & place
under your glass, (they bend to shape easy cause their only 0.003" to 0.005"thick)
depending on how wide you spread the carbon fibers. Or use a Uni Carbon with binders
attached, then sand the edges flat later; but Don't forget the peal-ply !
The straight cuts under the glass look real professional. Other parts that have
no core can also be done at "near" Max that the pump can deliver.
On another note :
Ya can place a garden hose or small diameter tube on the exhaust from
the pump, and keep the fumes from the part outside of your
work aria by running the tubing out a hole in the wall. Works good in winter
when Ya wanna keep the temp at 77+ degrees while waiting for parts to cure.