Untitled - Wood Tools

q meosuring mystery
SONIC VS. LASER
ANSWERS
I'm confused by all the new measuing deuices on the market. Can you teII me what
the dffirence is betureen a laser measuing deuice and a sonic measuring deuice?
JohnWatkins
Concord, NH
--^'
JOUNd
Loser
Beom
Loser
Device
A While sonic devices colculote
distonce with sound woves, loser
devices use o concentroted beom of
light, moking them more occurote.
Sonic measuring devices (such
as those from Zircon) calculate
distance by bouncing sound
waves offan object and measuring the
time it takes them to return. (The "laser
dots" are sirrrply a targeting device.)
Sound expands as it travels, so the further
away a target is, the less refiable the
measurenrent (Fig. 1).Thts rnakes sonic
devices great for estimates rather than
accuracy.The units retail for $30 to $60.
Laser measuring devices (such as
those from Leica and Spectra) work in
a similar fashion, only they measure the
path ofa laser beam rather than sonic
waves (Frg. 2). Light is more focused
than sound, and the speed of light is
more reliable, so laser measuring devices
can boast accuracy to within 1/*" o,ret
a distance of several hundred feet.This
technology comes at a price, however.
Expect to pay at least $300 for one.
A _fine laycr of rust has deuelopcd
on my band sautabletop.What\ tht
bcst way to ramouc the rust?
Kcuin Schmueckcr
Wa cmail
There are a nurnber of products
oLlt there to combat rust. One I've
had particular success with is Bull
Frog l\ust Renr over (u,'rvur l}-rll-Fxrg. conr).
All you do is apply a layer of remover
to the tabletop and let it soak in for about
15 rninutes ('lop Photo).Then wipe the surface
clean with a rag. It takes a rusry table
down to a shiny, ah-nost new surflace.
For additional protection, spray the
table with a sealant such as BostikTopCote
to prevent further rust (Bottom Photo).
woRKBENCH t-t .1uur 2004