How accurate of a machine can be made from wood? I am considering building a
small 3"x6" slide table (x/y positioning device) but ultimately it will have
to be accurate to .001 so I am thinking I would be better off in some sort
of plastic or metal...
Take a look here... http://www.patwarner.com/routerfence.html and read the
tolerance Pat specs it at. I built the fence when it was featured in FWW
two years ago and it's as accurate now as when I built it.
So to answer your question - yes you can as long as you use the right
materials and plan accordingly. Your design needs to include a zero
reference capability in both the x and y axis. Even if you make it out of
other materials you still need a calibration capability.
You have to more clearly define the objectives. If the objective is to be
able to move this thing in precise .001 increments, then yes, it is easily
done with wood (I could push a noodle that close). If your requirements
include it being (and staying) flat and parallel to .001,, wood is not
going to do it. If, when moving in X, motion has to be confined to the X
axis only within .001, wood is not going to do it. Metal is your best bet.
Even with metal, if you are using unmachined stock, it will not fit the
requirements unless all you are looking for is linear positioning without
regard to variations in other axis. without equipment that is not normally
found in the home shop, just getting the slide surface parallel to the ways
is going to be quite a trick.
Velmex makes good slides that are inexpensive (that's relative) and
functional. You can buy various configurations and there are a lot
of selections and engineering tools on their site. Try this and
see if it will fit your needs:
Good Luck, Phil
The device you seem to want sounds like a slightly larger version of the
mechanical stage used on microscopes to position slides at very high
magnification, such as 1000x. While I don't recall the exact parameters, I
do know that it's possible to locate a single bacterium, remove the slide,
do other things with the scope, then replace the slide and re-locate the
same bug within seconds.
To be fair, one usually reads the stage verniers relatively grossly and then
homes in on the subject by using landmarks within the field of view, but a
good mechanical stage is a fairly decent precision instrument. Other
manipulators allow one to insert an extruded glass syringe into the middle
of a single nerve cell - or an ovum. Good enough?
If you need more range than one of these stages can provide, could you
attach it to a moveable base that would allow you to position it grossly,
lock it down, and then use the finer capabilities of the stage itself?
http://www.greatscopes.com/acc.htm is just one location. They sell one for
$39. I've never dealt with them, so this isn't an endorsement of the
company, but Google "mechanical stage" and see for yourself what turns up.
You can go all the way from this low-end device to spending beaucoup de
bucks on a Zeiss. Also, don't overlook the used market. There are loads of
companies selling relatively inexpensive high-end microscope products in
outstanding condition that have been re-cycled, damaged in some way that
won't matter to you, reconditioned, upgraded, etc.
Why don't you say exactly what it is you are trying to do. It would be a lot
easier to come up with something that way. If you are going to use it for
grinding, your requirements are different. It needs to be a shielded or
sealed unit for that use. An open way type device will wear out in no time.
At this point I am just trying to create a free moving x/y positionner, that
I can butt against a pair of micrometer heads, and feed an item held by a
small vise into a rotating cutter. All I was asking was that if I made the
slide-table aspect of this from wood or whatever, how accurate could I get
and not be affected by the material. I am coming to believe that something
like a steel dovetail way slide will be necessary, and that will make the
whole idea cost prohibitive. Of course, I may be fine with a small milling
table, but I am still looking at sources on those.
If you are actually interested in the actual project, I will be happy to
discuss it in email, as I am not sure it pertains to woodwork, especially if
I don't use wood to make it :)
"CW" < firstname.lastname@example.org> wrote in message
Harbor Freight cross-slide vise 4x7" travel, $25, Table play
guaranteed to be less than 3/16"...once it's fine-tuned.
- Let Exxon send their own troops -
http://diversify.com Comprehensive Website Programming
I'm sorry, I really wasn't trying to be as vague as it seems.
What I am attempting to do is an improvement on an existing product. It is a
machine that is used to make keys from a brass blank with a steel cutter, by
knowing the cut position and cut depth. Currently it works on the principle
of a carriage that rides on a rod. It is stopped (for depths) by a
micrometer in front of the carriage. It can be controlled laterally by
rubbing it against a micrometer to one side set to the current position. It
is fed into the cutter by a movement best described as an arc.
I am trying to come up with a replacement for the carriage to 1. feed
straight into the cutter instead of on the arc. 2. Make lateral positioning
and forward movement more accurate and convenient.
I am currently researching about 3 or 4 different methods of doing this,
including stepper motors and actuators, dovetail way slides, milling tables,
and a few really oddball ideas. At some point there is diminishing returns
as this is approximately $300 machine (not really though) and the next
better machine is about $1600. So as the costs rise to improve it, the
benefits of doing so decease.
Are you familiar with Grainger?
Or Reid? http://www.reidtool.com /
Between the two of them, I'll bet you can find something that will work for
you. They are the tinkerer's F.A.O. Schwarz....
What's a "vernier" screw? Sounds like what I could have used. I tried to
build a... um? A focusing rail? A flummy to mount on my tripod to let me
slide my whole camera forward and back in teeensy increments, in order to
focus one of those macro/zoom combo thingies more easily. I built it out
of aluminum bits, pop rivets, and a couple of carriage bolts. It never did
work to my satisfaction, and I've since recycled all the bits. I could
still use one though.
Michael McIntyre ---- Silvan < email@example.com>
Linux fanatic, and certified Geek; registered Linux user #243621
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