|
In a message dated 10/28/2002 3:55:00 PM Central Standard Time, jj5412@... writes: Why would you choose a multistart screw over a single start screw?
Are acme thread screws more efficient that generic threaded rod?
JJ: I am NOT a "trained" machinist; I am just one of those hobbiests who THINKS he "can DO that!". So, lemme try to answer your questions: First, a two- to four-start screw causes MORE linear move (of the "nut") per turn. A "four-start, 1/8"-pitch screw" causes a full 1/2" per turn move! I have used some "four start" from BSA on a couple of plotters I have built, and the "speed" of movement of the pen is significantly greater than you might have, say, on a little mill or X-Y Table, etc., with only single-start! Second question: Certainly! That is why the stuff exists! a "V-thread" "jambs up" somewhat, when "tight", and you do NOT want this in any kind of "CNC machine", etc! Even the BETTER ordinary vices have ACME thread! Besides, "gerneric" threaded rod---you mean the rolled, zinc-plated stuff from Home Despot? UGH! That is for FASTENING, not MACINE-lead-screws!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! HTH! Jan Rowland, old ugly troll
|
(Hoping this is on topic)
In my quest for constant upgrades to my CNC mill/router/pcb thing, I
have a couple of questions:
Why would you choose a multistart screw over a single start screw?
Are acme thread screws more efficient that generic threaded rod?
ADVthanksANCE,
JJ
Be Kind, Be Careful, Be Yourself
|
Hi, I am no expert but a few things to think about. Multiple lead acme
screws means you have several threads instead of one so they tend to last
longer and are stronger. Rolled acme thread has been going on for a long
time and the acme rods i bought the other day are nicely finnished and a
quick check says their ok on the length. a "v" thread begins to wear quickly
and once it gets sloppy it weakens as it wears out. an acme thread stays
rugged even as its wearing to a point. As for efficient i cant answer but
there are ground threads of all kinds out there some last for many years
even if they are "v" or acme or even buttress thread. Each has a best use.
Take a look at the size you want and then look at the different grades
available. 1/2-10 acme b2 is the cheapest because of so much use, if you
order a 15/16-16 thread custom made to your spec's then expect to pay
premium big bucks. Sometimes the nut and the retaining method(back to back
bearings or nuts) is the most important part. cul brian f.
toggle quoted message
Show quoted text
----- Original Message ----- From: "JJ" <jj5412@...> To: <cad_cam_edm_dro@...> Sent: Monday, October 28, 2002 4:53 PM Subject: [CAD_CAM_EDM_DRO] Ball/acme screw question (Hoping this is on topic)
In my quest for constant upgrades to my CNC mill/router/pcb thing, I
have a couple of questions:
Why would you choose a multistart screw over a single start screw?
Are acme thread screws more efficient that generic threaded rod?
ADVthanksANCE,
JJ
Be Kind, Be Careful, Be Yourself
Addresses:
FAQ:
FILES:
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Brian,
Actually, I'm somewhat of an expert, and the reason for a multi-lead
screw is this. You want a nut that will advance 1" in 4 revolutions, but if
the shaft is fairly small in diameter, the depth of the thread, if you cut
it for a normal 4 threads/inch, would weaken the shaft considerably.
Instead, you cut it 4 threads/inch, but at the depth used for 8
threads/inch. You then have spaces between the threads in which to cut an
additional lead at the 8 threads/inch depth. You then end up with a screw
that appears to have 8 threads/inch, but the nut will advance 1" for 4
revolutions. The whole thing has to be done on a lathe, and sounds
complicated, but it really isn't. In the past, I've generated screws with as
many as 4 leads. They looked like the threads were very fine, but the nut
would fairly fly down the screw.
You just had a lesson in "Screwing 101".
Marv Frankel
Los Angeles
toggle quoted message
Show quoted text
----- Original Message ----- From: "Brian" <ka1bbg@...> To: <CAD_CAM_EDM_DRO@...> Sent: Monday, October 28, 2002 2:41 PM Subject: Re: [CAD_CAM_EDM_DRO] Ball/acme screw question Hi, I am no expert but a few things to think about. Multiple lead acme
screws means you have several threads instead of one so they tend to last
longer and are stronger. Rolled acme thread has been going on for a long
time and the acme rods i bought the other day are nicely finnished and a
quick check says their ok on the length. a "v" thread begins to wear quickly and once it gets sloppy it weakens as it wears out. an acme thread stays
rugged even as its wearing to a point. As for efficient i cant answer but
there are ground threads of all kinds out there some last for many years
even if they are "v" or acme or even buttress thread. Each has a best use.
Take a look at the size you want and then look at the different grades
available. 1/2-10 acme b2 is the cheapest because of so much use, if you
order a 15/16-16 thread custom made to your spec's then expect to pay
premium big bucks. Sometimes the nut and the retaining method(back to back
bearings or nuts) is the most important part. cul brian f.
----- Original Message -----
From: "JJ" <jj5412@...>
To: <cad_cam_edm_dro@...>
Sent: Monday, October 28, 2002 4:53 PM
Subject: [CAD_CAM_EDM_DRO] Ball/acme screw question
(Hoping this is on topic)
In my quest for constant upgrades to my CNC mill/router/pcb thing, I
have a couple of questions:
Why would you choose a multistart screw over a single start screw?
Are acme thread screws more efficient that generic threaded rod?
ADVthanksANCE,
JJ
Be Kind, Be Careful, Be Yourself
Addresses:
FAQ:
FILES:
Post Messages: CAD_CAM_EDM_DRO@...
Subscribe: CAD_CAM_EDM_DRO-subscribe@...
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Moderator: jmelson@... timg@... [Moderator]
URL to this group:
OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.
NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
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URL to this group:
OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.
NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........ bill
List Mom
List Owner
Your use of Yahoo! Groups is subject to
|
At 05:41 PM 10/28/02 -0500, you wrote: Hi, I am no expert but a few things to think about. Multiple lead acme
screws means you have several threads instead of one so they tend to last
longer and are stronger. Not at all. Think about it. Hint: consider the same length nut in each case. Regards, Hoyt McKagen To prevent virus propogation, don't put this addy in your book Belfab CNC - US Best MC - Camping/Caving - Two-Wheel-Tech List - If you torment a serpent, it will cough up a dead rat
|
--- In CAD_CAM_EDM_DRO@y..., "JJ" <jj5412@e...> wrote: (Hoping this is on topic)
In my quest for constant upgrades to my CNC mill/router/pcb thing, I
have a couple of questions:
Why would you choose a multistart screw over a single start screw?
Are acme thread screws more efficient that generic threaded rod?
ADVthanksANCE,
JJ
Be Kind, Be Careful, Be Yourself multistart screws are usedfull in situations where the threadprofile will be smaller then the pitch of the screw. for example a 1. wide nut with a 1. pitch screw would allow only 1 thread to be engaged this makes for a low loadbearing on the screw. multysthreading of this screw would add another thread of loadbearing capabilitie for every thread added. Add as many threads as there is room for them without overlaping. the efficency of Different threadprofiles depends on there intended use. example: Acme/ballscrew = in motion application sawtooth = one directional loadbearing roundtooth = in motion in contaminated environments there are many more possibles for me to list but you get the idee here. different designs favor different operating conditions.
|
Yep, I'll take a 101 from anybody. some think of a nut by its length i
consider a nut by the amount of thread engaged. If i used a 4 lead screw and
put the same amount of thread engagement on one of 4 threads then the nut is
long but stronger..cul brian f.
toggle quoted message
Show quoted text
----- Original Message ----- From: "Marv Frankel" <dcdziner@...> To: <CAD_CAM_EDM_DRO@...> Sent: Monday, October 28, 2002 11:11 PM Subject: Re: [CAD_CAM_EDM_DRO] Ball/acme screw question Brian,
Actually, I'm somewhat of an expert, and the reason for a multi-lead screw is this. You want a nut that will advance 1" in 4 revolutions, but if the shaft is fairly small in diameter, the depth of the thread, if you cut
it for a normal 4 threads/inch, would weaken the shaft considerably.
Instead, you cut it 4 threads/inch, but at the depth used for 8
threads/inch. You then have spaces between the threads in which to cut an
additional lead at the 8 threads/inch depth. You then end up with a screw
that appears to have 8 threads/inch, but the nut will advance 1" for 4
revolutions. The whole thing has to be done on a lathe, and sounds
complicated, but it really isn't. In the past, I've generated screws with as many as 4 leads. They looked like the threads were very fine, but the nut
would fairly fly down the screw.
You just had a lesson in "Screwing 101".
Marv Frankel
Los Angeles
----- Original Message -----
From: "Brian" <ka1bbg@...>
To: <CAD_CAM_EDM_DRO@...>
Sent: Monday, October 28, 2002 2:41 PM
Subject: Re: [CAD_CAM_EDM_DRO] Ball/acme screw question
Hi, I am no expert but a few things to think about. Multiple lead acme
screws means you have several threads instead of one so they tend to last longer and are stronger. Rolled acme thread has been going on for a long
time and the acme rods i bought the other day are nicely finnished and a
quick check says their ok on the length. a "v" thread begins to wear quickly
and once it gets sloppy it weakens as it wears out. an acme thread stays
rugged even as its wearing to a point. As for efficient i cant answer
but there are ground threads of all kinds out there some last for many years
even if they are "v" or acme or even buttress thread. Each has a best
use. Take a look at the size you want and then look at the different grades
available. 1/2-10 acme b2 is the cheapest because of so much use, if you
order a 15/16-16 thread custom made to your spec's then expect to pay
premium big bucks. Sometimes the nut and the retaining method(back to
back bearings or nuts) is the most important part. cul brian f.
----- Original Message -----
From: "JJ" <jj5412@...>
To: <cad_cam_edm_dro@...>
Sent: Monday, October 28, 2002 4:53 PM
Subject: [CAD_CAM_EDM_DRO] Ball/acme screw question
(Hoping this is on topic)
In my quest for constant upgrades to my CNC mill/router/pcb thing, I
have a couple of questions:
Why would you choose a multistart screw over a single start screw?
Are acme thread screws more efficient that generic threaded rod?
ADVthanksANCE,
JJ
Be Kind, Be Careful, Be Yourself
Addresses:
FAQ:
FILES:
Post Messages: CAD_CAM_EDM_DRO@...
Subscribe: CAD_CAM_EDM_DRO-subscribe@...
Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@...
List owner: CAD_CAM_EDM_DRO-owner@..., wanliker@...
Moderator: jmelson@... timg@... [Moderator]
URL to this group:
OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.
I consider this to be
a sister site to the CCED group, as many of the same members are there,
for OT
subjects, that are not allowed on the CCED list.
NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING
THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
bill
List Mom
List Owner
Your use of Yahoo! Groups is subject to
Addresses:
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Moderator: jmelson@... timg@... [Moderator]
URL to this group:
OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it
if you have trouble.
I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.
NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
bill
List Mom
List Owner
Your use of Yahoo! Groups is subject to
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URL to this group:
OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.
NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........ bill
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|
Yo Torston; Is, "roundtooth", the type that looks sort of like a piece of rope? Bill On Tue Oct 29 12:19:34 2002, torsten98001, <torsten@...> wrote: --- In CAD_CAM_EDM_DRO@y..., "JJ" <jj5412@e...> wrote:
(Hoping this is on topic)
In my quest for constant upgrades to my CNC mill/router/pcb thing, I
have a couple of questions:
Why would you choose a multistart screw over a single start screw?
Are acme thread screws more efficient that generic threaded rod?
ADVthanksANCE,
JJ
Be Kind, Be Careful, Be Yourself multistart screws are usedfull in situations where the threadprofile
will be smaller then the pitch of the screw.
for example a 1. wide nut with a 1. pitch screw would allow only
1 thread to be engaged this makes for a low loadbearing on the screw.
multysthreading of this screw would add another thread of loadbearing
capabilitie for every thread added.
Add as many threads as there is room for them without overlaping.
the efficency of Different threadprofiles
depends on there intended use.
example:
Acme/ballscrew = in motion application
sawtooth = one directional loadbearing
roundtooth = in motion in contaminated environments
there are many more possibles for me to list but you
get the idee here.
different designs favor different operating conditions. -- ---------------------------------------------------------------------------- RKBA! Blessings On Thee, Oh Israel! 4-19! ----------------+----------+--------------------------+--------------------- An _EFFECTIVE_ | Insured | All matter is vibration. | Let he who hath no weapon in every | by COLT; | -- Max Plank | weapon sell his hand = Freedom | DIAL | In the beginning was the | garment and buy a on every side! | 1911-A1. | word. -- The Bible | sword.--Jesus Christ ----------------+----------+--------------------------+--------------------- Constitutional Government is dead, LONG LIVE THE CONSTITUTION!!!!! ----------------------------------------------------------------------------
|
Thanks for all the info everyone!
One last (for now) question: Are acme screws their true diameter? Ie. If
I buy a 1/2" screw, do I plan on using 1/2" ID bearings?
Okay, one more: Does anyone make small mounting flanges for acme nuts? I
just can't see a 2.600" flange for a 3/8" rod.
Thanks again,
JJ
Be Kind, Be Careful, Be Yourself
toggle quoted message
Show quoted text
-----Original Message-----
From: Marv Frankel [mailto:dcdziner@...]
Sent: Monday, October 28, 2002 11:11 PM
To: CAD_CAM_EDM_DRO@...
Subject: Re: [CAD_CAM_EDM_DRO] Ball/acme screw question
Brian,
Actually, I'm somewhat of an expert, and the reason
for a multi-lead
screw is this. You want a nut that will advance 1" in 4
revolutions, but if
the shaft is fairly small in diameter, the depth of the
thread, if you cut
it for a normal 4 threads/inch, would weaken the shaft considerably.
Instead, you cut it 4 threads/inch, but at the depth used for 8
threads/inch. You then have spaces between the threads in
which to cut an
additional lead at the 8 threads/inch depth. You then end up
with a screw
that appears to have 8 threads/inch, but the nut will advance 1" for 4
revolutions. The whole thing has to be done on a lathe, and sounds
complicated, but it really isn't. In the past, I've generated
screws with as
many as 4 leads. They looked like the threads were very fine,
but the nut
would fairly fly down the screw.
You just had a lesson in "Screwing 101".
Marv Frankel
Los Angeles
----- Original Message -----
From: "Brian" <ka1bbg@...>
To: <CAD_CAM_EDM_DRO@...>
Sent: Monday, October 28, 2002 2:41 PM
Subject: Re: [CAD_CAM_EDM_DRO] Ball/acme screw question
Hi, I am no expert but a few things to think about. Multiple lead acme
screws means you have several threads instead of one so they tend to last
longer and are stronger. Rolled acme thread has been going on for a long
time and the acme rods i bought the other day are nicely finnished and a
quick check says their ok on the length. a "v" thread begins to wear quickly
and once it gets sloppy it weakens as it wears out. an acme thread stays
rugged even as its wearing to a point. As for efficient i cant answer but
there are ground threads of all kinds out there some last for many years
even if they are "v" or acme or even buttress thread. Each has a best use.
Take a look at the size you want and then look at the different grades
available. 1/2-10 acme b2 is the cheapest because of so much use, if you
order a 15/16-16 thread custom made to your spec's then expect to pay
premium big bucks. Sometimes the nut and the retaining method(back to back
bearings or nuts) is the most important part. cul brian f.
----- Original Message -----
From: "JJ" <jj5412@...>
To: <cad_cam_edm_dro@...>
Sent: Monday, October 28, 2002 4:53 PM
Subject: [CAD_CAM_EDM_DRO] Ball/acme screw question
(Hoping this is on topic)
In my quest for constant upgrades to my CNC mill/router/pcb thing, I
have a couple of questions:
Why would you choose a multistart screw over a single start screw?
Are acme thread screws more efficient that generic threaded rod?
ADVthanksANCE,
JJ
Be Kind, Be Careful, Be Yourself
Addresses:
FAQ:
FILES:
Post Messages: CAD_CAM_EDM_DRO@...
Subscribe: CAD_CAM_EDM_DRO-subscribe@...
Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@...
List owner: CAD_CAM_EDM_DRO-owner@...,
wanliker@...
Moderator: jmelson@... timg@...
[Moderator]
URL to this group:
OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru
Google.com to reach it
if
you have trouble.
I
consider this to be a
sister site to the CCED group, as many of the same members are there, for
OT
subjects, that are not allowed on the CCED list.
NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN
BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
bill
List Mom
List Owner
Your use of Yahoo! Groups is subject to
Addresses:
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Post Messages: CAD_CAM_EDM_DRO@...
Subscribe: CAD_CAM_EDM_DRO-subscribe@...
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List owner: CAD_CAM_EDM_DRO-owner@...,
wanliker@...
Moderator: jmelson@... timg@... [Moderator]
URL to this group:
OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com
to reach it if
you have trouble.
I consider
this to be a
sister site to the CCED group, as many of the same members
are there, for OT
subjects, that are not allowed on the CCED list.
NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY
POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
bill
List Mom
List Owner
Your use of Yahoo! Groups is subject to
Addresses:
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Post Messages: CAD_CAM_EDM_DRO@...
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List owner: CAD_CAM_EDM_DRO-owner@..., wanliker@...
Moderator: jmelson@... timg@...
[Moderator]
URL to this group:
OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com
to reach it if you have trouble.
I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list. NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........ bill List Mom List Owner Your use of Yahoo! Groups is subject to
|
In a message dated 10/28/2002 6:25:30 PM Central Standard Time, JanRwl@... writes: vices Duh... Make that "vises" ! ! !
|
JJ,
You do not use the O.D. of the screw in the I.D. of the bearing. The
ends of the screw are machined or ground to the next standard size down, to
a snug fit in the bearing I.D.. My R & D in this kind of thing, is usually
done in the McMaster-Carr web site. www.mcmaster.com . They have bearings of
every size and shape available.
Marv Frankel
Los Angeles
toggle quoted message
Show quoted text
----- Original Message ----- From: "JJ" <jj5412@...> To: <CAD_CAM_EDM_DRO@...> Sent: Tuesday, October 29, 2002 4:23 PM Subject: RE: [CAD_CAM_EDM_DRO] Ball/acme screw question Thanks for all the info everyone!
One last (for now) question: Are acme screws their true diameter? Ie. If
I buy a 1/2" screw, do I plan on using 1/2" ID bearings?
Okay, one more: Does anyone make small mounting flanges for acme nuts? I
just can't see a 2.600" flange for a 3/8" rod.
Thanks again,
JJ
Be Kind, Be Careful, Be Yourself
-----Original Message-----
From: Marv Frankel [mailto:dcdziner@...]
Sent: Monday, October 28, 2002 11:11 PM
To: CAD_CAM_EDM_DRO@...
Subject: Re: [CAD_CAM_EDM_DRO] Ball/acme screw question
Brian,
Actually, I'm somewhat of an expert, and the reason
for a multi-lead
screw is this. You want a nut that will advance 1" in 4
revolutions, but if
the shaft is fairly small in diameter, the depth of the
thread, if you cut
it for a normal 4 threads/inch, would weaken the shaft considerably.
Instead, you cut it 4 threads/inch, but at the depth used for 8
threads/inch. You then have spaces between the threads in
which to cut an
additional lead at the 8 threads/inch depth. You then end up
with a screw
that appears to have 8 threads/inch, but the nut will advance 1" for 4
revolutions. The whole thing has to be done on a lathe, and sounds
complicated, but it really isn't. In the past, I've generated
screws with as
many as 4 leads. They looked like the threads were very fine,
but the nut
would fairly fly down the screw.
You just had a lesson in "Screwing 101".
Marv Frankel
Los Angeles
----- Original Message -----
From: "Brian" <ka1bbg@...>
To: <CAD_CAM_EDM_DRO@...>
Sent: Monday, October 28, 2002 2:41 PM
Subject: Re: [CAD_CAM_EDM_DRO] Ball/acme screw question
Hi, I am no expert but a few things to think about. Multiple lead acme
screws means you have several threads instead of one so they tend to last
longer and are stronger. Rolled acme thread has been going on for a long
time and the acme rods i bought the other day are nicely finnished and a
quick check says their ok on the length. a "v" thread begins to wear quickly
and once it gets sloppy it weakens as it wears out. an acme thread stays
rugged even as its wearing to a point. As for efficient i cant answer but
there are ground threads of all kinds out there some last for many years
even if they are "v" or acme or even buttress thread. Each has a best use.
Take a look at the size you want and then look at the different grades
available. 1/2-10 acme b2 is the cheapest because of so much use, if you
order a 15/16-16 thread custom made to your spec's then expect to pay
premium big bucks. Sometimes the nut and the retaining method(back to back
bearings or nuts) is the most important part. cul brian f.
----- Original Message -----
From: "JJ" <jj5412@...>
To: <cad_cam_edm_dro@...>
Sent: Monday, October 28, 2002 4:53 PM
Subject: [CAD_CAM_EDM_DRO] Ball/acme screw question
(Hoping this is on topic)
In my quest for constant upgrades to my CNC mill/router/pcb thing, I
have a couple of questions:
Why would you choose a multistart screw over a single start screw?
Are acme thread screws more efficient that generic threaded rod?
ADVthanksANCE,
JJ
Be Kind, Be Careful, Be Yourself
Addresses:
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JJ wrote: One last (for now) question: Are acme screws their true diameter?
ie If I buy a 1/2" screw, do I plan on using 1/2" ID bearings?
My 1" acme leadscrews are 1" OD (ie 0.990 - 1.000" major pitch dia). As the minor dia varies (.7509"-.7800") you can use a .75" ID or smaller bearing. If you are looking at the 1/2" acme leadscrews, it is of course 1/2" OD and the minor dia varies( .3594"-.3800") so even a 3/8" id (.375") bearing is risky, so you'll probably need to go for an even smaller ID bearing! regards Doug Fortune <- Home of the 1KW BEaST power supply for Geckos .
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