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Old Aug 23, 2010, 01:02 PM
Dave H.
Guest
n/a Posts
Acme leadscrew supplier? DIY anti-backlash nuts...?

Hi, can any denizen of the group recommend an UK supplier for Imperial
leadscrews? I'm after a replacement for my cross-slide screw (5/8" x 8tpi
Acme, left-hand thread, very worn!) that won't be too expensive nor so
inaccurate there's no point swapping it...

I appreciate that I'll need to make a new bronze nut to fit, interesting
bit of screwcutting to try there! Were I to try making an anti-backlash nut,
is the simplest way going to be making part of the nut a separate item that
screws into the main nut via a *slightly* different pitch thread joining the
two parts? i.e make an insert with the 5/8" - 8tpi L/H Acme on the inside
and a (for instance) 7/8" - 9Ttpi Whitworth (also L/H) on the outside,
locknut to suit? The main body of the leadscrew nut would have most of its
length threaded for the Acme screw, the rest for the insert (approx. 1-3/4"
of Acme, 3/4" of Whitworth so that more of the wear would occur on the
adjuster Acme thread).

This I think would mean a full clockwise turn of the "adjuster" would
withdraw it by 1/9" and move 1/8" along the leadscrew taking up 1/72" of
slack (roughly 14 thou") as it wears - I'd hope it wouldn't *need* a full
turn though! I'm aware that at a couple of points in the insert there would
be "minimal" thickness between the threads (about 50 thou") but this should
only be for a fraction of a thread turn...

Why Whitworth? I'm trying to stick with Imperial and contemporary threads
if possible!

Any pitfalls, pratfalls, practical difficulties I should be aware of?

Cheers all,
Dave H.
--
(The engineer formerly known as Homeless)

"Rules are for the obedience of fools, and the guidance of wise men" -
Douglas Bader
Old Aug 23, 2010, 01:46 PM
stans4@prolynx.com
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

On Aug 23, 12:02 pm, "Dave H."
<hopefuldave_doesnt_eat_spiced_...@hotmail.com> wrote:

> Hi, can any denizen of the group recommend an UK supplier for Imperial
> leadscrews? I'm after a replacement for my cross-slide screw (5/8" x 8tpi
> Acme, left-hand thread, very worn!) that won't be too expensive nor so
> inaccurate there's no point swapping it...
>
>  I appreciate that I'll need to make a new bronze nut to fit, interesting
> bit of screwcutting to try there! Were I to try making an anti-backlash nut,
> is the simplest way going to be making part of the nut a separate item that
> screws into the main nut via a *slightly* different pitch thread joining the
> two parts? i.e make an insert with the 5/8" - 8tpi L/H Acme on the inside
> and a (for instance) 7/8" - 9Ttpi Whitworth (also L/H) on the outside,
> locknut to suit? The main body of the leadscrew nut would have most of its
> length threaded for the Acme screw, the rest for the insert (approx. 1-3/4"
> of Acme, 3/4" of Whitworth so that more of the wear would occur on the
> adjuster Acme thread).
>
>  This I think would mean a full clockwise turn of the "adjuster" would
> withdraw it by 1/9" and move 1/8" along the leadscrew taking up 1/72" of
> slack (roughly 14 thou") as it wears - I'd hope it wouldn't *need* a full
> turn though! I'm aware that at a couple of points in the insert there would
> be "minimal" thickness between the threads (about 50 thou") but this should
> only be for a fraction of a thread turn...
>
>  Why Whitworth?  I'm trying to stick with Imperial and contemporary threads
> if possible!
>
> Any pitfalls, pratfalls, practical difficulties I should be aware of?
>
> Cheers all,
> Dave H.
> --
> (The engineer formerly known as Homeless)
>
> "Rules are for the obedience of fools, and the guidance of wise men" -
> Douglas Bader


For anti-backlash, you use the same pitch, two pieces. Cheap and
cheesy just slices an existing nut mostly through perpendicular to the
hole and squeezes/expands the slit by whatever means you like to take
out the slop. Have seen some very elaborate adjustments, one
consisted of another threaded part insert into the main nut and finely
threaded on the inserted portion. The rim protruding had indexing
notches with a stop dog. Need less backlash, undo the dog and move
the thing a notch or two, ala Winchester 1897 takedown. Just depends
on how much space you've got to mess with things, this had to have
been a couple of inches long. There's a lot of these types of things
in those old "xxx Mechanical Mechanisms and Movements" books, www.archive.org
would have some downloads. Henley published a bunch.

Stan
Old Aug 23, 2010, 01:54 PM
Steve Lusardi
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

In the States, most machinery dealers. In the UK, make them yourself.
Steve

"Dave H." <hopefuldave_doesnt_eat_spiced_ham@hotmail.com> wrote in message news:VIyco.144858$ex1.16941@hurricane...

> Hi, can any denizen of the group recommend an UK supplier for Imperial
> leadscrews? I'm after a replacement for my cross-slide screw (5/8" x 8tpi
> Acme, left-hand thread, very worn!) that won't be too expensive nor so
> inaccurate there's no point swapping it...
>
> I appreciate that I'll need to make a new bronze nut to fit, interesting
> bit of screwcutting to try there! Were I to try making an anti-backlash nut,
> is the simplest way going to be making part of the nut a separate item that
> screws into the main nut via a *slightly* different pitch thread joining the
> two parts? i.e make an insert with the 5/8" - 8tpi L/H Acme on the inside
> and a (for instance) 7/8" - 9Ttpi Whitworth (also L/H) on the outside,
> locknut to suit? The main body of the leadscrew nut would have most of its
> length threaded for the Acme screw, the rest for the insert (approx. 1-3/4"
> of Acme, 3/4" of Whitworth so that more of the wear would occur on the
> adjuster Acme thread).
>
> This I think would mean a full clockwise turn of the "adjuster" would
> withdraw it by 1/9" and move 1/8" along the leadscrew taking up 1/72" of
> slack (roughly 14 thou") as it wears - I'd hope it wouldn't *need* a full
> turn though! I'm aware that at a couple of points in the insert there would
> be "minimal" thickness between the threads (about 50 thou") but this should
> only be for a fraction of a thread turn...
>
> Why Whitworth? I'm trying to stick with Imperial and contemporary threads
> if possible!
>
> Any pitfalls, pratfalls, practical difficulties I should be aware of?
>
> Cheers all,
> Dave H.
> --
> (The engineer formerly known as Homeless)
>
> "Rules are for the obedience of fools, and the guidance of wise men" -
> Douglas Bader
>
>
Old Aug 23, 2010, 01:58 PM
Richard Shute
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

On Mon, 23 Aug 2010 19:02:25 +0100, "Dave H."
<hopefuldave_doesnt_eat_spiced_ham@hotmail.com> wrote:


>Hi, can any denizen of the group recommend an UK supplier for Imperial
>leadscrews? I'm after a replacement for my cross-slide screw (5/8" x 8tpi
>Acme, left-hand thread, very worn!) that won't be too expensive nor so
>inaccurate there's no point swapping it...
>
> I appreciate that I'll need to make a new bronze nut to fit, interesting
>bit of screwcutting to try there! Were I to try making an anti-backlash nut,
>is the simplest way going to be making part of the nut a separate item that
>screws into the main nut via a *slightly* different pitch thread joining the
>two parts? i.e make an insert with the 5/8" - 8tpi L/H Acme on the inside
>and a (for instance) 7/8" - 9Ttpi Whitworth (also L/H) on the outside,
>locknut to suit? The main body of the leadscrew nut would have most of its
>length threaded for the Acme screw, the rest for the insert (approx. 1-3/4"
>of Acme, 3/4" of Whitworth so that more of the wear would occur on the
>adjuster Acme thread).
>
> This I think would mean a full clockwise turn of the "adjuster" would
>withdraw it by 1/9" and move 1/8" along the leadscrew taking up 1/72" of
>slack (roughly 14 thou") as it wears - I'd hope it wouldn't *need* a full
>turn though! I'm aware that at a couple of points in the insert there would
>be "minimal" thickness between the threads (about 50 thou") but this should
>only be for a fraction of a thread turn...
>
> Why Whitworth? I'm trying to stick with Imperial and contemporary threads
>if possible!
>
>Any pitfalls, pratfalls, practical difficulties I should be aware of?
>
>Cheers all,
>Dave H.


Hello Dave,
I used to use Halifax Rack & Screw for quality leadscrews, I'm happy
to see they are still going:
http://www.hrs-ccl.co.uk/

but I have no idea of how 'cost effective' they will be.

I have made an anti backlash nut arrangement on my lathe. I made the
two halves with a flange/face between the parts and a pair of axial
4BA cap heads to lock the adjusting part relative to the fixed part.
Simply rotating one part relative to the other and locking the screws
does the job. I did mill some arc slots for the screws.

I have also used the differential thread arrangement you mention for
other adjustment purposes and I suspect you would find it very tedious
and possibly impossible to use depending on the relative position of
the threads. If you do take that route, make the adjsuter threads
first and assemble the two parts and only then cut the Acme thread
through both parts together. You may need to use shims between the two
parts so that you can screw them hard together or some other means of
locking one relative to the other.

Richard

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
Old Aug 23, 2010, 02:01 PM
Andrew Mawson
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

"Dave H." <hopefuldave_doesnt_eat_spiced_ham@hotmail.com> wrote in
message news:VIyco.144858$ex1.16941@hurricane...

> Hi, can any denizen of the group recommend an UK supplier for

Imperial

> leadscrews? I'm after a replacement for my cross-slide screw (5/8" x

8tpi

> Acme, left-hand thread, very worn!) that won't be too expensive nor

so

> inaccurate there's no point swapping it...
>
> I appreciate that I'll need to make a new bronze nut to fit,

interesting

> bit of screwcutting to try there! Were I to try making an

anti-backlash nut,

> is the simplest way going to be making part of the nut a separate

item that

> screws into the main nut via a *slightly* different pitch thread

joining the

> two parts? i.e make an insert with the 5/8" - 8tpi L/H Acme on the

inside

> and a (for instance) 7/8" - 9Ttpi Whitworth (also L/H) on the

outside,

> locknut to suit? The main body of the leadscrew nut would have most

of its

> length threaded for the Acme screw, the rest for the insert (approx.

1-3/4"

> of Acme, 3/4" of Whitworth so that more of the wear would occur on

the

> adjuster Acme thread).
>
> This I think would mean a full clockwise turn of the "adjuster"

would

> withdraw it by 1/9" and move 1/8" along the leadscrew taking up

1/72" of

> slack (roughly 14 thou") as it wears - I'd hope it wouldn't *need* a

full

> turn though! I'm aware that at a couple of points in the insert

there would

> be "minimal" thickness between the threads (about 50 thou") but this

should

> only be for a fraction of a thread turn...
>
> Why Whitworth? I'm trying to stick with Imperial and contemporary

threads

> if possible!
>
> Any pitfalls, pratfalls, practical difficulties I should be aware

of?

>
> Cheers all,
> Dave H.
> --
> (The engineer formerly known as Homeless)
>
> "Rules are for the obedience of fools, and the guidance of wise

men" -

> Douglas Bader
>
>


The later Colchester Students and Masters use two sections of the same
pitch, with a Vee shape where they meet, with a wedge pushed into the
Vee on the cross slide, by an allen headed grub screw.

I have seen a dealer squash a bronze nut in a vice onto the lead
screw, but even if you pull my nails out I'm not naming names !!!!!!

AWEM
Old Aug 23, 2010, 02:06 PM
John S
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

On 23 Aug, 19:02, "Dave H."
<hopefuldave_doesnt_eat_spiced_...@hotmail.com> wrote:

> Hi, can any denizen of the group recommend an UK supplier for Imperial
> leadscrews? I'm after a replacement for my cross-slide screw (5/8" x 8tpi
> Acme, left-hand thread, very worn!) that won't be too expensive nor so
> inaccurate there's no point swapping it...
>
>  I appreciate that I'll need to make a new bronze nut to fit, interesting
> bit of screwcutting to try there! Were I to try making an anti-backlash nut,
> is the simplest way going to be making part of the nut a separate item that
> screws into the main nut via a *slightly* different pitch thread joining the
> two parts? i.e make an insert with the 5/8" - 8tpi L/H Acme on the inside
> and a (for instance) 7/8" - 9Ttpi Whitworth (also L/H) on the outside,
> locknut to suit? The main body of the leadscrew nut would have most of its
> length threaded for the Acme screw, the rest for the insert (approx. 1-3/4"
> of Acme, 3/4" of Whitworth so that more of the wear would occur on the
> adjuster Acme thread).
>
>  This I think would mean a full clockwise turn of the "adjuster" would
> withdraw it by 1/9" and move 1/8" along the leadscrew taking up 1/72" of
> slack (roughly 14 thou") as it wears - I'd hope it wouldn't *need* a full
> turn though! I'm aware that at a couple of points in the insert there would
> be "minimal" thickness between the threads (about 50 thou") but this should
> only be for a fraction of a thread turn...
>
>  Why Whitworth?  I'm trying to stick with Imperial and contemporary threads
> if possible!
>
> Any pitfalls, pratfalls, practical difficulties I should be aware of?
>
> Cheers all,
> Dave H.
> --
> (The engineer formerly known as Homeless)
>
> "Rules are for the obedience of fools, and the guidance of wise men" -
> Douglas Bader


Buy a second-hand early Myford ML7 leadscrew and cut the unused bit
off at the tailstock end, they are 5/8" x 8 tpi LH.

Try Jim Marshall over at http://www.homeworkshop.org.uk/ he's always
breaking Myfords for spares.
John S.
Old Aug 23, 2010, 02:07 PM
John S
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

On 23 Aug, 20:01, "Andrew Mawson"
<andrew@no_spam_please_mawson.org.uk> wrote:


>
> I have seen a dealer squash a bronze nut in a vice onto the lead
> screw, but even if you pull my nails out I'm not naming names !!!!!!
>
> AWEM


How about bribing you with a pair of kippers or two ?

John S.
Old Aug 23, 2010, 02:25 PM
Ned Simmons
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

On Mon, 23 Aug 2010 19:02:25 +0100, "Dave H."
<hopefuldave_doesnt_eat_spiced_ham@hotmail.com> wrote:


>Hi, can any denizen of the group recommend an UK supplier for Imperial
>leadscrews? I'm after a replacement for my cross-slide screw (5/8" x 8tpi
>Acme, left-hand thread, very worn!) that won't be too expensive nor so
>inaccurate there's no point swapping it...


A UK distributor
http://www.kugelmotion.co.uk/Products.htm
for this company.
http://www.nookindustries.com/acme/A...Info.cfm?id=26


Or get someone to order a piece from McMaster-Carr and ship it to you.

98940A343
4140 Alloy Steel Precision Acme Threaded Rod 5/8"-8 Size, 1/8" Travel
Distance/Turn, Lh Thread
$11.73/foot

--
Ned Simmons
Old Aug 24, 2010, 05:53 AM
Andrew Mawson
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

"John S" <john@stevenson-engineers.co.uk> wrote in message
news:13b011cd-62da-4249-850d-5d345be3da57@x25g2000yqj.googlegroups.com...

> On 23 Aug, 20:01, "Andrew Mawson"
> <andrew@no_spam_please_mawson.org.uk> wrote:
>

> >
> > I have seen a dealer squash a bronze nut in a vice onto the lead
> > screw, but even if you pull my nails out I'm not naming names

!!!!!!

> >
> > AWEM

>
> How about bribing you with a pair of kippers or two ?
>
> John S.
>


....ah .. well now THAT'S different <G>

AWEM
Old Aug 24, 2010, 09:14 AM
Pete
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

"John S" <john@stevenson-engineers.co.uk> wrote in message
news:432bec73-927b-4d6a-8f75-2112b82d77c1@z10g2000yqb.googlegroups.com...
On 23 Aug, 19:02, "Dave H."
<hopefuldave_doesnt_eat_spiced_...@hotmail.com> wrote:

> Hi, can any denizen of the group recommend an UK supplier for Imperial
> leadscrews? I'm after a replacement for my cross-slide screw (5/8" x 8tpi
> Acme, left-hand thread, very worn!) that won't be too expensive nor so
> inaccurate there's no point swapping it...
>
> I appreciate that I'll need to make a new bronze nut to fit, interesting
> bit of screwcutting to try there! Were I to try making an anti-backlash
> nut,
> is the simplest way going to be making part of the nut a separate item
> that
> screws into the main nut via a *slightly* different pitch thread joining
> the
> two parts? i.e make an insert with the 5/8" - 8tpi L/H Acme on the inside
> and a (for instance) 7/8" - 9Ttpi Whitworth (also L/H) on the outside,
> locknut to suit? The main body of the leadscrew nut would have most of its
> length threaded for the Acme screw, the rest for the insert (approx.
> 1-3/4"
> of Acme, 3/4" of Whitworth so that more of the wear would occur on the
> adjuster Acme thread).
>
> This I think would mean a full clockwise turn of the "adjuster" would
> withdraw it by 1/9" and move 1/8" along the leadscrew taking up 1/72" of
> slack (roughly 14 thou") as it wears - I'd hope it wouldn't *need* a full
> turn though! I'm aware that at a couple of points in the insert there
> would
> be "minimal" thickness between the threads (about 50 thou") but this
> should
> only be for a fraction of a thread turn...
>
> Why Whitworth? I'm trying to stick with Imperial and contemporary threads
> if possible!
>
> Any pitfalls, pratfalls, practical difficulties I should be aware of?
>
> Cheers all,
> Dave H.
> --
> (The engineer formerly known as Homeless)
>
> "Rules are for the obedience of fools, and the guidance of wise men" -
> Douglas Bader


Buy a second-hand early Myford ML7 leadscrew and cut the unused bit
off at the tailstock end, they are 5/8" x 8 tpi LH.

Try Jim Marshall over at http://www.homeworkshop.org.uk/ he's always
breaking Myfords for spares.
John S.

Why not make a tap from the remaining piece then use that to thread some
plastic for a cross-slide nut?
Old Aug 24, 2010, 01:18 PM
Dave H.
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

"Pete" wrote ...

>
> "John S" wrote...


>>
>> Buy a second-hand early Myford ML7 leadscrew and cut the unused bit
>> off at the tailstock end, they are 5/8" x 8 tpi LH.
>>
>> Try Jim Marshall over at http://www.homeworkshop.org.uk/ he's always
>> breaking Myfords for spares.
>> John S.

>
> Why not make a tap from the remaining piece then use that to thread some
> plastic for a cross-slide nut?
>


I had thought about a plastic nut, but due to a lack of physical space and
the way it'd be mounted (about 1-1/8" square section, a single 5/8" BSF and
a 1/8" dowel pin through the cross-slide) was concerned that it wouldn't be
a rigid enough assembly, hence the choice of bronze as per the original or
if not, some decent brass?

I think I'd rather spend a few extra quid to get a new piece of precision
leadscrew rather than take a chance with an used one out of a Myford heading
for the scrapper! I'll need upwards of 18" of screw by the time I've turned
ends down etc, possibly 24", which might well get me into the already-worn
bit of a scrapper's leadscrew, as my cross-slide has about 11" of travel
(which should come in handy when I want to mill things on the carriage, but
makes for a bit more expense!).

Tapping with a leftover hadn't occured to me though, might be better than
trying to screwcut an internal L/H Acme through two separate parts in one go
(erk), I suppose it should be easy enough to grind some flutes and relieve
the threads a touch[1] (another skill to learn - I'd need plenty of required
practice on some junk bolts first!) I have just spotted the Right Taps on
Ebay for not too much money, though! Presumably I'd have to pilot drill and
bore/ream slightly oversize to get about a 75-80% engagement depth in the
nut? Would I need to get as close as poss' to 100% to ensure accuracy?

Cheers all for the info, very much appreciated :)

Dave H.
--
(The engineer formerly known as Homeless)

"Rules are for the obedience of fools, and the guidance of wise men" -
Douglas Bader

[1] of course, if I had an Eureka relieving attachment... but I'd need the
lathe to cut accurately first so I could make it, of course!
Old Aug 24, 2010, 02:56 PM
Pete
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

"Dave H." <hopefuldave_doesnt_eat_spiced_ham@hotmail.com> wrote in message
news:V1Uco.9880$NG7.3924@hurricane...

>
> "Pete" wrote ...

>>
>> "John S" wrote...

>

>>>
>>> Buy a second-hand early Myford ML7 leadscrew and cut the unused bit
>>> off at the tailstock end, they are 5/8" x 8 tpi LH.
>>>
>>> Try Jim Marshall over at http://www.homeworkshop.org.uk/ he's always
>>> breaking Myfords for spares.
>>> John S.

>>
>> Why not make a tap from the remaining piece then use that to thread some
>> plastic for a cross-slide nut?
>>

>
> I had thought about a plastic nut, but due to a lack of physical space and
> the way it'd be mounted (about 1-1/8" square section, a single 5/8" BSF
> and a 1/8" dowel pin through the cross-slide) was concerned that it
> wouldn't be a rigid enough assembly, hence the choice of bronze as per the
> original or if not, some decent brass?
>
> I think I'd rather spend a few extra quid to get a new piece of precision
> leadscrew rather than take a chance with an used one out of a Myford
> heading for the scrapper! I'll need upwards of 18" of screw by the time
> I've turned ends down etc, possibly 24", which might well get me into the
> already-worn bit of a scrapper's leadscrew, as my cross-slide has about
> 11" of travel (which should come in handy when I want to mill things on
> the carriage, but makes for a bit more expense!).
>
> Tapping with a leftover hadn't occured to me though, might be better than
> trying to screwcut an internal L/H Acme through two separate parts in one
> go (erk), I suppose it should be easy enough to grind some flutes and
> relieve the threads a touch[1] (another skill to learn - I'd need plenty
> of required practice on some junk bolts first!) I have just spotted the
> Right Taps on Ebay for not too much money, though! Presumably I'd have to
> pilot drill and bore/ream slightly oversize to get about a 75-80%
> engagement depth in the nut? Would I need to get as close as poss' to 100%
> to ensure accuracy?
>
> Cheers all for the info, very much appreciated :)
>
> Dave H.
> --
> (The engineer formerly known as Homeless)
>
> "Rules are for the obedience of fools, and the guidance of wise men" -
> Douglas Bader
>
> [1] of course, if I had an Eureka relieving attachment... but I'd need the
> lathe to cut accurately first so I could make it, of course!
>
>


Dave.

I am just about to make a cross-slide nut from plastic, and had the same
concerns about rigidity of the mounting (though I think we are both
under-estimating the structural rigidity of the material). My nut has a 5/8"
stud machined in it that plugs into the bottom of the slide. What I'm
thinking of doing, is boring the quite substantial nut that I have and
in-setting it with a slug of delrin or ptfe, then threading that plastic
slug.

Just for fun my cross-slide screw has an imperial OD and a metric pitch, so
the only way to replace a nut is to make it. I figure that making a plastic
nut will reduce wear on the odd-ball screw.

I'll keep the group up-dated with the results.
Old Aug 25, 2010, 03:55 AM
Richard Shute
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

<...>

>
> Tapping with a leftover hadn't occured to me though, might be better than
>trying to screwcut an internal L/H Acme through two separate parts in one go
>(erk), I suppose it should be easy enough to grind some flutes and relieve
>the threads a touch[1] (another skill to learn - I'd need plenty of required
>practice on some junk bolts first!) I have just spotted the Right Taps on
>Ebay for not too much money, though! Presumably I'd have to pilot drill and
>bore/ream slightly oversize to get about a 75-80% engagement depth in the
>nut? Would I need to get as close as poss' to 100% to ensure accuracy?
>
>Cheers all for the info, very much appreciated :)
>
>Dave H.


Dave,
A couple of points. When I made a (leadscrew) nut I initially tried
tapping it. I found it quite impossible. It's not like a 'normal' tap,
it shifts a LOT more material. In the end I thread-cut the thread and
cleaned it out/finished it with the tap. The tap I bought did have
very little lead-in and it is possible that my life was also a little
harder because I was using some gun-metal which I happened to have,
lovely bearing material, but it seemed quite 'sticky' to machine.

As part of the process I discovered that it is usual for an Acme tap
to be significantly oversize, 030" I think on a half inch (ie 0.530"
OD), further, I found that the cheap RDG tap I had bought was an
additional 025-odd in excess of that, so that's around 055" over the
nominal size. You do need some oversize to give clearance to the
thread tips, but it plays havoc with thread depth infeed until you end
up reading the book (Machinery's) to find what went wrong!

Machining a left hand thread is in many ways less stressful than RH as
you are coming out, away from the chuck so there's no worry about
running into the chuck or other important bits inside while you are
concentrating on the thread. Give it a go, fear of the unknown is
usually far worse than the reality.

Depth of engagement should not have any significant affect on
accuracy, just longevity and ease of manufacture.

Richard

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Old Aug 25, 2010, 04:36 AM
david homer
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

"Dave H." <hopefuldave_doesnt_eat_spiced_ham@hotmail.com> wrote in message
news:VIyco.144858$ex1.16941@hurricane...

> Hi, can any denizen of the group recommend an UK supplier for Imperial
> leadscrews? I'm after a replacement for my cross-slide screw (5/8" x 8tpi
> Acme, left-hand thread, very worn!) that won't be too expensive nor so
> inaccurate there's no point swapping it...
>
> I appreciate that I'll need to make a new bronze nut to fit, interesting
> bit of screwcutting to try there! Were I to try making an anti-backlash
> nut, is the simplest way going to be making part of the nut a separate
> item that screws into the main nut via a *slightly* different pitch thread
> joining the two parts? i.e make an insert with the 5/8" - 8tpi L/H Acme on
> the inside and a (for instance) 7/8" - 9Ttpi Whitworth (also L/H) on the
> outside, locknut to suit? The main body of the leadscrew nut would have
> most of its length threaded for the Acme screw, the rest for the insert
> (approx. 1-3/4" of Acme, 3/4" of Whitworth so that more of the wear would
> occur on the adjuster Acme thread).
>





You could try these, I have bought from them but not cheap.
http://www.kingston-engineering.co.uk/data/frame3b.htm
Old Aug 25, 2010, 07:25 AM
Pete Keillor
Guest
n/a Posts
Re: Acme leadscrew supplier? DIY anti-backlash nuts...?

On Wed, 25 Aug 2010 09:55:12 +0100, Richard Shute
<sharkface.pilot@toucansurf.com> wrote:

<snip>


>Machining a left hand thread is in many ways less stressful than RH as
>you are coming out, away from the chuck so there's no worry about
>running into the chuck or other important bits inside while you are
>concentrating on the thread. Give it a go, fear of the unknown is
>usually far worse than the reality.
>
>Depth of engagement should not have any significant affect on
>accuracy, just longevity and ease of manufacture.
>
>Richard
>

I machined a right hand thread (for a mop handle adapter) by placing
the boring bar / homemade threading tool on the back side, running the
lathe in reverse. That makes the bit come out of the hole, very handy
at 5 tpi.

Pete Keillor
 


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