Darwin Rod Size

I am having trouble finding any info in the wiki... what is the size
of the rod used in darwin? is it all 8mm? I'm just wondering because
I think i'm going to buy some on mcmaster or somewhere and see what
happens. =)

~Zach
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On Sat, 2007-03-17 at 19:52 -0400, Zach Hoeken wrote:
> I am having trouble finding any info in the wiki... what is the size
> of the rod used in darwin? is it all 8mm? I'm just wondering because
> I think i'm going to buy some on mcmaster or somewhere and see what
> happens. =)

I believe so. 5/16" should also work in theory.

I've been using the mild steel, which is cheaper than the stainless
stuff. It's gone a little rusty over the last year or so but still
functions fine. If there's a big price difference, I might just use the
stainless for the horizontal slides.

Vik :v)

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where exactly do i get the stuff? is mcmaster a good supplier?

On 3/17/07, Vik Olliver wrote:
> On Sat, 2007-03-17 at 19:52 -0400, Zach Hoeken wrote:
> > I am having trouble finding any info in the wiki... what is the size
> > of the rod used in darwin? is it all 8mm? I'm just wondering because
> > I think i'm going to buy some on mcmaster or somewhere and see what
> > happens. =)
>
> I believe so. 5/16" should also work in theory.
>
> I've been using the mild steel, which is cheaper than the stainless
> stuff. It's gone a little rusty over the last year or so but still
> functions fine. If there's a big price difference, I might just use the
> stainless for the horizontal slides.
>
> Vik :v)
>
>
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On Sat, 2007-03-17 at 21:37 -0400, Zach Hoeken wrote:
> where exactly do i get the stuff? is mcmaster a good supplier?

I've found my local small metal fabricator. He gets regular supplies in
from the commercial suppliers and he'll order stuff up for me. I might
get a bit of 8mm extruded aluminium tubing too, and experiment a bit.
The aluminium is cheaper than the steel around here - in small
quantities at least.

Vik :v)

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On Saturday 17 March 2007 21:37, Zach Hoeken wrote:
> where exactly do i get the stuff? is mcmaster a good supplier?
>
Yes. mcmaster is reliable, if expensive for some things. You would also have
success by calling your local metals suppliers and fasteners suppliers and
asking for 8 mm (or maybe 5/16") steel rod - check your phone book. Home
depot may have 5/16 rod as well. You're probably going to end up buying it
in 36" lengths (914.4 mm).

8 mm is 2.5 mil (thousandths of an inch), .0635 mm smaller than 5/16" rod.
5/16 should work, maybe. (I don't really have an intuition for tolerances and
fits yet.) 5/16" is more common over here in North America. One thing we
might end up doing is carefully drilling out 8 mm holes to 5/16" if we need
to. (And if we have to, go to the next size drill bit up. 5/16" = .3125";
the next size up is a .316" bit aka Letter Size "O".)

Looking at mcmaster (searching on 8 mm drill rod), this looks good:

36" of 8 mm steel rod for $4.50 Each.
Grade O-1 Oil-Hardening Tool Steel
Part Number: 88625K67
$4.50 Each

I also found
36" of 5/16" rod for $3.19 Each
General Purpose Water-Hardened W1 Tool Steel
Part number 8890K41
$3.19 Each


-Sebastien

> On 3/17/07, Vik Olliver wrote:
> > On Sat, 2007-03-17 at 19:52 -0400, Zach Hoeken wrote:
> > > I am having trouble finding any info in the wiki... what is the size
> > > of the rod used in darwin? is it all 8mm? I'm just wondering because
> > > I think i'm going to buy some on mcmaster or somewhere and see what
> > > happens. =)
> >
> > I believe so. 5/16" should also work in theory.
> >
> > I've been using the mild steel, which is cheaper than the stainless
> > stuff. It's gone a little rusty over the last year or so but still
> > functions fine. If there's a big price difference, I might just use the
> > stainless for the horizontal slides.
> >
> > Vik :v)
>
> _______________________________________________
> Developers mailing list
> Developers@reprap.org
> [reprap.org]
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Quoting Zach Hoeken :

> I am having trouble finding any info in the wiki... what is the size
> of the rod used in darwin? is it all 8mm? I'm just wondering because
> I think i'm going to buy some on mcmaster or somewhere and see what
> happens. =)

Yup - all the smooth rods are 8mm; all the threaded rods are M8.

Best wishes

Adrian

Dr Adrian Bowyer
[staff.bath.ac.uk]
[reprap.org]
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Quoting Vik Olliver :

> I believe so. 5/16" should also work in theory.
>
> I've been using the mild steel, which is cheaper than the stainless
> stuff. It's gone a little rusty over the last year or so but still
> functions fine. If there's a big price difference, I might just use the
> stainless for the horizontal slides.

Except for the slides (which should be greased), there's nothing to
stop people painting it...

Best wishes

Adrian

Dr Adrian Bowyer
[staff.bath.ac.uk]
[reprap.org]
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Quoting Vik Olliver :

> On Sat, 2007-03-17 at 21:37 -0400, Zach Hoeken wrote:
>> where exactly do i get the stuff? is mcmaster a good supplier?
>
> I've found my local small metal fabricator. He gets regular supplies in
> from the commercial suppliers and he'll order stuff up for me. I might
> get a bit of 8mm extruded aluminium tubing too, and experiment a bit.
> The aluminium is cheaper than the steel around here - in small
> quantities at least.

Ed's Darwin desin uses steel-on-steel 8mm rods at right angles (point
contact) for the sliding motions. This should be good (lower wear than
plastic on steel, and easy to fix when a flat does eventually wear on
the rods: just slacken them off and rotate them by 20 degrees), but I'm
not sure Al is hard enough for that. Maybe use Al for structure, and
steel for the 4 sliding rods?

Best wishes

Adrian

Dr Adrian Bowyer
[staff.bath.ac.uk]
[reprap.org]
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Ed - didn't you try 5/16" (I seem to remember) and it worked? If not,
might be an idea to send one of the corner blocks across to
Sebastien/Forrest/Zach so they can try it for fit. Alternatively
search the Mech Eng Stores (Dungeon Section) for an old offcut of 5/16"
rod.

Anyone know the nearest non-metric thread to M8? Pitch doesn't matter
(fix in software).

Best wishes

Adrian

Dr Adrian Bowyer
[staff.bath.ac.uk]
[reprap.org]

Quoting Sebastien Bailard :

> On Saturday 17 March 2007 21:37, Zach Hoeken wrote:
>> where exactly do i get the stuff? is mcmaster a good supplier?
>>
> Yes. mcmaster is reliable, if expensive for some things. You would
> also have
> success by calling your local metals suppliers and fasteners suppliers and
> asking for 8 mm (or maybe 5/16") steel rod - check your phone book. Home
> depot may have 5/16 rod as well. You're probably going to end up buying it
> in 36" lengths (914.4 mm).
>
> 8 mm is 2.5 mil (thousandths of an inch), .0635 mm smaller than 5/16" rod.
> 5/16 should work, maybe. (I don't really have an intuition for
> tolerances and
> fits yet.) 5/16" is more common over here in North America. One thing we
> might end up doing is carefully drilling out 8 mm holes to 5/16" if we need
> to. (And if we have to, go to the next size drill bit up. 5/16" = .3125";
> the next size up is a .316" bit aka Letter Size "O".)
>
> Looking at mcmaster (searching on 8 mm drill rod), this looks good:
>
> 36" of 8 mm steel rod for $4.50 Each.
> Grade O-1 Oil-Hardening Tool Steel
> Part Number: 88625K67
> $4.50 Each
>
> I also found
> 36" of 5/16" rod for $3.19 Each
> General Purpose Water-Hardened W1 Tool Steel
> Part number 8890K41
> $3.19 Each
>
>
> -Sebastien
>
>> On 3/17/07, Vik Olliver wrote:
>> > On Sat, 2007-03-17 at 19:52 -0400, Zach Hoeken wrote:
>> > > I am having trouble finding any info in the wiki... what is the size
>> > > of the rod used in darwin? is it all 8mm? I'm just wondering because
>> > > I think i'm going to buy some on mcmaster or somewhere and see what
>> > > happens. =)
>> >
>> > I believe so. 5/16" should also work in theory.
>> >
>> > I've been using the mild steel, which is cheaper than the stainless
>> > stuff. It's gone a little rusty over the last year or so but still
>> > functions fine. If there's a big price difference, I might just use the
>> > stainless for the horizontal slides.
>> >
>> > Vik :v)
>>
>> _______________________________________________
>> Developers mailing list
>> Developers@reprap.org
>> [reprap.org]
> _______________________________________________
> Developers mailing list
> Developers@reprap.org
> [reprap.org]
>



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On Sun, 2007-03-18 at 12:57 +0000, Adrian Bowyer wrote:
> Ed's Darwin desin uses steel-on-steel 8mm rods at right angles (point
> contact) for the sliding motions. This should be good (lower wear
> than
> plastic on steel, and easy to fix when a flat does eventually wear on
> the rods: just slacken them off and rotate them by 20 degrees), but
> I'm
> not sure Al is hard enough for that. Maybe use Al for structure, and
> steel for the 4 sliding rods?

Sounds sensible.

As an aside, I've been running Zaphod with ABS-on-steel slides. You can
discern the wear.

Vik :v)

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great. the one thing i was worried about was not being able to use
these skate bearings, but i got out my calipers and measured them...
the inner hole has a diameter of 8mm. if you havent experimented with
them yet adrian, get yourself down to a skate shop (wish i could be
there to see it) and get some replacement bearings. you should be
able to get them for cheap... i got mine for $1 / ea online and they
will make all the rotating parts move SO nicely.

also, 5/16" == 7.8mm so it will probably work as an american
substitute. we could go up one size to 3/8" which is 9.53mm.
Probably not a very good candidate. Worst case scenario we could do a
simple redesign with 5/16" holes and drill them out for metric. then
again, metric parts are easy to order and things will probably work
"as-is" so no worries =)

On 3/18/07, Adrian Bowyer wrote:
> Quoting Zach Hoeken :
>
> > I am having trouble finding any info in the wiki... what is the size
> > of the rod used in darwin? is it all 8mm? I'm just wondering because
> > I think i'm going to buy some on mcmaster or somewhere and see what
> > happens. =)
>
> Yup - all the smooth rods are 8mm; all the threaded rods are M8.
>
> Best wishes
>
> Adrian
>
> Dr Adrian Bowyer
> [staff.bath.ac.uk]
> [reprap.org]
> _______________________________________________
> Developers mailing list
> Developers@reprap.org
> [reprap.org]
>
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On Sunday 18 March 2007 16:16, Zach Hoeken wrote:
> great. the one thing i was worried about was not being able to use
> these skate bearings, but i got out my calipers and measured them...
> the inner hole has a diameter of 8mm. if you havent experimented with
> them yet adrian, get yourself down to a skate shop (wish i could be
> there to see it) and get some replacement bearings. you should be
> able to get them for cheap... i got mine for $1 / ea online and they
> will make all the rotating parts move SO nicely.
>
> also, 5/16" == 7.8mm so it will probably work as an american
> substitute.

> we could go up one size to 3/8" which is 9.53mm.
> Probably not a very good candidate. Worst case scenario we could do a
> simple redesign with 5/16" holes and drill them out for metric. then
> again, metric parts are easy to order and things will probably work
> "as-is" so no worries =)
>
Please ignore my earlier post where I said that 5/16" was larger than 8 mm. I
did the conversion properly, and read the results wrong.

-Sebastien
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quick tip: try typing 5/16 inches in mm into google... it will
automatically do all sorts of conversions for you. the format is:

Unit1 in Unit2

pretty handy for sure.

~Zach

On 3/18/07, Sebastien Bailard wrote:
> On Sunday 18 March 2007 16:16, Zach Hoeken wrote:
> > great. the one thing i was worried about was not being able to use
> > these skate bearings, but i got out my calipers and measured them...
> > the inner hole has a diameter of 8mm. if you havent experimented with
> > them yet adrian, get yourself down to a skate shop (wish i could be
> > there to see it) and get some replacement bearings. you should be
> > able to get them for cheap... i got mine for $1 / ea online and they
> > will make all the rotating parts move SO nicely.
> >
> > also, 5/16" == 7.8mm so it will probably work as an american
> > substitute.
>
> > we could go up one size to 3/8" which is 9.53mm.
> > Probably not a very good candidate. Worst case scenario we could do a
> > simple redesign with 5/16" holes and drill them out for metric. then
> > again, metric parts are easy to order and things will probably work
> > "as-is" so no worries =)
> >
> Please ignore my earlier post where I said that 5/16" was larger than 8 mm. I
> did the conversion properly, and read the results wrong.
>
> -Sebastien
> _______________________________________________
> Developers mailing list
> Developers@reprap.org
> [reprap.org]
>
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On Sunday 18 March 2007 09:02, Adrian Bowyer wrote:
--snip--
> Anyone know the nearest non-metric thread to M8? Pitch doesn't matter
> (fix in software).
>
> Best wishes
>
> Adrian

There's 5/16" threaded rod, which is 7.9375 mm

You can find 5/16"-18 UNC and 5/16"-24 UNF. 5/16"-18 is more common than
5/16"-24; looking in the travers.com catalog, for hex cap screws they offer
5/16"-18 but not 5/16"-24.

I think for threaded rod in the next sizes down and up, 1/4"-20 and 3/8"-16
are more common than 5/16"-18.

-Sebastien
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cool, thanks for the info... i think 5/16 is just fine. you can get
it in nearly any hardware store in the US. it should 'just work' in
place of the M8 which is awesome.

On 3/18/07, Sebastien Bailard wrote:
> On Sunday 18 March 2007 09:02, Adrian Bowyer wrote:
> --snip--
> > Anyone know the nearest non-metric thread to M8? Pitch doesn't matter
> > (fix in software).
> >
> > Best wishes
> >
> > Adrian
>
> There's 5/16" threaded rod, which is 7.9375 mm
>
> You can find 5/16"-18 UNC and 5/16"-24 UNF. 5/16"-18 is more common than
> 5/16"-24; looking in the travers.com catalog, for hex cap screws they offer
> 5/16"-18 but not 5/16"-24.
>
> I think for threaded rod in the next sizes down and up, 1/4"-20 and 3/8"-16
> are more common than 5/16"-18.
>
> -Sebastien
> _______________________________________________
> Developers mailing list
> Developers@reprap.org
> [reprap.org]
>
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Ed's a 'boarder, so doubtless he'll know where the shop is...

Best wishes

Adrian

Dr Adrian Bowyer
[staff.bath.ac.uk]
[reprap.org]

Quoting Zach Hoeken :

> great. the one thing i was worried about was not being able to use
> these skate bearings, but i got out my calipers and measured them...
> the inner hole has a diameter of 8mm. if you havent experimented with
> them yet adrian, get yourself down to a skate shop (wish i could be
> there to see it) and get some replacement bearings. you should be
> able to get them for cheap... i got mine for $1 / ea online and they
> will make all the rotating parts move SO nicely.
>
> also, 5/16" == 7.8mm so it will probably work as an american
> substitute. we could go up one size to 3/8" which is 9.53mm.
> Probably not a very good candidate. Worst case scenario we could do a
> simple redesign with 5/16" holes and drill them out for metric. then
> again, metric parts are easy to order and things will probably work
> "as-is" so no worries =)
>
> On 3/18/07, Adrian Bowyer wrote:
>> Quoting Zach Hoeken :
>>
>> > I am having trouble finding any info in the wiki... what is the size
>> > of the rod used in darwin? is it all 8mm? I'm just wondering because
>> > I think i'm going to buy some on mcmaster or somewhere and see what
>> > happens. =)
>>
>> Yup - all the smooth rods are 8mm; all the threaded rods are M8.
>>
>> Best wishes
>>
>> Adrian
>>
>> Dr Adrian Bowyer
>> [staff.bath.ac.uk]
>> [reprap.org]
>> _______________________________________________
>> Developers mailing list
>> Developers@reprap.org
>> [reprap.org]
>>
>



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> Ed - didn't you try 5/16" (I seem to remember) and it worked?

Sorry to be slow all, got the lurg. Yeah, I tested the 5/16's and it's all
good. Difference feels negligible when in the brackets.

The imperial nuts and bolts closest equivalent also worked fine, though I'll
have to look up what I used when I'm in work next.

eD

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