Finding Smooth Rods

Hi Everyone,

I am currently building a Reprap Prusa Mendel and am definitely feeling the initial learning curve when it comes to finding instructions and parts. I live in Canada where we work on a metric system yet it is next to impossible to find Metric bits, especially the small ones!

If anyone can provide me with some help in where to find the proper metric smooth rods would be much appreciated. I am trying to do this relatively bare bones so think I am looking for raw stock versus pre-cut (unless I can get a good price).

Also, is there an SAE equivalent to M8 that would work with the LM8UU bearings?

Thanks for the help in advance!

Evan.

Hi Evan,

I purchased 8mm Bright Stainless Steel rod from the local steel merchant. It comes in a high finish, but has a fine grind finish.

I cut my lengths with an angle grinder, then i carefully sanded the surface with 800 grit wet & dry abrasive paper, then 1200 abrasive paper. I put the final polish on the rods using a metal polishing paste - same as what people use to polish their car wheel etc. The rod came up really bright and well polished. It took about 2 hours to polish all the rods.

The stainless steel rods cost me AU$30.00 for 3 metres. It was the cheapest solution I could find with the time I have available.

Hope this helps.

Dan

ReprapDan Wrote:
-------------------------------------------------------
> Hi Evan,
>
> I purchased 8mm Bright Stainless Steel rod from
> the local steel merchant. It comes in a high
> finish, but has a fine grind finish.
>
> I cut my lengths with an angle grinder, then i
> carefully sanded the surface with 800 grit wet &
> dry abrasive paper, then 1200 abrasive paper. I
> put the final polish on the rods using a metal
> polishing paste - same as what people use to
> polish their car wheel etc. The rod came up really
> bright and well polished. It took about 2 hours to
> polish all the rods.
>
> The stainless steel rods cost me AU$30.00 for 3
> metres. It was the cheapest solution I could find
> with the time I have available.
>
> Hope this helps.
>
> Dan

I'm from the UK but have used the same approach with polishing, using A2 stainless steel rods. Seems fine, if you stick the rods in a drill then you can polish them fast! I brought my rod in 500mm lengths off eBay. It was very cheap, like £2-3 a rod.

I am in Ontario, Canada. So far prices are a bit high. A local nuts and bolts supplier has M8 in 304 inox. mill finish. They want $29 for a one meter length...

I like the idea of polishing it. I'll give that a try if mill finish turns out to be too rough.

---

Yvan

Singularity Machine

konwiddak Wrote:
-------------------------------------------------------
> ReprapDan Wrote:
> --------------------------------------------------
> -----
> > Hi Evan,
> >
> > I purchased 8mm Bright Stainless Steel rod from
> > the local steel merchant. It comes in a high
> > finish, but has a fine grind finish.
> >
> > I cut my lengths with an angle grinder, then i
> > carefully sanded the surface with 800 grit wet
> &
> > dry abrasive paper, then 1200 abrasive paper. I
> > put the final polish on the rods using a metal
> > polishing paste - same as what people use to
> > polish their car wheel etc. The rod came up
> really
> > bright and well polished. It took about 2 hours
> to
> > polish all the rods.
> >
> > The stainless steel rods cost me AU$30.00 for 3
> > metres. It was the cheapest solution I could
> find
> > with the time I have available.
> >
> > Hope this helps.
> >
> > Dan
>
> I'm from the UK but have used the same approach
> with polishing, using A2 stainless steel rods.
> Seems fine, if you stick the rods in a drill then
> you can polish them fast! I brought my rod in
> 500mm lengths off eBay. It was very cheap, like
> £2-3 a rod.

why would you polish stainless steel rods?

I'm also from Canada.

All the automation guys up here use Misumi.

[us.misumi-ec.com]

Mill finish can be pretty rough. It depends what you get a hold of. If it has been ground, it is usually very smooth.

BTW ShadowRam, thanks for the link to Misumi. Lots of good stuff there!

---

Yvan

Singularity Machine

In North America, McMaster-Carr (www.mcmaster.com) is a good source for raw materials. Very fast shipping, too.

[www.vxb.com] is a great source in the US for bearings and smooth rods.

McMaster-Carr is amazing! But they stopped shipping to Canada a few years ago. Arrrggh....

---

Yvan

Singularity Machine

I went with VXB on price and simplicity. I am cutting my own rods, and have the equipment to do so. If you don't have the capability of cutting your own rods, Misumi can set you up with whatever you want. Rod smoothness is a choice that must be made along with choosing bearings or bushings. While smoother rods are better with bearings, some bushings perform better with rods that are less smooth.

chris33 Wrote:
-------------------------------------------------------
>
> why would you polish stainless steel rods?

I'm not sure if your asking why stainless steel or why polish?

1. Stainless steel is pretty hard wearing, sure there are harder steels out there but #2
2. They were cheap, to a good tolerance and readily available.
3. They needed a polish.

because stainless steel doesn't rust, its smooth and using sand paper would remove material from the bar

What exact size are the rods you guys are finding? The ones on both printers here vary between 7.92mm and 8.07mm. Also, the cheap LM8UU bearings are all inaccurate. They all have play on the shafts. No surprise there, given how much the shafts vary.

I checked some some 1 inch thomson shaft(what linear bearings are suposed to be running on) that I happen to have and it is way smoother than the inox 8mm rod on the printers. I guess polishing them wouldn't hurt much.

BTW Maxx, thanks for that hint about VBX. Glad I have that in my bookmarks now!

---

Yvan

Singularity Machine

konwiddak Wrote:
-------------------------------------------------------
> ReprapDan Wrote:
> --------------------------------------------------
> -----
> > Hi Evan,
> >
> > I purchased 8mm Bright Stainless Steel rod from
> > the local steel merchant. It comes in a high
> > finish, but has a fine grind finish.
> >
> > I cut my lengths with an angle grinder, then i
> > carefully sanded the surface with 800 grit wet
> &
> > dry abrasive paper, then 1200 abrasive paper. I
> > put the final polish on the rods using a metal
> > polishing paste - same as what people use to
> > polish their car wheel etc. The rod came up
> really
> > bright and well polished. It took about 2 hours
> to
> > polish all the rods.
> >
> > The stainless steel rods cost me AU$30.00 for 3
> > metres. It was the cheapest solution I could
> find
> > with the time I have available.
> >
> > Hope this helps.
> >
> > Dan
>
> I'm from the UK but have used the same approach
> with polishing, using A2 stainless steel rods.
> Seems fine, if you stick the rods in a drill then
> you can polish them fast! I brought my rod in
> 500mm lengths off eBay. It was very cheap, like
> £2-3 a rod.


Hi, Which ebay supplier did you buy those rods from? I'd like to purchase some too, I'm from the uk too.

I am also about to purchase rods.. here in the U.K

what dimension rods would I use with SC10UU bearings ?

10mm with h6 tolerance to work properly with linear bearings.

---

[www.hydraraptor.blogspot.com]

Here's where I found smooth rods

CLICK HERE FOR RODS

If you are using linear bearings and not bushings, stainless 304L is not suitable material. It is not hard enough.

As a general rule stainless is costlier and not useful in most guiding applications, but you can use induction hardened to 55HrC X90 CrMoV1 and never 304L or even worse 316L.

The right materiel is 100CrMo6 or variations, plain hardened to 60HrC and ground steel rods. Any 1% Carbon with Chrome or Vanadium (molybdene is useful too) above 1.2% is ok as they will have high trempability and low deformations. 100C6 is the nuance used to make balls in bearing. Dont use chromed rod, we want the chrome inside steel not on top.

Will cost less than 1/3 the price of stainless and offer much better performance. Wont rust because you want to put in some oil in any case.

h6 tolerance (+0/-13µ) as indicated by Nophead is good and straightness class 3. such rods, pre-hardened are easy to find by manufacturing suppliers. g6 will have a bit more play (7µ) but is usable.

such a rod though not the best price : [shop.hpceurope.com]
edit: I checked and the rods above are Cf53 induction hardened. That works too, with a bit more flexibility, but 100c6 is better

At industry prices, you can source that at less than 4€/m in D8

Edited 1 time(s). Last edit at 06/02/2013 05:50PM by alj_rprp.

@ alj_rprp:

So you highly recommend hardened steel ( 100CrMo6 ) over stainless steel since I'm using SCS10UU linear bearings.

Is there really that much difference in print quality using hardened 100CrMo6 rod that's less than half a meter long.

I'm new to the world of 3D printing... & as such have no idea how much these rods can flex... but they're not under considerable loads.. are they ?

I can understand a rod must be smooth flowing, so oiled rods maybe beneficial but also suffer from gathering dust generating friction... so I guess every few days one would have to clean the smooth rods, yes ?

The problem is not flex under load. The contact between a small ball and a cylinder along a generating path is about the worst case you can encounter in contact mechanics. As good linear bearings have some preload, the hertz pressure is generated on a very small area, and the cylinder must be ideally harder than the ball so that the deformations on contact point stay in the elastic domain.

[www.scielo.br]

This is never the case, balls are 62 HrC usually, but it is acceptable to have less than 10 Rockwell points of hardness difference. If the rods are then softer than 52 hrC, they will be marked very quickly (this is often too small to be seen to the naked eye but you can feel it with the nail), and the balls will stop rolling and start sliding inducing high friction.

There is scraper seals on any decent linear bearing, and you really need very little oil, so dust is hardly a problem unless the environnement is very harsh.

note that bushings dont have that requirement of hardness for the rods, this is specific to the ball/cylinder contact.

So after reading up on Rockwell hardness...

Is there any advantage to using a SCS10UU bearing apposed to the LM8UU bushing ?

Edited 1 time(s). Last edit at 06/03/2013 09:21PM by Mickman.

10 mm rods will reduce flexion under load over 8mm (hardness wont change that). As it depends of area, stiffness is 50% greater for a 10 mm rod.

Structural stiffness of the Mendel is almost correct but not great and going 10 mm will improve a lot that. It means especially less prone to vibrations and that higher speeds are then possible.

SCS10UU is just the housed version of the LM10UU, the bearing inside is the same

In answer to the original question about sources of smooth rod, a very good source of 8mm highly polished rods is retired printers. The material is very straight and accurate, but is not hardened - hence better with bushings than LM8 bearings. HP printers seem to use 8mm even in the cheapest printers.

Mike

For ppl looking for smooth rods, I checked around for this because I need quite a lot of it. Stainless is definitely out of question due to its high price, and I thought to find the most economical option. Tool steel would be good only if it was hardened to max. to get out all the stiffness, in its plain supply form it is no better than normal structural steel. Stainless steel has lower yield than cold drawn structural steel, so only real benefit is the corrosion resistance. The practical answer is cold drawn S355J2C steel bar, which has H9 tolerance finish and is available to most hardware stores at quite low rate. This can be polished at lathe with 1.2-2k grit sandpaper and even further with finishing paste. Applying a coating of CRC of WD40 one can expect these to last very long.