jgro machine - drill rod for rails?

[creative_mind]

I am considering building myself a CNC router using the jgro plans. I would like to subsitute the gas pipe linear rails with drill rods. The drill rod is much smoother - I think. The rails will be used with skate bearings. After looking at McMaster Carr and MSC, I'm a bit confused as to which types of drill rods to choose. There are three types - air, oil, and water hardened. Which one? I would like to go on the "cheap" path (don't we all?) but it should be durable enough for the skate bearings to roll on.

Thanks!

[mvaughn]

I used drill rod on my machine and chose the oil hardened stuff based on price. I would suggest getting what you can afford. You can always replace it or turn it a little to expose the skate bearings to a un-worn path.

[Jimmy Southern]

Hello everyone,

I am also looking at the JGRO. My plan is to use cold rolled steel rod. From my personal experience, I have found it to be quite accurate.
Since you are replacing gas pipe which is not very accurate at all, it should be a major upgrade. Considering the design appears to work well with the cheaper pipe.

I am also going to do a few more things different.
The main one is I am going to put the gantry uprights on the otside of the pipes to increase the Y axis useable area. This will also protect the X rails from dust and shavings. I am also going to change from .875 rails on the X to 1.25 CRS this should considerably strengthen the entire machine.

IMHO, if you do not have any issues with rust where the machine will be placed, I would not spend the extra money on the drill rod. You can get the CRS for a fraction of the cost.

Good Luck
Jimmy Southern

[creative_mind]

Isn't true that the drill rods are a bit tougher than the cold rolled steel rods? IMHO the tougher the material, the better durability for the skate bearings to travel on, thus less wear.

Of course you can't beat the highly polished chromed types which is Rockwell C65 hardened and cost lotsa moolah!

[Jimmy Southern]

Hi Creative,

I am a firm believer in the weakest link philosophy. I do not believe that the rods or bearings either one will be an issue as far as wear are concerned. The JGRO machine is not designed for long term durability, IMHO of course.

From my experience with MDF the joints will cause more problems with wear than the guide system ever will. Also for the difference in the cost of the drill rod vs the CRS you could replace the bearings or rods several times before you reach the cost of the drill rod.

All of this is my opinion but if it were me I would save the extra cash for the second, much more expensive version of the machine. Use this one as a learning experience.

I am planning on letting the first one pay for itself, then build a much more accurate and solid machine. I work in the sign business and have been around these machines and in most cases the worst built machine on this site is better engineered than most of the so-called budget commercial machines. So don't worry about minor issues such as rockwell hardness and so on.
Several of the guys using the JGRO machine are cutting aluminum with it, on gas pipe, so what we are discussing is overkill. (IMHO)

Thanks for letting me rant,
Jimmy Southern

ps I apoligize for my accent
I am just a country boy from North Georgia
one of the lines above should have said:
"the least well built" not "worst"

[creative_mind]

jimmy southern,

Thanks for the feedback.

Can you point out which CRS rods from McMaster-Carr's catalog? I'm looking for 1" rods and there are too many types to choose, but which one!?

[Jimmy Southern]

Hi Creative,

I really don't have an answer for your question since I buy mine in 20' lengths from my local steel supplier. I never realized there were that many grades of CRS. If I were you I would call around to my local welding shops and see what steel supplier they use and buy local. I believe you can use whatever standard material that the steel yard has in stock. Just remember to specify CRS and tell them to bundle carefully so as not to bend or ding the material. I think this will save even more money than ordering from McMaster.

For example: I am buying a 20' piece of 1.25 CRS and I am paying about $75.00 for it. DELIVERED TO MY DOOR!!!!!

Hope this helps. Good luck
Jimmy Southern

[Alex_Rider]

Hi Creative,

I am planning on using guide rods from flat bed computer scanners. I had a pile at work which where dead/old and I scrapped them. They are stainless steel and I managed to get 4 bronze bushings for them each. They will make up my Y (up/down) axis as they are a bit small for the x axis (12mm or 15/32"). I found some proper linear bearings for that ID size but they weigh in at $80 AUD.

I will cast some mounts for the bronze or some better bushings, out of Al.