Newbie- Drawer Glides vs. Pipe & Skate Bearings?

[DPF]

So I've followed cnczone off and on for a year now wanting to build a CNC machine. I've finally got my dollars in order, so it's time to make this happen! I'm trying to keep this economical by using materials I have gotten for free, but I'm not above spending a little extra to make this thing reliable.

With that in mind, I've collected, for free, four 60" heavy duty ball bearing drawer glides, four 32" heavy duty ball bearing drawer slides, and five ~30" long pieces of extremely rigid & smooth stainless steel tube.

I'm hoping to build a router that can cut a 12"x24" area. Are drawer glides workable as a linear bearing on a small router? Is the pipe & skate bearings a better performer at this size of machine?

Your wisdom is appreciated!

-DPF

[DIYaholic]

DPF,
You must be psyched, to start building that is. I only wish I had a shop to build in.
You asked about drawer slides vs. S.S. tube & skate bearings. Having not built a machine (yet), my opinion is not based upon any experience, so take it for what it is, a newbies opinion. I would think that the "Tube & Bearing" setup would be much more ridgid than the "Drawer Slide" set up. The tube could be supported, as in the "Joe's 2006", where as it may be very difficult to "Remove" any slop or play that exists in the drawer slides.
Of course, only you can determine the precision and accuracy that you need/want from your machine. Many people have built machines utilizing both methods.
The real question is: What do you want your machine to be capable of doing and how precise do you need it to be?
With all that being said, good luck with your build, whichever road you choose to go down.

Randy,

[DPF]

Thanks, I am quite psyched to get this thing built!

Just to clarify:

These drawer glides are honking heavy duty. Rated 300lb capacity, not exactly what you'll find on your kitchen drawers! Just jiggling them by hand (I know, real scientific ) I don't feel any slop in them, but they also seem a little stiff rolling in and out. I guess you have to expect that with all those bearings packed in thick grease. Hmm, maybe they would roll easier if I replaced the grease with with oil? Off to the search page!

Also, regarding a shop to work in... that's kind of an interesting story. I don't have my own shop to keep this machine in. I'm building small and putting it in an enclosure, so I can run it in my office/extra bedroom in my apartment. However, I do have access to all sorts of tools at work: bandsaw, drill press, mig welder, tablesaw, miter saw, hydraulic shear, punch, giant press brake, etc. Additionally, I have friends that can do some manual lathe & mill work.

As for accuracy, I need at least as tight as 1/64".

[ger21]

How are you going to use 60" drawer slid to get 24" of travel? Are they going to stick 4 feet out the end of the machine?

If done properly, the skate bearings should have less play in them than drawer slides, and they'll also have less friction.

[MyCattMaxx]

I agree. Skip the drawer slides. You will be happier with the pipe and skate bearings.
You can get the skate bearings dirt cheap on fleabay.
Also bigger diameter pipe is better to cut down on flex.
You will be surprised how much 1/2'' will flex under load.

[DPF]

If I can't come up with a clever way to hack the drawer slides, maybe I need to sell them and buy real linear components. I didn't realize how much they are worth until this morning, about $300 per pair x 2 pairs = $600 = Hiwin rails? I'd settle for a lot less than that!

http://www.reidsupply.com/Detail.aspx?itm=AI-9360

Has anyone seen any good posts on modifying drawer slides for CNC use? In the few builds I've found with drawer slides, nobody seems to modify them at all. That surprises me because any drawer slide's travel can be doubled by removing the stops and letting them extend "backwards."

In my case I was considering sawing the drawer slides down to just the length I need, taking the smallest section out of the slide assembly (which cuts extension length in half), then removing the stop tab so the slide can extend backwards, which would then double the range of motion. I thought having only one stage of rolling instead of two would reduce the overall slop in the assembly.

[MyCattMaxx]

People will buy a better rail system before wasting time to TRY to modify drawer slides.
Pipe and bearings is a cheap way to start the adventure. Once done you will be hooked and so will your wallet...;-)

If you make your first build with the slides you will be very disappointed with the end result.
But since you have them go for it.

[Drools]

Before I built my router I had available drawer slides from old servers. These drawer slides are very nice, no play and slide very smoothly however I decided to use skate bearings and cold rolled steel round. I will use the drawer slides as drawer slides to mount my controller enclosure under the router table along with making a drawer for the computer and tools etc. I should add that I have upgraded the skate/round bar solution to the carriages and flat bar that cncrouterparts.com sells. Ahren’s stuff fits my 80/20 frame perfectly and this is the main reason I upgraded.

[mlabruyere]

You should check the parts Ahren sells over at www.cncrouterparts.com with some CRS (cold rolled steel). Much better option than slides or pipe.

[DPF]

Okay, you guys + tons of reading have me convinced: use the drawer slides for drawers, not CNC linear bearings.

I like that cncrouterparts.com idea, make a carriage that rides on (relatively) cheap CRS strip, bolt the strip onto a rigid frame, and you're done.

Similarly, the Mechmate & Joes 4x4 hybrid machines, use (relatively) cheap steel angle as a track with v-groove rollers (cheap @ vxb.com).

So here's what I'm getting from this: steel track bolted along a solid frame, with roller bearing carriages, is the way to go if you are okay with spending some money, but don't have the budget for precision ground profile rail from THK/NSK, right?

-DPF

[DIYaholic]

As you have figured out, designing/building a machine (all design engineering for that matter), is a series of compromises.
You need to determine what compromises you want/need to make. Speed vs. Precision, Budget/parts availability vs. design/rigidity and the compromises go on and on.
Ultimately, you need to determine what you want/need your machine to be capable of doing. What materials will you be cutting/milling? How fast do you want to cut and/or rapid? How much precision do you require? And probably the defining question; What is your budget, to accomplish these machine performance characteristics?
So, yes, V-bearings or carriages & CRS bolted to a rigid structure will yeild a much more accuate machine (as opposed to drawer slides).
Looks like you are on your way to a design concept.

Good luck and happy designing.

Randy,

[arizonavideo]

You should post a picture of the drawer slides. They should be fairly straight and if the wheels have OK ball bearings and you want to make a 24 x 12 then you could cut the 60" rails in half and have two 30" rails per side.

You might use two rails per side and preload them against each other to remove the play. This might be fine for a wood and plastic cutting machine.