DIY Linear Bearings

I built a MDF CNC router based on the original plans from buildyourcnc.com a few years back - I moved house a couple of years ago & the machine has been sat in the garage unloved, in bits, slowly warping & becoming unusable.

I'm now redesigning the machine from scratch. I'm basing the design on the FLA-100 (Fine Line Automation - Complete 2'x3' Router Kit) but tweaking it to use metric ally profile & making have a 2x4 cutting area etc.

I like the linear bearings that are on the plan & that are sold by cncrouterparts but they are sized for imperial profile. I have also inherited 4 of the original version of these (not adjustable) - using these would mean that I have to use aluminium (imperial) flat bar for the rails rather than steel (metric)...I think these would wear out pretty quickly - not ideal.

So the point of this post is to ask about the current preferred trend of DIY linear bearings - i've been looking around & haven't been able to find anything that looks right for me. I'm trying to keep costs as low as possible, but want to keep it all as solid as possible.

Other than your normal diy tools I also have at hand:
Table saw
Chop saw (can cut ally/steel)
Drill press
Router table
Angle grinder

Any thoughts or input would be greatly appreciated.

Thanks

Tom

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Originally Posted by CraftyGeek

Any thoughts or input would be greatly appreciated.

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I'll give you Input.!! . . .Don't bother messing around with making your own rails it's false economy.!

In the early days I use to see this time and time again and it always ended up going the same way.?
They would work for a fews weeks then become baggy and trouble some. Constantly sticking and stalling motors, crap building up on rails and jamming bearings etc etc etc with same result for everyone.!! They become frustrated with chasing problems and either scrapped the machine or changed rails for real thing.
Over the last few years, which wasn't the case back then, supported linear round rail has become so cheap it's just not worth the hassle of not buying them.
SO do your self a favour and buy supported linear round rail to start with you'll only end up doing so any way and the machine will perform twice better, give trouble free use from the get-go and last for years.

Ok, i'll be honest - I haven't looked at supported rails or the cost of the bearings for them. I remember them being extremely pricey when I looked last time round...can you point me towards a reliable source of these said 'cheap' supported rails? so I can look at the cost involved vs what i'm looking at currently.

You won't go wrong with this seller (known as Chai). Most of us use him as he's cheap and will machine ballscrews to whatever you want for next to nothing.

linearmotionbearings2008 | eBay

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Originally Posted by CraftyGeek

Ok, i'll be honest - I haven't looked at supported rails or the cost of the bearings for them. I remember them being extremely pricey when I looked last time round...can you point me towards a reliable source of these said 'cheap' supported rails? so I can look at the cost involved vs what i'm looking at currently.

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Chai is the one I use and bought many £1000's of stuff from him so know he's good guy to deal with but there are many on Ebay who sell them and could be slightly cheaper.? . . .They are all pretty much the same rails and probably come out the same factory.!

Forgot to say I converted a mainly wood use machine that used Cncrouter-parts bearings and rail because the guy got so pissed off with having to cleaning the rails!! . . And that was after much messing about with wipers etc.:thumbdown: . . . (Don't ask I've already gave them away. . Lol)

Ok - it looks like i'm looking in the £200 ballpark which is a lot more than the DIY route...but I know i'm not looking at like for like here.

I'll carry on drawing up the rough design & then look at the exact rail lengths involved.

If i'm using aluminium profile for the table sides (I think the sides are 80x40 from memory), whats the best way to attach the supported rail to them given that the mounting holes won't match the slot spacing?

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Originally Posted by CraftyGeek

Ok - it looks like i'm looking in the £200 ballpark which is a lot more than the DIY route...but I know i'm not looking at like for like here.

I'll carry on drawing up the rough design & then look at the exact rail lengths involved.

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Send Chai an email for quote here [email protected] with lengths and number of bearings and you may find it's bit cheaper.
Either way i'd wait and save up a bit before take the DIY route because you will end up disappointed and wasting money trust me.!!

Another thing to consider is the small extra investment will pay back big time further down the line when your ready to upgrade because you'll easily sell the machine and recoup most the cost (If done well you'll make money). DIY route you'll struggle get anybody to look at it and even then they'll want it for nothing.!!
Also look at it this way your first DIY effort ended up in the bin so any outlay was lost.!! . . . . For the slight extra cost of doing with better materials it would still be alive, same goes here but this time you do plan on using better materials but will let the machine done with crappy DIY bearings. . . Better but only just.!!! . . .Not worth skimping on IME.

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Originally Posted by CraftyGeek

If i'm using aluminium profile for the table sides (I think the sides are 80x40 from memory), whats the best way to attach the supported rail to them given that the mounting holes won't match the slot spacing?

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You can just tap the profile but a better way is to fasten 10-12mm strip of aluminium with counter bored holes down centre and fasten into slots then fasten rail to that by drill/tapping into it.
Problem with fastening straight to profile is there's not much material and the threads strip.!!

Edit: Have you considered using steel.? It's much cheaper than Alu profile, stronger and taps no problem so no messing around.

I have it in my head that i'll use supported rails now...I know that its worth the extra pennies. Looking at chucking a load of old hobby bits on ebay to help with the funding.

I had previously been planning on using steel box - I think we exchanged messages about it ages ago.
I like the convenience that ally profile offers - I also have concerns about getting a frame built with steel box square...although since looking at the supported rails I did think it could be easier to attach them to a frame made from box rather than profile.

On the subject of rails, for a 2'x4' machine, what size rails would you recommend?
I've just been reading a load of build logs & have seen mention that 20mm is overkill for a machine this size & that 16mm may be a better fit...but then there were comments about the bearing size being harder to work with - found it all a little less than clear :-p

Personally, I really dislike the aluminium profile sections as they always feel a bit flimsy. I guess I've always made things in steel, so associate weight with strength. Your frame doesn't have to be perfectly square, it's the rails that have to be parallel and square to each other. The framework could easily be a couple of mm out of square and you'd still be able to build an accurate machine if you mount the rails correctly.

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Originally Posted by CraftyGeek

I had previously been planning on using steel box - I think we exchanged messages about it ages ago.
I like the convenience that ally profile offers - I also have concerns about getting a frame built with steel box square...although since looking at the supported rails I did think it could be easier to attach them to a frame made from box rather than profile.

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What makes you think you'll get it any squarer using Profile than steel.? To be honest it's actually harder to get and keep square than steel.!
With steel (presuming your welding) it's just case of tack it up knock square then when happy finish up the welds while keeping eye on it moving. After that it will never move again.
With profile your messing around with corner diagonal braces and shims etc then first time you move it or shaking thing about a bit while cutting it's moved again.!!!

Like Birchy says with steel it's strong and doesn't need to be micron square. The rails are what matter and steels much more workable than profile so more flexible regards alignment etc.

By the time you have bought the profile and all the T-nuts etc which can cost has much has the profile you'll be into £200 plus with steel you'll do it for £60-80 and still have some left. That's £150 towards your rails.!!!

Meant to ask this before.? What you doing regards screws etc . . Your not thinking threaded rod are you like lots of DIY rail folks do.?
If so then again don't waste your time and go straight for balls screws and get them at same time has rails to keep costs down £300-£350, can get you a set of rails and screws with all end fixings and machining. Wouldn't or Don't even consider Lead screw has again it's not worth the small difference ballscrews cost.
You'll have a proper machine that can do some serous work all day long and will be worth at least double the cost you put into it if done right.

Steel is the way to go IMO Esp if your on budget. Profile looks bling but that's about the only thing it's got over steel all the rest that matters it's behind on.!!

Ok - so it looks like its about turn time & back to the drawing board.
Are we talking 50mm x 3mm mild steel box?

It'll be bolted, not welded as I don't have the gear for that - but I do have a pillar drill & some taps, so should be able to cobble something pretty sturdy together.

Screws - i was looking at a Marchant Dice package on ebay...but given that i'm now looking at supported rails from Chai, i think it makes sense to get some screws from him as well - i'll need to look at what he offers & the pricing. If the steel does work out that much cheaper, then the budget shouldn't be an issue.

I'll call my local metal supplier tomorrow to get a quote for the steel box & then start drawing something up.

Also, if you're following that design..... don't... the single central screw for the X-axis will cause you hours of pain if you plan to cut anything stronger than cheese at the full width of the Y axis. Plan and budget for two screws and either 2 drives & motors or a single motor and pulley system unless you make the x-axis bearings really long to counteract racking. Go re-read some of the build logs, its been discussed in depth many times. If you're investing in a serious machine, best to get it right at the outset!

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Originally Posted by irving2008

Also, if you're following that design..... don't... the single central screw for the X-axis will cause you hours of pain if you plan to cut anything stronger than cheese at the full width of the Y axis.

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While I agree completely 2 screws are best route in this case it's marginal Irving has he only wants 600mm cutting width, if he has wide enough bearing spacing on X axis and builds ridged Gantry it will be fine for upto light Aluminium work. On a budget this will work fine and with bit of thoughtful design could easily be incorporated later if needed.!!. . . . .Carry on Sir I say.

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Originally Posted by CraftyGeek

Are we talking 50mm x 3mm mild steel box?

I'll call my local metal supplier tomorrow to get a quote for the steel box & then start drawing something up.

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Yep 50 x 3mm and the last time I bought some which was 2-3months ago it cost me £26 for 7.5mtr length. That's was plus vat but if like my friendly supplier they will some times do without Vat.

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Originally Posted by JAZZCNC

While I agree completely 2 screws are best route in this case it's marginal Irving has he only wants 600mm cutting width, if he has wide enough bearing spacing on X axis and builds ridged Gantry it will be fine for upto light Aluminium work. On a budget this will work fine and with bit of thoughtful design could easily be incorporated later if needed.!!. .

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Ok, on that width maybe you're right, but in that case the X bearing spacing on that design is nowhere near wide enough IMHO, so don't underestimate the extra X travel length.

Cheers chaps - My original plan was to build it using a single x-axis screw...see how it goes then add a second at a later date if I feel I need it.

I'm now ditching the FLA-100 as a base design & am starting a new design from scratch with 50mm box.

My local supplier states £4.10/m +VAT as a base price, then depending on quantity it could be cheaper...they also quoted for cutting - 50p/cut as a rough ballpark but cheaper on multiples.

I'll get a bit further with the design & then start a build thread - then you can start ripping my plans apart again ;-)

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Originally Posted by CraftyGeek

I'll get a bit further with the design & then start a build thread - then you can start ripping my plans apart again ;-)

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We don't Rip apart we give Con-crushing Criticism.!! . . . Opp's mean constructive Criticism.:stupid:

So 4.10mtr = £30.75 for 7.5mtr, so that's same price has just 2mtr of Alu Profile or put another way you get 5.5mtr free for same money. . . . . Bit more pleasant on the Old wallet isn't it.!!

Crack on and let the fun begin.:yahoo:

Yep - t'is cheaper...but more work involved in assembly.

One more question while i'm designing...
I've been thinking more about dual leadscrews with a single motor for the x-axis - what's the most cost effective way of doing this & a good place for parts?
(looking more at costs rather than exact setup at the moment)

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Originally Posted by CraftyGeek

Yep - t'is cheaper...but more work involved in assembly.

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Not has much work has you may think, profile still has to be drilled, tapped etc and it's not always easy has folks think it's shitty stuff to drill and even worse to Tap good threads into.!

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Originally Posted by CraftyGeek

One more question while i'm designing...
I've been thinking more about dual leadscrews with a single motor for the x-axis - what's the most cost effective way of doing this & a good place for parts?
(looking more at costs rather than exact setup at the moment)

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The best way is to use 15mm HTD timing belt and pulleys running around 2 idle bearings to central motor.
Your local bearing company may be the best place to ask, I use lots belts & pulleys and this what I find cheapest. . . . But failing that then there's likes of Bearing boys etc on-line. If you look around the forum others have posted links to places they've bought.