Thread: round rails
I just wouldn't like someone to be put off, because all of a sudden it got too expensive !.MDF is 'almost' free LOL and a great way to learn. Major components can be re-used later if neccesary
Steel box section is relatively cheap and 50mmx3mmx7.5mtr lengths compares roughly around the same price has 25mm 8x4 Mdf sheet, I pay £26 per length of steel.
For a small machine then it would probably take a full sheet MDF. One 7.5mtr length steel will build the same small machine.
The sundries involved IE Screws, nut's & bolts etc both need. Steel doesn't have to welded and can be bolted thou for sake of £50 a welder makes slight work of it.
Just because something looks expensive or hard to do doesn't mean it is.?
The difference in performance and longevity are night and day and it's a one time affair still with lots of learning and enjoyment.!! . . . The fun just last's longer.!
Well that's my take on it anyway.!!
I found steel to be more than that in 1 off's, it came down a bit if you bought 2 or 3 lengths.Maybe I'll shop around a bit, as I have nothing against steel except it's price for a 1st timer. I was pricing up for an 8x4 machine though, so was looking at a lot more steel and larger sections. Even then, I've heard of 2x3" steel box gantry's need beefing up because they were flexing when cutting wood.
Most people that build a machine, use it for a while and want to change it or make it bigger. So it doesn't necessarily need to last
Oh, and I built mine out of 12mm MDF LOL, it gets 3 or 4 hours use most days for the last 6 months ... the parts come out the correct size and everything !
I got my steel from 'The Metal Store' who do some smaller lengths like 1.5M and 3m and also offer a free cutting service at the checkout stage (cutting not 100% accurate but that doesn't stop you putting your screw holes in the right place).
Sorry hope I'm not hijacking this thread but I was looking for some info on rails & wasn't sure where to look being new to all this. Is there some sort of guide as to what diameter rail should be used when looking to build a machine. Realise there are probably a lot of factors to take in to account but just a very general guide that maybe gives some sort of idea what size rail to use for different length or width tables.
Really thou it's not rocket science and it will ultimately boil down to a few factors like Budget and machine size/use. Here's a quick run down for typical DIY use.
Stay away from unsupported round rails unless short lengths =<400mm and even then 20mm or more.
My rule of thumb with Supported round rail is 16mm for small light duty machines =< 600mm. 20mm =< 1500mm 25mm => 1500mm
If Profiled linear rail then it's a completely different and 15mm will be more than most DIY users need in terms of load capacity's but maybe not physical size so 20mm tends to get used often has the bearings sizes etc suit better. It also tends to be more common second hand has it's common size in industry.
hope this helps.
Also, depending on budget, and how much "DIY" you want to do, there are lots of other home made options, like angle and skate bearings, or steel tube, or steel plate and bearing tucks etc. etc.
If they do get them working they are high maintenance and usually lacking in precision. I think I have helped folks who have used just about all the available options and all of them regretted it.
I know what your probably going to say " It's a cheap entry to CNC" BUT IMO it's also a good way to drive newcomers away has well when they try fail and give it up has a bad job.!! . . If they only knew before hand that for not lots of money and far less time they could have real rails and bearings that are far more accurate and reliable I know for sure they surely would have taken that route on hind sight.
Yes I know there are some very capable machines running DIY setups and someone you've mentioned earlier Gerry(Ger21) who I know quite well runs a very nice machine but think even he'll tell you it's not a simple affair and takes very good design, patience and care to get it right. . . . Do-able Yes, easily No, success rate Low, frustration levels high.!!
My advice save up and save the stress.!!
Jazz I understand what you are saying but from the little I have seen during researching building a machine Profile rails are very expensive & this would be more likely to put me off trying to be honest. If you are lucky enough to have money then I suppose you may not think of them as being expensive but on the limited amount of money I have available it's just not really possible & at my age I would probably be dead before I could save up enough lol.
If I do manage to build a machine I'm not actually sure just how much use it would get or what sort of accuracy I would require. Yes I can think of one or two things I would like to do with it & I realise that once it is done I might be able to come up with other ways to use it but I still can't see it ever getting more than a few hours a month run time.
having said that if you check out trickyCNC's thread you can see what can be achieved by not using supported rails and by using mdf to build the frame, i feel this may suit you somewhat better.
the reason i asked this question about the round rails was to clear some things up... the outcome is that my planned 20mm round rails wold be better replaced by 16mm supported rails and have less room for error at roughly the same cost
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