my first build

[irving2008]

Hi Wires

The root diameter is 7.69mm have a look at; http://www.nookindustries.com/acme/A...Info.cfm?id=15

Regards.

Ivan

As an alternative to turning the screw down you could look at these components from dumpterCNC

Note when specifying TR12X3 make sure you say whether its single or 2 start thread - the common one is single start. 2-start is faster (6mm lead) but the components etc are more expensive.

As to the Root Dia, DIN103 spec say max 8.5mm, min 7.68mm depending on fit and load spec. In my experience, generally expect it to be around 7.95mm making it a good fit on 8mm ID bearings.


jonm - I must type faster - Roy's site is a good place to bookmark...

[wires]

thanks for all the info guys, i think i now know enough about them to order some. going to go with merchant dice as you guys seem to reccomend them. cheers

[wires]

i knew this would happen. i wanted to keep this cheap but i have been looking marchant dice online store and i see lots of stuff i like at reasonable prices

they do hardened high carbon round rail
http://www.worldofcnc.com/products.asp?recnumber=14
from reading other threads i think i need 16mm for the bed. they have this...w16 (h6) at £1.90 per 100mm. now i assume that product is 16mm diameter, not sure what the h6 means though.

also have these http://www.worldofcnc.com/products.asp?recnumber=17
at £5.40 for the LME16UU i assume that is to suit a 16mm rail.

they do rail supports as well not too dear.

now, i am only guessing when i browse all this stuff. all the stuff looks really nice but i am not really certain what to get. i have guessed the above two products and eyeballed a few others, left to my own devices i would probably go with these. am i right in thinking that i can get away with thinner rails in the gantry?

i am now considering putting off the purchase of the controller/steppers untill maybe february so i can spend some money on these. does anyone know if these guys accept paypal.

this is all your fault by the way:heehee:
this is turning out the same as my main hobby, nitro rc racing. i keep getting tempted by nice shiny new stuff and spending a fortune on it, the rc car i currently drive is worth over €1000

for anyone interested

xray xb808
2 x hitec 7955tg
go tech gx7r
spektrum dx3s

any comments on the stuff i am looking at?

[irving2008]

they do hardened high carbon round rail
http://www.worldofcnc.com/products.asp?recnumber=14
from reading other threads i think i need 16mm for the bed. they have this...w16 (h6) at £1.90 per 100mm. now i assume that product is 16mm diameter, not sure what the h6 means though.

The h6 is the tolerance on the diameter I believe which is as you surmise 16mm... However these are not supported rail. They will deflect and bounce on long runs and are not really suitable for more than 300mm on a lightweight machine. Although they can be used where accuracy is not paramount, really you need to be looking at fully supported rail. If you want to use unsupported rail you need to be considering 20mm or bigger...

also have these http://www.worldofcnc.com/products.asp?recnumber=17
at £5.40 for the LME16UU i assume that is to suit a 16mm rail.

That is correct, however these round units are hard to use without the matching pillow block

am i right in thinking that i can get away with thinner rails in the gantry?

Yes, but 16mm unsupported rail will deflect 0.2 - 0.3mm with a 6kg router/z-axis in the middle on a 600mm run, so this limits your depth accuracy and surface finish.

i am now considering putting off the purchase of the controller/steppers untill maybe february so i can spend some money on these. does anyone know if these guys accept paypal.

MD accept PayPal, but dont expect fast turnaround... you could be looking at a few weeks based on some recent experience by members... they are a tad overloaded...

[wires]

hmm, there is always something. guess they would be fine for the gantry but not the bed. i will still definatly go for the tr12x3 but i will have to have a good think about the linear stuff. this is why i havent cut anything yet. thanks for the info

[wires]

i was also looking a the drylin stuff but honestly i am lost in the specs. i have no idea what i need to handle the loads i will have. every time i try to bluff my way through it i get a pretty high price. the bed length will be 1500mm. im sure you guys are sick of answering noobie questions at this stage but does anyone have any ideas on what might suit from drylin?
i just dont know what to go for, round rail or angular, single or double carriage. or maybe i will just go back to plan A