View Full Version : BUtting Racks (R&P) end to end

13-07-2010, 03:59 PM

I just saw these 500mm racks on rs-online. It's hard sourcing longish rails here in my country so I'm thinking of butting 3 of these for my Cnc machine. Will it work? Also I saw some delrin racks, will these work for a cnc router?

^Thanks a lot.


13-07-2010, 06:27 PM
got a link?

13-07-2010, 06:55 PM
I was looking around for Rack and Pinion the other day, and the longest available seems to be 2 metres long.
I would use a full length if you only need 1500mm
Delrin Racks would wear out pretty fast on a CNC Router I would imagine.


14-07-2010, 01:55 AM
Shouldn't be a problem the rack on my lathe is made up of 6 or so 100mm sections, (don't know why) the ends have been perfectly cut and then they have also been dowel in place as well as the screws.

Alternatively you could leave a small gap between the racks (gear teeth will push against the sides not the trough) and use a short piece placed on top (upside down) to set the correct distance (add a bit of epoxy or tread lock if you are worried.)

14-07-2010, 04:55 PM
Try WMH Transmissions (http://www.wmh-trans.co.uk/Products/COMMERCIAL_AND_PRECISION_QUALITY_SPUR_RACKS_AVAILI BLE) This is where i got my Linear guides and bearings from.. excellent service and next day delivery to! Based in Tamworth

14-07-2010, 10:11 PM
Bet they won't do next day to the Phillipines tho!

15-07-2010, 12:25 AM
I would for 7000 :D

15-07-2010, 11:34 AM
Thanks for all your answers guys,

Here's a link. They don't have the actual pictures so I'm not sure if ross77's suggestion will work.

lol Thanks for offering to send them here, adCNC.

I guess I have to search harder. If I can't find them here, there's always mcmaster-carr in the US, but it's gonna be a whole lot harder on the wallet.

15-07-2010, 01:22 PM
Since RS dont manufacture anything, there must be someone else stocks the same part... 5min with Google finds http://www.qtcgears.com/RFQ/default.asp?Page=../KHK/index_Racks_files/khk144.htm Look at SR2-500 third section down, identical spec with DXF/PDF/DWG files. These are not 'machined ends' (thats elsewhere in the catalog) so i suspect these don't butt, you will have to machine the ends. Indeed you can tell this from the measurements. Circular pitch = Module * pi = 2 * 3.1416 = 6.2832mm so 80 teeth would be 80 * 6.2832 = 502.656mm which is the length of the 'machined ends' version. These have a length of 505mm!

15-07-2010, 09:44 PM
Here's a link. They don't have the actual pictures so I'm not sure if ross77's suggestion will work.

Sure it will :smile: just get the angle grinder out, or better still bench grinder, and shorten to the right length. dosnt matter if you go a bit over just leave a coresponding gap.


This is from a stair lift, not really precision kit, but you get the idea.