View Full Version : TR12x3 description inconsistency

06-12-2010, 04:51 PM
I'm considering buying some spindles, but I'm a bit confused regarding the description of the multi-start spindles. The one I'm considering is the TR12-6P3 spindle:

I've read through the following page to make sure I don't mix up pitch, starts and lead. But I feel the difference vendors do mix these up, making it difficult to know what will fit.

As the single-start spindle (TR12x3) has 3mm pitch, I thought TR12-6P3 was a 3mm pitch as well and with 2 starts, making it move 6mm per revolution (6mm lead). In the http://www.worldofcnc.com/images/multistarttrap.pdf file that the page at worldofcnc links to it says "Part number "P" indicates the number of starts. Ie P3 = 3 starts." and this would make it 2mm pitch I guess.

However, this ebay seller uses the same description, TR12x6-P3 but states it's start 2, with 6mm per revolution (lead), but goes on saying it's 6mm pitch (which doesn't make sense):

So what I really want to know is: Is this a start 2 or start 3 spindle, and what is the lead and pitch? And will it fit these nuts: http://www.dumpstercnc.com/trapezoidal_12x3x2.html ? To make matters worse, DumpsterCNC it says 3mm lead start 2, which would mean 1.5mm pitch which I doubt it is.
edit: Got a (fast) response from dumpstercnc, and the description is now fixed so it says 3mm pitch.

Right now I consider going for TR12x3 single start just to be sure. I'm in the planning stage of a simple DIY cnc, so I'm not locked to start 2 in any way. I'll attach an image just to give you an idea, the xyz axis rails are 800mm x 500mm x 300mm, and hopefully I can cut some wood and plastics with it.

06-12-2010, 06:38 PM
Hi elenhinan

I've had a similar problem when trying to buy from several ebay suppliers too, I've found it best to buy both screw and nut from the same supply company to ensure a match. Having said that, if you buy from a company based in your locale there shouldn't be so much trouble or expence if they send you the wrong thing, but you'll certainly be paying more for it.

There's a lot of 16mm ballscrews with antibacklash nuts for sale on ebay from our Chinese friends at not a lot more cost than local trapizoidal screws, it's worth a thought and some will even machine the ends to your specification if you ask nicely.

I use Trantorque keyless bushings to locate and lock my timing pulleys, they require a 26mm x 10mm stub on the BK12 end, though the standard BK12 end machining is a 15mm x 10mm stub, the extra charge was only a few dollars and actually cheaper than getting a woodruff key slot cut over here in the UK.

Happy hunting