my build

[jonm]

hi tribbles
i am looking at this page http://www.ondrives.com/commercial-g...ype-steel.html looking down the mod column it relates to the width of the rack, the pitch line is down from the top of the tooth so measured down there i could have mod 1.5 .... i think .... maybe .....well i am getting confused with this

[tribbles]

Not sure why they've measured P based on the height, but that could be where they're measuring from (I am doing this from memory).

I've got some mod 1.0 rack in the garage - I'll go and measure it - it should tally with what they've got.

[tribbles]

Just measured it - it's 3.15ish mm, so I'm willing to go with 3.14.

Looking at this page (which I'd been to earlier):

http://www.ondrives.com/precision-ge...ear-racks.html

it sort of indicates that half the pitch is (pi * m / 2) - although the end marker isn't exactly where I would expect it.

ETA: Looking at Kn8's document - reference pitch is pi * m, which is what I thought it was all along.

[tribbles]

The "P" is the reference pitch height - i.e. where you measure the pitch from.

[jonm]

hi tribbles
will go and get the calipers to measure the rack

[tribbles]

Just had a thought about the meaning of the "P" value - this is actually the height at which the pitch diameter would ride at.

So, if you had a 60mm diameter gear, and "P" was 10mm, then the centre of the gear would be 40mm from the base of the rack.

[jonm]

hi tribbles
get 11mm pitch 3.1mm at the crown of the tooth
and rack is 12mm wide , i am still confused cant seem to find anything similar, unless im measuring at the wrong place

[tribbles]

Going from crown to crown, then 11mm is near as damn it mod 3.5. However, I've not seen that many mod 3.5s.

This seems to indicate this company makes them: http://www.rushgears.com/Tech_Tools/geargages.php

I take it you didn't find any gears with it, did you...

[jonm]

hi
tribbles yes you'r right it looks like mod 3.5
no, no gears with it im afraid
mod 3.5 looks hard to find

[jonm]

v groove bearings arrived from ebay this morning, the t slots on the back of the beam just happen to be size for a 10mm bolt head...
the x and y are rock solid much better than my first mdf creation
apparently this ali beam came from a stenna stair lift 190mm x 90 no flex at all even after cutting out the middle section . screw will go through the middle of the beam , gives me 600mm on the y

new trend t4 coming from santa for spindle...