my build

[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...

[jonm]

this ali beam is becoming a source of many parts .... with the centre section cut out it makes a very sturdy motor mount






the skate bearing is in the mdf with another thrust bearing on the other side ... have some delrin may make a bearing block from that

[Ross77]

Looking good, those beams look promising. I,ve got some similar ones that are also from a stair lift. Not sure I would of cut so much out of it tho.

I plan to mount the rails on the other side with the T-slots, why did you choose to mount them as you did?
It will be interesting to see how it performs, save me some R&D

[jonm]

hi ross
even with the centre section cut out there is still no flex in the beam, also reduced the weight , it was very heavy... wall section is 6.5mm.
was intending to put a few 8mm threaded rods through from top to bottom , along the lenght, with 2 nuts inside and and 2 outside which would have held it rigid, also could have adjusted the preload on the bearings (as a adjustable spacer) but think its going to be ok. can always be added later

with the screw inside keeps the y axis and z axis very close , going to cut the centre section out of the z as well , to keep router as close to the y axis , to reduce cantilever

holidays start tomorrow so plenty time to rebuild

what type of rail are you going to use?

[Ross77]

Hi Jon
Fair play on the weight issue It seems that when you modify stuff you have to compromise, the removed section will reduce its strengh and torsional stiffness but as you say the reduced weight and the fact you can bring the leadscrew closer will probably be more benificial.

I'm just cautious now after setting up my lathe, it a fair old chunk of steel but it dosnt take much for it to flex and cause poor surface finish. I suppose it depends on what you are using it for.

My machine will be bit of a monster (stength not size) cus I want it cut seasoned hardwood and Ali. the rails are THK HSR 35's on the X axis and HSR 25's for the Y and Z. 30mm ground ballscrews and 750oz servos. just need the time to build it. :whistling: