If we are going to nerd out, we could look up the coefficient of thermal expansion of aluminum and delrin and compare the numbers. Personally I have not found a problem.
Yes, I would check the bushing on the x-axis. Just today I was tuning some bushing to match the rails on my latest machine. The bushings where .865" in diameter and interfered with the rail. Just shaving off .005" made a huge difference. Shaving off .002" from the rim of the top hat made the bushing perfect. It's amazing what a few thousands can do. We go from an interference fit to a true slip fit. I need some time to read the rest of your message. It's been a long day preceded by a very short night. -Tim ----- Original Message ----- From: "Andy" <atmarti...@gmail.com> To: "Legacy Ornamental Mills" <legacy-ornamental-mills@googlegroups.com> Sent: Monday, January 23, 2012 8:14 AM Subject: Re: router carriage racks when using template follower > Perhaps it would help if i shared my plans, and I use "plans" lightly > because if this doesn't work i'll just go with a simpler design: > > a family member asked if i could make a new pepper grinder. the guts > of the pepper grinder have a lifetime warrantee but the wood body is > falling apart. The request was for something modern, the design is > left up to me. So, was going to make the body with a square cross > section that spiraled 1/4 turn over the length. The length is 3.75" > therefore i used a 15" spiral gear setting. The side profile was going > to be concave, I drew up the curve in AutoCAD, printed it out, and > traced and cut the curve into my crude template shown in the picture i > posted. Its a varying curve but probably close to a 3" radius. So > basically, i was going to have the y-axis follow the template as i cut > the twist from the side using a spiral upcut bit. > > In this case, mounting the template on the front did alleviate the > binding originally in the x-axis because my pivot point was the front > rails and x-axis screw. The template follower had a moment arm length > from the front rails to the template follower pin (probably 18"). > Mounting on the front changed that moment arm to 5 or 6". This > drastically reduced the racking. However, now it is racking between > the carriage and the y-axis rails. When i assembled my machine, i did > have to sand the tophat bushings down so everything slid well. > However, the carriage was already assembled to the Y-axis rails in the > box. So i didn't do anything to those. It does take a good amount of > pressure to move the carriage but was never a probem since i've only > moved it using the screw. Perhaps i need to take it apart and work > those bushings as well. > > When i was looking at the 80/20 carriage system, they use plastic T's > that are the length of the carriage and ride in the t-track. Would > this be a better design than the tophat bushings? > > Sorry to "nerd out" but i am an engineer so i feel is required from > time to time; If i sand the bushings to fit now (its 30-40 degrees in > my garage), will i have excessive slop in the summer when my garage is > 80+? Anyone notice any difference in this due to seasonal changes? > Aluminum does have one of the highest coefficients of thermal > expansion. I know its still small but this is the reason we don't use > aluminum wiring in houses anymore. Perhaps this is why my carriage is > so stiff in the y-axis. I seem to remember it moving much smoother/ > easier last time i used it (when it was still warm in my garage). > > -- > You received this message because you are subscribed to the Google Groups "Legacy Ornamental Mills" group. > To post to this group, send email to legacy-ornamental-mills@googlegroups.com. > To unsubscribe from this group, send email to legacy-ornamental-mills+unsubscr...@googlegroups.com. > For more options, visit this group at http://groups.google.com/group/legacy-ornamental-mills?hl=en. > -- You received this message because you are subscribed to the Google Groups "Legacy Ornamental Mills" group. To post to this group, send email to legacy-ornamental-mills@googlegroups.com. To unsubscribe from this group, send email to legacy-ornamental-mills+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/legacy-ornamental-mills?hl=en.
