surface plate/layout table
I am going to build a layout table using 80-20 for the frame. The surface will be high density polyethylene instead of granite. Much cheaper and lighter and accurate enough for my purposes. I need to determine the dimensions. Measuring my bikes, it looks like 36 inch square would be an adequate size/shape but maybe I am missing something. The worst thing would be to make it too small and the second worst thing would be to make it needlessly large. What is recommended? Jerry
mine is 35"x 22" With that size, you have to do some workarounds. If you really want to be able to measure most bikes, you probably want something more like 42"x30" 48x36 would be really nice. I think if you go with 36" square you might be annoyed with yourself for getting so close, but still having to use workarounds for some bikes.
Yeah I agree, go 36" x 48" and you'll be happy. Similar to a garage or shop, the extra space you add in will always get used. I always have something on my table whether its a height gauge or drawing of a frame or whatever it'll get used. I wouldn't care if mine was 4' x 5'.
My favorite size is 36" X 48" too. It is possible for a table to be a little smaller if you are really tight on space. I think the Bringheli table is 30" X 45". If you don't care that the rear triangle is on the table than you can get by with a 24" X 36" with the holding post in the southeast corner.
It isn't just that you want the frame to fit over the table but also want to be able to use a surface gauge to check alignment by moving it around the outside of the frame. I wouldn't want mine to be taller than 36" because I would have to reach in more than my liking to work on the frame.
Granite is cheap if you find it in the form of tossed out surface tables. I thought to myself "that will never happen". Immediately found several on CL. One guy was selling a 6'x4' Starret inspection surface, along with some smaller ones including the one I bought. Gorgeous. The only guy who had showed interest had wanted the 6x4 for his woodstove!
That said, I don't really see why one needs one. I guess one can say that about any single piece of the puzzle, one needs something, but not necessarily any one part. I design in CAD, not bikecad at this point. I also consider my fixture part of the picture, as I sorta consider space while staring at it (I don't do customer bikes, but obviously if I was doing a numbers based build I would follow those, but for looking at one-offs I hold stuff in the jig), it also holds my stuff in position for assembly. I check straightness in a variety of ways, I use stuff that fits to my welding table which is a 48 inch long milling machine table, but only 8 inches wide. I don't really find the inspection grade granite surface that useful for bikes, and that is before discussing the terrible things people do to them. I'm keeping mine along with my cast straight edges to do repairs on the surfaces of my machine tools, like I otta...
To everyone who replied, thanks. I will build a 36" x 48". Using high density polyethylene instead of granite eliminates the problem of finding, paying for and lifting the actual surface plate and size is whatever you order. I have had a piece of it in the shop for several years and can find zero warpage. Of course, you would not want to get it too hot.
So far, looking at the various retailer sites, I have not found a picture of how their surface plate is set up. There must be a post to set the BB Shell on. I would love to see a pic. I assume the BB shell is never moved but the rest of the frame can be adjusted relative to it. Is this the case or do I have it all wrong? Jerry
I would look at framebuilder flickr accounts to see how their alignment tables are set up. I always look at Engin Cycles when I want to feel inadequate. There really are too many sites to list.
I could have gotten a larger piece of granite but I don't have enough room and I didn't want another incredibly heavy object I had to move around. So there is that. I used the Egyptian method to lift my granite plate into place; just lift a little and put 2x4 underneath, then lift again. This is a picture from when I had just lifted it into place and cleared away all the beams and 2x4s.
Last edited by unterhausen; 08-08-10 at 12:00 PM.
My current table for the granite is my lifting table, the same one I use to move machines. when I am not using it I can lower it to the floor and tuck it under something else. Or I can leave it on some jack stands and run off with the table. It cost me less than 100 bucks from an HF type place up here. I wouldn't put my hands in the scissors though!
There is a current thread on Velo Salon about stands for granite tables over there. I can`t probably see all of them since I don't have an account, but one of them was pretty nice. Look at David Bohms. Some people on that thread where worried about the 3 point supports being unsteady If I had room for a fixed table, I would make it something like bohms, but with crosspieces that would support the three points and only be about .25 in above the perimeter rails.
Your assumptions are correct about the post. Look at the Paternek manual free download for further info.
I started that thread. Turns out a compliant bed was lots easier for me, I have some of the rubber matting made for machinery mounting and just put 6 strips of that around the edge. It isn't going anywhere. I'm not using the granite for any cold setting, no need.