Surface Plate Questions

[Eric Siepmann]

There are many ways to skin this cat but I think you'll find that a surface plate, whether bicycle specific or general industrial, is the most convenient and cost effective approach and that CI, steel and granite are the most suitable materials for most circumstances. Certainly one could use other approaches with varying degrees of success and hassle; I tried a CI tablesaw extension wing for a time (lousy) and parallel beams (also lousy), but there is a reason that professional builders and many serious amateurs use a standard surface plate with the typical accoutrements.

I think the real reasons have more to do with availability, price and what is practical given the requirements faced by building a frame. Other, better options from the Professional Welder are becoming available and affordable that far outweigh any benefits the traditional surface table can offer. You can make a table in more than one dimension to fit specific requirements with the example above. You can also fixture the example above and safely weld on it without worrying about loosing the the accuracy of your table as well (within reason). So in essence, you can combine the surface table and frame fixture over time and as the need arises. The Pro Shops have all the cool stuff! I am just thankful that there are more ways to skin a cat and everyone can benefit if more of them are explored and put into practical use. Lots of cool things happening with the hobby machinist world as well. Accurate and portable table top CNC machines that can replace the need to find the scarce good old stuff out there.

[jclay]

I think the real reasons have more to do with availability, price and what is practical given the requirements faced by building a frame. Other, better options from the Professional Welder are becoming available and affordable that far outweigh any benefits the traditional surface table can offer. You can make a table in more than one dimension to fit specific requirements with the example above. You can also fixture the example above and safely weld on it without worrying about loosing the the accuracy of your table as well (within reason). So in essence, you can combine the surface table and frame fixture over time and as the need arises. The Pro Shops have all the cool stuff! I am just thankful that there are more ways to skin a cat and everyone can benefit if more of them are explored and put into practical use. Lots of cool things happening with the hobby machinist world as well. Accurate and portable table top CNC machines that can replace the need to find the scarce good old stuff out there.

Your first sentence summarized my point nicely; recapping - convenient, cost effective, suitable to the task. Aside from portability, which is of no import to many, the tables you noted offer no advantage that I can see relative to building conventional diamond frames. "Far outweigh" any benefits of traditional ....? That's a strong statement that doesn't square with my perspective. None of the addnl flexibility buys me anything and the fixtures in the photo made me want to run and hide. What a PITA to set up! If I wanted my frame fixture to be part of the table I'd get Doug's excellent, highly evolved, very efficient to configure, bicycle frame building unit and put it on my table! If that's how one wants to build I doubt one can do better.

While the welding table and accoutrements are very slick and flexible in their application to other types of fabrication it's the very nature of that generalist approach that makes the system sub-optimal for conventional frame fab or other specific tasks for which specialized gear is available; the fixed whipping post, vee blocks, et al. are extremely efficient and well suited to the FB task. If one envisions doing other types of work as well as FB, say you want to build motorcycle frames too, and you want one fixturing system that can accommodate both, then I think you have a good case for the more universal approach of the tables you noted. What is given up is the efficiency due to the specialization of the surface plate equipped with the usual framebuilder accoutrements. It's horses for courses; if conventional bicycle frames are the only item on the menu then I'd recommend the track record of suitably equipped surface plates as the clearly more efficient approach. If, on the other hand, you need the flexibility to fixture other types of work pieces then these welding fixturing systems might be a good compromise. Note that last word.

[rauce]

Update for anyone interested:

I ended up purchasing a 2x3' 4" thick granite plate. I paid $150 and it came with a homemade cart although the same plate would only be $400 or so new which is not really prohibitively expensive either.

I did two frames earlier this year using it by clamping the shell directly to the plate. I used nuts and bolts to level the tubes checking with a surface gauge. Rear end alignment was done on a simple 80/20 fixture with the use of true wheel and a park tool FAG.

Just a few days ago I got a BB post made by a machinist friend. Sized so that the center of a 68mm shell is exactly 4" off the plate. This way I can use readily available v-blocks and 1-2-3 blocks as simple fixtures for holding things in place.





I really don't think I could have done any better for the money. Between the post, the plate, the blocks and the necessary stuff to drill the hole I'm only out $500 or so.

[Andrew R Stewart]

I always like to see beginning tooling. But I will say that relying on a BB shell to be true to a labeled dimension can be frustrating. Andy.

[rauce]

I don't see much harm if the shell is a little wide or a little narrow. The faces being parallel to the tube is most important, the width of the shell being offset 0.5mm or whatever to one side isn't a big deal to me. I face my shells before I even start building anyways.

Realistically the v-blocks etc. are a stop gap until I have a nice fixture at which point the plate will just a be a reference surface to be used in conjunction with a fixture.

[Michael Gordon]

Here is a great thread to revisit on this topic: http://www.velocipedesalon.com/forum...tmo-21294.html

Some face the shell, some don't, some face before building, and some face after building. All of these different perspectives come from reputable builders.

There is more than one way to skin a cat, as well as build a frame. Add in the quality of the materials and the skill of the builder, and I can see how any of these techniques could work.

[Andrew R Stewart]

I liked that thread on alignment. Total agreement on there being many ways to end up with a well aligned frame though a few ways I won't do any longer

My comment on dimensional trust is for the newbies. Andy.