sanding set ups for blades??

[DN5135]

We are making 40 runners of various types and are thinking on how to set up a grinding/sanding operation. I am interested to hear what some f you guys have set up for yourselves to grind edges from scratch and to sharpen and maintain.

[Ken Smith]

You guys are making a huge investment and only going here for research?

There are several ways to go depending on what equipment you have.  WIth a NC mill and some special set-ups, you can cut and grind the runners directly from the mill.  Not easy.

Most easy is to build a jig to hold teh blades curved in a slight arch, concave side up.  THe blades are held at the angle appropriate for your desired final cut.  FOr 90 degrees, two blades at 45 with teh edges close by, held rigidly in a jig with the middle pulled down further than the ends.  Then a flat mill pass will put a first cut on teh blades.  Reverse the blades and another pass will put a 90 degree cut on the blades.  THe profile will be a gentle arc.  Adjust or figure the initial bow quantity and you an get reliable profiles.

If you do this practice without the bow, you get flat profile, and can add the curved profile on a 45 degree table and long edge sander or specialty built runner edge sander. Hand work.

Good luck.

[DN5135]

Actually, we are water jet cutting the shapes.

I am looking for ideas on edge grinding, both the initial and regular tune ups. The mill idea with a bow is interesting to create the edge, I've seen a few set ups with long belt sanders with tables at the 45 degree angle parallel to the sanding belt. I'm wondering if anyone has actually made the edge with these or just used to tune/maintain. Is it worth the effort to build a 96" or longer sander?

I have a Sarns fixture that would allow me to do a pair on a surface grinder as well (after some time making sure it is true to the table).

What other methods have worked out?

[ERIC ANDERSON]

There are a number of methods of getting a reliable profile on a runner. Many involve some type of jig.
As far as I know, Jeff Kent is using a CNC sander to do all his  profiling and sharpening, there is also a setup where a radial arm saw with a grinder wheel was modified to run in a track that had 18" of 8/1000 flat and produces consistant profiles.  Jeff Brown uses a jig where the blade is clamped in a sled that rides along  a curved track.  The blade is run across a grinder. 
The mill with a bow idea works with the blade not in a body.  I think once the runner is in a body it does not work.
The other thing to keep in mind is that when you are mouting the blade in the body, it is very hard to get the steel perfectly straight in the body.  The best I have been able to do is about 0.003"  once the epoxy dries and I unclamp it.  Some of mine have been as far off  as 0.010.  In the end I don't care because I sand it so the edge is straight and parallel.

 I think you will find however that the vast majority of racers use a belt sander with a very flat platten.  It helps if it is adjustable.  You have two options, 1 a long belt  89" or longer and the blade can fit on the table full lenght or a short sander and slightly different technique.  This requires a great deal of practice to get good at sanding runners.  Once you have a runner the way you want it you will have to sharpen it  infrequently if it is a hardened runner ie 440C.  Mostly you will hand stone it only.  The advantage of this is you can change setups to deal with different angles

Generlay speaking  you are going to have different profiles on your runners depending on type and length.  You may chose different angles also or simplify and go with all 90° blades. 
Sail fast,
take chances
US 5193