Re: [CAD_CAM_EDM_DRO] Re: dovetails for cnc

Jon Elson <elson@...> wrote:
skykotech wrote:

>I am hoping the made-in-usa carbide insert dovetail cutter and my
>bedmill will hold 0.001" over the 5 inches or so of dovetail I
>need. I would think I would mess it up trying to improve things
>better than that by scrapping, heh heh. Still, it is an art that
>might be fun to learn.
>

If you want it to slide smoothly and have a wide contact area to spread the
load of cutting forces, you really need to scrape it. The Hardinge beds
I'm familiar with on the standard toolroom lathes have a mirror-like finish,
and need a similarly smooth surface to slide over it well. A surface
cut with
a dovetail cutter is likely to have a lot of roughnes on the surface.
Get some
Hi-Spot dye, at least, and apply a very thin layer to the bed. Then
place the
new carriage on the bed and wipe it against the mating surfaces while
sliding
it an inch or so along the bed. Then remove and inspect the pattern of dye
transferred to the carriage. You will almost certainly see it has hust
a few
spots or stripes. That pattern of stripes will soon wear ridges in the
lathe's
bed.

Jon


Yeah you are right Jon. Scraping is the best way to mate large planes like found in a dovetail. And just as you are saying doing it. Alot of those methods are almost lost arts. Sometimes we machinists pretend to live in a perfect world. I live near Henry Ford Museum and go over there quite a bit. And every visit leaves me awestruck surveying the machines of yesteryear that were all handscraped to fit. The big Corliss steam engines with 30' diameter flywheels. Huge generators and machine tools. Some are running and are dead quiet. We really lost the romance of mechanics when we left the steam engine behind. Its puzzling that even before the automobile they had that level of ability. The machinists have always got alot of credit but it was the scrapers that made it all fit.

Ron


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