making the plunge...

S

SkaerE

Joined
Sep 9, 2001
Messages
428
how do you guys make a good clean defined plunge cut?

any of you use a jig of sorts to keep from overcutting?

what grit belt do you use? at what point in the grinding process?

do you track the belt over just to the edge of your wheel/platen or past it?

thanks
 
I dig in good with a 50 grit belt and then set the plunge with a 120 grit belt tracking over the edge and broken down some on the edge with a scrap piece. I then go to 220 grit to set them up evenly. I've found that practice and good steady pressure are key. Oh yeah, sharp belt are the only way to fly.
 
One thing that helped me when I first started was to make a filing jig or sorts. It was just two pieces of steel that the blank was placed between. I had two bolts and nuts to hold the jig in place and basically clamp the blank in. The front edge was where the plunge was cut. After going past say, 120 grit, I took the jig off.
I no longer use it but it was invaluable when I first started.

Another thing that you can do is to clamp the blade in the jig or a vise for that matter and cut a radius'ed plunge with a chainsaw file.
I know a number of folks that still do that.

C Wilkins
 
excellent, thats exactly what i was going to make.

did threading it before heat treat cause any problems? (threads changing shape etc)
 
Absolutely no problem at all with heat treating the threads. In fact I even heat treaded it assembled with the case hardened screws in place. I didn't care much about the screws because they could easily be replaced. I heat treated it assembled so I could quench both sections at the same time. I left a gap between the parts (screws loose) so that the parts would heat more uniformly more quickly. I heated to 1475 F. and held for only about a minute and quenched in 140 F. oil swishing back and forth while counting to seven. After pulling the steel still smokes but does not flame. I did this three times (heat and quench) before tempering three times at ,I think, 350 F.. I may have tempered a bit high for this but I did it so the thing could flex a little on smaller blanks without cracking.

...and there is no reason for case hardened screws except that I had them on hand so I chose to use them.

I made mine to accomidate up to about a two inch wide blank (measured from inside of screws).

Roger
 
The plunge cut are one the most difficult part to make for me...
I asked Neil Blackwood how it makes its plunge cut (I like much
his plunge cut and his grinding...) It answered me this:

To get the rounded plunges, I move the knife to the side as I'm plunging in. As I'm working the plunge area the blade is always moving sideways!! Besides practice there is no other trick other than how I move the blade against the belt. No wheel radius, no breaking down the edges of the belts!! I rough my blades with fresh 36 and 50 grit belts. After heat treat I do the final, more complex grinding with a 120 and 220. I spend a little extra time polishing the plunge areas with a 45 Norax belt, slightly overhanging the wheel to make the hand finishing easier. At some point, I'm going to set up another grinder to run 1" wide belts for doing more complex grinds on smaller blades.
Click to expand...

Original post here: http://www.bladeforums.com/forums/showthread.php?s=&threadid=237386&highlight=Headed+to+Vegas

Alain M-D
 
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