grinding q's

S

SR_matt

Joined
Jan 4, 2007
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I know there are a lot of grinding threads up lately but i havent really seen what im wondering in them or at least in any real depth (i probably missed the answer though) quick question about starting grinds with belt grinders, i know that you are supposed to use an old belt to start the grind since the edges can rip up the belts but how much do i need to start into the blade (just enough to take off the 90* or more ) and how far up should i grind (just the edge or should i at least scratch into all the parts im gona grind?

second how much should i go up between each belt change liek starting with 40 then going to only 80 or 100 or 150 or 220 or farther up?

thanks
-matt
 
as far as iv'e always heard just enough to break that sharp edge is fine. maybe 1/16" or 1/8" up

then with switching between belts it realy depends on what you're using for belts and how you grind.

some belts cut better, some seem to wanna do nothing at all. give it a 1/16" or so between each belts to be on the safe side. but when you're talking hardened steel once you get up to the high grits they barely bring the line up.
good luck
 
Michael J. Spangler said:
some belts cut better, some seem to wanna do nothing at all. give it a 1/16" or so between each belts to be on the safe side. but when you're talking hardened steel once you get up to the high grits they barely bring the line up.
good luck
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kinda confused on that part, do you mean take my grind like up 1/16'' between each belt?

-matt
 
sorry. well i'm saying if you're at 60 grit figure you're gonna grint up about 1/16" or so to get to 120 grit, and 1/16" more to get the 220 grit in there.
but thats just a figure. could be more or less.
then figure after HT you gotta re grind, thats gonna take some off too.
but once you get up to say 400 or 600 grit on hardened steel, you barely make a difference in grind height.

hope this helped more than it confused:D
 
ya kinda, only part im still confused is if you mean thickness or vertical height from blade to spine.

the grits i have are 40 (supposed to be ceramic) 180 ceramic, 320 SC, 600, cork polishing, and then i got compounds that are 800, 1500, 2000 for the buffing wheels that are supposed to be comming in from harbor freight.

i probably will have to order another grit inbetween 320 and 600 (probably 400-500ish, the big problem i have is that im using a 4X36 so the higher end grits are harder to finde even at supergrit)

thanks
-matt
 
i hear ya. have you tried trugrit?

i mean vertical height towards the spine.

give a few a try and see how it works for you.
kind of one of those things you need to feel out
 
Don't fool around, grind the whole thing at 50 grit, remove scratches with 180 grit then clean up with the greaseless compound if you have it available.
 
SR_matt said:
how much do i need to start into the blade (just enough to take off the 90* or more ) and how far up should i grind (just the edge or should i at least scratch into all the parts im gona grind?
Click to expand...

Hi Matt, For large blades I usually start with a 36 grit belt. Like you said, start with an old belt and knock a 45* on the edge. I layout a scribe line on the edge (actually 2, leaving a .015 land), like has been described here so many times (I know you're still with me ;) ) Take the 45 right to the scribed lines. It's that simple, grind a 45 up to you edge layout lines.Then go to a fresh sharp belt and start your grind, be it a flat, convex or hollow.

SR_matt said:
second how much should i go up between each belt change liek starting with 40 then going to only 80 or 100 or 150 or 220 or farther up?
Click to expand...

From a 36 to about a 60-80. Then a 120-150. I usually don't use anything above a 320 except for sharpening, then I turn to a micron belt. This is how I do it, I'm sure if you ask ten guys you'll get ten different answers :)
 
A good rule of thumb with belts and hand sanding is to roughly double the grit each change.
e.g. - 36,80,180,400,800,1500,3000,8000
60,100,220,400
or 80,180,400,black compound,white compound (this is what I use most of the time)
Stacy
 
ok very cool, i guess the belts i have will be fine for the most part

hmm black compound? the black i have seen was a 200 "cutting" compound i assume the compound your using is either a much finer grit or its just labbled wrong

thanks everyone
-matt
 
I approach it a tad differently than others, I guess.

I'll essentially rough to shape in 36, jump to 80 or 120, then 220. The shaping/bevels are done in 36. There's a little refining in 120, but mostly it's done for finish. 220 is almost entirely for finish for me. That means, the finer grits are not removing a lot of stock--certainly not 1/16. Maybe .010 for 120 and less (maybe .005) for 220.

"Different strokes," I guess.:)
 
I go with 36, 40 or 60 zirconia or Blaze for rough grinding, then up to a 120 yellow Klingspor for refining and getting the plunge cut right (ha, ha) then a bit on the 220 Klingspor. After heat treat, i do the heavy removal part usually with a blue Norton in 100 or 120 and then back to the 120 and 220 Klingspor. After that, it is hand sanding with 220 to get all of the grinder scratches and then 400, 600 and 1000. Just started using windex as a lubricant and it seem to work well. Haven't tried my 1500 and 2000 paper yet. Guard materiel gets taken to at least 600 if not`1000.
 
"Just started using windex as a lubricant and it seem to work well".





Try Simple Green:thumbup: :thumbup: :thumbup:
 
hmm well i did get a big bottle of simple green to use for cleaning AL and never got around to it, i might have to try that, will leaving the belts wet be bad?
-matt
 
o ok, that makes sence. ya now that reread what was said thats exactly what he said.
thanks for all the good info, hopefuly ill be able to get soem of these blades done to be shipped to HT with in a week to post up in here
-matt
 
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