Plunge line problem

D

DHackney

Joined
Jul 12, 2004
Messages
178
Hi folks,

I've partially completed about a half a dozen knives (1 hollow ground and 5 flat ground) to date and am getting more confident with each knife. My grinds are turning out pretty well but my problem area is still the plunge line.
I'm getting them to meet, from side to side okay but I still cannot seem to get the plung lines nice and straight and crisp :mad:

I know it takes a lot of practise but I thought I'd ask for some detailed advice on how you experts start the grind on the plunge. Do you begin the grind with the belt bent over the edge of the platten/wheel and grind forward or do you keep the belt even with the edges of the platten/wheel, or.....?

I am ordering the Art of Hollow Grinding with Johnny Stout in hope this will help but I would appriciate any/all suggestions.

Best regards,
Dana Hackney
Monument, CO
 
what i do is have the belt even with the platen, not over the edge, back into
the plunge line, dont start there, use and new or sharp belt and it should turn
out nice and crisp!
 
I'm far from an expert, but I'll tell you how I seem to keep my plunge lines straight. I decide where the cutting edge will start and mark it with a file mark from a rat tail file. I grind horizonally from the heel to the point alternating hands. I get the inital bevel started then work the grind up the blade to the height I want it. Alot of it is feel and learning the amount of pressure needed on the belt. Like everyone says, practice, practice, and more practice. ;)
Scott
 
I am no expert, but like you already said -- practice, and more practice. :)

I usually grind the plunges with a 60-grit that is even with the platen (before heat-treat), then after heat-treat, I'll run a j-flex over the edge and even them up.
 
for the much appreciated advice. I'll give all these suggestions a go and report back to let you know how I'm doing.

Best regards,
Dana
 
Was practice mentioned?

Here's a little tip for matching them up (you said that wasn't your problem, but what the heck).

Wrap a piece of masking tape over the ricasso where you want the plunge. If the tape goes all the way around the blade and matches up, then you have two lines on opposite sides that match perfectly.

Do most of your grinding a 1/4" ahead of the tape. When you are 80% done, go back and make the plunge. Tilt the blade edge to the belt. Hold perfectly parallel to the platen. Now roll the spine closer and closer. This will cut in the plunge without any back and forth. If the belt is right on the edge you get a crisp even sharp line. If the belt is over the edge it's rolled. You can cut it sharp with an 80 grit. Then roll it with a 320 grit flex belt - like Micheal said (that's what I do).

Like Fetz said, for the remainder of your grinding, always start 1/4"+ away from the plunge, move into the plunge, then do the grind.

Still doesn't work for me, but I get close!

Steve
 
The Johnny Stout video will help you a lot. I have a copy of the old one kicking around somewhere. Bear in mind that Johny does it one method and someone else will do the same. I've watched a lot of makers do their hollows, and I've tried to take the best from all of them and adapt it to my own style. Like Dave and mike and a host of others will tell you: Practice is the best medicine for your grinding ailments. There have been some good tips so far, so I'll give you another...

Start your plunge line about 3/16th of an inch off of where you want it to end up. As you work your way up through the grits, take another swipe back into your plunge. With practice, you'll end up with your hollows smooth, your grind lines crisp, and young hot teenage... er... plunge lines exactly where you want them.

*pulls collar*

*clears throat*

:rolleyes:
 
plunge lines are hard for me to do also...the problem i get is a dignal line instead of a horizantal one :confused: does any one know how this ocours.??
i use a sharp 60 grit followed by a 220 or so grit belt and then hand sand.if i missed some major scratches i just stick the plunge line on a buffer to take out the scratches. (just hold it there for about 30 seconds on each side.)this usualy gives me a crisp line only it is diagnal :confused:
ps anouther option is filling the grind line.
jv
 
I'm gonna cut and paste all these replies and stuff them into a word document for reference. Can't wait to leave work and get to work on my grinds with this information.....yeeehaaaa!

Many thanks,
Dana Hackney
Monuemnt, CO

P.S. It would be great if we could get something set up like our Great Lakes friends did, here in Colorado.
 
JV, try the tape idea.

When you are lining up you can see if the tape that's towards you is really up and down.

Steve
 
jonvalblades said:
plunge lines are hard for me to do also...the problem i get is a dignal line instead of a horizantal one :confused: does any one know how this ocours.??
i use a sharp 60 grit followed by a 220 or so grit belt and then hand sand.if i missed some major scratches i just stick the plunge line on a buffer to take out the scratches. (just hold it there for about 30 seconds on each side.)this usualy gives me a crisp line only it is diagnal :confused:
ps anouther option is filling the grind line.
jv
Click to expand...


Don't know if I'm understanding. Are you talking about where the plunge meets the spine? How is it diagonal? Any pics?
 
I use a "cheater", and start all my grinds at the plunge. I've always been different. :rolleyes:

My cheater is two pieces of 1" angle iron, connected with bolts. The bolts are a slide fit in one piece and threaded in the other. I clamp this around the blade where I want the plunge and go to town...

I start my grind with 36 grit, move to 60 then 220. When everything is smoothed out at 220 I remove the cheater and move the belt about 1/8" off the wheel to grind in the radius, then continue through 400 before HT.

Just my method, *usually* works for me. ;)
 
Dana, Dave's use of a "cheater bar" is a good method. If you want to invest a good $20, go to Sheffield's catalog and look up "filing guide". Page 95 of the catalog, P/N "JIG-01".
 
I use a "cheater", and start all my grinds at the plunge. I've always been different. :rolleyes:

My cheater is two pieces of 1" angle iron, connected with bolts. The bolts are a slide fit in one piece and threaded in the other. I clamp this around the blade where I want the plunge and go to town...

I start my grind with 36 grit, move to 60 then 220. When everything is smoothed out at 220 I remove the cheater and move the belt about 1/8" off the wheel to grind in the radius, then continue through 400 before HT.

Just my method, *usually* works for me. ;)
 
a filing jig for the plunge line last night! I'll defintely give this a try.
I did do the tape trick last night, as well as starting the grind ahead of the plunge, and both were a big help.

I am also contemplating trying Ron Claiborn's plunge line jig. I saw this somewhere on the forum a little while back and will have to locate the thread again for the design.

You guys are great! Thanks a lot for all the help.

Take care,
Dana Hackney
Monument, CO
 
Dana, are you speaking of the platen modification for cutting plunge lines?

If so, the platen idea came from Jerry VanEizenga of Michigan. Jerry got it from someone else and can't remember who. Jerry demonstrated it at Ron's hammer-in last fall, I believe.

I say this not to take anything away from my dear friend Bowie (Ron), but because he winces every time he hears it attributed to him. Bowie is VERY big on credit being accorded to the right person..........

Good luck with your plunge lines. It is obviously one of the tougher grinding skills, and even after years of practice one gets buggered up occasionally regardless. You just keep practicing, practicing, .......and developing a richer vocabulary! :eek: :)
 
for the correction regarding the credit due to the inventor of the plunge line jig, and thanks for the words of encouragment. I definitely will be practising, and, as soon as I get a digital camera, will post some pictures for you experts to critique.

Kind regards,
Dana Hackney
Monument, CO
 
I saw the one in Sheffield and was too cheap to spend the $20 so I made one form two pieces of O-1 I find it helps what would probably help more is a better grinder in my case the cuts at the plunge line aren't as sharp as I like. I am using a 1" X42"belt grinder and it walks sometimes.

Abe
 
How do you do the curved ricasso? Is it best to forge a high fuller and plunge from its tangent or is there a way to just grind it?
 
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