Flat Grind help?

Surthriver

Surthriver

Member
Anybody know of a good way to flat grind on a 4x36? All I've been able to do so far is kinda a scandi/convex grind and its really to thick for good cutting.
 
Let's see a pic of the grinder. I'm guessing the platen needs some work. Have you done any mods to the grinder?
 
I can't get the computer to upload the pic....buts its a EAGLE TOOLS 4x36 with 6in sanding wheel attached. Model 301.
 
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You need to get a secondary platen under the belt. Something like a sheet of ceramic glass glued with an epoxy like JB Weld and reinforced on the lower edge with a couple of machine screws through the existing platen. That will allow the edge of the plunge line to overlap the edge of the secondary platen.

This was a mod that a machinist did to one of his machines so that he could grind knife blades on it.

Doug
 
I have a Harbor Freight 4x36 grinder that I use. I had a terrible time getting anything remotely resembling a good grind until I did two things. First I bought the Bubble Jig from Fred Rowe. An excellent investment, well worth the money.

Secondly I modified the platen. I screwed a piece of 3/16" steel to the middle of the platen and then ground it smooth with an angle grinder. It's still not the best, the sides aren't even (need to correct that). But you can do a fairly decent job this way. It gives you two things, an edge so you can create a bevel and a small area that's kinda sorta a slack grind.

It's a huge improvement for a 4 x 36. I'll post some photos later tonight or tomorrow.
 
( droppoint ) im useing a harber freight 4x36 need to mod you have any photos of what i need to do
 
DropPoint said:
I have a Harbor Freight 4x36 grinder that I use. I had a terrible time getting anything remotely resembling a good grind until I did two things. First I bought the Bubble Jig from Fred Rowe. An excellent investment, well worth the money.
Click to expand...

I'm terribly excited for my bubble jig to come!


On a different note, how is the platen? and how much space is their between the belt and platen?

The belt should be less than a 16th from the platen to keep grinds from curving.

Good luck!
 
OK...this really shows how not to do this mod. I did this when I was first starting on this stuff and really had no idea what I was doing. I'll explain a bit further. What I did was very simple. I took a piece of steel and screwed directly into the current platen. It's about 1/8"-3/16 I believe. Then I cut off ground down the screw heads and that was it.

OK...the biggest error on my part is not getting it square and not all the way to the edges. You want to take the piece of steel, or ceramic glass, all the way to the edge and have it as square as possible.

After posting earlier that I'd post pics, I feel embarrassed at what I have, but that's what I've got. The biggest drawback with not having it go to the edge on both sides (evenly) is the two sides of your grind won't match unless you adjust for it. So be sure and get it square and to the edge and this will help until you can get something better.
 

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So what ya'll are saying is, I need the platen to be the same width as the belt (4 in), or does it need to be the same width as the existing platen? The existing platen is about 4 1/2 or 5 inches wide so the belt doesn't even cover the whole thing.
 
I'm not sure how the 4X36 works, but on my 6X48 sander, there is an adjustment at the top where the belt is tightened that allows moving belt from side to side. Adjust belt so it moves to left side, then re-adjust so belt moves to right side. Of course, having a platen that's say 3-7/8" wide allows moving from left to right without having to re-adjust belt.

Ken H
 
KenH said:
I'm not sure how the 4X36 works, but on my 6X48 sander, there is an adjustment at the top where the belt is tightened that allows moving belt from side to side. Adjust belt so it moves to left side, then re-adjust so belt moves to right side. Of course, having a platen that's say 3-7/8" wide allows moving from left to right without having to re-adjust belt.

Ken H
Click to expand...

Mine has a adjustment like that too. I guess what I'm still confused about is, does the edge of the belt and platen need to be flush so I can get decent plunges?
 
Yes, the edge of belt needs to be even, OR slightly over hanging the platen edge for grinding the plunge line. I've never ground a decent plunge line - it seems like the "perfect" plunge line should be straight and make a perfect 90º turn at top. I sorta like a soft curve at the top rather than an exact square.

I tend to use a file to clean up the plunge line on my blades - but then realize, most of my meager knowledge comes from reading on this site, NOT actual experience. I'm still learning.

Ken H>
 
I did it the way KenH says. I grabbed a chunk of steel....put down some two part epoxy and stuck it down....I let it overhang the edge of the existing platten just a little. By using the epoxy, I can whack it with a hammer and it pops right off if I need to remove it.
 
Did you say it let the new platen epoxied on "overhang" the edge of existing platen? What width belt do you have - 4"? Now, how wide is the new platen you epoxied on? Can you use the adjusting screws to move the sanding belt all the way from side to side? The belt needs to move right to the edge - maybe over hang the platen a tad (1/8" maybe?) on the side your grinding plunge lines.
 
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