Platents, ughhhhhhhhh!

L6steel

L6steel

Joined
Sep 23, 1999
Messages
5,855
Why is it impossible to grind something flat on a stinkin platent?
I even broke out my super special platent plate made of precision ground heat treated 440c and bolted it on and I still couldn't get my bolsters flat. No matter how careful I am there's slight curves at the outside edges.
How do you guys flatten the material you use for bolsters so there's no gaps between them and the liners?
Surface grinder owners please keep your traps shut, ugh!! :barf: :eek: :footinmou :D :yawn: :p
 
When you have a belt moving over a stationary platen, by it's very nature it won't get everything truly flat.
That's why I true up my blade flats, and tapered tangs on the 9" disc, after the belt grinder.
A pyroceram platen liner will help a great deal.

On bolsters, I use the mill to get them real flat.;) :D
 
What happens when the belt is moving across the flat platen at a high speed is that it is bowed to some degree, especially with a heavier weight belt. If you look closely at say a 36 or 60 grit (X) weight belt that is running across the paten, it is bowed out somewhat. The lesser weight J belts aren't nearly as bad but it does occur to some degree.

One other thing that we have to remember is that platens do wear. We all have "sweet spots" where we like to make contact on. This will account for a lot of the unevenness as well.

As Mike Hull mentioned, a flat disk is a good answer. Look at the granite plate as well. A piece of glass works OK as long as it is stationary and doesn't slide around.

One thing I do with guards is to get them close with "both flat surfaces parallel" and then go to the "sandpaper on the granite plate" to make sure they are flat. With bolsters I am primary worried about the surface next to the blade.

Craig
 
I run my wheels on both sides of the platen a little farther back distance wise so only the belt tacks on the platen. I can flatten stuff by starting on the top and let the material ride down the belt till I get it on the flat section and then move it around with even pressure to get it flat. I used to have that problem with my backspacers bowing at the front and back but now they are cut and the inside is completely finished before its put on the assembled knife. Then I cut the excess off, profile the entire knife and there is no air gaps. This also works for the bolsters, if you leave them a little big, cut to length while on the liners with the scales attached ( I do this one side at a time) and the profile the knife to shape when you assemble it. When I remove all the pieces afterwards I am real carefull to just lightly sand the back sides of the bolsters to remove any little sharp areas that may be left, usually there isnt much. You need to be carefull not to put too much pressure on it at thia stage or you will then get the bowing. I have also gotten bowing when I try to get too much use out of my belts. If you piece is bowed, try putting a new belt on and see what happens. Usually the bows goes away.
 
One of the biggest issues for me is slowing down the belt. At high speeds the belt does indeed tend to torque the piece off to the sides and create rounded edges. But this is greatly minimized at slower belt speeds.

Even so, now that I too have a disk grinder, I am looking forward to those truly flat flats! ;)
 
I use pyroceram attached to my flat platen with JB Weld. It just doesn't seem to wear and I've doing a lot of flat grinding lately.
 
I have a cheapo belt grinder now (sears) and it has a real problem with this (hope to get kmg soon...other topic though). What I do is follow up my grinding with draw filing with a 14 inch single cut. For me, it does a good job of flattening everything out.

Tim
 
i'd have to agree with Mike Hull on this, the disc grinder is a definate on getting things flat, its what i use for fitting anything i need to be flat or that needs a perfect 90 degree edge from bolsters to slabs and spacers etc. one of the smaller models is good enough for bolsters and such, discs cost less and you can get more grits, but the larger like a 9" disc grinder is a nescesity for flatening up slabs and such
 
Hi L6........I use the belts for the most part....but then a simple few minutes on the granite flat platent with a fresh 220, and then 400 does the trick....
 
Disk grinder is the way to get stuff flat, but until you get one, you can use files. Get it close with the belt grinder and finish with a hand file.
 
I have one of those Delta 1" belt 5" disk sanders. Would that do the trick to getting things flat, or would I need a horizontal disk?:confused:
 
I'm with Jim Smyth. Make everyting oversized and trim those rounded edges after.

Next up is the 9" disk.

But on small parts I want dead flat I use SC paper over granite. It just doesn't take very long. new 320 paper cuts pretty darn quick.

Steve
 
Originally posted by ErikD
I have one of those Delta 1" belt 5" disk sanders. Would that do the trick to getting things flat, or would I need a horizontal disk?:confused:
Click to expand...


I can't figure where the horizontal disk thing got started.
I understand the horizontal belt grinder, and would like one myself.
But the horizontal disk is very hard to hold the workpiece on, compared to the vertical disk, AND, if a workpiece slips, you have a blade, or ? flying across the room at waist height, versus downward into the floor with a vertical disk.:confused:
 
The horizontal disk really isnt that bad to use. I dont have one but years ago I used one at Darrel Ralphs shop and it worked real well. He had it set up as a variable speed with forward and reverse on it. It was mounted so you could use it while sitting down and it did a great job at contouring handles and doing great flat grinds. Someday I may add one to my shop.
 
I haven't done much flat grinding but I heard that a couple of makers deal with uneveness that you get from working the platen on 2" wide belts... by finishing up with 6" X 48" cheapie belt sanders. It seems like it would be very helpful especially with big bowies and swords, where there is a lot of area to get even.

Has anyone heard of using 6X48s for flat grinding- or finishing up flat grinds?
 
In addition to my 2X72, I also have a 6X48 Wilton. What a machine except don't expect a perfect flat grind from it either. The belt will bow out to some degree on it as well.

Craig
 
Originally posted by Kumdo

Has anyone heard of using 6X48s for flat grinding- or finishing up flat grinds?
Click to expand...


Knifenaker J.P. Moss uses a 6X48" almost exclusively for grinding his blades.
His bevels are as good as it gets, flat as a machinist's square edge.

He modifies them for better blade grinding performance.
 
The great Lloyd Hale also has used a 6 X 48 on his famous bowies. That's a pretty good recommendation to me, though the couple of those machines I've seen would need some adjustment at the edge of the platen to be able to control the plunge area well enough. No "elbow room" along with the fact you'd most likely be grinding both bevels from the same side of the platen, therefore edge "upstream" one direction and edge "downstream" the other. This is not impossible - I've done it and Bruce Evans has done it - but it's sure not optimum.
 
One thing that helps when using a disk grinder is to hold the workpiece on the disk then start the machine then shut down the machine before removing.
 
You must log in or register to reply here.
Back
Top