How do you make your "Flats" ??

Lerch

Lerch

Well-Known Member
Hi all,

For the past couple of years I have been doing all my flats just using the flat platen on my grinder. I think i am able to do a pretty decent job but I would like to take my knives to the next level and produce some really sharp lines and crisp edges. I have seen the desk mounted flat disc grinder by KMG and I was thinking I had seen that in some guys shop photos


What do you all use to produce a truly flat side in roughly 200-400 grit ?


Thanks
steve
 
Flattening on the platen with variable speed is better than full speed. Flattening with a disk is better than on a platen. Flattening with a surface plate can be flatter than with a disk. Personally, I go from the platen to the disk, then put it all together.
 
Disc then to a granite plate with sandpaper on it. In between if you are die hard a high grit diamond sharpener, then granite plate.
 
Thank you Mike


What disc grinder do you use ? What I am wanting is a disc grinder that is flat that I can do around 220 or 320 grit
 
I built my disk grinder, with a KMG 1 degree disk that I purchased from USA Knifemaker. I have the flat disk as well, but haven't used it.
 
Variable speed disc. Up to 320. Hand sand with precision ground hardened steel lengthwise. If you want crisp lines you'll need to hand sand with a truly flat and solid sanding block. The transition is better and crisper if your bevels are hollow ground

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The transition is crisper if your sanding bar it's not totally flat, but almost imperceptibly convex (think very very big radius).
For the disk, just ask a machine shop to make an 8 inches flat steel disk hubbed for your motor....spray 3m feathering adesive and slab a sheet of sandpaper on it, then trim the excess.
 
A "trick" that I found/use on my disc grinders is to use a backing directly on the disk, made of FelPro gasket material from NAPA. Its approx. 1/16" thick rubberized cork gasket material, available in sheets or rolls. I use 3M 90 spray adhesive to attach the gasket material directly to the steel disc, then use the feathering adhesive to attach a Sheet of sandpaper. Trim with a razor knife and go. The gasket material backing is pretty hard, but has just enough "give" to produce a better finish then a bare steel disc with paper on it. It will also give you more longevity out of the sandpaper.

I have a number of different disc faces, both flat and 1 degree, and can verify that the 1 degree disc faces will produce a very slight hollow. Its something that I didn't notice until I was hand finishing, and its not a show stopper....but it can be frustrating if you don't realize what you're dealing with.
 
I finish my flats to whatever grit on the platen, heat treat and then (usually) bead blast the blank then grind. Other wise I will clean up the heat treat on the platen with the same belt I finished with and then grind. I never touch the flats after grinding. These are some Murray Carter designs.

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I use the Norax U264 belts after the Blaze belts and the lines seem to stay pretty crisp. If I'm doing my part.
 
Lerch several years ago I bought two discs that had been made by Bill Kennedy. I had an one inch shaft turned and bought pillow blocks. I put it all together with the help of Rick Menefee.
On one side, I keep a 60 grit disc directly on the disc
On the other side, I have a 1/8. Rubber pad , that I put 120,240,400, -and 1000 grit sandpaper cut to size.
 
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I use, and am totally pleased with a Rod Neilson variable speed magnetic disc grinder I have. It allows me to have different grits without having to remove a half used one for another. This does give me a very flat surface with sharp corners. My usual running speed is about 25% of motor output. I use the thin gasket material on the discs as Ed does.
Frank
 
I'll be getting the Rod Neilson magnetic setup as soon as cash flow allows. I've been running a 1degree disc from Beaumont for about six months now and I really couldn't live without it. I fought it for a while until I learned how to get the most out of it, and the rubber backing pad was a HUGE leap forward. However, I don't use the rubber for sanding wood because the wood just gets eaten. Wood does well with the sandpaper directly on the disc. Steel does infinitely better on the rubber backer.
 
Thank you all, I appreciate the info

Mike I was talking to Bill Kennedy the other day about this and I need to go by his shop and take a look at his set up


So originally I was looking at ordering the KMG 9" vertical disk grinder with a flat face, http://www.beaumontmetalworks.com/shop/category.aspx?catid=2

But Bill Kennedy mentioned that his set up uses two sides so that he can alternate which side he is using, so he can keep the scratches switching sides so he can see when he is done with that grit.

I dont know if i would be better off with the single face on the KMG or if i should build one with two sides.


thanks
steve
 
with the 1 degree disc you can alternate your grind line direction by sanding tip-to-center on one grit, then going heel-to-center on the next grit. Of course you can do this with a flat disc, but crossing the center causes the work piece to jump if you aren't super careful. The benefit to the 1deg disc is that you only make contact with one half of the disc.
 
Do you all have any recommendations on which assembled disc grinder set up to buy ? willing to spend up to about $1000.00 if need be , I would rather buy once and be happy

I have looked at the Rod Neilson magnetic setup on his web page
 
for a grand I would get the Nielson setup, a 1.5HP motor and a KBAC vfd and never look back.

i already had a vfd running my belt grinder, so dropping 150 bucks on a motor and 80 bucks on a disc was a no brainer. I use the VFD for both motors via pigtails with Hubbel plugs.

if i had the cash at the time i would have gotten the Nielson magnetic discs.


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I use platen for the 60 grit roughing and follow with 120, then jump over to the variable speed reversible disc grinder for 220, 400, 600 ,800 grit before HT. After HT, back to 600 then 800 with disc grinder, finish off by hand up from 1000, 1200 and finally 1500. Then its Miller time! (hopefully:biggrin:)

Peter
 
I have found the variable speed is a very important feature for a disc grinder. I have yet to run mine at 100% of output at any time .
Frank
 
I have found the variable speed is a very important feature for a disc grinder.
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I TOTALLY agree. In fact I'd go one step further and say that without a disc grinder being variable speed, you'd only ever get about 25% of it's potential usefulness. I can't remember a time when any of my disc grinder were run more then 30% on the VFDs/speed controllers. I own three different models of disc grinders (all have the Neilson disc/interchangable face plates on all of them), and my favorite is the one from Beaumount Metal Works. (the 9" horizontal shaft one)...... its just the best overall that I've used/owned. Something I think that's worth noting....on all of my disc grinders, as well as my drill presses and buffers, I have foot switches installed (clipper foot switches) that just make them much nicer and safer to use.
 
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