Disk Grinder question

G

Greenhead

Active Member
I am looking into getting a varible speed disk grinder to help flatten parts. I buy my steel percision ground and Im not looking at removing much stock with this grinder. I was wondering if there are any tips that I need to know or do I need to do something else.

Thanks,
Jamie
 
A disk grinder seems like it would be hard to flatten parts - I've used a disk sander for that with 120 grit disk. I use my homebrew 2X72" belt grinder - hold the blade with a magnet, and press against the platten - does a good job of flattening. My forging isn't all that good, so there are some pretty heavy hammer marks when I finish. That is how I remove the hammer marks using the platten.

When I think of a disk grinder, I tend to think of a "Wildcat" or one of those 7" to 9" disk grinders like that. I've got a nice heavy duty Makita Model GA7911 - http://www.amazon.com/Makita-GA7911...&qid=1363977151&sr=8-1&keywords=makita+ga7911

I'd never try to flatten metal, but it'll sure "Hawg" the metal off - when you pull the trigger, you'd better have a good hold of it.

Ken
 
Greenhead said:
I am looking into getting a varible speed disk grinder to help flatten parts. I buy my steel percision ground and Im not looking at removing much stock with this grinder. I was wondering if there are any tips that I need to know or do I need to do something else.

Thanks,
Jamie
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If you want mirror polished flats a disk grinder is the way to go…..I have 6 in my shop from 3" up to 9" Don't use the big one cept for rough grinding with 60 - 220 grit, I use the smaller ones for doing the flats on everything with the finer grits. We take the flats to 2000 grit with these, then when we hit them on the buffer it only takes a swipe or two……the fact of making things flat works really well with the disk grinder…..all of ours have foot pedals on them to start them up and only have up to 1800 rpm motors. The smaller ones run slower and have one with a reverse switch on it to run in either direction. We use a lot of bolsters on our designs so flat is a must…..only way to get things flatter with as good of a finish would be to lap the parts.

So, yep, would highly recommend one (or more) especially the smaller diameter disk……saves on paper and multiple disk setups allow you to go from one grit to the next without having to change the paper.

Oh yeah, almost forgot…..all of ours except for one is mounted horizontally, not vertical.

Thats how we do it…..good luck with it….hope this helps.
John I.
 
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There is a problem with disc grinders that requires a learning curve, and that is the outside of the disc takes off more material than the inside. If you are staying with precision ground material all that is necessary is a flat table made out of say granite or even thick glass. Lay your sheets of sandpaper on this and away you go. Frank
 
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Frank Niro said:
There is a problem with disc grinders that requires a learning curve, and that is the outside of the disc takes off more material than the inside. If you are staying with precision ground material all that is necessary is a flat table made out of say granite or reven thick glass. Lay your sheets of sandpaper on this and away you go. Frank
Click to expand...

Frank, you're dead on with that one. I have a 20" 2hp VS disc grinder, its a monster of a machine, and it ate 3 or 4 knives before I noticed that the outside spins much faster than the center. Its now relegated to flattening handle material and squaring edges up. I'm half tempted to sell it and get a couple more small ones.
 
messermacher said:
If you want mirror polished flats a disk grinder is the way to go…..I have 6 in my shop from 3" up to 9" Don't use the big one cept for rough grinding with 60 - 220 grit, I use the smaller ones for doing the flats on everything with the finer grits. We take the flats to 2000 grit with these, then when we hit them on the buffer it only takes a swipe or two……the fact of making things flat works really well with the disk grinder…..all of ours have foot pedals on them to start them up and only have up to 1800 rpm motors. The smaller ones run slower and have one with a reverse switch on it to run in either direction. We use a lot of bolsters on our designs so flat is a must…..only way to get things flatter with as good of a finish would be to lap the parts.

So, yep, would highly recommend one (or more) especially the smaller diameter disk……saves on paper and multiple disk setups allow you to go from one grit to the next without having to change the paper.

Oh yeah, almost forgot…..all of ours except for one is mounted horizontally, not vertical.

Thats how we do it…..good luck with it….hope this helps.
John I.
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where can i find smaller discs? trugrit and beaumont sell a very nice 9". are there other sizes available?
scott
 
The most useful and versatile disk grinder is Rod Nielsen’s Interchangeable Disk System at http://www.nielsendesigndiscgrinder.com/Welcome.html
I am the distributor in the US and you can check out the motor, VFD and disk system at my web site.
Call me if you would like some additional information or would just like to discuss the system.
 
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scott.livesey said:
where can i find smaller discs? trugrit and beaumont sell a very nice 9". are there other sizes available?
scott
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Hey Scott, I made mine…..couldn't find smaller ones so I bought some Alum round stock off Ebay and turned it myself. First one I made I took a 9" one from trugrit and turned it down on a lathe. That's too spendy, if you don't have access to a lathe or can't get one turned down let me know….I have several that I have made.

Frank, you're right about the learning curve, thus the reason for me to go with smaller disk.

I do full hollow grinds on my knives….so there is only the small ricasso flats that need to be disked out to a mirror finish…..the smaller disk work great and allow me to concentrate on that small area as the blade is hollow ground, the tangs are tapered, the ricasso is flat.

John I.
 
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Thanks for all the input and advice. It's going on my short list for sure. I'm glad you touched on the horizontal mounting. I was wondering about that. It seems that for flattening parts horizontal would be best. That way you have gravity working in your favor.

Mr Coe , I'm heading to your site now to check your grinders out. Thanks!

Jamie
 
I'm in the processing of building my own. I bought a 1 hp motor a disk from Beaumont a controller and a two way directional switch. The first motor came in damaged from shipping , I'm just waiting on the other one to come in so I can start assembling. I saved a good chunk of money . I'll send pics when done.
 
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