Home made Surface grinder

[Ray Rogers]

Terry,

Those discs will have to be perfectly flat, perfectly parallel, and perfectly rigid and one of them will have to rotate in the opposite direction than the other. Could be a handful trying to change the sand paper and get everything aligned again,

Aside from those issues, it might work but I'm not sure it would be worth the trouble. If I were going to build a surface grinder, I think I'd do something along the lines that JAD followed....

[JADknives]

Hey Chip
I hold the blank down with a screw below the surface.

It works but if the blank bows up on either end it kinda rounds the edge of the blank.
Really need a thin magnet or somthing.

[tmiller5087]

Thank you for your wise insight Ray. I have read many threads that you have given much appreciated advise so I know you know what your talking about and I do respect it. But I am stubbern lol. So heres the thought , Two arbors facing each other mounted on the same bed. One is fixed and one moves back and forth. The movable rides on linear slides like THK or thompson and is adjusted by a feed screw. in between pillow block bearings of each shaft is a pully and each pully is powered by the opposite shafts of a bench grinder. Wouldn't that put the disk rotating in oppisite directions but both of them rotating say towards you? I am thinking of only surface grinding metal the thickness of a knife blank . to me thats 1/4 inch or less. so movement forward to grind 1/16 or a 1/8 " wouldn't cause to much strain on the belt. can slide the one arbor back 6" in order to change the paper. Would have to remove the belt from the grinder pully. Then one would need a fixture thinner then the stock you are grinding that is absolutly parrall to the wheels also to hold the stock from flying around, now that could be the hard part. I just got a vision of a piece of metal flying back at me and lodging about 4" into my chest. See just as I said in the begiining you always give good advise and your right as usual it is doable but not very practable for a home made machine. lol

seriously though..I surfaced ground a piece of damascus today on the surface grinder at work. I flipped it quite often taking off only a few thousands at a time. every time I flipped it it was cool to the touch. But I noticed a slight warpage. Anyone know why that would happen if it never got hot?

[Ray Rogers]

I just hate having odd pieces of metal stuck in my body at random locations, don't you? Avoiding that dual disc project is probably a good idea.

QUOTE: "I flipped it quite often taking off only a few thousands at a time"

Define 'few'. Sometimes on rough, scaly damascus I can cut as much as 5 thou in a pass. But, when approaching the final finish and final dimensions you need to take no more than one thou in a pass, or even less. Taking too much in a pass will gouge the surface and induce a warp. There are other possible explanations too like stresses in the damascus bar which could show up if the bar isn't fully annealed, or just plain old bad juju, but taking too much in a pass is guaranteed to cause a problem ....

[Chris_Crawford]

JAD, That grinder is very impressive. Would you mind posting a few more photos from deferent angels. I would like to see how it all goes together, and how your down feed works. Thanks -chris

[tmiller5087]

looked at the warpage again...ain't gonna tell you where its at but it wasn't from the grinder lol......ok I will tell you I welded a piece of mild steel about 3" long onto the damascus it warped there....sad thing is I know better but the good thing is a couple three blocks of wood and a well placed hammer blow should straighten it up. its very slight.

[Suicycle]

Ray is onto it with the few thou idea. With the surface grinder at work I usually take no more than 1 thou and as I finish a pass or two at about 2/10s leaves mirror bright and smooth work. At .001 a pass I considder it hogging off material, but then again I have seen a 2X12" wheel shatter. Actually heard it and examined the pieces.........then cleaned underware out.

[tmiller5087]

I am thinking I shoulda started my own post. Sorry Jad didn't mean to hog in on yours. I saw your fine grinder and it reminded me of the dual wheel commercal grinders I saw and had a thought it be nice /faster if one could surface grind both sides at one time.

I can't remember how much I took off on each pass , my main concern was to take off 1/16" Totaly. equaly removing stock from each side as to preserve the pattern on each side. All I remember is the first cut was .006 on each side and the last few where .001 on each side. For instance I ground .006 on one side then flipped it over and cut .006 on the other. did that for each grind.

[JADknives]

No Problem, tmiller

Chris, It's all quite simple, the motor is on a hinge, with a threaded rod to crank it up and down, only has about a half inch travel but I don't think I'll be surfacing anything thicker than a quarter inch.



On the second pic you see the track is simply an angle iron frame. I don't know what ya call the thing that slides back and forth but it has small bearing that roll on the track.


Plenty of room for improvement.

[Carcar?_BR]

Very nice. I?m startting to thing to do something like that too..

[markd]

Originally Posted by Ray Rogers

Terry,

Those discs will have to be perfectly flat, perfectly parallel, and perfectly rigid and one of them will have to rotate in the opposite direction than the other. Could be a handful trying to change the sand paper and get everything aligned again,

Aside from those issues, it might work but I'm not sure it would be worth the trouble. If I were going to build a surface grinder, I think I'd do something along the lines that JAD followed....

If one were on a sturdy swing arm that swung to meet the other, I think he may be ok. Also, if they faced each other, they'd be spinning opposite, I think.

I say, give it hell, that's how we learn.

As for me, I'm WAY more comfortable letting you guys make mistakes and injure yourselves before I try anything.