Precision ground flat stones?

[Jake M]

I did a bad thing.... I'm on the outside looking in right now, with youtube knowledge only, and as I'm sure you all know.... That is what it is. I'm thinking that a flat stone is probably what I need, but I'm hoping someone can tell me that they've done this, or that I'm way off the mark. These things aren't cheap to begin with, and my budget isn't extensive. Fair enough though, I'm pretty sure I understand why there's expensive, but they're still expensive. Plus it'd have to have an angled side version to even get in where this damage is.

So, the problem- I was downstairs, messing around at the lathe. It's a South Bend 9 inch, so nothing is hard. I was endmilling a slot in a new tool holder, powerfeeding the cross slide, and all considered, it was going well. But at some point, some way, some how, I got a chip under the cross slide, on the flat bottom area of the saddle, just inside the dovetail, and it's made small groove. Ouch....

It's a very light groove. I can't measure it, but if I use my little 90 degree "dental pick with a mini screwdriver handle", I can feel it with the pointy end (respectfully of course, I'm not trying to make it worse). If I turn it over and try to feel with the 90 degree bend area where it's not pointy, I can't feel it. What I can feel is in the leadscrew. As soon as I crank onto that scratch, I can feel it tighten. Very slight, but very much there and predictable. I can stop at the exact spot within a few thousandths if I'm looking away. So it small, but it's real. Ouch....

So, I'm kinda thinking that a flat stone (a pair of course) might be my best weapon, and this is where I'm hoping somebody could share some similar experience before I go and burn up the toy budget again. I kinda understand how and why these work, and can easily see them taking care of "points of impact" type of damages, but what about this type of thing, with a 3.5 inch long raised section? Is that too much raised area to allow it to work it's magic? Am I on the right track? Is there a better way?

 

[jwmelvin]

I made some flat stones on one of my grinders and I use them all the time. They seem very good for maintaining flat surfaces.

 

[C-Bag]

I bought my tool room stones on eBay. They were around $100, not biggest ones but have proven themselves worth every cent. I don’t get exactly what the OP is doing, but for taking down nicks and burrs they are the stuff! I had a set of Brown & Sharp tool room squares that I’d gotten of eBay and an unbelievable price. But when I got them a couple didn’t seem square. But when I stoned them they were perfect. There has been innumerable times like that where they have saved the day.

 

[Jake M]

I don’t get exactly what the OP is doing,

Sorry if that wasn't explained well enough. So for you and anyone else reading, let me say it differently.

While the cross slide power feed was running, at some point a chip became wedged under the cross slide, in the way area, between the cross slide and the carriage. The power feed dilligently "dragged" that wedged chip for the duration of the cut, and left a groove. So I do not have a "ding" like I had dropped a tool on it, but rather a three and a half inch long scratched line of damage, which has raised up a very slight but very long edge. My concern is if that type of damage has too much surface area to allow the flat stone to work well.

 

[C-Bag]

Sorry, I’ve got it. Personally, with care I believe it could be ok, not perfect, but functional. Of course it’s not like new and it sounds like you’re going to have to work on both parts. They make little angled stones made to fit into dovetails. i could work out the surfaces to take the high spots out. Trick is to stop there, don’t try to take gouge out, just the displaced metal and get it flat again. Just think of it as an oiling groove

 

[SLK001]

Your carriage is grabbing because one (or both) of the grooves is proud of the surface. Take the high spots off and all will be okay.

 

[Larry42]

I think you could get rid of the bur w/o damaging the area with most any reasonably clean flat stone. Just don't go any further than getting rid of the bur. Be sure to clean the area very well so no grit is left behind. Yes, a precision ground stone would be ideal but with care you can just remove the bur(s. ) Are there wipers that need replacing?

 

[jwmelvin]

I’ve also flattened stones on a DMT diamond plate. I’m sure not as flat precision-ground but it can definitely improve an iffy stone. I imagine sandpaper on a flat surface would also work to flatten a stone. For a dovetail, you’ll want a pretty small stone.

 

[benmychree]

Personally. I would use a slightly dull carbide scraper pulled backwards with considerable down pressure to attempt to force the displaced metal back where it came from instead of removing by abrasion.

 

[homebrewed]

Another approach might be to make what's called a "dead file". Take a sharp file and run a diamond hone across it. That knocks the cutting edges off so flat surfaces are not at risk, but it will still remove burs. They are used to remove burs from items you are surface scraping.

If you don't want to do that, carefully using a fine file to go after the raised area might work.

A third alternative would be to get yourself a flattening stone to improve a stone you have. They are used to flatten worn sharpening stones so you could use it to get yoursel a very flat stone for the purpose. Not too expensive, in the $20-30 range.