Precision ground flat stones?

[Jake M]

OK, here's a cool update. Two actually. First, while the scratch on the carriage way is real, the chip never got under, it just "stuck" where the casting on the cross slide is not really square to the machined area, it makes a place where a chip can get caught and pushed. So the damage to the under side cross slide is (almost) zero. I (apparently) caught it before it escalated (much). Second cool thing, I took a couple of things up to my favorite job shop, (an equipment shop that has almost a machine shop in the back corner of the repair shop), and I had the opportunity to ask a fella, with the random crap you do here, you must ding up the lathe bed now and then. He didn't hesitate, showed me some battle scars, and offered me to use the gauge block stones through this weekend... No way I can use that if you're gonna use them on gauge blocks, right? No he says, don't worry. We pick up used up worn out gauge blocks and use them for shop blocks, these came with a set. Use 'em however you want, just bring 'em back when you pick up your bushings. He gave me the bit about use them a little, rub them a little, use them a little... So I'm gonna have that opportunity to find out how these work. Cute little fellas, about one quarter inch thick by four inch long, and an inch wide. I dunno if they're "proper" gauge block stones or not, but they are clearly flat and smooth on six sides, with the nicks and dings in the edges and corners that you'd expect from someone using gauge blocks that way. Nice....

Another approach might be to make what's called a "dead file". Take a sharp file and run a diamond hone across it.

You made my day with this.... I used to have what I believe was such a file. It was given to me by an auto mechanic at our old location, a hunnert years ago. Awesome guy, great mentor. He just told me it was a good file, be careful of it. He used it for cleaning cylinder decks and heads in cars, and that's why he gave it to me. You could run that thing on a MLS gasket surface and it wouldn't scratch. (20 or 30 RA if you speak that language. I don't except to recite it out of the manual, but it's pretty shiny....) I used it for the same in larger trucks. In a split instant you just convinced me that this was not just a "really good file", but bought or made, it was a specialized one. I'm not quite ready to experiment with home brew tools on my lathe, It's too good, and too original, I'm gonna start as easy and gently as I can (yes, I'm being a chicken here) and I'll escalate slowly if needed.... Time has moved on at work, different engines, different methods and all, but some of the crap things I manage to get into when I'm down in my shop.... I've got a couple of candidates that leave scratches on stuff... Or I wonder if lapping that down would put me in the range to get past the damage on an old dull file.... Hmmmmm.... Science is gonna be done, and files are gonna suffer.

 

[homebrewed]

Science is gonna be done, and files are gonna suffer.

I love it!

 

[Jake M]

So, the cleanup of the damage has gone well. The stones I borrowed are quite interesting. By that I mean I can't change any word of any description of them, yet somehow not what I expected as well. Really cool stuff there. As it turns out, my worries were justified though, a three inch long scratch is just too much bearing area. They really don't want to take that down easily. Polish the heck out of the very tip top of the ridge, but not remove it. BUT..... I have knowledge now. I like that. I will own a set one day. Not this day, but you know.... Anyhow, enter the home made "dead file" that homebrewed suggested. I'm sure this is gonna shock you as much as it shocked me, but the files you get at the stores these days are just about junk.... I was kind of not surprised to find that there's so much warp, twist, and cupping going on in those that I couldn't knock down a file. Parts of it, sure, but the "teeth" aren't as deep as the crooked. So I took a broken one, and broke it some more. Six pieces out of a 10 inch file. (Probably 12 inch? 10 inches of actual teeth). Out of those, I got a couple that I was able to get at least some "shiny" on ALL of the "teeth" around the entire perimiter. I guess if the middle ones are not touching, then they're not gonna dig in much..... It turns out I don't have a lot of precision surfaces around that I just don't care about. It was scary, it took a bit to get going, but this worked, and surprisingly well. I took one of the workable candidates of broken file, bench grindered a very slight chamfer around the four edges, so no "digging in". Assuming that those grinds left a burr, I gave it one last trip across the 400 grit paper I had on my surface plate (that I didn't pay enough for, came from a woodworking store, and is the same size as a standard sheet of sandpaper..... So I'm SURE that the 0.00015inches flatness claim is probably absolutely true...) and had at it. Carefully, slowly, and a little bit petrified at first, I went after the ridge from the end, filing ON TO the ridge, never off of it, as I'm quite sure that filing off of the ridge would (or at least "could" allow me to dig the file into the undamaged surface with the leading "tooth". But that little inch and a half chunk of hammer smashed file did exactly what I needed. It knocked the ridges down to where the stones were able to fine polish them. That brought the total "valley" low enough that while I can still see it, it is shallow enough that I can no longer "feel it" with my little 90 degree pick. (That probably makes it sound absolutely horrible. And to me it is, because I did it, to MY machine, with previously did NOT have any damage..... Ya know.... Anyhow, both methods combined have left ZERO marks beyond the actual damage, and the damage is now small enough, flat enough, I can see it. I can feel it looking at me... But if any of you were to look at it, you'd lave to look straight at it to see it. (Then you'd freaking see it every freaking time you walked by the freaking machine. I think I'm as happy as I'm gonna be. And thanks again homebrewed, I obviously don't have all the details worked out yet, but that tip with the file was a good one.

 

[homebrewed]

Like you, I broke a file and turned one of the best pieces into my dead file. Good job!