PRECISION GROUND TOOLROOM STONES

hello everyone welcome to my shop I'm Robin today we are going to do the precision ground flat stones finally going to get to this and I think these flat stones are probably one of the most essential pieces of equipment to have for precision tool making working with any kind of precision instruments or parts fixtures gauges vices anything that you're going to work with that has the possibility of having a burr on it you really should have these precision ground fat flat stones I didn't invent these I became aware of them from professional instruments I've let some professional instruments air bearing spindles for a company I used to work for where we were doing some very precise rotary spin grinding of spacers and as the spindles are absolutely phenomenal they're sub 1 micron range TIR yes 1 millionth of an inch TIR and and they just are just an unbelievable piece of equipment to work with now in the process of using those they recommend precision ground flat stones and the people there are very helpful and educational if you if you're someone who's interested in prompting them for every bit of information though they're willing to give you and they said the flat stones are somewhat of a must for assembling these things mounting them you have to be very careful about not distorting the air spindle frame or the spindle itself because we're talking about extremely small clearances that these things operate under so the flat stones back when I bought those spindles I think we're in the 250 300 dollar range and now on precision instruments website they are five hundred dollars a pair and that's a little steep and there's really no magic to them other than diamond grinding surface grinding the surface of the stone so it's perfectly flat in my opinion and as all it is in the opinion there are no other methods to do it that work you can't lap them you can it doesn't matter what you've tried lots of things doesn't mean I that's not possible but I've tried all the other things to make it work and dust doesn't work you need a good surface grinder diamond wheel and you need to diamond grind the surface of these stones so they're perfectly flat the whole principle of this is that the stones have almost no bite these stones are literally to only shear off burrs that protrude above the surface think of them as a heavy-duty gauge block stone why is the absolute flatness essential it's because the nature of abrasives grinding cutting tools whatever there is a pressure required to make a cutting particle cutting edge actually and this you get a cut below that pressure the part will just the the cutting particle tool will only skate and not engage to it any appreciable depth then you have to reach this threshold pressure to get where it will actually bite in and and start to cut so in regular stones that aren't very flat and they have been addressed by normal methods they they have surfaces of the particles that are sharp and can begin readily and because they're not perfectly flat when you apply pressure the pressure is only hitting on a very few very small spots and that allows the actual pressure at the particle to get high enough to get that cutting action going when you have a stone that has been diamond ground you have basically machined off all the particles the natural cutting particle shape of the of the particles in the abrasive stone have been are no longer there you have a flat plateau all the plateaus of all these particles all the particles are obviously in different orientations and different heights so you're going to get ones that are cleaved off in the middle the ones that are knocked off on top the principle is is the top of these particles is completely on the same plane they're all flat so that the only abrasion that can occur because there's so much surface area engaged it's impossible to get enough pressure to get anything to actually dig in so what happens is the plateaus just glide on the surface and what happens when you have a small burner that burr can poke up into the pores that are still in the stone and get sheared off it's not a big sharp particle coming over hitting it it's just the the Spiritist asperities as they're called dents raised the metal whatever you want to call it right being able to get up into the stone and penetrate up into it the paper that I will give the link to from professional instruments in Penn State shows some of the testing they had done that showing how a precision ground flat stone actually improves the surface finish of whatever you stone it with now one of the things that is critical about precision ground flat stones is you must have two why must you have two well as we all know metal particles just love to embed into stones it's impossible no matter how careful you are no matter what you do you were going to get metal particles embedded in stone you're not worried about getting them out all you do is take the two stones work them on each other you'll feel the particles that are embedded getting sheared off anything is stuck in there until you get this smooth gliding motion on the stones once you've done that then you go into the part so the procedure for using the stones is always you never doesn't matter if you if you've just done something you go to summon something else you always stop rub the stones together and to knock any particles down and embedded part ability you look at the I'll show you some pictures of these stones and the part that's full of embedded particles they don't keep the stones from working the nature of this is completely contrary to normal stoning like mold polishing or things where you want the abrasives to be aggressive you want to be able to remove some material this is a completely different tool just because it's made out of stone forget normal stoning this this is its own its own thing and once you get used to using these and see how valuable they are you had pretty sure your old creeks you can buy the stones for every one sale fifteen or sixteen bucks for this does the students that are used are the ones that are the orange India on one side and I think the not sure what the other side is when there's crystal on or whatever but the important part is the orange India side is the side that is the most I find most useful it's the finer side of the stones here's an example of something that you would not want to stone with anything but a gauge clock stone or a precision ground flat stone this is an optical flat and I'm using a monochromatic helium light source and those bands are showing that this thing is easily within 10-15 millions of straightness flatness in the in the one direction in the opposite direction there's actually maybe a ten ten millions gully on purpose in where the screws are I will demonstrate that by moving this moving the optical flat to the opposite position where I could share that the crossways I'm intentionally manipulating the angle the flat to show the flatness in the other direction so that's a good clean ten-millionth gully that you're seeing in the bottom and that's on purpose so that this thing sits firmly on the two outer edges so it doesn't affect the usefulness of this it's actually on purpose this was hand lapped with a small block lap to to correct these things so this is an example of a very finely finished gauge this is a two four six block I'll turn the lights on now so you can see it so this is a two four six excuse me Oh a one six six block that I made to match my other one two three blocks and this is square parallel and everything easily within 20 Millions so a very handy thing to have but this is a prime example of something you do not want to attack with anything but a precision ground flights down so I can take my precision ground flat stone and do my normal technique where I make sure that this is very clean and smooth and I can make sure this is clean come up on here and I can stone till I'm blue in the face I am NOT going to hurt this thing or decrease the surface finish it'll just remove any burrs that are on there and this is this is what these are designed for and other work that doesn't have to be this precise but this will not hurt the surface and it won't change the surface they won't put any delay of scratches on there they will just maintain this beautiful surface so that's a prime example of that something like ashen anything from Schmidt that has a beautiful left or ultra ground surface on it this is something that you don't want to touch with anything but something like a precision kind of flats here is a scrapers block it's just a block tool steel block hardened lapped parallel and it's used for bridging the topography and scraping such as you get a smooth surface you can indicate on to get a consistent reading so just something that has a surface finished it's better than just a plain surface grind you can see the reflection there of the meters in the background so we can demonstrate the effects of precision ground flat stones versus the regular stone so precision ground flats down here working it on itself as always before every time you touch come on here and bear down I can put all the weight I want on this as long as it's nice and even and this will not remove any any material it's only going to burnish and brighten what's here okay so wipe this off and you can see there's the sheen on there is actually improving and we can we can go on here forever it doesn't matter which direction there is no lay to our to what we're doing here because this isn't removing material it's literally just gliding over the surface and only removing of something that might be poking up from the surface so you can see what's going on there you can see the finish still reflective it's not mirror finish but it's typical of what might be on a sign plate or a precision vise now I'm going to take one of these these stones at out of the box something that people would typically use for stoning and I'm going to take a stroke on here and just listen now look there's what we don't want we are not trying to remove material here that basically has removes material and you do that every time you stone that you're going to start influencing the shape of your parts your your sign plate your vise whatever it's not what you're after that's the purpose of service grinding these then that's the beauty of the proceeding around flat stone here's a piece where I share the techniques using these using the coarse side you don't have to have match the sides it's just important to use the two stones against each other it doesn't matter if the course of course find a fine so I'm rubbing these together got a good sound I know I don't have any anything going on on the stand going over here to an unknown piece unknown condition you always want to clean it off it's best as be greased or at least not oily and so it doesn't make a pasty film when you come on here you want to feel for what's going on and right now I'm feeling oh I've got some big clunkers on here that are actually going to require some work so I'm fairly letting I'm just using the weight of the stone I take a look at them saying oh okay whew I see I've got I've got a raised mark right there I've got a I got a dent here on the on the corner and I've got an actual dent right here that that I'm working on okay so I'm identifying okay I've got stuff here that's going lost carrying on so until I feel that I've gotten down to where I've got the worst of that off I don't put any real pressure on the stand once I feel that I've removed the majority of this and I'm starting to get break and feel the whole entire staring started there then I can stop take a look see what's going on and I say okay all right big shiny here you can see where the where that varnish is over here is the other one and there's that dent now you can see how it just it just polishes off around that debt now that then might be a little high and I'm going to show you a technique here that's pretty to be aware of and that is as we talked about the reason these don't cut deeply is because there's so much surface area engage that you'd never achieve the unit pressure required to get them as the cut to initiate so when you have something like this you cheat come over here and take your corner you don't lift the stones but you put all your pressure on that corner and that allows you to get much higher pressures than you normally would in that area and I'm actually going to flip over go to my other side notice I never ever touch the work without stoning first stone on stone and I can come in here and I can bear down on that corner where I can get higher unit pressure because it actually tends to tilt a little bit I'm doing this slowly because my camera's going to shake if I don't because then I can take the gentle gentle rub on this whole thing okay now one of the things I want you to take notice of is this what stones are marvelous at showing you how crappy your grind is you thought was so wonderful you start to steal your wheel hop from imbalance you start to see your stripes from your cross feed and your wheel has a little shape to it and all of a sudden the grind you thought was so hot all of a sudden isn't so hot after all so it's an excellent thing to analyze your your grind see what's going on because this really makes it obvious what's happening so as you can see there now that that burr is gone it's burnished off we've also burnished the peaks now like I said the reason that this stone is removing some material off the tops of these is because since this surface area actually is not as great as you would think it would be because there's a lot of small peaks there's small Peaks are getting abridged away just like these did but that's the controlled nature of how these precision ground flat students work now this is smooth as glass this will going to chuck won't or am eating part or whatever and you can see that it just removes the bird beautifully another place that you might not think of using these is they work extremely well on cylinders and papers here's a cat 42 holder and has a half-decent finish on it it's uh it's pretty nice I'm going to be able to stone on this and just ride on this and you'll see that I'm not removing any material but I'm brightening up that surface and I'm removing all the little just minut nicks and things from just Dustin and things that in the air to get on these and going to holder and I'm going to show you here at the end when you get around this that these are not super high quality holders and I'm going to show you where I can see because of this and the fact that it's bridging I think you'll actually be able to see where this this stoning has revealed the actual Traverse bands of the grind it's not the greatest grind winner it's not bad but you see the spiral bands here from the from the Traverse grind that's the precision ground flat stone is only hitting the peaks of this and because they're speaks here and the unit pressure is getting high enough to remove the material it's actually brightening up that surface and making the finish or lack of good finish more obvious on these so very good on cylindrical parts and tapers you can actually run this in a lathe and gently stroke these and do a nice job you can literally stone the taper on your grinding your surface grinder Arbor the spindle itself and stone that for any burrs using the edge of the ground edges of the stones once once you get used to these you there's just no end of the places where you use these to remove my new burst it's another place where if you're very careful on the precision ground flat stone is great for knocking burrs or Nick's from calipers if you bump them or drop them and you get a pearl on the edge this is something that you can rest line up on the surface make sure you're good and parallel and just give a slight slight rub and you can feel any irregularities and it will be or all of those burgers or anything that's on the edges without removing any significant material this measuring and the caliper can often get beat up pretty severely and you can feel just when you slide on here you can actually feel the any burrs that are on there just removes the high spots places where it was dinged probably making it better than it was originally originally ground same way on the tail end this is something you can sit on there you go really to use good feel here you got to be able to sit on there and feel when you're actually Square and slide on this without moving and that takes some skill no no getting around that if you don't if you don't know you have those skills that don't do this because you can you can make things worse in a hurry but if you're used to being able to feel when the stone is flat and not influencing it and making sure you're staying seated go for it it's typically a lot easier with a lot smaller a lot to understand it's not just hardened items also these work perfectly well on softer material obviously since they're good for scraping they're good for other things this is my my gang tooling setup one of the holders for my gang - one set up that I've made and the everywhere that you put something down on the gang plate itself or the tools you take these knock all the burrs off and you can just feel things just slide and the burrs disappear and just really makes things work really well and obviously we stone the whole gang plate off before we start our setup so here are the flat stones that are about the size that a professional instrument sells if I remember correctly so these are like inch and 3/4 by 4 or the metric folk 100 by 45 and these are now these are dirty and actually what I'm showing you is in the dirty condition before I stick them in the ultrasonic here's the orange India that I'm talking about and whatever the other grit is on the other side these are well used which get like I said everything every time something goes in the grinder every single piece every part everything gets gripped it's toned so as I mentioned about the embedded particles see all the shiny spots there obviously are little pieces are embedded and that's not a problem that's why when you put the stones together before each use you put these and work them on each other you can hear the sound difference there as they started and you can just feel all the embedded particles get sheared off and smooths over so that now we've got a smooth plateau then you come take from this condition here that you can go stone and obviously if you're going to send something else you do it again because they just pick up stuff all the time just stuff pulling it from here on the backside here you can see some big shiny pieces from the coarse side the coarse side works really well on one for rough rough scraping and then for finer scraping we used the other side here's an example of some scraping that has been stoned with the orange side you can see that doesn't look like your average scraping I'm talking about the actual sheen that's purely because of the stones that's the kind of finish that you end up with this sometimes this is called in scraping once you reach the limits of what you can measure with a high spot blue you do pinpointing where basically you look for the burnished plateaus and this basically helps me you can see how reflective that is and that's that's the power of the flat stones if you used your normal knife edge stone on that it wouldn't look anything like this and you'd be destroying the geometry in the process here are the same flat stones after a trip in the ultrasonic you can see that's removed a lot of the black and dark and really clean the pores out ultrasonic cleaners do a really nice job one stones of any kind these would probably come a little bit cleaner if I used this is just a water-based solution that I use in my cleaner all the time that Li is a non rust film on metal parts but if I did these in alcohol they would come even even a little bit brighter but gloomy no what's the point it's going to get dirty again so this is more than clean enough and you can see it's really cleaned out the the pores in the in the material now this is a good chance to see some of the embedded metal you can see chips here sometimes you just come in here with a like exactly blade with any kind of piece of sharp object you can actually pop some of these out the ones that give the huge huge pieces you just hit them from the side just kind of poke down a little bit and pop them out and that's all you have to do if you get some large ones there's some here on the sides from rubbing the rail of the surface grinder but these actually don't keep the stones from functioning like I said that's the whole point of being able to rub these two together is to get rid of any any that's smoothness now listen on the other side and you'll hear some crunchy crunchy and then just that little place where I pop that out how to add its own burr and then you the smooth action and that's when you're ready to go in the park so this is a chance to look at the lip I have on line this is something that is not on the stones that professional instruments makes and I do this lip so that when you have something like a D block where the relief groove or anything with an undercut that the stone goes through and can get and hit the entire edge without that you can have a chance to leave a little tiny radius in a short corner or whatever or in an undercut corner where the stone doesn't quite make it to the edge this way it reaches underneath reaches underneath the reference rail of the gavel on your surface grinder unless you make sure that your stoning all the way to the surface where the parts going to contact on these stones I did the lip on both sides along the next big that I'm going to actually show you grinding I'm only going to do them on one side so the other side can be used for shorter tapers or things make a little more useful when you get these studs these are as received out of the box these are six by two by one stones and I have an 8 by 2 by 1 stone over here these larger ones are for just larger parts and also for scraping where the larger stone bridging the more surface area just helps in deburring the scraping and basically I think it's a flattening agent in itself you look at these you'll see I'm holding these two together see the gap there on this end and this end that's how out of flat they are and on this side you'll see same well huge so when you go to grind these when I put these on the grinder Brent to make sure we shim these so that they're not rocking when we're grinding them and we're going to need to rough these down on both sides to relieve any stresses in them so that when we do the final grind they stay nice and flat sides typically are going to be slightly better and you can see that they are better so we'll go over to the grinder and set up two duties we are holding these stones on the chuck with magnetic hold downs similar principle to hold downs used in a vise which pretty much you hardly ever see any more but they they work well this is the same principle except for magnets there's a slight bend in this there's a flex section here principle is this part gets sucked down tight to the vise this part once - but because the angle as it rolls down and it pinches the part the angles here is just like finger board on a table saw e as this things move this way it tends to self grip and the individual pieces allow this to conform somewhat to undulation Xin the surface of the part if you go to make this this is literally just homemade this is a piece of 60 thousandths or 50,000 spring steel if you make these yourself one thing to remember is that things like spring steel has a severe grain orientation to them it's very important that that grain orientation is running in this direction axial to the flexure if you're on the grain this way if you flex this very much this will crack because this is the grain is just like grain would if this was wood and you had the grain running this direction you pop it this way we just crack instantly if the grain was raining this way the individual fibers would would have to bend and it would hold up so important note for that this is only about five thousand stick right here and so that's the principle they do they do sell these and ideally especially if you have a large pole chuck these should be thicker so there's more lines of flux passed through them to the hole tighter but these actually on this this serum acts Chuck work just fine so when you put these on you load you press down but you pull push hard against each other so that you're getting a bite it off right off the bat and then you turn on and just make sure that they don't pop flat if they look flat you haven't put enough lateral pressure on them while you're holding them now these sermons as is are all kinds of shapes there they're just definitely not flat so I'm using kinematic principles here of three points I've got three pieces of 15,000th plastic shim stock stuck under this in a three point situation so this is stable and a block back here to take all the axial forces from the grinding wheel so this is this is a good solid it's not going anywhere I'm going to I have also I have pencil marks on here you don't wanna use a marker because the marker sucks down into the stone and will actually disappear so this is just pencil on here to make sure that I get cleaned up completely I'm going to rough this by doing a full wheel width and plunging until all the lines are gone whatever that depth is I will repeat that across as I go across here plunging allows you to use the full face of the wheel and not get a bunch of edge wear on the wheel and change its shape drastically such that when we go after we've roughed it then we'll take a nice slow traversed asked across here to get a nice flat surface there may be stresses in this when I relieve this side when I grind this off and flip it and grind the other side to make these dresses so we may have to do this a couple times still it lays flat I know it's been so long since I ground the other one I don't know if these tended to move or not so we're going to tear into it here and fire up the grinder and get grinded these whole browns can be contrary at times and get an example here when I turn this on my chance this just happened to stage but lots of times these will slap down and they will just won't be get enough grip on the part and I'll show you a little technique here that works really well is to take something non-magnetic so this happens to just be a couple piece of phosphor bronze and slide them under your leading edge of the parallel so that it keeps it propped up even if it doesn't have a grip push your parallels in Snug them turn your chocolate one then take your your ass and just gently tap with your finger down here on this and your feeling for this to skid okay I can feel that I'm actually moving the whole assembly down now you can pull these out and knowing they've gotta fight and now the magnetic pressure is pulling down on the edge here and getting a fight on that and pulling the part down to the chuck using a half-inch wide seven inch diameter 150 grit resin bond diamond wheel I'm plugging four wheel width down till the part cleans up and move over a wheel with and once I've gone back and forth and cleaned up there at reverse pass across there to get a smooth finish reverse pretty slow and then we're all done here you can feel the surface and it should baby bud smooth air on on that they are flipping over to the other side I've stoned the Chuck and putting the seminole on the chalk feeling for smooth went up against the hole down in the back got my stop block on left-hand sides apart putting together down on pressing firmly against it turns back on making sure that they don't pop down and got a good grip on the part and pencil lines on the outer edges so I can tell when I cleaned up okay we have the vise on we have parallels sitting here to support the edges of the stones they're on an angle to straddle the poles of the Chuck so that they'll actually hold you don't straddle the poles you won't get any magnetic one holding power and grind this side flat and then we'll flip it over I flip these over to the other side now I am about 40,000 subway from the center line of the two stones punch down 20 thousands moved over four wheel width plunge down 20 thousands again and then to come back take a few thousand depth of cut fun plunge in and then traverse across slowly to get a good finish on that surface which will be used against the reference rail here's a view of that lip the two stones obviously are against each other and that lip is about 20,000 deep and just allows you to get underneath the reference rails and edges you could break the edges on on all these preserves they're very sharp from the 90 degree it's pretty heavy devil out here we find the file around the corners round over the corners here and just so that these don't pick up and catch and also those chip is easily just as a little check it's interesting to see if these hinge at the 30 percent point if they like they should and you'll notice that these are our hinging very nicely at that 30% point and that's just because they're as slight as my grinder grinds which is pretty pretty flat so that's just another check and to see how they're how they are whether you not you have to know these can be affected by whether or not you relieve both sides first if there's a real big bow you take a lot of material off these are in a different than any other material huge material removal on one side is probably changing the balance of stresses and apart therefore you need to take another cut on the other side and spring cut if you will and go back and forth until you know the part is sitting still here's a view of before and after grinding on the coarse side and a view of before and after on the fine side just to give you a visual reference [Music]

Channel: ROBRENZ

Views: 166,119

Rating: 4.9497356 out of 5

Keywords: sharpening stones, flat stones, ultra flat stones, flattening stones, precision flat stones, precision stoning, stone flattening, toolroom stones, toolroom stoning, deburring stones, toolroom deburring, diamond grinding, diamond flattening, abrasive stones, precision deburring, magnetic holdowns, combination stones, instrument deburring, gage deburring, tool deburring, machining, toolmaking, toolmaker, machinist, gagemaking, gagemaker

Id: DVLXsq7pi9Y

Length: 35min 12sec (2112 seconds)

Published: Sun Jun 11 2017

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[u/fiskedyret]

What technique are we talking about? The video isn't timestamped.