MAKING ULTRA PRECISION TOOLROOM SPINDLES #2

welcome back to part two of making ultra precision tool room spindles here i'm going to cover some aspects about engineering relative to heat treatment and in this case we're talking about anticipating the growth that's going to occur when this part is heat treated uh all metals aren't the same but we're going to just focus on what a2 does so i'm using my hudson's metals tool steel black book to look up the heat treat response for a2 which is the material that we're making that us these out of and this chart shows hardness relative to temper temper temperature rising temperature obviously comes down gets softer and then toughness is shown here also and obviously higher temperature the toughness gets higher on this side we're looking at size change during hardening and at these are all tempering temperatures and you can see there's quite a variation of where the where the material goes to relative to its uh initial unhardened condition to the hardened condition and here we're seeing it roughly um 200 degrees fahrenheit which would be the highest hardness that this would would be done at we would probably get seven and a half ten thousandths of an inch per inch of growth but it's better to historically know from pieces like taking this piece itself measuring pieces beforehand and recording what they were and when they come back measure what they are and we know historically that a2 actually has a tendency to be more closer to a thousandth of an inch per inch or 0.1 percent growth so all of the dimensions on everything i make in this are compensated to be 0.999 the actual dimensions so that when it's heat treated it's actually at the sizes that we want so we're making it smaller because it's going to grow and that's what you have another important thing that i mention often is you don't want hardness tests in the part most heat readers will not they have to do a test on their parts they're not allowed to not test but you can send a test puck and say test on the test puck only so a piece of the same material i don't typically worry about it being the exact same material like from the exact same bar if it's a2s a2 i'm not typically worried about super precise rockwell values so i don't worry about it but you send a piece along make sure it's got smooth flat surfaces and because that can influence the the hardness reading if you don't have a good bearing on the anvils when you're testing so good tip send test bucks put in the order do not test parts test puck only and uh you're good to go method of heat treat vacuum hardening is relatively inexpensive i realize for hobbyists that's easy to say but a minimum batch for the people i use solar atmospheres is 105 dollars and you can get a lot heat treated for 105 dollars that's vacuum hardened air tempered what that means is vacuum hardening is this is done in a vacuum chamber it's taken up to temperature through the the recommended cycles for the material how long you take it up to what temperature let it soak and then carry up to the to the actual heat treat temperature and then the quench well in the vacuum furnace the quench is actually done with a high pressure gas that's recirculated through the uh the heat treat oven and has a heat exchanger on the outside to rapidly remove the heat that it's absorbing out of the parts take it out of the gas and when it goes back in again it's chilled so you're basically running cool gas past the parts to bring them down to temperature at the rate required to harden them all materials can't be done there's limits to how rapidly the crunch rate can be using gas but they can do pretty good but some materials just um their quench rate required exactly as an example water hardening tool steel you can't send that out and have it vacuum hardened because the quench rate is is uh too slow uh because water is a very very quick rapid quench but everything else vacuum heat treat works really well and is is relatively economical and the parts don't get moved from one from their from their position when they're staged or staged that their circulation around them and the gases circulate evenly so these parts are rarely have any um distortion that can amount to anything very very small distortions um on these parts doesn't mean there are things that have to be straightened and whatnot but uh as things go it's it's definitely the safest heat treat method this is an example of the type of thing i'm talking about very thin wall shell this is the collet nut and collet nose for the smaller spindle and has a very thin wall this thin shell has virtually no distortion as does this nice and round nice and uniform just because everything is extremely uniform about how they're heated and quenched so yeah just big pluses for that it's also a chance to show the actual coupling set up here that is the nut system that i'm using here because these actually stick together 2 degrees taper that i showed on how these were done these engage and there's no no tendency to slip out this actually engages and if you tap it it'll actually stick fast you can see that's held just because of the tapers matching so this is the actual wrench to tighten the collets in in both cases this fits this one as you can see that one's tight and fits this one also same same situation this is the larger spindle when you have precision parts like this to be sent out for a service like heat treat or anodizing it's very important to make packaging that allows the people doing the job to easily be able to put the parts back where you want them with basically no instructions you can't expect them to wrap pieces like you would wrap them so fitted packaging like i've shown here is just extremely important in getting your products back in pristine condition without any nicks or dents one more little side note about heat treatment heat treating a steel that is hardenable only moves its yield point and changes its hardness it does not change the modulus of elasticity of the steel so modules of elasticity just meaning if you have a beam sticking out a certain amount you put a certain weight on the end how much does it deflect that amount of deflection won't change whether it's fully hard or whether it's soft but the amount of weight that it can take before it takes a permanent set and does not spring back to its original condition does change that's the yield point so it's very important to realize that steel is not stiffer in its heat-treated condition its yield point has just moved meaning it can take an immense amount more force before you permanently deform it so here is how the blind mounting system works on my tool room spindle this is the larger tool room spindle that has this mounting method this is the eccentric pin you saw from before that we've made this is my four and three quarter inch magnetic chuck and then i come over here and this is my 10 inch magnetic chuck and this goes in the same way and these lock up these are have allowance for needing to grind some off the face of the spindle when it's when it's done so these don't actually rotate around far enough these have to be obviously in the three-quarters the uh from 90 degrees down to the bottom just like a d1 spindle on a uh on a lathe so once i grind these these will be the correct location where they'll start to lock up at 90 degrees here and then as it sweeps down through to the bottom it will be full tight here we have the parallel sitting across two pins or 180 degrees apart meaning that this is the center but i actually want to drill the hole in this pin off a little bit so that we can crack it loose when it's aligned to the center so i'm doing that by moving over one pin like that aligning the bar that we put on here so the hole goes through like this so now i just put some super glue gel on top here take my block that i've degreased hold my parallel tight press down on top here and press it over give it a little time to cure like that break this loose take this over to the mill and we'll drill the hole here's that same pin over here in the setup in the bridgeport for drilling the hole got a just a piece of scrap cold rolled here with a hole drilled in it to clear the threaded part so this is just a slip fit this is just a reference shoulder so uh i can have a fixed distance an edge found over here got my 0.240 distance out to the center here this is the piece that we glued over on that you saw um i used the one two three block here against that as i clamped this is just a another jaw in here to act as a spacer to clear my two vice grip uh clamps in the back and uh then when each one since this is a variable position i edge finder off the back and move to the center on each one and take the drill just a regular job or excuse me screw machine drill a uh solid carbide um 5 30 seconds end mill to go through and then this is a hand done uh well hand slash um single lift cutter grinder uh job where i turned a quarter inch end mill into a 60 degree piloted uh chamfer tool the reason that i use the pilot is because i can do this side in this position but then i have to do the other side freehand in a v block so the pilot will maintain position so here we just broke off the glued joint and we're going to put this back in because we need it for positioning the next piece and if we check we can say okay tightened this drill is past center here showing that it's over and that means that when it's cracked loose it will be on center so that this pin can float and get centered in the in the spindle news here's a technique that wouldn't be recommended for mass production but for specialty tool room items one technique i like to use is turning the heads of socket head cap screw to a nominal size in this case i turned the head of an m5 socket head screw down to 5 16 of an inch 0.3125 from its original 0.3 59 i believe diameter the purpose of that is so that i can do a very precise fitting counter board that only has a few thousands of clearance these are these only have like about two thousands clearance and several things that does it leaves these with the maximum material possible it does not really decrease the strength of the screw at all and it leaves a situation where this can be sealed by just using some wicking loctite number 290 after this is installed to seal that gap so that coolant doesn't get in there grit doesn't get in there and cause corrosion problems and makes it easier to blow these things off when they've um when they've been you know covered with grit and coolant and been in service so important feature sometimes even for just clearance reasons you can see here that the clearance between this and the mounting screws if i did the normal size counter board this screw couldn't exist and just by trimming these heads down i got to a situation where these could be where they needed to be and not be a problem extra clamps on the punch grinder to make it seat on the chuck a little bit more firmly other than just gravity and that also blocks the grinder in so it can't skid on the chuck and this allows the differential screw setup that we have here on the back allows very uh precise tilt adjustments um you know easily one arc second or less adjustments of tilt so that you can get it adjusted to get a very flat grind in this case i was easily easy to get within about 20 to 30 millionths flatness over that five inch diameter i have all my tool room spindle parts that many of them are ideal candidates for this rotary spin grinding which can give very good results better than the normal xy normal surface grinding and obviously the round parts require the rotary aspect so i'm going to grind up these parts this is a ryubi screwdriver that i have taken the handle off of and put a bearing system in the front to drive this punch grinder and i'm using a old power designs power supply for variable speed driving the motor which works very nicely i've fully automated this harrow grinder using micro stepper motors those hand wheels uh have encoders acting as manual pulse generators and then i have various screens uh two screen locations here where i have various things programmed for automatic cycles and just general use of the grinder so let's talk about rotary grinding a little bit and obviously that's when we have a flat spin table here a bearing system that rotates a magnetic chuck or a face plate in this orientation such that when we traverse in these directions like this we can grind a circular path and we can put round parts on but we can also put parts on like this where we have a square cross section but this minimizes the actual grind time because compared to traversing this and cutting air a lot and also having vastly varying areas of engagement rotary we have at least uniform engagement here and then out to this so the amount of actual wheel in contact with the part time goes way up when you're rotary grinding parts like this or cylindrical parts so that's the advantage of the rotary grinding can also give you inherently more parallel parts because you can grind the chuck and then this surface will be running on its own bearings it will be as good as the bearings run and it'll be true to that bearing system and if you've got reasonably good variance you can get very parallel parts just by truing your chuck and then grinding the parts on there now geometry the axis of the spindle whether it's tilts like this or this is actually going to determine whether or not you grind a concave cone convex cone or grind a perfectly flat part that's why the tilt adjust of these needs to be able to adjust in very fine increments and repeatably if you want to be able to tune your grinder into grind very flat parts on the same token you have to be very careful uh when you're getting down to very small numbers about the wheel wear the change in surface footage from here to here in the the actual part surface footage as it's spinning got very slow surface footage here higher here material removal rates higher here all kinds of dynamics are involved but if you're careful you can get very very true parts with this and also like we see in the the examples in this video of grinding round parts grinding up to a shoulder things like that why can parts off of here be generally flatter than on the surface grinder well in this the only thing that controls the trueness of the surface ground along here is the trueness of one axis the z-axis of the grinder moving in this direction back and forth so however straight that is it's the only axis that's in motion other than this rotary axis and this rotary axis typically is going to be a lot more accurate than the traverse can be on a grinder because the traverses on the grinder can have roll and yaw and twist and things that will cause the surface to not be flat as you traverse across you can end up with a part that has an actual twist in it because the grinder is grinding with a twist as long as one axis the z-axis of the grinder here is reasonably straight you're going to be able to get a part that is very flat now flat meaning parallel in a sense but if you adjust all the all the conical and this out of the part if you want to call it that and get it to be where it measures the same thickness out here and in the center then you've got parts that are extremely flat so it it basically enhances the ability of a grinder to produce very parallel cylindrical parts better than you can do in the chuck and the other aspect of grinding when you're reciprocating grinding uh if you have a grinder that's using oil film the speed of grind the speed of the traverse affects the actual oil film height i guess we're talking very small numbers sub 10th numbers of difference in oil film heights depending on your traverse speed but it's there so that affects the shape of your part also so a ball bearing style or an air bearing style of rotary spindle can give you very very flat parts one very important aspect of the precision grinding at this level and trying to get very good finishes and geometry same time is thermal growth of the column of the machine as it warms up in my case my grinder the spindle runs hot because of i have poor quality of three-phase coming out of my phase converter i have a vfd that i plan to put on but at the moment it gets pretty warm and that puts a lot of heat into the column until it settles out it probably runs about 110 degrees i have a fan cooled but it still generates heat and in the background you can hear a trickle going on and that's the lubrication system the hair grinder that's continuously pumping oil up to the top of the column and then it runs down through lubricates everything lubricates all the ways and that oil generates uh some heat as it warms up probably ruins the grinder column up about five or six degrees from ambient temperature um from that oil just the the oil shear effects and everything in the pump that causes that heat generation so when you're trying to remove very small amounts of material or you want your grind height that you've just dialed in to actually remain consistent if the grinder is not totally warmed up where everything's thermally stable the column is growing it's it's getting longer from the base up to the where it's supporting the grinding wheel and um in this particular situation here where we're grinding on the on the setup here there's roughly about 17 inches between the base and the spindle uh of the grinder and the let's just pick a round number of that's six six micro inches per inch per degree fahrenheit growth of of steel or iron it's roughly close to that um for one degree rise that is 17 inches that's in one ten thousandth of an inch of rise of the comb and um so any thermal changes that are that are occurring while the grinder is warming up the column's constantly growing up away from the part so when you have a grinder that's capable of down feeding very small increments 50 millions 10 million it's 5 million down feed increments you can be fooled because you take those amounts but it doesn't take any material off because the column is growing away at a larger amount than that so that's one of those this grinder takes probably a good uh half the day to warm up and stabilize and if i'm doing work where it's very precise i will not shut the grinder off overnight i'll leave everything run leave it just continuously run with the oil running everything on so that it's completely stabilized then things stay put some may say you're talking about 10 millionths 5 millions whatever 20 million it's down feed increments and hogwash that's just an ordinary old hulk you know harrow grinder with uh scraped ways and you know you got stepper motors on it um you know you know you can't get those kind of down feed increments and um they're uh if you do everything properly you can and number one the scraping and the finishing of the scraping on the column ways of this are extremely precise and they're lapped and that to give an extremely precise oil film that's consistent and there's weights on the spindle system to minimize the moment loads on the way system so that's just traveling vertical but the real key is to not expect the machine to move just a single five millionths inch move or ten millionths inch move and that's because of stick slip of static friction and that breakaway so with a programmable machine by moving up let's say 50 000 and then moving down 50 000 and 10 millionths you basically have changed the lubrication and the motion regime into the dynamic uh friction realm and um you can easily do these motions so my down feed button that i hit which is i can program anything i want in five millionth increments up to like five thousandths of an inch per per increment i just haven't limited that for safety purposes um it does exactly what you say you know is it exactly 5 millionths or 10 minutes no it might be 9 1 time 11 the next but it's close enough for what we're doing here but there's an example of just using a very simple principle of getting it out of the static mode and running uphill downhill you get your oil film um you know moving and you're in the dynamic friction mode and it repeats extremely well and the mechanical resolution of the system with the microstepper motors is five millionths on the vertical here i will do an incremental feed and you'll see it moves up about fifty thousandths and then down fifty thousands in this case fifty thousand and fifty millions because i'm doing it fifty million stand feet so wow that's what it does do it again you can put in a negative value to go up if you'd like uh so it's easy to go back up an exact amount uh but it works extremely well so when you hear me talking about taking 20 million sir 30 millions or whatever i'm not blowing smoke here it really does respond that way and it's also a way to be able to see exactly what's going on and i always put the purple sharpie on between cuts so that i can actually tell whether or not i'm whether the column's still growing away because obviously you can't always wait for the machine to stabilize so i actually run with it with it the warmer so there's often times while it's warming up that i'm uh in order to get it to take a 10 minutes cut i'll have to you know do 20 or 30 millionths down feed to get it just to actually cut the sharpie marks off there and to know that you're actually taking a finish pass and with normal grinding slowing the actual traverse rate of the path across the part in this case working radially out off the part when you slow that way down you can get greatly improved finishes but it also increases that thermal time for it to grow up as it's doing that changing the shape of the part now these parts are going to get lapped where it's important anyhow so it's not critical that they're uh you know perfectly flat as ground but the closer they are the easier it's going to be to uh lapping it and it's always fun to just practice on getting good geometry as ground another important aspect to keep in mind when you're talking about very high precision grinding is uh as you've heard me say many times everything is rubber and the entire mechanical loop of this grinder meaning from the grinding wheel back to the spindle down to the column over to the saddle up through the saddle to the table up through the actual rotary spin table and in its bearings all of that is the mechanical loop and that has a certain spring rate meaning if you push up on the wheel with a with a certain amount of force you're going to get a certain amount of deflection and also increasing the load on the table is going to have the table you know deflect some so there's there's always deflections involved and i'm bringing that up because of of talking about a situation here where we are in any grinding and this rotary just points out a situation where it's easy to get a good example to explain a phenomenon when the grinding wheel is engaged here it's got a continuous bearing meaning it's it's engaged with the part and it's actually pushing on the part trying to cut continuously and um but and when it moves down here where it's off the part but it engages this intermittently you know four times per evolution in this case it climbs up onto the part you have a situation where here it's loaded continuously but here the as it comes off the part this can actually um unload and drop because it's not sprung but then when it comes here to to grind up there's and there's mass to this whole system and as it comes across here and the part tries to push the wheel up because of the resistance to grinding it can't move that grinder spindle up as quickly as it is it needs to it's going to actually be grinding lower here where it had to jump up than this here was continuously loaded and just held up so what you'll find is it where you have the grinder com this this tweaked in to be grinding perfectly flat you'll find that when you're doing your roughing passes and everything this will be high here and low here and with your roughing and really you know barking material off as i did in some of these you'll find that it can take maybe this might be five ten thousandths of an inch lower than here just from this phenomenon of what i'm talking about here where this is unloaded loaded and this impulse cut where this has the wheel basically has to jump up on here because of the loading um causes the grind um deeper now there's things that a lot of things involved in how much cutting pressure there is the wider the wheel engaged wheel with the more pressure so if you're out to get the most accurate results from the grinder then sometimes narrowing your wheel width for that condition especially on hard to grind materials can give you more accurate results but then you have the situation where that narrow wheel width is also going to wear faster so now you have to consider wheel wear in the traverse of the parts depending on how much surface area you're grinding so it's always catch 22 and what works there the other thing is the how you dress the wheel and how much the wheel has been used or how how how much the wheel has worn and how dull it is um a lot of people use coarse wheels and dress them fine and that automatically creates a situation where the the pressure that it takes to initiate a cut on the wheel is higher than if the wheel was really dressed what it's designed for meaning dress it to cut with the grit size that it is don't try to dress it fine and get a shiny finish shiny finish the shinier it gets typically means the more that wheel's burnishing instead of cutting freely so there's a trade-off there um it pays to use much finer grit wheels that are dressed properly meaning open like use a you know 150 grit wheel or 220 grit wheel sometimes to get the finish you're after without dressing the wheel in a glazed condition that sharp wheel is very important for this high precision stuff that it can cut freely and the amount of pressure needed to initiate a cut is very low so that's a trade-off to keep in mind and and also to think of the dynamics that that the wheel this wheelhead's not infinitely rigid it responds to the cuts that it's going on it has to climb up onto the part and down again so um that's where the the uh keep those considerations in mind is important also if this was just a cylindrical spacer you have the situation where and people are probably familiar with this that have ground much is when when you come off the part the engaged with the wheel is changing as you get off the part so if we're moving over here and we're and we're on this side the edge of the wheel starts on the full wheel width is engaged and off you can have a tendency to have a curved situation on here where that the the grinder grinds higher when the full wheel width is engaged and then as the edge of the wheel tails off and the engaged width keeps decreasing it's able to grind deeper and deeper because there's less and less wheel to support and the wheel actually flexes down into the part deeper on each side of the cut on each side of the part so um just something that lots of grinder people that you know have been doing it for years know all about this but that might be some something for people who are new to surface grinding to really think about the dynamics of what's going on in the grind because that just lets you do a better job of analyzing what's going on so that's why grinding is somewhat of a art rather than exact science because there's just so many variables involved in what you end up with and having a clear picture of how they all interact and which ones may or may not be the major contributors in your in your setup uh can be very helpful we're going to check the four sides and the where it's the thinnest here there's zero 90 degrees plus 30 millionths plus 10 millionths minus 10 millionths see what our repeat is like pretty good zero now i'm running over the four corners looking for the amount of change from inside the outside very little there probably ten millions maybe 20 on this one nice 10 millionths there and that's low in general that's a low probably uh 20 25 millions from the other zeros but still well well flat enough for what we're doing this is a perfect example of the use of the magic sanding plate to make sure that the surface you're sitting on is basically flat enough that it will not warp when uh it touches down on the grinder and the chuck pulls it down tightly so this is flat enough that you can put this on as is not have to worry about it being out of shape and uh being warped enough that when you release it from the chuck it springs up and give you a different size so it saves an immense amount of time lets you see what's going on i'll indicate this in by looking for our high point tapping it in to basically halfway mark between the sweep and the variable speed control lets me just drive this i'm turning the knob down here on the power supply that's plenty good enough for grinding then i'm going to stop where the place is to turn the chuck on and we'll touch off and grind i have places to electronically set the z plus to z minus locations of where my automatic grind is going to traverse across and the x plus location is when it lines up with the center line of the spin fish what the wheel does x minus is where it retracts to so i'm above the part and i can crank to my v-plus setting that's where it's going to run off the part on one side and run across to the z minus location where i'm just off the part on the inside set my g minus and that's going to set where everything is and i can jog back here's what that grind cycle runs like it's in the correct c minus position runs up to the center of the chuck and x reverses across at whatever feed rate i have set so it gets to the z plus position and retract [Music] here's the first grind pass just taking off enough to make sure where we are it's just traversing across at a fixed feed rate that's set on the control panel wraps off now down feed again and this is at 8x speed and we're taking two more cuts to clean up release part use a lever plastic lever to break it loose from the chuck that's pretty nice grind it's a 60 grit wheel here you see the bubbles from the air purge system that i have in the punch grinder to keep the coolant out of the bearings and the regulator and hose that uh supply its power this is the coolant system got a 5 micron felt filter bag in there and some other filters in those household cartridges that do a pretty nice job this parts washer brush that i can clip on instead of the coolant nozzle is really great for washing down the grinder to clean everything out so this is the untouched face of the part back from heat treat i'm going on the magic sanding plate to see what it looks like changing positions and we'll come up and see what's going on you can see heavy here heavy here might not be easy for you to see the camera but uh light light out here but this is bearing enough that it's going to touch on the chuck evenly and not cause any distortion and this cross section here is thick enough that it's not going to do much anyhow here's our five inch two room spindle body but the problem here is is this hole completely misses the magnetic lines of flux in this chuck so what are we going gonna do we have this fixture plate that i use grabbing a one-inch collet here and bolting things on the lathe so this is nice and flat been on the on this magic sanding plate has a 3 8 16 tap hole and this fits inside that housing without hitting anything so i'm going to put this on the magnetic chuck and then use a cover plate inside to just physically mechanically hold the part touching this outside band so basically clamping it to the base of the magnetic chuck even though the magnetic flux is not running through the part itself it's simply holding this on i've tapped this in to run with a thousandth or so which is severe overkill doesn't need to be that good here you can see i have that indicated in with a few thousands which is plenty and i will grind that upper face so [Music] these are lighter finish passes that i'm doing in this view this is at 2x speed that's not too shabby a finish there just flipped it over indicated it in smoke the screw and we're ready to grind the other side slide two finished for the final passes i've slowed my rotary speed way down and what that does is it lets the whatever amount of in out of balance there is still left in the wheel even after balancing it allows the scallop from that the basically the high point touching which still shows up uh unless you're absolutely perfectly balanced which is balanced very well but not to the point where you don't have some hop slowing the traverse makes those scallops occur much closer together and then my traverse rate across the part is also very very slow this is a half an inch a minute and uh i can still hear it grinding so uh this was a 30 millionth uh cut but you don't know whether it's actually 30 millionths or not because the system still sprung some so i'll take two spring passes in this location for it to be able to truly relax and remove uh you know down to the minimum amount of material and that will give a really good finish you still have to remember that if the wheel is a little dull or whatever you could get some shape from the intermittent cut and change in shape but uh i think where we are here we'll be pretty good generally when doing parts like this with a larger face and a smaller face it pays to reference off the large face and grind the smaller this will generally give you less material removal required to get parallelism there's the larger face ground parallel to the smaller face we did earlier and here we're doing a painfully slow finish pass 0.3 inch per minute and 10 millionths downfeed on that pass finish this side now we'll flip over and hit this face and get it cleaned up oh nice finish on that 10 millions per division on the upper scale the black scale zero to one is one ten thousandth of an inch moving in towards the center top of the counter bore back out again yes the indicator really is moving you can see here um i'm going to check four spots around here just for parallelism we're zeroed on this spot 90 degrees 50 millionths 25 millions 30 millions back to our zero here i'm relieving the side of the wheel because i'm going to be getting down close to the shoulder full length shoulder and i need to clear this out so it doesn't run into the part here i'm touching off my z position on the control for where it's going to stop and start actually start its grind position here it's down feeding and traversing off the part that's the automatic cycle and now we'll see a overall view of it up and down it just did there for the actual down feed increment moves into the z position comes in feeds down dwells and then slowly traverses across the part at whatever feed rate you have until it reaches the z plus stop position that was set and retracts here you can see the purple sharpie has been removed by the wheel touching down and it's barely touching it's maybe 10 15 million says taking off there but it's enough to remove the the sharpie and you can see each revolution as the wheels moving out it's cleaning off that uh that sharpie that's how i can tell if i'm actually down feeding and touching the part while the grinder is still warming up and the column's moving there's the bearing race surface that was ground and the seal surface that was ground and the upper bolding surface that was ground here we're measuring the back clamp face that we did first actually here's zero there 10 millionths but in millions 5 10 millions back to our zero you'll notice down here that we've got some taper or it's conical it's high in the center low on the outside and uh that is from the fact that i'm taking a full half inch wheel diving in here and and moving out and that's not an ideal situation where these other surfaces we could get completely off on the inside use the full wheel width so none of the shape of the wheel got into the grind but that doesn't matter because it is going to be lapped anyhow so what i'm doing here is i'm i've got a mark there so i know when i'm kind of full revolution and we can just watch up top and say okay what's our tir look like as far as facial tir and that's probably well within a micron 40 millionths there so that's not too bad plenty good enough for where we are in this stages of building this indicating in the smaller spindle and there's a smaller spindle ground in as always finding some feature of the part to be able to lever the part off the chuck grinding the seal surface on the rear plate that's it for this video what's next we'll be grinding the outsides of these the the outer four faces of the housings hard turning the boring faces here where the bearings ride hard turning these surfaces the the cylindrical diameters here where the bearings ride and uh that'll probably be it for the next video hope you found this interesting and i'll be back

Channel: ROBRENZ

Views: 77,844

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Id: X2h-YgvSNx8

Length: 46min 14sec (2774 seconds)

Published: Thu Sep 02 2021

Reddit Comments

[u/kosmonaut_hurlant_]

Love this channel. Miss when him and Oxtool were cranking out vids on the regular.

[u/Vintage53]

This truly is next level.