what to do with a free scrap dumpster find ?

i watched a couple of video's on tool changers and i have seen a few where they go into a great deal design to keep the compression force away from the bearings? i don't get the concept there? the draw bar always has force on it to keep the holder in place. the only gain is the extra force for compression to eject your tool but the stroke is so small the the force would not be much more than the clamping force. the big thing i would say is to make sure the bearings in the spindle can take the load of a spring loaded draw bar to begin with and build off that.

the bearings i went with are 45 x75 x 16 mm on the angular contact and rated at close to 24,000 N on a dynamic load each. then i have two 40 x 68 x 15mm deep groove on the drive end and those are rated around 14,000 N each. pretty big bearings i would say for the size of the machine. seems like they should handle the force ok.

yeah mine is the same way, just something i seen some talk about but made absolutely no sense to me. i am no expert on the matter but humble enough to have someone explain it to me in case i am missing something the way mine is build the eject stoke is taking any load off the bearings if it were transferred up the shaft anywhere. only place it can be is in the upward direction, bearing load ratings was just to be safe if i was wrong i'm just a chip slinger

i did not see any mention of the force your spring washer stack produces but this is a good PDF file for a lot of good info on spindle tappers and draw bar requirements for anyone who has an interest on the topic,

 

i started roughing the spindle shaft last weekend but did not want to finish any of the bearing fits until i have bearings in hand. last weekend i learned a new trick for very close size lathe turning over 30 years of machining under my belt and still learning something new

when i roughed my shaft in i was trying to keep things pretty close to making finishing easy. well i always knew shaft work was done between centers and ground to size. so i started to wonder if i could turn between centers which you can i knew this too but i don't have drive dogs and did not feel like making one so i got curious to see if i could drive the shaft with friction and my answer was yes you can i checked my runout on the shaft before any finish passes and i had about .0003 of run out. i then friction drove the shaft and took a small pass down my test area and after the run out was around .00005 so 5 to 6 times better one other good thing is if you want the entire shaft concentric and straight to one another the more you can do in one set up the better. by friction driving the shaft the entire length can be finished in one shot. so this is a big deal on a spindle shaft.

this method puts me in the mind set of surface grinding with the magnetic chuck turned off to make things really flat just for machining rather than grinding. this is pushing the limits a bit but if it does better i am all for it

something like that would work too. i doubt my little 10 x 22 lathe tailstock has enough gripping power to put any stress in the shaft since it is better material and decently robust in size. the large end is 2.75 inches in diameter and it steps down to 1.5 inches at the drive end. the wall thickness is pretty thick all over too.

on a bigger lathe this might be something to keep in mind but not so much on my little lathe from what i was looking at in the PDF i posted the shaft is the most important part of the spindle. the housing has a little more give and when it comes to the drive side sizes open up a little more. basically what i got out of the PDF was that the the run out on the diameters needs to be .0002 or better and the shoulder runout needs to be with in .0001 on the run out. then the ID and OD need to be concentric with in .0002 and this is all imperial sizes for reference.

setting the second operation to do all the internal work is the hard part. you have to spend some time setting the shaft. i usually indicate the drive end first the get the far end to match then check the outer face to make sure it matches the rest. then since you need the outer end to have support you need to set a steady rest on the far end for support. i have the lathe running and an indicator on the shaft to make sure the shaft is not getting pushed around by the steady rest when setting that part up. then a final check on the 3 indicator points to make sure nothing moved.

after everything is set i put the indicator on the shaft while it's running to see if the cutting force is moving the shaft while i do the internal work. it's a process for sure

i like doing shaft work on lathes for personal use and as long as the material is not to expensive if you mess up it's not the end of the world. but i worked for an industrial pump company in the shaft cell of the plant and when the shaft is 10" x 14 ' and costs 250k that makes it stressful to say the least but i am glad i had the time in doing that kind of work so i know what i am doing now

i spent a solid day just working on the OD of my spindle shaft. it still needs threads for the lock nuts but that's something i can't do at home so it will come later. when i redo my lathe i will be looking into the index for threading but until then i will manually cut them on another lathe.

one other thing that is helpful when turning a shaft is to get as much as the tapper out of your turns by adjusting the tailstock. yet another good reason to leave a little extra stock for finishing. one other thing to keep a close eye on is the temperature of the metal when finishing. it's good to just get your hands on the shaft to sense how warm it is. my shop is not heated all the time so letting the part normalize for a few hours is good too. typically close stuff is done in a controlled environment of 68 degrees so you have to keep this in mind while working on stuff like this.

all on the outside turned out well and i am happy with it so far. the bearings should just need a light heating on the internal race when fitting comes. you can heat the inner race a few ways but want to keep the heat to where it's needed and not over heat the bearings. a heat gun works or a hot plate with a spacer to channel the heat to the inner race only would probably be my first two choices.

light press fit on the shaft is what i am after. to much difference and you can distort the bearing races or have trouble with the bearings seating properly. fun stuff

if things are off a little you can always touch up the tapper by ID grinding it once the spindle has power to it but that's more work so hopefully i don't need to resort to that.

today i mess with the tapper these spindle tappers are a 7/24 tapper but i think i will set a holder up between centers and run a indicator up the tapper until i dial the angle in and compare that to the math and see where i am at and go from there.

spindle tappers are tough but if your pigheaded and determined you will get something good sooner or later

theory said one thing and i landed somewhere else but it was pretty close and fell at 8 degrees 12 minutes 49 seconds for my angle.