[acannell]

i just got some pull studs that were custom made for BT30, and they are slightly too large in diameter, about 0.020" over. the rest of the measurements are perfect. the part that is too big is the flat part between the two angles on the little ball at the top. (bt30)

i have access to a hardinge super precision hlv-h at work, im wondering if its okay to turn down the diameter and call it a day? or will i be removing the hardened shell and causing problems of some kind?

btw i dont use the lathe very often..im thinking to do this ill chuck a piece of 1" aluminum bar stock in a 5c collet, the center drill, drill, and tap for the pull stud threads in the end of the bar. screw in the pull stud, check to make sure its running true, then turn it down. does that seem right?


why do they harden them anyway? just to be resistant to scratches and pits, or is it because of some engineering requirement in the drawbar or to increase the tensile strength?

[underthetire]

They are case hardened so drawbar balls or collets don't gouge the retaining angle.
I personally would say send them back and get the right ones, simply because ive seen several times what happens to spindles when those break. Saying that, the part your talking about has very little to do with the retaining strength. IF i was to turn them, i would just stick the threaded end in a collet, take 2 passes, and call it a day.

[acannell]

They are case hardened so drawbar balls or collets don't gouge the retaining angle.
I personally would say send them back and get the right ones, simply because ive seen several times what happens to spindles when those break. Saying that, the part your talking about has very little to do with the retaining strength. IF i was to turn them, i would just stick the threaded end in a collet, take 2 passes, and call it a day.

returning them isnt really an option because there arent any sources for these pull studs..they've got to be custom made, and these were just slightly off for some reason..not really surprised given how funky these mills are..

so i tried chucking the 1/8" deep pilot surface of the pull stud in a 5C collet..as you would expect didnt go very well..best runout i could get is about 0.002".

then i tried making a little adapter of aluminum rod with an M12 thread (pull stud) and a pilot bore...also didnt work out...i think the key was to get the pilot bore very close fit but i accidentally made it 0.005" over..so the runout ended up being 0.002" again

so finally i tried chucking the M12 adapter i made into a zero-set 3 jaw chuck..adjusting all the screws on the check i was able to get runout down to 0.0005" or better..at a cost of about 10 minutes per pull stud to get the alignment right..turning the stud down was easy then...

i suppose i didnt really need to get the runout down that low to turn down the pull studs but it just makes me feel ill having 0.002" runout on a hlv-h hardinge and i dont do lathe work very often so whatever i do needs to be a "teachable moment" lol

i only did 2 studs and i have 8 to go...id like to figure out a way to do the same thing on my sherline at home, i think ill need to buy the 4 jaw chuck from sherline to get the runout down, the 3 jaw chuck i have has about 0.003" runout..

or what about this: mount the m12 adapter in the sherline chuck that has the high runout, but mount it so the side of it that normally gets chucked is the side im turning..then shave off a few thou..since there is so much runout, an off-center circle will result. then flip the adapter around and just rotate the off center part until the runout equals 0? aha! self-eliminating!

[underthetire]

Not sure how well a sherline is going to like turning Case hardening. Next time, try retention knob supply.
http://www.retentionknobsupply.com/

If they don't have it...well, no one will.

[Fastest1]

On a Sherline? Yeah I want to see that. Tryally would do it. Maybe with a tool post grinder. I am sure I would have no success.

[acannell]

On a Sherline? Yeah I want to see that. Tryally would do it. Maybe with a tool post grinder. I am sure I would have no success.

are you guys talking about something else? im only taking off 20 thou off of a 0.5" diameter. i certainly dont know what im doing on a lathe and i was able to turn down the pull studs in about 15 minutes...the pull stud cut like butter with no chatter. im actually really happy i was able to do this at home..using the sherline is sort of hypnotic..not like the mill at all..i could definitely see rotting away into my elder years at a bench

i made the offset pull stud holder to try and eliminate the runout. i actually dont think it helped..i tried rotating it to see if the runout would go down and i didnt have much control. runout would jump from 2 thou to 20 thou with the slightest rotation of the adapter..i think it sticks out so far and the chuck jaws are so short that angle starts coming into play and how its installed in the chuck is the dominant factor..

but i got lucky after about 5 minutes and suddenly runout dropped to 0.0005!!!

so using a old, dulled, hss bit probably ground to the wrong shape and with aluminum welded to the tip i quickly turned down the pull stud from 0.470 to 0.450 in two passes..the 2nd pass didnt even need wd40. i ran it fairly slow..probably 700 rpm or so guessing...

who needs a hardinge?

[acannell]

welp i just had a very enjoyable 30 mins on the sherline boat. i found a much better way to deal with the problem of runout. instead of repeatedly adjusting how the adapter is clamped in the chuck and checking runout, i just tighten the adapter in the chuck fairly tight but not too tight, then run a live center into it to center it and force it to run true, while simulatenously monitoring the runout with the test indicator. this method allowed me to finish 10 pull studs in about 2 minutes per stud, all while easily reducing runout to 0.0005" and the accuracy of the diameter to within 1 thou. i guess thats what live centers are for! or not! i have no idea..but im really happy and the sherline made my day so maybe ill treat it nicer

[neilw20]

Mounting arbor fine.
Put that in the 3 jaw chuck, slightly loose.
Now put the clock on it, and turn around and find the high spot.
A light tap with a hammer, and tighten jaws a bit.
You will do it quite quickly with a little practice.
This is the complicated way to do it. :devious:

[Fastest1]

I don't know why I doubted the mighty Sherline's ability. It is my go to machine quite often (mostly because it is operable) and gives me better finishes than my 12 x 36.

[acannell]

I don't know why I doubted the mighty Sherline's ability. It is my go to machine quite often (mostly because it is operable) and gives me better finishes than my 12 x 36.

it makes me wonder what its capable of with a proper setup and sharp tools lol..

[Fastest1]

Tryally always comes thru with some seemingly impossible creation via a Sherline.

OTOH, Though I am still as green as can be. The Sherline has been an incredibly forgiving machine. Bigger machines would have destroyed themselves, vises tools and the parts. The Sherline merely stalls, maybe breaks a tool.

[acannell]

Tryally always comes thru with some seemingly impossible creation via a Sherline.

OTOH, Though I am still as green as can be. The Sherline has been an incredibly forgiving machine. Bigger machines would have destroyed themselves, vises tools and the parts. The Sherline merely stalls, maybe breaks a tool.

turning a part with half thou runout on the sherline is alot more satisfying than doing it on the hardinge for some reason...the same feeling as getting a really really good deal on some rare item at a garage sale or something like that...