Any lathe owner/operators?

[kellys_eye]

I have a couple of stepper motors with 6.35mm shafts (1/4") that I require turning down to 5mm diameter and shortening in length. Is there anyone who has a lathe and the required experience to help? Or pointers to someone who can perhaps?

TIA

[big-all]

how critical is the 5mm ??
if it doesnt have to be 100% 5mm and perfectly cylindrical
i would use files/ emery /diamond sharpeners whatever would wear it down whilst it rotates
just use something [cardboard disk with a 6mm hole?]to stop the dust filings getting into the motor or other unwanted area

[kellys_eye]

It has to be accurate and I mean accurate - it's the drive shaft of the stepper motor that controls my telescope tracking....... I have a new drive pinion that has a 5mm bore and as it's hardened steel I can't drill it out (which also might not leave enough material to allow the grub screw to catch) although suggestions for how drilling out might be done instead of shaft-shortening would be useful....

Just for fun....... Final drive accuracy required is of the order of less than 0.1 arcseconds per step of the motor (200 steps/revolution). I can micro-step the motor to 1/128th (i.e. 1/128th of a single step) making 25,600 steps/rev - combined with a 540:1 reduction drive (worm/wheel) this gives me 0.09375 of an arcsecond (theoretically) accuracy....(I wish ).

Non-centric shafts/bores introduce a periodic error (repeatable error every revolution) but whilst any errors can be electronically compensated for the inaccuracies 'multiply' due to the gear ratios involved and the tracking accuracy desired. The idea is to have the errors as small as possible to begin with. Practically impossible to achieve even using a good lathe but impossible to achieve by hand (!) hence the need for a lathe.

I've had this done before on a smaller set of stepper motors - it involves dismantling the motors to get them in the lathe but that's by-the-by - but the earlier version doesn't have enough oomph to move the telescope assembly fast enough between targets so I'm upgrading the motors to bigger ones. The last time I had the machining done was years ago by someone who (then) lived local to me but who is now I-don't-know-where

Sorry for the technical lesson and thanks for the suggestion anyway

[wrinx]

That's my Myford out of the running then....it's too old and worn to be that accurate

wrinx

[nick200]

Sadly I do not use lathes anymore and not sure if my fathers (or father) is up to it. Can you not get a new drive shaft?

[Hitch]

Bit delicate for anything at work , not much help

[village idiot]

is it possible to get a reducing boss arrangement 6mmF x 5mmM & move the motor slightly further back???



(yes I know, new contender for the dopey question of the month award )

[kellys_eye]

is it possible to get a reducing boss arrangement 6mmF x 5mmM & move the motor slightly further back???
(yes I know, new contender for the dopey question of the month award )

Far from it - it was an idea I had considered anyway but the only bush/adapter I can find is rather 'wide' (20mm diameter or thereabouts) but it's still on the cards if I can't get the shaft machined.

It takes the stepper motor shaft in one end and a short length of 5mm SS rod at the other - overall length of this arrangment is MORE than the original motor shaft meaning the motor will have to have a fairly substantial stand-off and makes the setup less rigid than I'd like but it may be what I have to go with.

[Richard Lionheart]

I have a 7x14 minilathe, but it struggles on hard steel.

[Agile]

I know little about it but was thinking that hardened steel may well need grinding rather then turning.

Don't think my CL300 with digital readouts would be accurate enough and Oban is a long way away.

[big-all]

I know little about it but was thinking that hardened steel may well need grinding rather then turning.

Don't think my CL300 with digital readouts would be accurate enough and Oban is a long way
away.

but iff you change your initials to LMS your there