mounting flexible couplings to 17mm shaft

[cowanrg]

hey everyone. i was getting tired of cranking my table by hand (i have the HF 33686 or whatever), so i decided to build some simple power feeds. well, i got some motors that are geared and seem plenty powerful (maybe a bit on the slow side, but that's ok). i did some searching and found lovejoy flexible couplings to be just the ticket to connect the motor shafts to the shafts on the table.

HOWEVER, the shaft size on my mill is 17mm. i accidently bought 5/8" couplings, which didnt work. oh, and my motor shaft size is 5/16". so, the question is, of these three options, what would you do? 1) modify the shaft on the mill, or modify the opening on the coupler so they work together, 2) buy a 11/16" coupling (i cant find a 17mm, especially one that will work with mm and inches), or 3) something else.

ultimately, i just want to know how bad it would be if i mounted a flexible coupling that measures 0.6875" to a shaft with a diameter of 0.6693". will this be a terrible thing? could i use a piece of tape or paper to "build it out"? it doesnt have to be super accurate, its just for a power feed. if i do CNC, i will do something else.

i must say that i just found a good deal on some motors and i have all the parts neccessary for power supplies, electronics, enclosures, wiring, etc. already. so, with the couplings and motors, im really only spending like $40 on this whole thing. im not expecting much. im really only expecting to not get tired from turning those handles.

eventually, when i have the funds and more knowledge (more of the latter), i will do a full CNC upgrade. so, this is just a temporary thing. any ideas? thanks.

[Torsten]

Seams like a easy choice, couplings are the cheaper component and
you have bought them for this purpose.
So why not bore them out from .625 to .669 an your done.
If you want to change back just toss the coupling and your machine
is back to the original configuration.
Good Luck

[Al_The_Man]

If I read you right, you have a 17mm (.669") shaft and the coupling is 5/8" (.625") . In a situation like this most couplers have a tolerance where you can bore them out to suit your shaft size, are these Lovejoy couplers that look like contra-rotated spings?
To fit the other end to your 5/16" motors shafts, you could turn a couple of sleeves to adapt the motor end.
Al

[cowanrg]

yeah, i have the lovejoy ones. i have two hubs, one for the 5/16th" and one for 5/8th". there is no problem with the smaller shaft size, it fits perfectly. the other size just doesn't work right.

if i were to bore it out, how would you suggest i go about doing that? if i am going to have to order a $20-$30 bit to do so, i would just rather order a new flexible coupling. i would rather not waste the money on something i will use once.

is there a cheap way to do it effectively? i have several decent hardware stores around me that have a variety of stuff. would you suggest a regular drill bit to open up the hole? or something else? like i said though, if i have to spend a lot of money to rig it, i can just get all new hubs for like $20... it wont be perfect, but it will be close.

edit:

sorry, i forgot to thank you guys for replying, i appreciate it. im new to this stuff, so im just not quite comfortable with it all, and certainly not confident boring something out that i need to be relatively precise, any ideas help.

[ViperTX]

Well since you're going from inch to metric....you will still need a reamer after you drill them out unless you have some metric drills.....probably 4 to 8 bucks for the reamer......so, your choice

[cowanrg]

ok, sounds good. could i simply just use a 17mm reamer to get me there? or would i need to do both?

[ViperTX]

Cowarng...hmmmmm.....that might be pushing it a bit.....find an inch drill to get you close...hopefully you have an Index Drill bit Set.....then use the metric reamer......

[cowanrg]

yeah? well, i have a TON of drill bits in various sizes, but i dont have anything THAT big. plus, i would need a 32nd fractional bit right? the next size up from 5/8" is 11/16" right? and that is 0.6875". i need to get to 0.6693". its only 0.182". i would need like a 21/32nd" drill bit (which would probably be impossible to find!).

i guess if i have to track down and buy a 21/32" drill bit for $20 online, then get a $20 17mm reamer from somewhere, i might as well just get a 11/16" hub, shim it with something and call it a day. i just got some more cash, so im really that much closer to going CNC. but, i need to learn, so i would like to do this first, even if i only use it for a week or so. i just dont want CNC to be my first attempt at modifying this machine, i need the practice.

all the index sets ive seen only go up to 1/2" though. i need just slightly beyond that.

[2muchstuff]

Enco has a jobber length 21/32" drill bit for $4.86 and no 17 mm reamers but they do have an adjustable 21/32"-23/32" reamer that would cover the 17mm size for less than $11.00

[Al_The_Man]

Do you know anyone with a lathe that has a small enough boring bar that would do it for cheap?.
Al

[cowanrg]

unfortunately, im the only person i know with tools. i know some people that do water-jet cutting for me, CNC stuff, etc... but they arent "friends". they charge real money.

im in the denver area. if anyone is out there, let me know

edit:

i just checked enco, and they have a 17MM jobber bit. would JUST using that work out ok? im really only boring out 0.0443" worth of material.

[cowanrg]

cool, i figured it out.

i went to my local hardware stores, and luckily one had a bit that seemed to work. it was a 43/64" bit. this was VERY close to what i needed (0.6693"). i just decided to go for it. i bored out the two hubs and it seems like it will work great. they have a LITTLE play in them before you tighten them, but its VERY little. i put a tiny piece of tape on the opposite side of the set screw and it fits very snug and the motor turns it just fine.

im going to mount the motors in the next day or so and will have a power-feed table.