Motor Pulleys

My motor shafts are bigger than the pulley holes. Does anyone have any tips on drilling out the pulleys? I am worried that drilling out the pulleys by hand would lead to off-center pulley that would lead to uneven prints. I've also read that I should file the shafts flat. Is that correct?

what shaft diameter and what hole diameter? There are practical limits. As far as flats are concerned, a flat will hold a set screw better than a round, so there's some value in it...if the pulley uses set screws.

I never measured the diameter of the pulleys, but the shaft is 5mm. How are you guys filing down the shafts?

It is quite an easy job to put a flat on a shaft with a dremel.

Really, you mind sharing how it's done.? I have a dremel and would love to know how its done.

to prevent the shaft from turning, use a small vise grip or similar. then just file it using a small (fine) machinist file, although I suppose a dremel *could be used to accomplish it as well.

You'll want to file back onto the shaft a little farther than the location of the set screw on the gear so it has something to grip

please forgive the image. it's just something I *very quickly threw together

ah...and a 3d representation...a better idea of what needs done...(see the one with "3D" on the end

edit3: ok one last thing. For shafts of this size, I'd suggest jeweler's files. In fact, they're a good tool set to have around for small work. A cheap, Chinese packet of 10-16 variously shaped files, ~$20 or your local equivalent from HomeDepot, Lowes, or a similar bigbox. Can of course be purchased from a variety of online sources as well..

Edited 3 time(s). Last edit at 08/17/2012 12:00PM by xiando.

Good advice thanks. What about drilling the pulley and advice there?

Sure. you didn't offer the diameter of the existing hole. Is it an SAE pulley with a slightly undersized hole or significantly undersized?

If significantly undersized, idk...you may be SOL if there isn't enough material to allow the set screw to do its job and will have to order the "right" part.

If not, a #8 drill bit will cut a slightly oversized hole (5.0546mm). For a true 5mm hole, you'll need to source the appropriate bit yourself. but drilling an existing hole is pretty easy. If you have a press, use it, if not, just be steady and use cooling fluid...In fact, always use cooling fluid when drilling or cutting metal. saves the blades/bits and cuts a better hole with less likelihood of seizing. The existing hole should provide you with a degree of self-centering if you're careful.

Use a soft-clamp to hold the part. If all you have is a regular vise, wrap the body with plenty of padding and don't clamp it too tight.

When I want to cut a hole with a reasonable degree of precision and don't have access to nice tooling, I usually step my drilling from smal to the final size to reduce the amount of material I need to remove during each step.

Edited 1 time(s). Last edit at 08/17/2012 12:16PM by xiando.

If you have a lathe use that, if you have a drill press use it, otherwise just do what you can with a hand drill.
Unfortunately the hole being central does matter, in practice the drill will seek to align to the exiting hole anyway.
If it's off center you'll see ripples in the offending axis as movement will be none linear, if thats what happens you can get the right part.

Agreed re: lathe or drill press (I abbreviated on the drill press to "press")., but even with a hand drill, it should not be too hard to get a clean, centered hole if the existing hole diameter is relatively close to the target, since the bit will want to auto-center itself, as long as the OP drills slowly and carefully. Just don't use step drills (the ones that electricians use that have multiple hole sizes on a single shaft...look kinda like a top. they're awful at self centering.

If it is nearly the right size a reamer is much better than a drill. The first 15mm or so is tapered so should go in a 4.5mm hole. They centre better than a drill and make a much cleaner hole. In fact the way to make an accurate hole is to drill it undersized and then ream it. Twist drills tend to leave a spiral surface.

Edited 1 time(s). Last edit at 08/17/2012 01:07PM by nophead.

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[www.hydraraptor.blogspot.com]

I use the drum attachment with emery paper on it. I have also done it in situ this way you do not nead a square end at the end of the flat as the grub screw only neads to be on a flat part to stop the rotation.

re: reamer. Good point. However, at a guess I'd say that many or even most of us don't own or have access to a set of reamers, and a decent set isn't a small purchase. In my experience, a drill bit is fine for enlarging a 0.1875" (4.763mm) hole to 5mm, as long as a steady hand or a drill press/lathe is used, the bit is sharp, and oil or proper coolant is used. I might even be inclined to use a hand spindle and do it manually, since the gears seem to be made of aluminum

oh...lol, and IFF the set screws are removed before drilling!

Worst case, although they're a bit more expensive than I'd like, (@$~10 ea) one can always buy the gear direct from someone like
[www.ebay.com]
for $10 US, or a similar part from one's locale or distributor.

Thanks for all the sugestions. I believe it's a SAE pulley with a slightly undersized hole because I have a SAE kit, but I'll have to meause the exact hole size when I get home. I think I might use my drill press stand that takes a power hand drill. Never used it before now though. lol

I buy reamers individually on eBay. They cost a bit less than a pulley.

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[www.hydraraptor.blogspot.com]

nophead Wrote:
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> I buy reamers individually on eBay. They cost a
> bit less than a pulley.

Sure but you lose some of the value of a reamer if you don't have either a lathe or at least a drill press.

On your question of filing a flat on the shaft, Adrian has a pict and description on the process here on the Reprap Wiki. It's about half way down the page on the wiki.
Note: it's important you protect the bearing on the motor from stray filings, whether you use a dremel or a hand file. Place some bluetack or plasticine around the shaft near the motor while filing the flat.

You don't have to have the flat the whole length of the shaft. If you can judge where the lock screw is going to meet the shaft you can just file the flat there.
Regards.

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[numbersixreprap.blogspot.com]

Thanks good website, so is yours by the way. Just got home and the drill bit that fits inside of the pulley hole is 11/64-inch.

Edited 1 time(s). Last edit at 08/17/2012 06:46PM by JRMN.

FYI - I bought some belt pulleys from Misumi and you can specify a 5mm bore (min 16 teeth on mxl). For about $6 each you get a nice aluminum pulley with the correct bore:
[us.misumi-ec.com]

Thanks JazzyMT. One last question, do I have to add a flat to all the motors?

JRMN Wrote:
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> Thanks JazzyMT. One last question, do I have to
> add a flat to all the motors?

Three of the five motors need flats. One each for the X and Y pulleys, and one for the extruder small gear. The two z motors have clamps that don't require a flat.

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Thanks Cameron.