Quick question regarding Lovejoy couplers

[HereinCS]

I bought some of these

lovejoy couplers

lovejoy couplers

and just received them. They seem to work differently than the couplers that I'm replacing. My current couplers have a bore size that is tightened by a screw which never touches the motor shaft. The lovejoy's screw seems to drive into the shaft. Will this damage my motor shaft?

[Eurisko]

Most motor shafts have a flat spot ground on one side of the shaft for a set screw. If your motor's shaft doesn't have one, then tightening the screw into the shaft can raise a burr and make it difficult to remove the coupling later.

It won't actually hurt the shaft. You can use a small file and file a flat on the shaft. This will make it easier to remove the coupling later.

[louieatienza]

I have similar Lovejoy couplers in my machine. I have also filed a small flat on my leadscrew for the set screw to seat on. Makes it a lot easier to remove. I do like the clamp-style attachment better but they are pretty expensive.

[HereinCS]

Thanks for the answer guys. I'm worried a bit since my servo motors have over 1000oz of torque. Seems iffy that one screw will hold that. I wouldn't mind spending a bit more on the clamp style couplers, but I can't find them in the exact size and I don't think I have the capability of milling out a coupler to proper size. Which sucks. I wish end mills and motor shafts are more standardized.

[louieatienza]

Lovejoy makes some really huge couplers! I would think if you had a flat (or a round flat bottom hole larger than the set screw) on your shaft, you should have no problems with the setscrew

[Phife]

you shoulda gone for the clamp style helical couplers, ive seen some lovejoys that have alot of play in them, I hope yours are tight..

[louieatienza]

Originally Posted by Phife you shoulda gone for the clamp style helical couplers, ive seen some lovejoys that have alot of play in them, I hope yours are tight..

Yes... I have this exact problem, and I feel the source of the "play" is the soft elastomer material used for the spider. Not sure if they used harder compounds, or have different spiders, never looked into it.

[krak]

Mcmaster carries the good couplers starting at about 20 per unit.

[HereinCS]

I thought I found helical couplers at mcmasters, but my motor has a metric end shaft, my ballscrew has 5/8 inch end mill. Looks like the only choice are those spider types. They are supposed to be zero backlash. I'll get the spider type with the clamp instead of the set screw.

[Al_The_Man]

If you want a good selection of couplers, especially metric and non backlash types such as Oldham type, check out Misumi.
I found the spider type with the Blue material offer very low to non backlash, they also offer set screw OR clamping, I would suggest that any machine builder get one of their catalogues, even only as a reference.
They have application examples included.
If you use helical on motors, they should be stainless IMO, otherwise the aluminum do not last, their OK for encoders.
Al.

[HereinCS]

Originally Posted by Al_The_Man If you want a good selection of couplers, especially metric and non backlash types such as Oldham type, check out Misumi. I found the spider type with the Blue material offer very low to non backlash, they also offer set screw OR clamping, I would suggest that any machine builder get one of their catalogues, even only as a reference. They have application examples included. If you use helical on motors, they should be stainless IMO, otherwise the aluminum do not last, their OK for encoders. Al.

That's a great idea. I did find one with the red spider that can easily handle the torque. Pretty expensive though.

[spoiledbrat]

I agree with Al the man regarding the stainless vs aluminum helical couplers. Although the Aluminum ones are cheaper, I burned through 6 of those on my first router before I tried the stainless. A lot of this has to do with how precise your alignment is to begin with. Mine was, and still is terrible. I think the aluminum fatigues/work hardens from the flexing, and breaks. No problems on the stainless helical beam couplers for the last few years.

Rob