RFQ - Quick Turnaround Wanted - Milling Keyway into Shaft Coupling

R-Infrastructure · Apr 12, 2017

Hello,

My company is a general contractor that has had concrete screed pulley fail on us because of what we determined is an inadequate design. Currently the shaft of the motor that turns the pulley is held onto the coupling by set screws. The shaft has a keyway already milled into it - 1/4" by 1" keyway, I will need to verify the depth but I believe it has a slight radius to the slot.

I am looking to get a matching keyway milled into our couplings (2 total) so that I can insert a key so that the set screws will not continue to shear off under the load of the screed knocking down the concrete.

I have attached some pictures. I want the keyway cut to be half the thickness of the coupling, on the same side as one of the set screws.

I will need both the couplings back and ready to install by April 24th. If nobody is able to turn around the project in this timeframe, I can arrange to do it after our next concrete pour on April 26th and just use it again with new set screws.

Hopefully this is enough information to receive a quote. I apologize for not having a design as this is just a modification of an existing product. Thanks.

edit: Just wanted to say we are based out of Chicago, Illinois, local is preferred just due to the fact that shipping times can be avoided, but not a requirement.

Toms Wheels · Apr 12, 2017

I could do this, but first I need to know if the shaft hole in the coupling goes entirely through the coupling, and same size. I am guessing to say it does not. But a small light will show. If it does not go through I can not do it. What you could do is this, Find a drill bit that will fit into the setscrew hole, without damaging the threads, slowly drill a dimple into the motor shaft, remove coupling, an drill the hole with the size drill to match the size of the setscrew, 1/4 " setscrew 1/4" drill bit, drill about 1/8" deep, buy a slightly longer setscrew and reassemble. If there are two setscrews do both, BUT! do not start the second hole until you have finished the first and screwed it tight. Then mark and drill the second. If there is only one setscrew, find someone to drill and tap you a second hole in the coupling, about 1/3 turn away. If no one can help with that send them to me, and I'll put a hole in them for you.
Tom

R-Infrastructure · Apr 12, 2017

Tom,

I talked to one of our workers who was familiar with machining. He confirmed what you said and I youtubed a video on broaching / cutting a key in a coupler. The bit must go the entire way through the coupling. This coupling does not. It bottoms out 1.5" into the coupler.

The coupling does in fact have two set screws, only 1 keyway. He referred to the keyway as a 1" half moon key.

It sounds like I would be better off commissioning an entirely new coupling piece than trying to rework this one. I may perhaps just try buying new set screws and monitoring how they are used to see if it was user error or a design flaw.

michiganbuck · Apr 12, 2017

When you have enough thread it is good to put a set screw on top of the other.. yes you would need 1/8 of body or more for a 1/4 set screw..Yes a shaft with a key way should have a key through mating parts. key way attachments to a mill can Up and Down or In and Out make a key way to a stop shoulder.. some guys can do the on a lathe...Yes with the part not turning just the bit moving. handy guy with a shaper could do it.

R-Infrastructure · Apr 12, 2017

Is it possible with my coupling to have a keyway milled with the following tool?

National Machine Tool: Milling an Internal Keyway in a Blind Bore - YouTube

Toms Wheels · Apr 12, 2017

A blind hole can have a keyway cut into it. I only have broaches which won't do
blind holes. A keysetter, or shaper, slotter can do blind holes. You could just look at flex couplings that already have keys cut and buy.

michiganbuck · Apr 12, 2017

R-Infrastructure said:
Is it possible with my coupling to have a keyway milled with the following tool?

National Machine Tool: Milling an Internal Keyway in a Blind Bore - YouTube

Yes that is not a very common device.

michiganbuck · Apr 12, 2017

Think you need post more information..Motor shaft diameter, ID keyed or not. | The driven end diameter, ID keyed or not.

What coupling part has the ID step? .. and why..what are the ID sizes?

What is the cross notch in the longer part at the end face?..and does it go all the way across? Does that notch drive something?

Reason I ask is there may be a coupling you might buy with buying both ends.

You might put a female cross notch on the end of both couplings and then make a cross key part to go between the two parts .. yes it would be like a 1/8 spacer with a face key to both sides.

You might grind a male notch key to one part end face and a female notch key to the other part end face so they nail
together (Perhaps a 1/2 hour surface grinder job needing one wheel side dressed to the notch size perhaps 1/4" or 1/8" set tall in a V block or just securely blocked in on the chuck.)

But buying an off the shelf coupling might be the best bet.

Going down to number 9 see a three key face to face key drive.. that is what l purpose with having two drive keys.. yes a decent grinder hand could make three key.
Google

Some jobs this might fit the bill *Copy paste is it does not just click on..

https://www.grainger.com/product/CLIMAX-METAL-PRODUCTS-Coupling-29NK87?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/29NK87_AS01?$smthumb$

lodge&davis · Apr 12, 2017

I may be able to help you out. Please private message me.
Thanks,
lodge & davis

cgmaster · Apr 12, 2017

Just wanted to let you know from experience. Before I knew better I "fixed" a coupling like you have there by making it stronger because I kept breaking bolts. Well the bolts may be there asoon a weak link to shear offor if you hit something. After I "fixed"it I ended up replacing the gear box. You might want to make sure that they aren't designed to shear off if it gets overloaded or hits something.

If you do decide to do this I you may be able to use a lovejoy coupling.

R-Infrastructure · Apr 13, 2017

michiganbuck said:
Think you need post more information..Motor shaft diameter, ID keyed or not. | The driven end diameter, ID keyed or not.

What coupling part has the ID step? .. and why..what are the ID sizes?

What is the cross notch in the longer part at the end face?..and does it go all the way across? Does that notch drive something?

Reason I ask is there may be a coupling you might buy with buying both ends.

You might put a female cross notch on the end of both couplings and then make a cross key part to go between the two parts .. yes it would be like a 1/8 spacer with a face key to both sides.

You might grind a male notch key to one part end face and a female notch key to the other part end face so they nail
together (Perhaps a 1/2 hour surface grinder job needing one wheel side dressed to the notch size perhaps 1/4" or 1/8" set tall in a V block or just securely blocked in on the chuck.)

But buying an off the shelf coupling might be the best bet.

Going down to number 9 see a three key face to face key drive.. that is what l purpose with having two drive keys.. yes a decent grinder hand could make three key.
Google

Some jobs this might fit the bill *Copy paste is it does not just click on..

https://www.grainger.com/product/CLIMAX-METAL-PRODUCTS-Coupling-29NK87?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/29NK87_AS01?$smthumb$

To help illustrate what this pulley does, here is a picture http://i.imgur.com/XMCZBbR.png

Basically there is a handle on the end of the pulley that allows you to engage or disengage the power of the motor, that is what the notches are for. When it is engaged the power goes into the winch, when it is disengaged it spins freely.

The reason I do not want to grind a male / female notch onto the end is grinding into the motor is not very feasible, none of the hose connections are quick disconnect so it would have to be done in the field or a lot of extra labor involved in getting the shaft or the entire motor off.

We have considered if the purpose of the key is to provide a fail point, the carabiner or the cable clamp that the end of the winch is tied down to would be a better fail point as it would require no disassembly to replace. It is direct drive so the only risk would be overloading the motor but any of the winch mounting points would be first to give well before the motor.

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