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Black Forest
03-16-2016, 11:51 AM
A friend needed two couplings out of steel. The couplings join an electric motor to a hydraulic motor. OUtside diameter of the coupling is 40mm. Overall length 60mm. One bore is 25mm diameter 40mm long with a 8mm keyway. The other end is a 20mm diameter bore 20mm long with a 6mm keyway.

I made one. The difficult part was cutting the 8mm keyway in the 25mm bore that butts up to the 20mm bore. So a shoulder 2.5mm to deal with. I milled a slot 10mm wide 13mm long at the shoulder for the shaper tool relief.

My problem was the stick out of the HSS cutter 7.5mm for the 8mm slot. I broke two cutters. If I had too much positive relief on the face of the cutter it would dig in if I took anything over a few thousandths of a depth of cut. With no relief I got lots of chatter. The shaft holding the cutter was 18mm diameter. The clapp box was locked down.

I thought about trying to cut the second one backwards, meaning start the cut in the slot and push out the back end. Or cut the slot backwards with the cut on the return stroke.

How would you all make this part and how would you grind your cutter? My shaper is quite heavy duty with 24" travel on the ram and it weighs 800 Kilos I think. Not sure about the weight. In the 3D model I don't have the slot modeled.

http://i853.photobucket.com/albums/ab91/burnandreturn/coupling%20v1_zpsx633dfy3.jpg (http://s853.photobucket.com/user/burnandreturn/media/coupling%20v1_zpsx633dfy3.jpg.html)

metalbender
03-16-2016, 12:01 PM
Personally I would look for Love joy brand couplers, either proper size or modify to fit.

Black Forest
03-16-2016, 12:06 PM
Personally I would look for Love joy brand couplers, either proper size or modify to fit.

There is no room for a LoveJoy type coupler.

mars-red
03-16-2016, 12:44 PM
I'd be tempted to try making the smaller diameter coupling a separate piece that is pressed (or otherwise fastened) into the larger outer coupling. That would at least allow to you to cut keyways completely through both parts, so that keyway cutting is no longer your headache. Depending on the tooling at your disposal, it seems like machining that outside profile of the inner coupling would be less of a headache.

Bob Ford
03-16-2016, 01:30 PM
B F,

Back rake 15 - 20 Deg. Front rake or clearance 1 - 3 deg. Side clearance 3 deg. Cut the 6mm slot first all the way through the coupling then widen the 8 mm slot. Depth of cut .01 to .02 mm

Bob

elf
03-16-2016, 01:33 PM
Rotate the 6mm keyway 90 degrees and then you can cut both all the way through.

mars-red
03-16-2016, 01:39 PM
I like elf's idea!

If, for some reason, you need the keyways to be aligned like your drawing shows, then I thought of a variation of my idea that doesn't involve trying to machine a difficult outer profile on the inner piece. Rather than try to use words, here's a quick sketchup I did:

https://lh3.googleusercontent.com/CvlNxCljhlX_bpfl5MMVEDaQK5bBjmR7yBTdD1iRGuJRWdLNah 6Tvy39HZ8NyZSWne9juHw_xamkEdWKnLYnYsJFp1vGM8X6Z6iA trHmakl1qo2eMur8N2psuW8Xn9lu5KTnCQu5_2RoY7zuTKzmAw Oq4oTzHDdn7zeyiMIdFvVxkWFspg7ITz1eo5zXG1mgtlU1nOh0 gQgX8pLsAiJPFoZo7qDx3kcRLD-Kb4Q4CQGlNfaoPj5VgJsrzlhgVSYMqzNlxg5JL3Ef2FFAQF-MX5D6lYF0QDgUvLaqlWgHnzMS06sosIFnwqwhpHagzB-91Z8bfPpRKuWzi2mO3iSo0GGbAJaQ7mhxxzp03F2hQqqJUlcwd iJHuLCFhQhyl532n1hl8A1tJyd7Yz7spWyX7Wm9DV6EaE0sN8e eGv7Llg5jr4V1WjUDYJnIKE-TlYK4x38IL9wLryEkMx0CLrqO5cNX3wdUzh22VQkpiKLWGJG42 4-COx6UPFgVt12h0sO-bfHsCugFS51k9GMKJNEDOBYZkw-wq5UntQy21zXKQAXSvBuSQNvL3lwXiU4UnVAGHYeu=w1425-h928-no

awemawson
03-16-2016, 01:42 PM
Rotate the 6mm keyway 90 degrees and then you can cut both all the way through.

Yes that would be my preferred method. If absolutely necessary you could then loctite a bit of key in the smaller bore and turn it down if cosmetics are important.

Paul Alciatore
03-16-2016, 02:09 PM
My first thought is your bore sizes tell me we are talking about multi-HP motors. 3HP? 5HP? That makes me wonder about the square edges between the two diameters. A tapered section, with a round fillet would be much better. At least add a fillet to that internal, square angle.

I like the idea of offsetting the keyways, that would make the overall part stronger. But I would not cut the 8mm one all the way through. That will weaken the coupling. I would go a bit into the smaller end but not all the way through. A hole drilled at the end of that keyway would provide a place for the chips to go while cutting and would not weaken it as much as a full length keyway will.

I hope your customer realizes that this non-flexible coupling will be hard on the motors' bearings unless they are aligned almost perfectly. I would use some kind of flexible coupling. And any misalignment will produce a cyclic, once per revolution, stress on that middle point of the coupling which will tend to produce stress cracks at that sharp edge between the two bores. I would not be at all surprised to see this coupling come apart at that point. This part needs to be beefy (large OD).

Carm
03-16-2016, 02:59 PM
Mr.Alciatore raises very good points.
I would make two parts, each with their respective keys, and threaded holes for setscrews.
The interface of each would have two projections @ 180 and two notches 180 apart but 90 from the projections.
Leave clearance between the tang/slot. Assemble w/ high durometer urethane caulk.

Black_Moons
03-16-2016, 03:32 PM
A friend needed two couplings out of steel. The couplings join an electric motor to a hydraulic motor. OUtside diameter of the coupling is 40mm. Overall length 60mm. One bore is 25mm diameter 40mm long with a 8mm keyway. The other end is a 20mm diameter bore 20mm long with a 6mm keyway.

I made one. The difficult part was cutting the 8mm keyway in the 25mm bore that butts up to the 20mm bore. So a shoulder 2.5mm to deal with. I milled a slot 10mm wide 13mm long at the shoulder for the shaper tool relief.

My problem was the stick out of the HSS cutter 7.5mm for the 8mm slot. I broke two cutters. If I had too much positive relief on the face of the cutter it would dig in if I took anything over a few thousandths of a depth of cut. With no relief I got lots of chatter. The shaft holding the cutter was 18mm diameter. The clapp box was locked down.

Relief or rake?

You ALWAYS need relief or you can't cut anything, the tool just rubs. Rake is the angle that commonly causes dig in.

I would consider finding rectangular HSS to provide more tool rigidity for the same width.

Also make sure its sharp, and consider that lots of carbide tooling goes through steel just fine with *negative* rake. So don't worry if positive rake is not working for you. (Although that suggests a great lack of rigidity somewhere that it digs in so badly), you still have more options.

Yes, negative rake can still be sharp.

Also, How much does it matter if there is chatter? Yea its not great for the machine or tool, but I have done a number of jobs where the machine/work just sings (Sometimes fixable by applying weights, or pressing a rag or something.. Wrapping lead around the tool is an old timer trick to dampen vibrations)

Iv heard thin wall aluminum tubing just RING so loud I needed ear protection.. or to touch the tube with my finger ever so lightly while cutting it.

Sometimes, you need a good finish, Other times its a keyway that is going to be hidden by a key from every ones eyes and could easily be filed out to +- 0.01" with a poor surface finish and not matter. (Though most people can file a keyway much more accurate then that with a little test fitting!)

Also, You could consider using a narrower tool and side steping to reduce load on machine (less likely to chatter)

Large amounts of tool cutting edge in contact with the work basically guarantees chatter.

Richard P Wilson
03-16-2016, 04:09 PM
Like Paul suggested, drill a hole at the end of of the 25mm bore, to give the tool somewhere to start. Then lock down the clapper box and cut on the draw stroke. That would work just fine on my little 24" planer, so your 24" shaper should have no trouble at all.

ikdor
03-16-2016, 06:47 PM
A bit of a hack, but could you mill a slot where the large keyway is supposed to go and then braze a bushing over it to get the original diameter back?

sarge41
03-16-2016, 09:06 PM
Black Forest: I had a similar job a few years ago. I needed to cut a key in a blind hole. I drilled two small holes where the key would clean up the holes and the holes were just about a 1/16th deeper than the key needed to be. I also tilted the angle of the holes slightly so that where the key ended, there wasn't hardly any metal . This key was cut in the shaper . I hope this makes a bit of sense. It worked well.

Sarge

boslab
03-16-2016, 09:14 PM
The drawing shows the key ways meeting, I would rotate them 180 degrees apart and run them right through.
Easier as you can then broach them or shape them as clear cuts instead of blind keys, much more difficult
Mark

Carld
03-16-2016, 09:39 PM
I too would have cut the keyways with broaches 180 deg from each other. If you just had to use a shaper to cut blind keyways just drill a hole at the end of the large keyway for cutter clearance.

becksmachine
03-16-2016, 11:08 PM
There is no room for a LoveJoy type coupler.

This space constraint may invalidate this suggestion also, but here it is anyhow.

I would have suggested a two piece assembly, each piece having a hub and flange, with hubs bored and keyed to fit the respective shafts.

The flanges would each have a matching bolt circle, the mating faces of the flanges could also have a shallow counterbore and matching shoulder to ensure concentricity.

Each flange/hub would be installed on it's corresponding shaft, the two assemblies shoved together and bolts inserted to secure the two flanges together.

Dave

macona
03-16-2016, 11:12 PM
Rigidly coupling the motor and the pump us usually not a great idea unless you can get them perfectly aligned on their mounts. It can kill bearings. A gear coupling would have probably about the same shaft to shaft spacing: http://www.lovejoy-inc.com/products/gear-couplings.aspx

For your design I would have made it from two split collars with a third split collar that clamps the two together.

boslab
03-17-2016, 01:58 AM
I must admit the last one I fitted was one of those rubber throwing star ones (don't ask, but they do hurt when they are thrown at you by idiots! ) it was on a bobcat between the hydraulic pump and engine
Mark

awemawson
03-17-2016, 03:42 AM
Two hubbed chain sprockets, face to face, with a piece of double roller chain around them, makes a good coupler that gives just a bit of mis-alignment tolerance

Has the advantage that you can work on each hub independently then slip on the double chain and its joiner after the event.

oldtiffie
03-17-2016, 07:26 AM
Two hubbed chain sprockets, face to face, with a piece of double roller chain around them, makes a good coupler that gives just a bit of mis-alignment tolerance

Has the advantage that you can work on each hub independently then slip on the double chain and its joiner after the event.

That is my default/preferred method as well for the reasons given.

I'd prefer to use the keyway cutters using a press. Make a guide bush/mandrel to suit the job/key-way cutters.

https://www.machineryhouse.com.au/Keyway-Broach-Sets.

Edwin Dirnbeck
03-17-2016, 07:57 AM
Forget about the keyways ?
You say its for a friend,so what about no keyways. Consider 3 plus 3 modified set screws . Start out with the apropriat sized High quality CUP POINT set screws,now grind the front OD to be a slight clearance to the sides of the shaft keyways.This will now look like a DOG point set screw with a CUP point,When you tighten the set screws the cup points will dig into the FLOOR of your shaft key ways. I have done this a few times on pulleys when I had bad or mismatched key ways. good luck . Edwin Dirnbeck

Carm
03-17-2016, 02:56 PM
Mr.Alciatore raises very good points.
I would make two parts, each with their respective keys, and threaded holes for setscrews.
The interface of each would have two projections @ 180 and two notches 180 apart but 90 from the projections.
Leave clearance between the tang/slot. Assemble w/ high durometer urethane caulk.

This morning I went to pick up an Amish neighbor, we were going to see a mutual friend who is in the hospital. While I was at his house his 14 year old son walked in, hands completely black. I kidded him, what, you're digging coal? No, fixing the log splitter.
On the way to the hospital I quizzed the Dad about was ist los mit der holzspalter?
It's the thing between the motor and the pump, the third one in as many years.
Oh? When we get back, show it to me. He described what sounded like a Lovejoy, I'm thinking there has to be massive misalignment, especially when I hear it's a lash up with an old vertical shaft lawn mower engine.

Nope, somehow nobody installed the spider, it was running essentially as described in my first post, #10. After heavy use (he burns and sells firewood) the tongues were chewed off.
Therefore I apologize for my poor design, it will not last, although possibly longer with electric vs. gas.

Norman Bain
03-17-2016, 04:16 PM
The coupling is to join an electric motor to a hydraulic motor; hence the direction of rotation (torque) is all in one direction.

How about:
* Turn the part and bore both the 25mm and 20mm holes.
* Broach (or shaper cut) an 8mm keyway all the way thru.
* Create (mill) a custom key for the 6mm end.


Cheers,
Norman

Black Forest
03-21-2016, 03:45 PM
I made another one today. I made it in two pieces. One side 25mm inside bore with a 8mm keyway. The other side 20mm inside bore with a 6mm keyway. Then I turned a mandrel with a shank 25mm and 20mm with a threaded end for a 20mm nut. When I turned the two parts I put a bevel on one end of each of them. These bevels formed a V and then I mounted the mandrel in my welding positioner and TIG welded them together and finally turned down the outside diameter to 40mm. Came out pretty good and looks clean. As you can see in the picture I offset the keyways from each other as per a suggestion on here.

http://i853.photobucket.com/albums/ab91/burnandreturn/tapping%20head%201%20copy_zpszb1nsvzt.jpg (http://s853.photobucket.com/user/burnandreturn/media/tapping%20head%201%20copy_zpszb1nsvzt.jpg.html)

hermetic
03-21-2016, 04:10 PM
Rigidly coupling the motor and the pump us usually not a great idea unless you can get them perfectly aligned on their mounts. It can kill bearings. A gear coupling would have probably about the same shaft to shaft spacing: http://www.lovejoy-inc.com/products/gear-couplings.aspx

For your design I would have made it from two split collars with a third split collar that clamps the two together.

+1 Without perfect (impossible)alignment, it will kill the bearings.
Phil

dave_r
03-21-2016, 04:14 PM
Now you will find out it's a 1" shaft...

Black Forest
03-21-2016, 04:39 PM
Now you will find out it's a 1" shaft...

No problem! It is then called a press fit. He asked for 25mm. That is what he got. If it doesn't fit it is his fault not mine. If he wants me to bore that .4mm it will cost him another chocolate bar. That will double the cost to him.

HWooldridge
03-21-2016, 07:52 PM
Real Swiss chocolate, I hope...