Securing gears on shafts

[Cory]

Originally Posted by vivek16

How do you machine the groove needed for a circlip(snap ring, e-clip, etc)? Do you need a special lathe bit or will a triangular insert dealie suffice?

thanks, Vivek

You can grind a toolbit, or buy a thinbit style toolholder, and then a 0.030 grooving insert.

They're not cheap. I had to go buy some from our local distributor during build this year, since we needed them ASAP and couldn't wait to purchase them online. Each insert was about $12.

The holder is probably $40-80 as well.

[vivek16]

Originally Posted by Cory

You can grind a toolbit, or buy a thinbit style toolholder, and then a 0.030 grooving insert.

They're not cheap. I had to go buy some from our local distributor during build this year, since we needed them ASAP and couldn't wait to purchase them online. Each insert was about $12.

The holder is probably $40-80 as well.

Ok, thanks. Good news is that our sponsors let us use their machine shop to build in so they just might have the holder or insert.

thanks, Vivek

[dlavery]

You don't need to resort to expensive insert systems for a basic operation like this. Grinding a cutting tool to cut a retaining ring groove is a fundamental lathe skill that you will want to practice. Based on the size of the retaining ring you are using, determine the groove width and depth. These standard dimensions can be found in Machinery's Handbook (if you don't have a copy, get one; it is possibly the most useful reference manual you will get in a long time). For certain size shafts, you can also look up the dimensions here.

Once you know the groove width, use a bench grinder to grind a piece of HSS tooling to the width of the groove. You basically want to grind the HSS to the shape of a parting (cut-off) tool, but shorter (there is a nice tutorial showing how to grind a parting tool here). The length of the cutting portion of the tool does not need to be significantly longer than the maximum depth of the groove. Grind in a 7-10 degree rake to the top of the tool, and appropriate relief angles to the sides and face (so only the tip of the tool actually cuts and contacts the sides of the groove). Mount the tool bit in a holder, and you are good to go.

Unlike carbide inserts, HSS tool blanks go for about a dollar each if you are a careful shopper.

-dave


.

[=Martin=Taylor=]

I'd like to try these some time. They can securely lock a gear/sprocket/whatever to a shaft. preventing both slippage and side to side movement.

The best part? No machining or accuracy required the trantorques will expand to fill over-sized holes.

[AdamHeard]

He has already told us that a clearance issue exists (like in the AM toughboxes). The larger gear of gear cluster A (arbitrary name) is too close to the shaft of the large gear of gear cluster B for any spacer or collar to be added (The small gear of cluster B is on the same shaft as A). Please correct me if I am wrong, but this is what I am imagining.

A roll pin like in the AM gearbox is the least labor intensive solution I can imagine that doesn't have the possibility to move. I have used the press on retaining clips like Travis suggested, but they have the possibility of drifting (You could still use them, just be prepared to verify the alignment often). Snap rings would also work very well, have a lower profile than roll pins, and look better. They do require machining that is a tad more difficult, but still is a pretty simple machining operation.

[vivek16]

Originally Posted by AdamHeard

He has already told us that a clearance issue exists (like in the AM toughboxes). The larger gear of gear cluster A (arbitrary name) is too close to the shaft of the large gear of gear cluster B for any spacer or collar to be added (The small gear of cluster B is on the same shaft as A). Please correct me if I am wrong, but this is what I am imagining.

A roll pin like in the AM gearbox is the least labor intensive solution I can imagine that doesn't have the possibility to move. I have used the press on retaining clips like Travis suggested, but they have the possibility of drifting (You could still use them, just be prepared to verify the alignment often). Snap rings would also work very well, have a lower profile than roll pins, and look better. They do require machining that is a tad more difficult, but still is a pretty simple machining operation.

Yep, that's exactly right. I'm using AM gears and that is exactly the clearance problem I'm having. Thanks for clarifying.

It seems like roll pins would be the best way for me since they are cheap and we have a local grainger warehouse that supplies them.

thanks, Vivek

P.S. I had no clue how e-clips worked before this thread. Thanks for the information.

[Brandon Holley]

Originally Posted by vivek16

How do you machine the groove needed for a circlip(snap ring, e-clip, etc)? Do you need a special lathe bit or will a triangular insert dealie suffice?

thanks, Vivek

If you are not looking for something super precision, you can kind of fudge a ring groove, I have done it before.

E-clips are nice for assembling after the fact (meaning while you are assembling everything at once), I was taught that if you can use a snap ring, use it, they tend to be stronger in the side to side load your talking about.

[vivek16]

Hmm. Since I am using hex shaft, wouldn't fudging a hole be more effective than on round shaft?

My side to side load should be very minimal. I will look at getting Eclips as well as roll pins.

Roll pins wouldn't require a lathe but e clips might be better.

thanks, Vivek

[Dick Linn]

Five piece set of HSS blanks for $2.99, including a cutoff bit:

http://www.harborfreight.com/cpi/cta...emnumber=40641

If you have to fudge a retaining clip groove (like using a hacksaw blade ground to proper width), I'd try to use a full external retaining ring and not an e-clip.

[Andy Brockway]

If you have a good fit between the gear and the shaft you can use Loctite #609 (green). I have been using it on my gearboxes since 2004 with zero failures. Clean both parts with acetone and glue.

[Tom Line]

We don't have a machine shop handy most of the time.... so I'd just grab a hacksaw, notch each edge of the hex shaft with it, and use a circlip or an e-ring in the notches.

To make it "round", you can chuck the shaft up in a drill press, start it spinning, and hold the hacksaw against it lightly by hand so your notches are in line.

[vivek16]

I got the sideplates milled out and attached the gears to the shafts yesterday using roll pins (spring pins). A few of them are too long and keep binding against other gears so I plan on grinding them down. Otherwise, they were very easy to use.

If anyone else plans to use roll pins, I would definitely recommend getting a roll pin punch like this one: http://www.grainger.com/Grainger/items/1Q760

It makes insertion a million times easier and prevents the tip of the rollpin from spreading out from the hammer. I had someone gently hold the pin with a needle nose pliers and put the punch on the pin and hit it with a hammer. It went in without any problems whatsoever each time. Without the punch I ended up bending a few pins.

thanks, Vivek

EDIT: thanks for all the information on e-clips, I will definitely use them in some of my other projects. I bet we could save a pound or two by replacing shaft collars with them!

[dlavery]

Originally Posted by Tom Line

To make it "round", you can chuck the shaft up in a drill press, start it spinning, and hold the hacksaw against it lightly by hand so your notches are in line.

Please, NEVER EVER do this. This is a very unsafe practice. First off, the bearings in the quill of a drill press are not designed for side loads. There is a significant probability you will damage the machine if you do operations like this. But more important, there is a real probability that the hack saw blade will shatter and spray pieces of blade back in your face. Hack saw blades are not designed for repeated shock loads (like they would get when striking the edges of a turning hex shaft). they are brittle and being held under tension. As the blade repeatedly strikes the edges of the turning hex shaft at a relatively high frequency, there is a very good chance the blade will fracture and fail. And in these conditions, the failure can cause the blade to come apart in multiple pieces which may be thrown back at you or across the room at someone else.

If you need to make notches in a hex shaft, please do it safely and properly. If you don't have access to a lathe and need to do it manually, grip the shaft in a vice and cut the notches with a hack saw by hand. Cut the first one, rotate the shaft in the vice, and cut the next one, etc. It won't take that long.

-dave



.

[Dick Linn]

On the subject of shaft collars, the Aluminum ones are very light and relatively inexpensive. The well made (USA) one-piece ones are only about $3. each. They fit much better than the cheap solid steel collars if the shaft is decent.

http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=3807

[Tom Line]

Originally Posted by dlavery

Please, NEVER EVER do this. This is a very unsafe practice. First off, the bearings in the quill of a drill press are not designed for side loads. There is a significant probability you will damage the machine if you do operations like this. But more important, there is a real probability that the hack saw blade will shatter and spray pieces of blade back in your face. Hack saw blades are not designed for repeated shock loads (like they would get when striking the edges of a turning hex shaft). they are brittle and being held under tension. As the blade repeatedly strikes the edges of the turning hex shaft at a relatively high frequency, there is a very good chance the blade will fracture and fail. And in these conditions, the failure can cause the blade to come apart in multiple pieces which may be thrown back at you or across the room at someone else.

If you need to make notches in a hex shaft, please do it safely and properly. If you don't have access to a lathe and need to do it manually, grip the shaft in a vice and cut the notches with a hack saw by hand. Cut the first one, rotate the shaft in the vice, and cut the next one, etc. It won't take that long.

-dave
.

Doh. I stand corrected. I guess I've done a little bit too much farmyard / garage engineering in my time