Elliott 10M Spur Gear Shaping Attachment

[Pete.]

Well I like it. Wish I could follow exactly how it works, but I like it.

Imagine you wanted to file a gear tooth shape into a part and you were half way there just making the curve. You would file a stroke, move around the curve a bit , file a stroke and so on. This is doing that same thing exceptinstead of moving and rolling the file it's moving and rolling the part.

 

[ronan]

Might it be done by a stepper and some electronics, Arduino or something?

I was watching Andysmachines doing that, using an ardweirdo.

 

[prepman]

If you've seen several videos on youtube of Heath Robinson creations for cutting spur gears on a shaper and liked them, you might like this. I watched videos by Geoffrey Croker and Paul Hopewell ("The Shed Dweller") and had struggled to come up with an improvement to their ideas, until a couple of months ago.

I wasn't keen on the wire and cylinder technique as it looks like a) it could slip and ruin the work and b) you need a different cylinder for every pitch diameter gear you cut. The idea that Paul came up with of replacing the wire and cylinder with a lever was better but a) it doesn't quite generate an involute (not far out though) and b) the mechanism for setting the rotation of the gear blank as it travelled didn't look that precise.

For the uninitiated, the idea is to use a simple HSS cutter with a shape matching a rack tooth (straight sides) to cut involute gear teeth. I can't be the only one who detests spending £25+ for a cutter each time I need to make a gear size I haven't done before.

The light bulb moment came when I was messing about with the vertical feed mechanism that I'd made for my Elliott 10M. The same mechanism is used to traverse the table side to side, but the gear wheel is moved from the vertical feed screw to the cross slide screw:

View attachment 327516

As the aim is to rotate the workpiece exactly proportional to the linear travel, I figured I could tap off the cross slide gear with another shaft as that achieves this. The next problem is to hold the work, index it but also rotate it as the table traverses. Well, I have an Elliott universal dividing head which achieves just that! So all that was needed was an attachment to join the cross slide gear to the dividing head with a gear train with the right gear ratio. I designed it initially on a 3D package (Designspark) because its quicker and cheaper than making mistakes in metal. One over-riding aim was that there should be no permanent mods to the shaper, no drill holes for example, just clamp on:

View attachment 327517
Gears here are just drawn as discs. The gear on the right picks up the drive from the cross slide gear. It has an internal spline to drive a shaft that runs side to side. The left hand end of this shaft is bolted to the table and moves left and right with it, hence the spline. A pair of 45 degree helical gears turn the drive through 90 degrees onto another shaft bolted to the T slot in the side of the table. The end of this second shaft will carry the first gear in a train that drives the dividing head universal drive spindle.

After a couple of months of cutting metal it's finally done and here it is bit by bit going on the shaper.

Pick-up gear assembly, clamped to the ways:

View attachment 327520

Splined feed shaft before its bracket is bolted to the table:

View attachment 327521

This is then bolted on so everything runs smoothly:

View attachment 327523

The next shaft has a bracket with slots for T nuts and studs so the mesh of the helical gears can be adjusted:

View attachment 327525

And here it is bolted to the table:

View attachment 327526

Finally the gear train is fitted to the dividing head banjo to join everything up:

View attachment 327527

Sorry about the blurred images. Note the spindle locking lever has been removed from the dividing head and replaced with a bolt to keep the chips out. Clearance is tight and there is a possibility of it rotating into the toolholder - the shaper wont care but it would do a lot of damage somewhere!

And finally the video of it chewing its way through a delrin blank:

At the moment this is as far as it's been tested. I have an aluminium blank and an en3 steel one lined up next, but this gear has already been ruined by me not indexing properly (lots to think about to run this) and starting with the gear train on the banjo ****-backwards thanks to an error on my spreadsheet.

At the mo this is a 16DP 26 tooth gear being cut with a tool I originally ground to cut an acme thread (the 14.5degree angle each side was very obliging!) Just the tip needed grinding wider.

If anyone's interested I can go into much more detail (yawn), like for example the helicals are 14T to 11T to approximate 4/pi as that unpleasant little irrational number crops up in the maths. I'll post a vidoe of the ally and steel tests when I finally get there, but I've been working on it since the beginning of November, and it all takes time.

Rob

Very impressive. I have an Elliot shaper and use it in preference to the miller. The tooling is inexpensive.
Making another QCTP holder at present. Easier to cut the dovetail than on the mill. Like you I watched the Heath Robinson gear cutting attachements and thought of using rack instead . But unlike you that's as far as I got.

 

[RobCox]

Like you I watched the Heath Robinson gear cutting attachements and thought of using rack instead

If you use a dividing head like I have to hold/rotate/index the gear a rack has the disadvantage of needing a higher gearing ratio - if your gear blank is the same PD as the gear engaging on the rack they need to rotate at the same rate, so with a 40:1 dividing head the gear train has to provide a 40x speed increase, however, the irrational number pi cancels out of the equations so the gear ratio is just the dividing head ratio x the ratio of pitch diameters of the rack gear/gear blank.

Tapping off the leadscrew has the advantage of having a gear ratio much closer to 1:1. Taking a 1 inch pitch dia for example for the gear blank, my 8TPI leadscrew rotates 25.1 times for one rotation of the gear blank. A ratio of 1.6:1 is needed in the gear train. If using a 1 inch pitch dia gear engaging with a rack to do the same the ratio would be 40:1.

I came across another video yesterday of some Australian chap who'd used a rack to rotate the gear blank on a shaper, but he'd made his own fixture to hold / index / rotate the gear blank without the 40:1 worm gearing. In that case it works fine.

 

[prepman]

If you use a dividing head like I have to hold/rotate/index the gear a rack has the disadvantage of needing a higher gearing ratio - if your gear blank is the same PD as the gear engaging on the rack they need to rotate at the same rate, so with a 40:1 dividing head the gear train has to provide a 40x speed increase, however, the irrational number pi cancels out of the equations so the gear ratio is just the dividing head ratio x the ratio of pitch diameters of the rack gear/gear blank.

Tapping off the leadscrew has the advantage of having a gear ratio much closer to 1:1. Taking a 1 inch pitch dia for example for the gear blank, my 8TPI leadscrew rotates 25.1 times for one rotation of the gear blank. A ratio of 1.6:1 is needed in the gear train. If using a 1 inch pitch dia gear engaging with a rack to do the same the ratio would be 40:1.

I came across another video yesterday of some Australian chap who'd used a rack to rotate the gear blank on a shaper, but he'd made his own fixture to hold / index / rotate the gear blank without the 40:1 worm gearing. In that case it works fine.

Yes also the Ozzy one. I also thought a gearbox somewhere would have helped. Having never in my entire life, ever cut a gear, I found it all intrguing. After buying a set of involute cutters for the miller and a dividing head, I realised that things weren't that straight forward. The shaper however opens up possibilties of being almost infinitely variable. The gear profile is such that the point of contact is tangential to the mean diameter. There's an army video on youtube explaining differentials. The approach is good as it start of with a simple lever which metamorphs into gears. It's just being able to visualise something that makes it viable.
My question though, is the gears you used to build it....where did they come from....Chicken/egg
Also it is one tooth at a time? Or have you perfected an auto advance in it?

 

[RobCox]

The whole thing is one tooth at a time. Start down the auto advance and you'll end up designing a proper gear hobber. Unfortunately my workshops too small for one of those and I won't make enough gears to justify the outlay... plus you need the hobs, and we're back to where we started, shelling out for expensive tooling every time a new gear DP/MOD comes along.

The gears on mine are a combination of ones I've cut on the mill - the 14DP ones on the shaper and the helicals - and some 16DP gears that came with the dividing head plus a few extra I've cut. It was the cost of a cutter every time that I wanted something different that set me off trying to do this.

While I'm on the subject of milling gears, milling 45degree helicals on an Omnimill stretches it's capability to the limit. It's not a true universal machine, so I have to use the vertical head turned to the helix angle. The result is an uncomfortable looking setup.

 

[prepman]

The whole thing is one tooth at a time. Start down the auto advance and you'll end up designing a proper gear hobber. Unfortunately my workshops too small for one of those and I won't make enough gears to justify the outlay... plus you need the hobs, and we're back to where we started, shelling out for expensive tooling every time a new gear DP/MOD comes along.

The gears on mine are a combination of ones I've cut on the mill - the 14DP ones on the shaper and the helicals - and some 16DP gears that came with the dividing head plus a few extra I've cut. It was the cost of a cutter every time that I wanted something different that set me off trying to do this.

While I'm on the subject of milling gears, milling 45degree helicals on an Omnimill stretches it's capability to the limit. It's not a true universal machine, so I have to use the vertical head turned to the helix angle. The result is an uncomfortable looking setup.

View attachment 327729

The vertical clearance with Senior Major is lmited....It came with vertical head and a very knackered 1ph motor. Ditched it and fitted 3ph and vfd.


It had no horizontal adaptors. So had to make them all and buy a beam bar. The arbor support is 3 pieces welded together. Spindle is only mild steel. It works but the cutters are so expensive. Never liked the shaper when I first saw them at tech' way back. They always looked a bodge job. Got just for the novelty, but now wouldn't be without it. Made an internal boring cutter for producing keyways AFTER I'd already made one hand filing for the lathe LO coupling. Such is life.

 

[fizzy]

If you've seen several videos on youtube of Heath Robinson creations for cutting spur gears on a shaper and liked them, you might like this. I watched videos by Geoffrey Croker and Paul Hopewell ("The Shed Dweller") and had struggled to come up with an improvement to their ideas, until a couple of months ago.

I wasn't keen on the wire and cylinder technique as it looks like a) it could slip and ruin the work and b) you need a different cylinder for every pitch diameter gear you cut. The idea that Paul came up with of replacing the wire and cylinder with a lever was better but a) it doesn't quite generate an involute (not far out though) and b) the mechanism for setting the rotation of the gear blank as it travelled didn't look that precise.

For the uninitiated, the idea is to use a simple HSS cutter with a shape matching a rack tooth (straight sides) to cut involute gear teeth. I can't be the only one who detests spending £25+ for a cutter each time I need to make a gear size I haven't done before.

The light bulb moment came when I was messing about with the vertical feed mechanism that I'd made for my Elliott 10M. The same mechanism is used to traverse the table side to side, but the gear wheel is moved from the vertical feed screw to the cross slide screw:

View attachment 327516

As the aim is to rotate the workpiece exactly proportional to the linear travel, I figured I could tap off the cross slide gear with another shaft as that achieves this. The next problem is to hold the work, index it but also rotate it as the table traverses. Well, I have an Elliott universal dividing head which achieves just that! So all that was needed was an attachment to join the cross slide gear to the dividing head with a gear train with the right gear ratio. I designed it initially on a 3D package (Designspark) because its quicker and cheaper than making mistakes in metal. One over-riding aim was that there should be no permanent mods to the shaper, no drill holes for example, just clamp on:

View attachment 327517
Gears here are just drawn as discs. The gear on the right picks up the drive from the cross slide gear. It has an internal spline to drive a shaft that runs side to side. The left hand end of this shaft is bolted to the table and moves left and right with it, hence the spline. A pair of 45 degree helical gears turn the drive through 90 degrees onto another shaft bolted to the T slot in the side of the table. The end of this second shaft will carry the first gear in a train that drives the dividing head universal drive spindle.

After a couple of months of cutting metal it's finally done and here it is bit by bit going on the shaper.

Pick-up gear assembly, clamped to the ways:

View attachment 327520

Splined feed shaft before its bracket is bolted to the table:

View attachment 327521

This is then bolted on so everything runs smoothly:

View attachment 327523

The next shaft has a bracket with slots for T nuts and studs so the mesh of the helical gears can be adjusted:

View attachment 327525

And here it is bolted to the table:

View attachment 327526

Finally the gear train is fitted to the dividing head banjo to join everything up:

View attachment 327527

Sorry about the blurred images. Note the spindle locking lever has been removed from the dividing head and replaced with a bolt to keep the chips out. Clearance is tight and there is a possibility of it rotating into the toolholder - the shaper wont care but it would do a lot of damage somewhere!

And finally the video of it chewing its way through a delrin blank:

At the moment this is as far as it's been tested. I have an aluminium blank and an en3 steel one lined up next, but this gear has already been ruined by me not indexing properly (lots to think about to run this) and starting with the gear train on the banjo ****-backwards thanks to an error on my spreadsheet.

At the mo this is a 16DP 26 tooth gear being cut with a tool I originally ground to cut an acme thread (the 14.5degree angle each side was very obliging!) Just the tip needed grinding wider.

If anyone's interested I can go into much more detail (yawn), like for example the helicals are 14T to 11T to approximate 4/pi as that unpleasant little irrational number crops up in the maths. I'll post a vidoe of the ally and steel tests when I finally get there, but I've been working on it since the beginning of November, and it all takes time.

Rob

Brilliant work - looks like it is time to fire up my 10M!
Yes would definitely like more details.
Only one little criticism - when you take videos hold your phone sideways - you get full screen that way. Vertical videos should be reserved for the Eiffel Tower

 

[RobCox]

It works but the cutters are so expensive

Which cutters? The involute cutters, yes, but run of the mill horizontal cutters are usually at bargain basement prices.

It helps if you've got one of these to sharpen them though

 

[gaz1]

The whole thing is one tooth at a time. Start down the auto advance and you'll end up designing a proper gear hobber. Unfortunately my workshops too small for one of those and I won't make enough gears to justify the outlay... plus you need the hobs, and we're back to where we started, shelling out for expensive tooling every time a new gear DP/MOD comes along.

not entirely true

heres one much smaller

can be used to make other gears for other machines as well

 

[RobCox]

Only one little criticism - when you take videos hold your phone sideways

You mean the poor lighting, blurry focus and hand held camera shake is OK?

I'll be posting more videos on it when I try it on aluminium and steel. Ally I'm expecting to be OK, the steel might be "interesting". 2 passes maybe. Its not as quick as a mill, thats for sure, but hey, thats shapers for you!

 

[prepman]

Which cutters? The involute cutters, yes, but run of the mill horizontal cutters are usually at bargain basement prices.

It helps if you've got one of these to sharpen them though

View attachment 327737

That's a financial outlay in itself.

 

[RobCox]

heres one much smaller

Aah, but thats a hobber, not a shaper...

 

[fizzy]

You mean the poor lighting, blurry focus and hand held camera shake is OK?

I'll be posting more videos on it when I try it on aluminium and steel. Ally I'm expecting to be OK, the steel might be "interesting". 2 passes maybe. Its not as quick as a mill, thats for sure, but hey, thats shapers for you!

Yes I can live with all that
Vertical videos are the spawn of the devil

 

[RobCox]

That's a financial outlay in itself.

Yup, but its been paying its way ever since!

 

[prepman]

Yup, but its been paying its way ever since!

Do you a grinding service our just saving on replacements?

 

[ronan]

 

[prepman]

I'm seriously thinking of 3d printing (I have a proper non artistic 3d gear generator) what I need then is casting it by 'lost wax' method.....in what is the question. Can't do cast iron..... too hot.

 

[RobCox]

I cut some more gears today with the shaper. The first in aluminium and the second in horrid mild steel.

Aluminium is easy, full depth tooth in one go. Steel, hmm. I'd like to see someone cut a steel gear on a shaper with the wire and disc technique! The forces were much higher. I did the first tooth full depth. That exercised the sphincter somewhat. On the second tooth, the block that adjusts the stroke of the shaper vibrated loose. First time thats ever happened to me! I backed off to cut 90thou depth first time round and finished to 135thou on the second pass.

I counted the strokes needed to cut a 16DP tooth... 120! It took well over an hour to cut the steel gear.

Pictures and (landscape!) video to follow later.

 

[My Old Landy]

I cut some more gears today with the shaper. The first in aluminium and the second in horrid mild steel.

Aluminium is easy, full depth tooth in one go. Steel, hmm. I'd like to see someone cut a steel gear on a shaper with the wire and disc technique! The forces were much higher. I did the first tooth full depth. That exercised the sphincter somewhat. On the second tooth, the block that adjusts the stroke of the shaper vibrated loose. First time thats ever happened to me! I backed off to cut 90thou depth first time round and finished to 135thou on the second pass.

I counted the strokes needed to cut a 16DP tooth... 120! It took well over an hour to cut the steel gear.

Pictures and (landscape!) video to follow later.

Looking forward to the video, shaper and gear cutting joined makes fascinating viewing!!