Stuart Twin Victoria (Princess Royal) Mill Engine

[JasonBModerator @jasonb]

I'm simply going by the sizes on Doc's drawing not 1/64th increments or 0.5mm increments nor even 0.1mm increments, to get an "accurate" reamed hole would need 0.01mm incremental reamers.

"I would assume though he might have the odd couple near what is required but if not then make the holes to a pre-machined plug gauge to any size you desire and then make the shaft to suit."

Isn't that what I have been saying except to use the shaft as the plug gauge thus reducing errors between shaft and gauge.

I'll leave it to Doc now, he has our two opinions and if a deciding factor is needed then in the article TC says bore the hole or ream IF you have a suitable reamer.

Edited By JasonB on 31/08/2022 13:00:06

[Dr_GMJNParticipant @dr_gmjn]

OK thanks all, so I've got more than enough information to get on with the shaft now! I'll report back with progress when I've got some EN1A 9/16" bar (hopefully tomorrow).

Moving on a bit – the keyway in the flywheel and governor pully: I see Arc do a broach and guide for a 4mm wide key, and 14mm bore. If I make the O/D of the crankshaft 14mm, I guess I could get this and give that a go? Could I push it through using my pillar drill, with the parts resting on the table?

This is the shaft based on 9/16" nominal diameter, turned down to 14mm max. O/D, and using equal stepped down to the crank web diameter:

The key would have to go to 4mm x 4mm up from 3mm x 3mm, but there's a bit of an increase in shaft diameter as well (0.88mm).

Maximum length for the broach is specified as 32mm, and the flywheel hub is 45mm. Not sure if the flywheel could be turned over to get the full length?

Would be good to try another new technique.

[JasonBModerator @jasonb]

I doubt you will push a 4mm one with your drill, I am on the limit with my 1/8" one on the drill press.

Also doubt coming in from either end will work but you could make a longer bush and push the broach through with an extension piece.

I'd also be tempted to come down to 3mm sq key particularly as you have two

[Dr_GMJNParticipant @dr_gmjn]

OK so I’d have to make a bush. The 14mm Arc item only comes in 4mm key size.

At least I could make it extend all the way through the hub.

[JasonBModerator @jasonb]

Whatever you go for you need to support the back of the broach for the whole length of the cut and preferably a bit beyond otherwaise it can deflect away from the cut and could even snap.

As for pushing them through I just did a quick calculation based on metal to be removed and number of teeth. The 3mm one will cut 0.125mm2 per tooth but the 4mm takes 0.25mm2 per tooth so likely double the force needed to drive it. Hope like me you have a friend with a hydraulic press which is how I drive my 3/16" one.

[Ramon WilsonParticipant @ramonwilson3]

Doc, a drill press, unless its a very stout one, is not a suitable drive for broaching, the force required is quite considerable. The standard Maarlco broaching press is a pretty sturdy affair in comparison along with low gearing and a long strong lever.

Though the keys are wider I broached my Corliss wheel using such when I was working, I had nothing at home that would cope for sure.

I have a small home made flypress that I use when it suits and though that does give a lot of force its over small movement for broaching useing a commercial broach

I think the modification shown earlier where the topslide is used for slotting looks to be a well worth diversion to take – after all it will always be there for other use in future. Slotting on the lathe with such is much easier than using the saddle.

Just my view – R

[Dr_GMJNParticipant @dr_gmjn]

Yes I think I can get use of a small hydraulic press from somewhere.

OK so I could get just the 3mm broach, then measure the depth of it from the flat part to the final tooth tip.

Then make a bush to suit the flywheel/pulley bores – extended just beyoned the thickness of the flywheel boss. The depth of the slot in it would be calculated from the measured max. depth of the broach, and the key depth required in teh bosses (3mm).

I suppose – if there's enough room – I could also mill another slot, 3mm wide, in the bush at 90 degrees to the broach slot, so I can re-orientate the bush and make the other slot in the bosses at exactly 90 degrees to the first?

On the face ot it, it's then a simple matter of milling 3mm keyways in the shaft (using the R/T in the horizontal orientation), and everything should fit together without too much fettling?

[Paul KempParticipant @paulkemp46892]

Posted by Dr_GMJN on 01/09/2022 19:27:04:

Yes I think I can get use of a small hydraulic press from somewhere.

OK so I could get just the 3mm broach, then measure the depth of it from the flat part to the final tooth tip.

Then make a bush to suit the flywheel/pulley bores – extended just beyoned the thickness of the flywheel boss. The depth of the slot in it would be calculated from the measured max. depth of the broach, and the key depth required in teh bosses (3mm).

I suppose – if there's enough room – I could also mill another slot, 3mm wide, in the bush at 90 degrees to the broach slot, so I can re-orientate the bush and make the other slot in the bosses at exactly 90 degrees to the first?

On the face ot it, it's then a simple matter of milling 3mm keyways in the shaft (using the R/T in the horizontal orientation), and everything should fit together without too much fettling?

Now, you’re talking, you could even go the extra mile and taper the bottom of the bush slot for a “proper” tapered key

I cut the spline keys in my half size traction engine gears (granted cast iron and nice and soft) with a bench mounted arbor press, no idea of its number or capacity, it is fairly hefty, a good 2 man lift to get it on the bench when it was placed there but it did the job just fine. From memory the keys were 5/16” and I made the bush as you describe with 2 slots, one for the broach and the second for a key to index it (8 splines).

Paul.

[JasonBModerator @jasonb]

Yes the smaller "backbone" of the 3mm broach should allow you to mill a slot for that and another to take a 3mm key at 90degrees so you can index the bush and get the two keyways in the flywheel at 90deg.

If you did want a bit more key then you could go for a rectangular 4 x 3mm one in a 3mm slot, It's just a case of adding an extra shim which you can make yourself but two 3×3 keys will be plenty strong enough when compared to the original grub screw and no keys..

Uncle Ketan's site has an article on broaching

Edited By JasonB on 01/09/2022 20:21:21

[Dr_GMJNParticipant @dr_gmjn]

Thanks all.

Paul, what would it take to align the flywheel boss under the press to cut the tapered keyway? Maybe some kind of 3D printed, angled holder arrangement? Or am I missing a really simple way to get the broach vertical? I imagine if it’s a bit off, it could easily snap the broach?

Do you cut from the small depth side first, or the large depth, or doesn’t it matter?

I just read Ketan’s article (from Jason’s post), and it outlines the same method of getting 90 degree spaced slots I thought of, albeit for 4 keyways. So that should be ok.

Edited By Dr_GMJN on 01/09/2022 23:28:25

[JasonBModerator @jasonb]

At 1;96 0r 1;100 taper I just don't bother to angle the flywheel which is a really simple way to do it

I do all mine from the outside (deep) side

Thought earlier we had decided parallel keys would be the best solution?

Also consider a small key over quite a long length that the doubled up flywheeel creates may result in a very shallow keyway in the hub at the shallow end. You would probably want to go deeper on the entry side so "standard" depth came in teh middle and then a bit shallower on exit. key made from rectangular key steel or gauge plate(Left soft)

Edited By JasonB on 02/09/2022 07:03:29

[Dr_GMJNParticipant @dr_gmjn]

Yeah two 3mm parallel keys, fixed with gun screw(s) is still the plan.

I was just wondering how you’d hold the workpiece for a tapered bore, but it might end up being too tricky to do for no real benefit apart from it would be more prototypical.

[Ramon WilsonParticipant @ramonwilson3]

The broach is designed to go in vertical 'guided by the guide' would you believe and designed to be pushed right through. The hole has to be in line with the broach not angled over. The depth of cut on each pass is the taper on the broach with each successive cut increased by inserting shims behind the broach in the guide until the required depth is reached or the broach 'bottoms' out on the shoulder (not recommended)

Other than stopping halfway along the length of the broach I cant see how a tapered slot can be achieved nor why one would want one but then we've been there before haven't we. The broach would have to be tapped back out and the subsequent tooth marks removed. (That may lead to a broken tooth or two too)

I thought it was two keys at 120 ?

 

If you are going to broach then yes, getting the two to match the shaft slots is as good as making the broach guide with two slots which is how I did the four on the Corliss flywheel

Edited By Ramon Wilson on 02/09/2022 07:59:54

[Ramon WilsonParticipant @ramonwilson3]

Posted by Dr_GMJN on 02/09/2022 07:38:04:

Yeah two 3mm parallel keys, fixed with gun screw(s) is still the plan.

I was just wondering how you’d hold the workpiece for a tapered bore, but it might end up being too tricky to do for no real benefit apart from it would be more prototypical.

That's just it Doc – it would not be prototypical, far from it, but I shall say no more on the matter.

Hope it all works out for you however you go about it

[Dr_GMJNParticipant @dr_gmjn]

Thanks Ramon but I don’t really get you comments.

It was discussed earlier that a tapered key in a tapered slot gives parallel outward load on the wheel with to tipping load applied. No we’re saying it’s not prototypical anyway?

I don’t understand the comment about stopping the broach part way, and hand finishing. Why is this even necessary? The method being discussed uses an angled slot in the bush, surely giving an angled slot in the boss? Obviously the workpiece has to be angled at the same ‘degree’ if the broach is to go in vertically (notwithstanding Jason’s comments about the necessity of that).

Yes, it’s 120 degree spacing I was wrong I think, but then just mill the guide slot at 120 degrees in the bush? Same principle?

Edited By Dr_GMJN on 02/09/2022 08:10:48

Edited By Dr_GMJN on 02/09/2022 08:11:26

[Ramon WilsonParticipant @ramonwilson3]

It was your comment "….to do for no real benefit apart from it would be more prototypical that lead to mine.

Sorry for any confusion Doc – it was Paul's comment on tapers and your response in how it could be done but I still think you have the broaching idea a bit awry

I was being facile I suppose – a broach is designed to cut a parallel sot in a parallel hole, not a tapered slot. The only way it could be done to my mind would be to use the broach taper itself – not the right way at all but a flippant remark on my part I'm afraid.

If you cut a tapered slot in the guide and tilt the object it might be possible but that's not how it it's designed to work, the taper increasing the cut of the broach as depth increases dependant on the angle – just not how its done and besides the fact that broaches are expensive items and easily broken which I would think trying to do so might lead to. Getting a broach stuck is a happy situation too.

Doc, I've offered my thoughts based on a fair bit of work experience, certainly did enough broaching in my time to comment for sure. I've only ever made one broach at home and that was for the Bentley prop washer – the pressure to get that through was inordinate so my money's still with saving yours and using the topslide as a slotter

I make no apologies for posting this image again – done on the lathe in a few minutes using a slotting head. Unfortunately it will not fit on an ML7 otherwise I would loan it to you.

Good luck – R

[Ramon WilsonParticipant @ramonwilson3]

Hi guys,

Following Jason post on another thread on the subject of broaching a slot…..

I broach my flywheels to match the angle of the gib head keys, plain milled slot in the shafts and not had one fall off yet out of about 25 done that way. No grub screws used either. Before getting some broaches I planed my keyways with the lathe moving the carriage in and out with a 1thou cut per pass, tilt the flywheel in the chuck or pack on the faceplate to get the seat angle.

and Paul's comment earlier…

Now, you’re talking, you could even go the extra mile and taper the bottom of the bush slot for a “proper” tapered key

I'd appreciate it if you could explain how you do that using a push through broach in parallel bore with a parallel guide.

Despite making my comment above on possibly tapering the slot (in the guide), I got my broaches out today and tried to envisage how the broach would act with the part tilted. I guess I'm being clouded by something or missing something completely but I simply can't see how that would work in practice let alone effectively and accurately.

On my slotting head, should I want to induce a taper in the keyway (and I have to say I haven't felt need so far), then it's a simple matter of setting the slotting head to the angle required.

I'd be interested to hear how you both go about it

 

Best – R

Edited By Ramon Wilson on 02/09/2022 21:58:18

Edited By Ramon Wilson on 02/09/2022 21:58:47

[Paul KempParticipant @paulkemp46892]

Ramon,

it is simple. Flywheel remains flat and perpendicular as any conventional operation ie parallel in all directions to the plane of the press ram. The way you get the taper in the keyway which is not on the sides of the keyway, these are parallel in all circumstances, the taper, as mentioned is only on the head of the keyway. To get that taper which as Jason points out is very small anyway either 1:96 imperial or 1:100 metric when you cut the slot in the guide bush to carry the broach you pack the dividing method (rotary table, plain dividing head etc) or if you are lucky enough to have a universal dividing head you can tilt it. If the total length of your bush is say an inch and we are working to the metric standard you need 10 thou of inclination across the length of the bush. Mill your slot in the normal way. Place your bush in the hole large end up preferably and broach. The taper in the base of the bush slot is what guides the cut of the broach and automatically you will have the required taper in your keyway. Use your shims behind the broach in the normal way to get the required depth. The very small angle of the broach to vertical caused by the guide will not cause the broach any distress at all.

I am afraid I am not CAD literate but I am sure Jason in the blink of an eye can produce a sketch that illustrates if this text is not clear.

Machine your key to the same angle on its TOP face and as long as you drive it in from the right side you will get a uniform contact over the length of the key and no tilting force to wobble ur wheel. If you drive it in too hard it won’t be coming out in a hurry!

Paul.

[Paul KempParticipant @paulkemp46892]

As an aside and not relevant to this conversation as Doc doesn’t have a shaper I believe I have also made a replacement clapper box for my hand shaper with a guide arbor that allows setting of a hole for a keyway of whatever size I desire to grind the tool to either parallel or at any angle I wish! That is a similar approach to Jason’s method of packing the work piece – you can do that with a single point tool but not with a broach. I don’t think in any of my posts I have suggested a parallel bush and tilting the wheel to use a broach and I don’t think Jason did either?

Paul.

[Dr_GMJNParticipant @dr_gmjn]

I must be missing some fundamental issue, because I can’t see any problem with the concept of milling the guide slot in the bush at an angle to the axis of the bush, and this giving a tapered keyway in the hub.

If the broach goes right through the hub, you get a keyway depth proportional to the highest tooth whether it’s at zero degrees or 30 degrees. All that changes is that the entry and exit depths from the hub are different, giving a taper relative to the bore axis.

A guide slot parallel to the bush axis gives a keyway parallel to the hub axis, so what stops an angled guide slot giving an angled keyway in the bush?

Its something I’d like to try in some scrap, and if I can do it, I’ll use tapered keyways and keys in the flywheel. If I mess it up, I'll JB Weld everything into submission.

[JasonBModerator @jasonb]

You are not missing anything doc, it's exactly as Paul explains. As I said with the very shallow taper the size broaches we are talking about will only lean by about 0.75mm do I don't bother to tilt the flywheel. The only time I have tilted the work is when doing much steeper angles as you might find on a tapered timing gear or flywheel bore that has a woodruff key

The broach is driven as Paul says which allows it to go right through just like doing a parallel keyway and can be driven from either side but I find it better to have it doing the deepest part at the top.

Better than draw it, I'll take a couple of close ups of one of the taper bushes from this lot, most of those loose custom made ones are for tapered keys

Edited By JasonB on 03/09/2022 07:13:05

[JasonBModerator @jasonb]

In the mean time for Paul and the Doc I have drawn it up with exaggerated taper so it's easy to see. Broach just has a few equal height teeth but enough to give the idea as it's only the last tooth that really matters.

Section with broach in place,

Section with broach removed you can clearly see the tapered slot in the bush and the broach will cut parallel to that and therefore give a taper to the keyway in the hub

This will give what is shown in Machenery's Handbook of matching tapered surfaces to key and hub keyway

If you have a slotting attachment for a lathe then that can be mounted at an angle to do the same, if a slotting attachment for mill or doing it on a shaper then the work needs to be tilted so the cut is at an angle to the works central axis.

[Ramon WilsonParticipant @ramonwilson3]

Well, I've read that through and I'm still not convinced by your sketch Jason or your description Paul

Forgive me for being thick but if the broach is pushed through as it is designed to do then the wide end of the broach is doing the final cutting and sizing the depth of the slot on each stroke. Cutting a taper in the guide slot is not a guarantee that the broach will follow, besides although diagrammatical, you have the broach tilted.

Paul , I'm well aware that the key is not tapered on the sides – how on earth could you broach anything if it was.

With regards to shaping I've already said that from the very beginning, and in my last post, the axis of travel defines whatever taper you desire – it's basic and easy to do by shaping on the lathe if you have the means to alter the angle of travel

This extension to the Bentley crankshaft required a key to be absolutely accurate to ensure concentricity. The picture is rather dark but you can make out the slot inside the mating taper

This shows it in place, the hole is where the tool bit ran out to clear the swarf. The tapered area between the two parts roughly in the centre is also tapered with a key though it cant be seen. The key slot is at the same taper

The mating part is slotted at the same matching angle but the drive is off the side of the key not the taper itself

So on that note "you broach how you want to" – I'll stick to what I know.

[Ramon WilsonParticipant @ramonwilson3]

Paul, I'll rephrase that remark , "I'm well aware that the key is not tapered on the sides" – brain fade on my part I was seeing this different to how you obviously meant.

To make a matching key tapered on the sides if you did however would require some pretty sophisticated machining of the key.

Obviously theres a big difference in being able to shape/slot the keyway than to broaching – but I'm not convinced on achieving a guaranteed taper with the latter as shown.

Machining matching tapers at any time on anything is not the easiest to achieve though not impossible but it brings me back to my early thought – make the key parallel such that it is slightly higher that required and then file a very slow taper on the top face until it just nips up as it drives home

On that note, this is taking far to much time from my plastic distraction so I'll bow out now

Good luck with it Doc however you do it

R

[Dr_GMJNParticipant @dr_gmjn]

Thanks all.

Work on the shaft is on hold because my centre drill is stuck somewhere due to the Royal Mail strike…

Jason – your CAD is how I imagined it would work. Is there any benefit to tapering the bush slot the other way to help keep the broach in contact – as Ramon mentioned – or do the cutting forces make this irrelevant?

Edited By Dr_GMJN on 03/09/2022 09:59:58

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