WHERE ARE THE SHAPER USERS ?

Do you ever read a post before commenting on it, John?

Neil

Does the recipricating hob cut more than one tooth space at a time when making an internal gear? A straight rack will cut several teeth of an external gear at a time and round off the corners, if the internal hob does the same then a standard profile may be OK for the hob as it will give the additional clearance that the internal teeth need.

Should not be too hard to download a CAD gear file and see what happens when it is overlaid on a blank internal gear.

Maybe you should put things a little clearer at times Neil or stick to one machine at a time.

John

-

Hi Andrew,

The 36 tooth gear that was made on the Dore westbury was only done as a
try out just to see if it would work.There is some additional information
on the thread " Pneumatic brake for CNC rotary table By Phil W " listed
under home building of cnc machine tools. In the thread he describes
how he cut the internal ring gear for a very nice radial engine that he made.

The hob at the start feeds in to the blank to the full depth of the tooth,the hob
is locked in position in the quill and does not rotate,the gear blank is mounted
on the rotary table and moves 2 deg and the machine moves X and Y to keep
in time with this.In this way the cutter rolls around inside the gear blank .
In one rotation of the rotary table only 20 teeth are formed to cut the 36 teeth
needs 1.8 revolutions.
It is not really a very efficient method of production but served the purpose in
proving that it worked

Going back to the epicyclic gear at 36 teeth the planet gears are 13 tooth
deducting 2 times 13 from the 36 would leave 10 tooth for the sun gear
this can't be used as it is not divisible by 3 ,so a 9 tooth sun gear was cut
(hobbed) on the Pcd of a 10 tooth gear.This is one of the problems that
one could encounter when trying to make internal gears especially if that you are
using single row form gear cutters as the gear blank sizes have to be adhered
to.
The planet gears are unmodified and left at standard size ,if you tried to fit
modified gears in the ring gear they will lock up ,this seems to be a peculiarity
with this type of gearing obviously the sun gear meshes ok with the planet gears
as these sort of modification do not affect normal gear trains.

Refering to the book "Gears and gear cutting" by Ivan law on page 30 and 31
refers to tooth proportions in particular the thickness of the tooth and space
at the pitch line quoting the tooth as .48 of the circular pitch and the space
as .52 of the circular pitch.
Hobbing the cutter in the way that i did this is clearly not the technically best solution
and really needs the cutter to be made to take account of the .52 space size.
The Arc euro hobs that i use i think are topping cutters so cut the correct tooth form
as they cut the the root the flanks and on the od ,unfortunately this means that when trying
to cut this type of shaper cutter there will be no clearance at the root of the tooth in the
internal gear ,to counter this the planet gears are reduced slightly on the od to give some
clearance.
The book that i have describes suitable tooth forms as , 20 deg full depth modified, 20 deg
stub and 14.5 deg involute is not recommended.

It is certainly an interesting subject i hope to see some more input from the forum on this,probably needs its own thread though.

John

I though two were plenty but you added the third!

I have a Boxford 7" shaper, one with the 'rare' [according to Lathes.co.uk] rotating table.

I will be the first to admit I don't use it much, but then I don't have much call for milling type work. A shaper can cope with the work that the milling head of my Warco WMT300 can't - such as flats on a circular steel bar. The milling head on the Warco isn't stiff enough to do the flats and flexes as the end mill tries to ride up the curvature of the bar. This in turn mashes the end mill. The shaper, on the other hand, does the job perfectly.

Due to the low level of use for my shaper, I keep it on a castored trolley made from 2x4" pallet timbers and store it out of the way when not in use. As the ram moves back & forth there is a tendency for the trolley to rock back & forth an inch or so. However, as the drive belt is quite ossified, I cannot run it at any speed other than 'slowest possible' with the lightest of feeds, and the movement of the trolley stays no more than 1".

The real thing about a shaper is just how fascinating it is to watch. There is extraneous movement every which way, and I always attend on the machine even though it goes so slowly I can usually leave it for 10-15 minutes to slowly progress through a cut. I am convinced Heath Robinson had a significant hand in the original concept..

One thing I have found the hard way is that carbide insert lathe tools are no good - The reverse swing loosens the screw and the tip moves all over the place, wrecking the finish.

Regards,

Richard.

Edited By richardandtracy on 26/09/2016 09:03:58

In addition to Richards remark re: inserts loosening. I've never tried an insert tool on my shaper so that's a new one on me. I have however tried brazed carbide tipped tools on several occasions but the tip flaked/chipped very easily. I have been told in the past that this is caused by the tip being dragged on the back stroke. I can quite believe this theory as I have successfully used carbide tipped tools on shapers and planers that have a tool post lift without tip damage occurring.

I did however manage to use a brazed tip tool to reduce the size of an old case hardened tool holder some time ago but it made a bit of a mess of the tip. If you click the link in my earlier post in this thread and scroll down to “Alba” you will probably tell from the noise in the movie that the tip was already damaged from doing the first side. Never mind though, it survived sufficiently to get the job done.

Rik

The easiest tooling to use is the cobalt type. It has an amazing resistance to wear compared with ordinary HSS and none of the chipping issues associated with carbide, especially when there are intermittent cuts

Something about shaperwork seems to suit that type of tooling

On my lathe, where the work revolves, even on intermittent cut jobs, carbide tooling is king and cobalt tooling is not noticeably different from HSS.

I presume that it's the grinding wheel action of lathework compared to the planing action of shaperwork that makes the tooling suitability different

I don't think Heath Robinson had much of a hand in them. They are good at what they do plus flexibility and simple tooling. The only problem compared with a miller is speed. They might be viewed as a lathe for flat surfaces. with the same degree of flexibility. Planers were used for larger things such as lathe beds. Not so common and the table moves. I'd have to find a rather old book but recollect that some of those cut on both strokes.

I suspect shapers were used a lot once. I worked at Butlers for a while, a more dated place and they had a couple of them just sitting there and not used that much. That's where I saw some on mess up cutting a dovetail on a replacement lathe cross slide on a big Butler. There was 2 lifting eyes on the ram and he had run rope down them attached to the clapper box and tugged on the rope to lift it at the end of each stroke. He was doing this while reading a news paper with a smile on his face as many people were looking rather worried. More down to him I suspect rather than the job. The shaper looked to have survived structurally but the work and tool didn't. There was a very irate foreman about so I just had a quick look and walked off. Lots of people walked through to take a look when the job was progressing well.

John

-

I wouldn't be without my Boxford 8inch shaper. Will have to be prised from my cold dead hands.

I have used it a lot for cutting dovetails, and cutting internal keyway slots in gears etc, and the finish on flat surfaces is can look almost as if it has been ground.

John: Thanks for the additional information. I understand the shaping function now. In retrospect it seems obvious that you need 1.8 revolutions, simply the ratio of the teeth in the 'hob' and the number in the internal gear. I'm not sure I follow the point Ivan Law is making regarding the tooth and space width at the pitch line. It will give more backlash, but as I understand it the standard way to increase backlash for spur gears is to simply cut a bit deeper. I don't know, but assume that commercial involute cutters are made on the basis that the chordal arc at the pitch is equal for tooth and space. When I first started making gears I spent a lot of time faffing around with gear verniers atttempting to fine tune the depth of cut. In the end I realised that it's darn near impossible to get consistent readings. So now I just design the gear and cut to depth according to the maths, cross referenced with the D+f value marked on the cutter if available. So far all my spur gears seem to mesh fine.

Having read a bit more I now understand the basics of the shape of internal gears, and how it is derived, as well as the tooth shape required for a reciprocating hob. What I need to do now is run through the maths to ensure that I really understand it. It's one thing creating the geometry in ones head, it's another trying to write down the equations and generate numbers. There are also a number of tweaks and adjustments for internal gears, and I need to understand what they are for, and in what circumstances they are needed. There is also the question of the minimum difference between tooth count to avoid interference, which seems to depend upon PA and the ratio of addendum and DP.

Andrew

I've also got a Boxford shaper, also one of the so-called rare models, not a rotating table but with a powered vertical feed as well as the usual cross feed. It also has a 3 phase motor, and I'm still in the process of setting up the vfd properly, though I've had it running and done a couple of small jobs with it. Doesn't stop me looking for a decent milling machine but, having seen the sort of work that Stefan Gotteswinter does on his, it is still going to remain in the workshop.

People don't realise how forgiving the involute shape is. It is tolerant of incorrect mesh and a few folk have demonstrated that it is quite practical to make working gears with either extra or missing teeth on a given PCD.

N.

Now I have a shaper (or shape as they commonly used to be called) I am wondering which jobs it does best.

Naturally slotting bores and some gear cutting. Maybe making dovetails. What else is the sort of task where the manual effort is worth it?

Neil

.

Would some photos of an Adept 'angle plate' table be of any help, Neil ?

I could probably photograph mine at the weekend.

MichaelG.

Actually I did know that. I also know there's a whole load of gear design that I don't fully understand. For instance with high performance gears the involute shape is sometimes adjusted to take account of the tooth deflection under load.

Andrew

It would indeed, thank you, although I have a few options. I have already figured out how to fit a surplus drill table to it and I'm hoping to pick up a big bit of angle next week.

Neil

Edited By Neil Wyatt on 29/09/2016 14:35:12

Can I suggest that the angle plate is the first job trued up on the shaper?

Weld one, then surface it off to 90 degrees with the shaper. That will be excellent experience.

Then do some V blocks.

Regards,

Richard.

I suggest a cast iron webbed angle plate rather than angle iron if that is what you are picking up. Steel will tend to flex. Original is 6in wide, 7in front to back and 3 1/2 in top to bottom though plenty of reason to make this more.
If it is a hand operated one then it is quite therapeutic but you want to have something worth listening to on the radio.

There's this from Arc Euro, but it looks bit too robust:

www.arceurotrade.co.uk/Catalogue/Workholding/Vee-Blocks-Angle-Plates/Tee-Slotted-Angle-Plate-65x5x45

My idea is to weld a pair of webs onto the angle and fit a tenon. Typical Adept quality there's a 1/16 deep by 1/2" machined slot along the middle t-slot, the other two are left wholly as cast and are decidedly wonky!

The drill table works, but does flex too much at least it let me get an idea of how it works and just how much space is needed.

A simple stepper with a belt drive to the feed handle will be easier to set up than fixing a ratchet, just needs a debounced microswitch to operate it.

Neil