Member postings for brian jones 11

Who invented the helicoil insert - life saver for my Lambretta with a stripped spark plug hole?

Obviously someone thinking out of the box

Now this rack thing needs more work

I could tilt Doreens pretty little head thru 90deg but this would mean a 1 ft diameter cutting tool - NOT

Does anyone know of a horizontal mill that rotates on the X axis rather than the normal Y axis?

I have joined the Gearheads corner with the gearotic 3 installed - lovely little app free but you have to pay $129 one time for a manufacturing licence - which is probably reasonable if that floats your boat and you need CAM files

You will be pleased to know I have already found faults with their Low PA forms but they welcome eccentric gear designs

You probably know about them already

Also never seen a mill with a cross slide maybe you don't know your mill from your lathe

Indeed I am, as ever, scrambling my glossaries

what is the mill X slide called in shop talk

I spose the Y slide would be a cross slide?

Now SOD you have not been paying attention in the back

the blank isn't free to rotate.

A rotating rack!!!!!!!!!!!

What are you on

One out of ten for imagination

You would need a mill with a freely moving cross slide

So I would put a lead-in taper on that cutter (just like a taper tap)

That would shunt the whole job in 5 mins NOT 5 hours

I didnt get where I am by sitting in an armchair sniping at "can do" MEH

JB - you never seen an ACME tap?

Edited By brian jones 11 on 21/09/2021 19:02:05

Well if a cutter like that had a helix?

I think there is carpet on the floor

Funny that - looks like my OP

and the concept of using a bolt with 6 straight flutes

Hmm

Must get on with that, too many distractions around me simulating gear rotation. Cant be doing with GIFs and all that stop motion stuff, its like cutting racks

Ok JB, I agree with all your comments AND

the fundamental limitation is the choice of screw thread pitches available for practical use

To keep it simple, and assume that the CP is approx = to screw thread pitch then you could realistically go from 2mm say 1/2 UNC (or M14 x 2mm) to M24 x 3mm to M36 x 4mm

This is equivalent of Mod 0.64, 0.95 and 1.27 so wont go far, only for modellers (stand by for incoming)

My plastic gear looked good enough to model, quick, cheap and easy to make

But fear not for I have a cunning plan which, if parts arrive, I will post a vid in a week

Rest a while in the SCR comfy club chair

Indeed you need precision gears for clocks with minimum friction - what PA would be used?

My method not suitable

No one has yet spotted the fundamental limitation with my method

I admit the PA will be 30deg. given a unified thread on the cutter but thats not it (noisy and inefficient).

Now for those who believe a lot of productive work is done sitting in a comfortable chair.

Here is a conundrum for the SCR that is bothering me

Why was the concept of DP Diametral Pitch introduced when the CP Circular pitch addresses the same size issue and is physically realisable ie you can measure it with calipers

CP is also analagous to screw thread pitch and is intuitive

Even in the Gear Hobbers vade mecum by Dr. Rainer Hessmer only the CP , PA and No of teeth are required, DP does not figure at all

I suspect foul play by AGMA

Edited By brian jones 11 on 19/09/2021 23:06:54

Piccie of the armchair, big trough in the squab is there?

Cant really see what happening at the business end, the spindle is clamped and you motor the y slide in and out to cut the tooth, then index along x wise for the next tooth is it?

5 hours phew, were you compensated by the hour?

Could this duty not have been done with a motorbike chain?

Well the OP set out to find a simpler way of cutting gears for the humble hobbyist

I'm not sure why we have to restrict ourselves to non-CNC solutions - if so, then why not restrict ourselves to a file and cold-chisel?

CNC guys should really stick to the senior common room with much more room for comfortable armchairs (I see are necessary to mind a CNC m/c) because you are operating in a far different orbit to mere hobbyists who will probably never own a such a beast - its way out of our league

I just marvel at the way you guys can cut a hole with a set of xy instructions - no more large drill stock etc. We cant do this on small manual m/c not without considerable effort with a face plate etc

Like Morris Minor with a Lamborgini Clarkson

Pass me the 4lb mallet, glove puppet, the EMS is playing up

For a Quick and Dirty job, a bike chain can make a rack . I always remember how inefficient RnP can be from misspent youth traversing canals and their locks. These had sluice gates to be operated with a hefty handle hauling on a victorian RnP

I like the cloth cap answer for 14,5deg, on a 5" sine bar its 1-1/4" height. That would suit a draftsman

much more plausible than my postulate of trial and error comfort (given by some rubbish from google)

more work needed here but Maureen is beckoning

BTW JB whats this

There is a clue in the abreviation Prescribed Circle Diameter

I am appalled at the way the industry presents its essential features and I am trying to de-clutter the nomenclature into categories of "need to know" and "nice to know"

I blame AGMA for this prolixity after all why use 5 words when 100 words looks good and sounds important and you can charge more money for it - geddit

rack thread pitch is 0.1566" so assume PA 20deg what is the pcd

this thread it's more likely to a a reality TV show than comedy

never watched that mucky stuff

is that where young persons with nothing on, go to an island and play lewdo. We machinists never take our boiler suits off for that. I prefer Radio 4 and Mrs Dales Diary (I think Jim is having an affair?)

but for the benefit of the noobs (and those who never knew how little they knew) we are unearthing the mysteries of gears and exposing things hobbers dont want you to know

must press on

PS

sin(14.5° ) = 0.250

is no coincidence regarding the use of 14.5° as a pressure angle.

now thats a revolution

Edited By brian jones 11 on 17/09/2021 20:39:03

I can see this thread being sent up to the beeb as a classic comedy series The MEWD Modellers - like the Detectorists with Gareth keenan, imagine himself with a huge horizontal ex WD mill called the Honey Monster which dims the street lights every time he switches it on

Ruston Horniman made a 1/4 scale Fowler steam traction engine in his front room. Erindoors wont let him get up a head of steam cos the soot will foul the Dralon drapes

and so it goes

Edited By brian jones 11 on 17/09/2021 20:12:27

she is showing some wear and is a bit bow legged under the apron.

kerriste dont say that in front of her, she'll have a cow

So there's another mystery solved, rack and pinion 20deg PA 40deg apex angle

now to de-bumf the base angle and unclutter the pitch circle from your diametral pitch and pitch circle. OMG do they make hard work of it all, mixing nomenclature with the cousins

Are thread forms independent of pcd, so a small pinion has the same tooth form as a large spur for the same circular pitch.(teeth per inch) I dont think it does

Hmm well I was going on what I read, maybe Maureen got a faulty rack?

How do you justify the angle of 67deg?

Now if you postulate Maureen would have had a PA of 14.5deg then the combined angle should be twice that ie 30deg

so if PA was 20deg then this should be 40deg

so this is a long way off?

but note that the rack form has straight sides no involution here. A rack is treated as a gear with infinite PCD

Now PA=14.5 was the historical value from victorian times as giving quiet operation and long wear (but only for medium loads and speeds), The AGMA had better ideas and chose 20deg since 1980 for greater power, reduced pinion teeth before undercutting, wider base (greater no of cycles before fatigue failure), but greater wear.

Whats not to like

I just read somewhere that a 60 thread angle - Unified produced a 20deg involute pressure angle and a straight line. the hobbing cutter has straight sides but its curved action produces the required 20 deg slope, I wish Id kept the reference, so the rack has straight sides

I had a look under Maureens apron (she a bit coy about that sort of thing - girls born in the 50's were like that)

As you can see the rack, straight sided teeth 60deg

That animation of meshed gears in the link MG has done my head in

Another avenue of pointless pursuit ahead of me - "life, life, dont talk to me about life" said Marvin the depressed robot

Its the unified thread angle

Well AJ excluding cnc I cant see how you made that on Maureen BTSOOM

Something intriguing I noticed, but i expect you all knew this, is that a rack and pinion system uses a 20deg PA form but the rack is a straight 60deg form.