cutting spur gears on a mill

Brian Wrote

"I wonder what DP Myford gears were made to? They look crude and square CI to me at first glance must examine one closely. I stole a spotty neighbours kids USB microscope (Bresser) and it provides very usable pix at 20X on my PC screen, at 80x I can even see little living amoeba in our pond water, maybe grow some tardigrads"

Why on earth would you need to go to the trouble of using a microscope to find out the DP of Myford gears?

With all the links to various gear calculation charts in this thread etc You should have no difficulty in working it out all you need is OD and number of teeth which should be easy enough to see and in most cases give you a usable answer. PA has also been mentioned here and probably DP too. This is the way a beginner with limited resorces can work out gear sizes I would have thought that would be right up your street.

Hopefully beginners have learnt from this thread but from your methods to work out the DP of Myford gears you certainly have not picked up much useful information and it is no wonder you have not been able to come up with 2:1 gears yet as it's these every things that need to be understood to be able to design simple gears.

Edited By JasonB on 08/10/2021 08:07:40

Um, 20 dp?

Posted by Jason B 8 10 2021 07:15:50

Brian Wrote

"I wonder what DP Myford gears were made to? They look crude and square CI to me at first glance must examine one closely. I stole a spotty neighbours kids USB microscope (Bresser) and it provides very usable pix at 20X on my PC screen, at 80x I can even see little living amoeba in our pond water, maybe grow some tardigrads"

Why on earth would you need to go to the trouble of using a microscope to find out the DP of Myford gears?

With all the links to various gear calculation charts in this thread etc You should have no difficulty in working it out all you need is OD and number of teeth which should be easy enough to see and in most cases give you a usable answer. PA has also been mentioned here and probably DP too. This is the way a beginner with limited resorces can work out gear sizes I would have thought that would be right up your street.

Hopefully beginners have learnt from this thread but from your methods to work out the DP of Myford gears you certainly have not picked up much useful information and it is no wonder you have not been able to come up with 2:1 gears yet as it's these every things that need to be understood to be able to design simple gears.

Edited By JasonB on 08/10/2021 08:07:40

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I just wonder who that this reply was aimed at as all of Brian Jones 11 's postings seemed to have disappeared from this thread ,shades of Barrie Lever .I thought that the posting that you put up in Home cnc the other day here

"From Previous posts on here the Wabeco machines seem to perform well, have a look back for posts by barrie Lever. "

was bit daft as all of his postings have been removed and is only referred to as Former member.

John

Well some cousins made a success of Free Hobbing as I suspected

https://youtu.be/tFaJv3PaunM

Gave up following this thread but do admire the patients responders hat with Brian.

Niko.

The best is yet to come, Elvis has not left the building and he will shortly be presenting the debut of the Anti-gravity Grinder - hold that thought. Is it a way to create extended spiral turns (as in pulling a spring apart) on a lathe without a CNC in sight.

Odd how this thread only appears in 'latest forum posts' on the righthand side and not in the larger 'latest posts' and opens on the last page.

Seems to work now ????

Edited By Dave Halford on 09/10/2021 11:29:19

It's the shape shifting lizards from the AGMA

Stand back from success

I made a predictable gear

OD 27.1mm got 28 teeth as I pre-calculated

Then I had a happyfanny moment and found a solution to the clearance backlash criticism

It has blown me away

I need to make a proper jig to mount spindles to test out pairs of gears more accurately and make vids

My desktop kids microscope (recently pooh pooh'd by the little modeller) has shown up some remarkable shots of Carbide tips and why PRC stuff my not cut mustard

PM me for details if you are interested

The worm turns

WaM

Another phantom post at 2205!

Another tedious naysayer at 23:03

What value does he think he has to this thread

Going back a bit nearer topic I am fairly sure the Myford manuals tell you the gear standards, so you don't need resort to measuring etc.

I must admit I have never thought the headstock gears and the change-wheels on my ML7 either "crude" or "square"; whatever those were meant to mean. If my screw-cutting comes out ragged, I blame the operator not the machine!

Or stray tardigrades....

Myford and most other lathe gears are 'good enough' rather than well made. The main disadvantage of their relative crudeness and imperfect curves is noise. Vintage car gearboxes use basic gears and the whine is all too obvious, but lathe gears don't work that hard. Backlash is also evident, but doesn't matter when screw-cutting or anything else lathe related.

Putting the best possible gearing into a lathe is a waste of money unless the machine needs to be as quiet as possible or is exceptionally powerful. Myford lathes, bless 'em, aren't powerful!

Dave

Though I doubt that they made especially crude gear cutters just for Myford! However they are 14.5* PA which I think will make them look squarer. This from the late great Sir John in 2012:

"Jim,

I can't comment on the rack or it's mating pinion as I don't have any details on these but could get them if I wanted.

However as regards the screw cuting gears they are all 14 1/2 degrees PA with the exception of the first 4 on the Super 7 and like family.

The first 4 being spindle gear, the two tumblers and the gear the tumbler drives. These are 20 degrees PA.

Outboard of this they are all 14.5 degrees.

The ML7 are all 14.5 including back gear but the backgear on the S7's is special and requires a special hob as the tooth form is modified.

John S."

Edited By John Haine on 10/10/2021 11:05:39

Edited By John Haine on 10/10/2021 11:06:08

It is a strange thing. Of every manual for every machine tool that I have ever come across, the gear specification is never mentioned.

As a few examples: Myford 7-series; Colchester Bantam, Chipmaster, Student; Harrison L5, 140, M-xxx class; Boxford. Look at every Asian-sourced lathe available new from UK suppliers - how many of them mention the change gear spec.?

You might also explore mills that use change gears (e.g. Harrison, Deckel, Alexander, early Beaver).

It is notable that change gear specs. are hard to find on lathes,co.uk, perhaps the most comprehensive resource available.

Also surprising is that in the many years since the web has been part of our life, no-one has produced a compendium of this information.

I guess if unkown gears seem to conform and mesh ok with std forms then you can guess what the spec was (all thanx to AGMA of course)

but if its a modified form, how do you measure it without resorting to sophisticated optical equipment?

let alone say you have to make a replacement to mesh with an existing gear

If its CI then you cant just TIG weld some new teeth and re machine AFAIK

I did some welding once using Nickel electrodes - I gues its akin to brazing which works

So Maureen's back gears are a challenge - how strange.

WaM

Interesting to hear the Myford back gear are 'modified'. Another odd one is the RanDa lathe back gears (not their changewheels) as was brought up on a thread last year. Info to store in the little grey cells.

As for quality of teeth I have some changewheels from a Britannia that are cast as 'pegs' straight sides and round top and not then machined. Minimum cost. I find when I pair a 60 with a 30 the ratio is somehow still 2:1 despite the crude teeth. How come?

Spec? I swear some people on this forum would need a fully dimensioned drawing with tolerances to BS blahblah to make a tommy bar.

I can't see any reason why the gear spec would be mentioned in the manual.

Tony

.

I know you are kidding, Bazyle … but just in case some innocent takes your comment seriously: Let’s just note that the the velocity ratio will vary whilst they are running [which does not bode well for accuracy of screw-cutting].

… The relevance of that will of course depend on the job that the resulting screw will be doing.

MichaelG.

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Edit: __ Jumping from the ridiculous to the sublime : Feast your eyes on this:

http://lathes.co.uk/bryantsymons/

Edited By Michael Gilligan on 10/10/2021 12:16:37

Must say when I had my geared head Emco there were no crude " lathe gears" or short cuts taken with the gearing and I seem to remember earlier in this thread Andrew mentioned helical gears on lathes to reduce noise.

As for straight teeth, really depends on what change gear you pick up and look at, my small 25T ones certainly have as easily seen curve to them compared to the largest 80T even without using a microscope. If I had a 127T gear I would not be expecting to see much of  a curve on that either.

Backlash on the screwcutting banjo is really all down to how the user positions the gears as the ctrs and therefor PCD are not fixed.

Edited By JasonB on 10/10/2021 13:21:12