you need a copy of Ivan Law's book on Gears and Gear cutting.

Ketan will provide, or even your local library book

Hi Calum,

To me it seems using a vertial slide is the best way if you don't have access to a milling machine. Any model engineers near you that could assist you? A horizontal milling machine would do those gears nicely. Module 2.5 are bigger than any gears I have cut, so I wonder if the lathe setup you describe would be rigid enough for that size of gear teeth.

Thor

Callum,.

I don't know your machine, and so, risk raining, / pouring on your parade.

The hobby lathes that i have come,across, admittedly few, all seem to use gears with Modules of 1, 1.25, or 1.5.

2.5 Mod is pretty coarse. Your 45T gear would have an OD of 117.5 mm ! Has it?

In Imperial, terms Myford 7 Series use 20 DP gears, whereas other machines use gears as coarse as 14DP.

In this case a 45T gear would be 3.351" ( 85.271 mm ) OD The 127T Myford Imperial to Metric translation gear has an OD of 6.45" (163.83 mm) The equivalent 45T gear would be 2.35" (59.69 mm ) OD

So your 2.5 Mod gears are pretty coarse!

Before trying to cut any gears, buy and study Ivan Law's "Gears and Gear Cutting"

It is No 17 in the Workshop {Practice Series.

It will ,be a help to you, and possibly prevent some costly mistakes.

May i suggest that you check your gears, before investing in cutters?

Take a gear and measure the OD in mm.

Count the teeth.

then use the formula

Module = OD / (Tooth Count +2 )

A 1.5 Mod 45Tgear would have an OD of 70.5 mm

A 1.25 Mod 45T gear would have an OD of 58.75 mm

My ETR BL12-24 which is 150 mm centre height (So not a small machine by hobby standards ) uses 1.25 Mod change gears, so the 120/127 compound has an OD of is 158.75 mm.

The 40T gears driving and driven to the gearbox are 52.5 mm OD.

The pinion engaging the rack to traverse the saddle is 13T, 1.5 Mod so is 22.5 mm OD,

Mini lathes use 1 Mod changegears, so the 80T gears have an OD of 82 mm

HTH

Howard

Just reread your thread on installing the lathe and the gears do look coarse.

Maybe this is why they stop at 45T

But you will still find Ivan Law's book a tremendous help. It gave me the data and courage to start cutting gears, not that I am good at it.

To cut gears in the lathe, you will need to find a way to mount a Dividing Head or Rotary table , with the axis horizontal so that the blank can be indexed.

Hopefully, the tooth counts that you need will be available with the division plates, (Not all are, sadly )

Howard

Howard

Posted by Bazyle 11/04/2022 19:02:00

If D is driving E you don't need the specific values – just something to give
you a 1:2 ratio. Since you have a 36 you could make an 18 to give you that with less
effort unless they are needed elsewhere.

——————————————————-

The problem with doing this is if you would wish to keep the original
splined hub ,the od of the splined hub on this machine is 34mm,
the OD of an 18 tooth  gear would be 50mm and the the root diameter
is 38.5mm which means that there would be only 2.2mm from the bottom
of the tooth to the od of the spline.
The maximum that the gear could be profile shifted is about .9 then the
tip diameter becomes 54.5mm and the root diameter would be 43.1mm
and would be about 4.6 mm from the root of the tooth to the spline ,the
tooth height is about 5.5 mm.
This would almost certainly need to be a generated gear ,solving these
sort of problems are not always that easy.

You can see the sort of problems that this can cause here with this
gear to fit on this type of lathe at 1.0 mod and 40 tooth even when
it is cut oversize there is not much left below the tooth roots.
As when it is used the lathe spindle is revolving below 2 rpm
so it is transmitting little power and is safe to use.

John

Edited By John P on 11/04/2022 21:53:17

No need to look for ER collet chucks with 5 MT shanks.

Get a 5 -3 MT sleeve and use the available 3 MT tooling.

My lathe, and many others like it came with a 5 – 3 MT sleeve.

Howard