Any suggested gear cutting sets?

[methuselah1]

Pre-war is 14.5 degs. That figure helped with the mathematics. During the war, the angle changed as this allowed pinions with fewer teeth to be hobbed.

Some companies never left the original standard (Myford Lathes in England is an example Deckel in Germany did the same) in order to preserve interchangeability between the pre and post war machinery that they made. This is well documented, so if it's old machine tools you're working on, a glance at www.lathes.co.uk's historical archive will probably have the info you need.

If any part of the same mechanism has a rack, the teeth become straight sided, forming an angle of 29 or 40 degrees inclusive, which can be spotted by eye and bevel protactor. Otherwise I'd be looking at optical means using a shadowgraph and templates.

 

[Ken I]

Personally I always generate my own profiles - much easier to then get over wire dimensions - to verify your assumptions of the gear you are measuring or intending to make.
Attached my tutorial on making your own gears and hobbs as well as "cheating" profiles and pitch circles.
Also gives you a far better handle on interference and understanding on what you are trying to accomplish.

Regards, Ken

 

[terryd]

Pre-war is 14.5 degs. That figure helped with the mathematics. During the war, the angle changed as this allowed pinions with fewer teeth to be hobbed.

Some companies never left the original standard (Myford Lathes in England is an example Deckel in Germany did the same) in order to preserve interchangeability between the pre and post war machinery that they made. This is well documented, so if it's old machine tools you're working on, a glance at www.lathes.co.uk's historical archive will probably have the info you need.

If any part of the same mechanism has a rack, the teeth become straight sided, forming an angle of 29 or 40 degrees inclusive, which can be spotted by eye and bevel protactor. Otherwise I'd be looking at optical means using a shadowgraph and templates.

Hi

We used to use shadowgraph equipment in both the toolroom and inspection dpartment I worked in and very useful piece of kit it was. Nowdays however I use my home scanner for most of this type of investigation, scanning in monochrome (B&W) format. Useful for threads especially if you can cut down the centre to get the thread profile flat on the scanner table. Of course it is necessary to thoroughly degrease the component and include some kind of a scale. I use a metric rule which has markings at 0.5 mm.

Best regards,

TerryD

 

[SmithDoor]

The problem I run into is everything I cut a gear I do not have cutter.
Today I made 1" diameter holder for single point cutter and hand grind the profile.
Saves money on cutters.

Dave

 

[deeferdog]

Ken,
Thanks for that missive on gear cutting, I don't pretend to understand all of it but I have filed it for future reference. I quite enjoy cutting gears. Cheers, Peter.

 

[David Shealey]

------------------------snipped---------------------
If I'm doing 3d printing, I usually design entirely in mm, just because that's how the printer is set up, and a lot of the screws and nuts that I use with 3d prints are metric. But "designing in metric" may include converting some inch-based measurements to mm if I need to accommodate something inch-based in the design.
------------------------

I do a lot of 3D printing, but the printer has no idea which standard is used. I create what I want in CAD, either Imperial or Metric, then create the .stl file, and send it to the printer. Parts then print correctly, no matter the measurement standard used on the CAD part. The part to .stl conversion is done based on settings in the CAD software, I am using SolidWorks, .stl output is set to metric, but it has been the same in other CAD systems I have used. Check your CAD system output settings to see if that is the way yours works. Makes things easier if you do not have to design in metric when an imperial part is desired. I use both often.

 

[awake]

I do a lot of 3D printing, but the printer has no idea which standard is used. I create what I want in CAD, either Imperial or Metric, then create the .stl file, and send it to the printer. Parts then print correctly, no matter the measurement standard used on the CAD part. The part to .stl conversion is done based on settings in the CAD software, I am using SolidWorks, .stl output is set to metric, but it has been the same in other CAD systems I have used. Check your CAD system output settings to see if that is the way yours works. Makes things easier if you do not have to design in metric when an imperial part is desired. I use both often.

David, you caught me in an over-simplification.

Note that .stl files include no information on the units of measurement - if the .stl file says that this particular triangle is 1 unit long, it doesn't know or care if that unit is mm or in or cubits. But there is a strong convention to treat the units as mm - and most (all?) CAD programs follow this convention when generating .stl files. IOW, there is nothing in the .stl standard that says that a 1" cube could not be output as (1,1,1), but in fact, your CAD program will output it as (25.4, 25.4, 25.4). Well, okay, .stl works with triangles, so this is not how it is output, but you get the idea. Likewise, you can instruct your slicer to treat the units of the .stl file as inches, but as far as I know, every slicer will assume that the units are mm unless you specifically tell it otherwise.

When the slicer produces gcode, there IS an indication of the unit of measurement - one of the first things the slicer should include in the gcode is either G20 (set units to inches) or G21 (set units to mm). From then on, all movements in the gcode must be expressed in the corresponding unit. (Technically, you could switch mid-stream - start in G21, do some movements using measurements in mm, then issue a G20 and issue movements in inches - but I don't know of any slicer that will produce such code.) Once again, to the best of my knowledge, every slicer in common usage will output movements in mm.

 

[Brian Rupnow]

As a rule of thumb---If you make models to the scale of those originally designed by Elmer Verbourg, then #32 DP are just about perfect. if you build models slightly larger as I do, then 24 DP seems to work very well.---Brian Rupnow

 

[David Shealey]

David, you caught me in an over-simplification.

Note that .stl files include no information on the units of measurement - if the .stl file says that this particular triangle is 1 unit long, it doesn't know or care if that unit is mm or in or cubits. But there is a strong convention to treat the units as mm - and most (all?) CAD programs follow this convention when generating .stl files. IOW, there is nothing in the .stl standard that says that a 1" cube could not be output as (1,1,1), but in fact, your CAD program will output it as (25.4, 25.4, 25.4). Well, okay, .stl works with triangles, so this is not how it is output, but you get the idea. Likewise, you can instruct your slicer to treat the units of the .stl file as inches, but as far as I know, every slicer will assume that the units are mm unless you specifically tell it otherwise.

When the slicer produces gcode, there IS an indication of the unit of measurement - one of the first things the slicer should include in the gcode is either G20 (set units to inches) or G21 (set units to mm). From then on, all movements in the gcode must be expressed in the corresponding unit. (Technically, you could switch mid-stream - start in G21, do some movements using measurements in mm, then issue a G20 and issue movements in inches - but I don't know of any slicer that will produce such code.) Once again, to the best of my knowledge, every slicer in common usage will output movements in mm.

I was speaking of your statement about designing in metric and converting inch dimensions. If your CAD application is set to output .stl as metric, you can design in any measurement system, no need to design in metric. I design things in both imperial and metric, but the CAD system does the conversion automatically and puts out the .stl to print properly on the printer that is expecting metric. If I always did imperial, I could switch both the CAD system and my printer to be imperial, but that would not really gain anything.

 

[awake]

I was speaking of your statement about designing in metric and converting inch dimensions. If your CAD application is set to output .stl as metric, you can design in any measurement system, no need to design in metric. I design things in both imperial and metric, but the CAD system does the conversion automatically and puts out the .stl to print properly on the printer that is expecting metric. If I always did imperial, I could switch both the CAD system and my printer to be imperial, but that would not really gain anything.

Gotcha, and of course you are correct. But the lead screws on the Z-axis of my printer are metric, and so are the belts that drive the X and Y ... and the display shows locations and allows manual movement of axes in metric ... and the layer heights chosen by the slicer are expressed in metric ... and the gcode produced by the slicer uses metric ... so I tend to think of the printer as metric, and tend to design that way. As an example, if I'm going to print using .25mm layer heights, I design bevels in .25mm increments - either a .5mm bevel, or a .75mm or 1mm bevel, or so on. Sure, if I told it to make a .025" bevel, it would convert that to the equivalent .635mm ... but when it comes time to print, it will have to fudge that measurement to suit the .25mm layer height.

It probably doesn't actually make any discernable difference - just the habit I have gotten into. Works for me, but as always, others' mileage may vary ...

 

[timo_gross]

The problem I run into is everything I cut a gear I do not have cutter.
Today I made 1" diameter holder for single point cutter and hand grind the profile.
Saves money on cutters.

Dave

I had the other problem that I could not find any gear cutters, but found a 2nd hand hob. I carried the hob back home, then tried to figure out what I bought.
And found this video made by someone.


Took ages until I had my first results.

I had to make a 2nd spindle aka 4th axis, a swivel to adjust the vertical milling spindle angle relative to the milling table, a tail stock. Tail stock helps a lot with the cutting. The program is so simple that I usually just program it on the fly manually. The cutter on the foto is metric M1, so a 24 teeth gear has a 26mm diameter.

I saw another video what I would call "pseudo hobbing" by robertt4522. "pseudo, because it does not rotate the gear continuous" I guess it works totally fine for a lot of applications in models
Same chanel shows lot of DIY gear cutting especially making tools for it.

Hope to see someone building a hobbing machine soon

Greetings Timo

 

[SmithDoor]

Looks great
I wonder how that work. It works great
Dave




I had the other problem that I could not find any gear cutters, but found a 2nd hand hob. I carried the hob back home, then tried to figure out what I bought.
And found this video made by someone.


Took ages until I had my first results.

View attachment 124744
I had to make a 2nd spindle aka 4th axis, a swivel to adjust the vertical milling spindle angle relative to the milling table, a tail stock. Tail stock helps a lot with the cutting. The program is so simple that I usually just program it on the fly manually. The cutter on the foto is metric M1, so a 24 teeth gear has a 26mm diameter.

View attachment 124745
I saw another video what I would call "pseudo hobbing" by robertt4522. "pseudo, because it does not rotate the gear continuous" I guess it works totally fine for a lot of applications in models
Same chanel shows lot of DIY gear cutting especially making tools for it.

Hope to see someone building a hobbing machine soon

Greetings Timo

 

[SmithDoor]

It looks like it straight cut not a DP thread.
I like size mill it is abot the same size mind.

Dave

I had the other problem that I could not find any gear cutters, but found a 2nd hand hob. I carried the hob back home, then tried to figure out what I bought.
And found this video made by someone.


Took ages until I had my first results.

View attachment 124744
I had to make a 2nd spindle aka 4th axis, a swivel to adjust the vertical milling spindle angle relative to the milling table, a tail stock. Tail stock helps a lot with the cutting. The program is so simple that I usually just program it on the fly manually. The cutter on the foto is metric M1, so a 24 teeth gear has a 26mm diameter.

View attachment 124745
I saw another video what I would call "pseudo hobbing" by robertt4522. "pseudo, because it does not rotate the gear continuous" I guess it works totally fine for a lot of applications in models
Same chanel shows lot of DIY gear cutting especially making tools for it.

Hope to see someone building a hobbing machine soon

Greetings Timo

I had the other problem that I could not find any gear cutters, but found a 2nd hand hob. I carried the hob back home, then tried to figure out what I bought.
And found this video made by someone.


Took ages until I had my first results.

View attachment 124744
I had to make a 2nd spindle aka 4th axis, a swivel to adjust the vertical milling spindle angle relative to the milling table, a tail stock. Tail stock helps a lot with the cutting. The program is so simple that I usually just program it on the fly manually. The cutter on the foto is metric M1, so a 24 teeth gear has a 26mm diameter.

View attachment 124745
I saw another video what I would call "pseudo hobbing" by robertt4522. "pseudo, because it does not rotate the gear continuous" I guess it works totally fine for a lot of applications in models
Same chanel shows lot of DIY gear cutting especially making tools for it.

Hope to see someone building a hobbing machine soon

Greetings Timo

 

[timo_gross]

Dave

It looks like it straight cut not a DP thread.
I like size mill it is abot the same size mind.

There are two different methods mentioned.

a) LSCAD is using a comercial metric ( imperial stuff works same) hob. The gear is rotating during the cut, for a spur gear it rotates usually one tooth per one rotation of the cutter. ( multistart hobs, or helical gears add new aspects ) So a 24 tooth blank is rotating 1/24 of the full circle for each revolution of the cutter.
Advantages are: ony one tool for all tooth counts (per DP) is required, once established helical gears can be cut. Wormgears to some extend possible.
Making a straight gear becomes a matter of 30min to 90 min dependent on toothcount and material.
Disadvantage: Heavy modifications on the machine. To rotate the gear in sync with the cutter. Aligning everything is the next challenge. To provide the low cutting speed for the cutter required to invest in a gear motor. Not very self explaining how it works. Was research. Making helical gears is still challenging.
Cutter is expensive, I guess about as much as a complete set of disc cutters. I own two hobs M1 and M0.5. I guess if I want to cut more than M1.25 I will run into all sorts of equipment related issues.

b) Robertt2544 is using a straight groove tool that he made all by himself. The gear is static for each cut and then rotated one tooth spacing after each cut. The workflow is the same as using a disc cutter. The advantages of this are, only one tool for all tooth counts (per DP) is required, tool is relatively simple to shape. Downside the gear will not be superperfect. ( If that matters is a question of required tolerances )

Greetings Timo