SOS SOS First timer using gear hob.

[gus]

SOS SOS SOS.

Need expert advice,how to align gear hob and gear blank. I have a total of 15 gears to hob. Set up foto attached.

 

[10K Pete]

Did you make that divider and tailstock? Good looking unit!

Pete

 

[Swifty]

Have posted a picture in my Howell V4 build of alignment method.

Paul.

 

[gus]

Did you make that divider and tailstock? Good looking unit!

Pete

Hi Pete,

Idea came from Harold Hall's book------------Dividing. I took some short cuts and used material from scrap bin and off cuts. A friend did the computer dividing for 16 21 32 holes. This method is simpler than using Indexing Plate and Dividing Head.

 

[gbritnell]

Hi Gus,
I'm sure there's many different ways to align the cutter with the centerline of the stock but the way I do it is to mike the tip of the cutter. I know there is a radius but I try to get as close to the tip as possible, above the tip radius. I know what the center distance of my dividing head is so I set up a stack of gauge blocks, (1-2-3 blocks with adjustable parallels) to the center height minus half the measured width of the cutter. I then bring the cutter down to where it just touches the gauge stack.
gbritnell

 

[Brian Rupnow]

I am going to jump in and put my ignorance on display here. That set-up looks exactly the same as my set-ups using a single width cutter. (I have a complete set of eight 24 dp cutters.) What does a "hob" do that my single width cutters don't do?-----Brian

 

[Cogsy]

What does a "hob" do that my single width cutters don't do?-----Brian

It's just the opposite Brian - what your cutter does that the hob doesn't. The home made hob has angled 'teeth' but no involute profile, so the first cut produces a 'v' at the centre line of the workpiece and 2 smaller 'v's each side of the centreline (but on a slight angle). As the blank is rotated for each pass, eventually all 5 teeth of the hob have cut slightly different angles for each tooth and approximated an involute tooth shape.

I guess the major advantage of a hob is that it can be made at home relatively easily and you only require 1 hob per DP or Mod, not a full set. Plus they're dirt cheap as you make them out of virtually any size drill rod.

 

[gbritnell]

Here's the way I set up to cut the gears for my transmission with a home made hob.
gbritnell
http://www.homemodelenginemachinist.com/showthread.php?t=9707&page=19

 

[gus]

Dear ALL. Please accept my sincere thanks for the expert advice received.
OK . Gear Hob aligned with gear blank. Good lesson learnt from first timer using Paul Swift's hob. I got greedy and took deep cuts after the first two teeth and job ruined. Gear blank can be re-used for the 21 t gear. Module 0.8 and 1.0 gears were easier to cut. 48 Pitch Gears are so mini. Looks like cutting all 14 gears will take 1 week plus.

 

[Brian Rupnow]

Cogsy---thank you for the answer.---Brian

 

[gus]

This is the first time Gus use gear hob and there are cutting speed and spindle speed to contend with. At long last I get some real good looking 48 Pitch tooth done. I moved to 2000 rpm spindle speed and a single past. Tooth depth and height is out by some thous.but at least I have some good looking gear teeth to look at. 500 rpm wasn't good for hobbing brass gears.
Its weekend fiiiiiishiiiing again.

 

[Swifty]

Hi Gus, I'm glad that your progressing with your gear cutting, although I would have thought that 2000rpm was way too fast. But so long as the end result is OK is what counts.

Paul.

 

[gus]

Hi Gus, I'm glad that your progressing with your gear cutting, although I would have thought that 2000rpm was way too fast. But so long as the end result is OK is what counts.

Paul.

Hi Paul.

2000 rpm was out of desperation and daredevil act. Please advice best speed.My worry is hob may premature wear. Please advise best speed.

 

[Swifty]

I can't recall the speed I used, but it was probably about 700rpm. If the teeth wear, just move the cutter a couple of pitches and use fresh teeth.

Paul.

 

[johnny1320]

Is there any info on making hobs?

 

[crankshafter]

Jonny1320
Have a look :

Is there any info on making jobs?

Its in German but I think Google translater is your friend
Regards
CS

 

[johnny1320]

Jonny1320
Have a look :


Its in German but I think Google translater is your friend
Regards
CS

Thanks for the info

 

[johnny1320]

Found this on centering thanks to crankshafter

 

[techonehundred]

There is an older youtube series on making gear hobs. Here is a link to the first video.

[ame="https://www.youtube.com/watch?v=nMS2un-kbg0"]https://www.youtube.com/watch?v=nMS2un-kbg0[/ame]

 

[gus]

Practice makes perfection. After practicing and ruining 6 gears, I am getting somewhere. My mini mill is now blind with cross feed dial missing. Have to resort to feeler gages and cross slide stops to get tooth depth of 45 thou. There is not space to put in a DIY DRO. I am 2 gear nearer to milling all 10 48 Pitch Gears for the Howell V-2 Engine.