# SOS SOS First timer using gear hob.



## gus (Sep 16, 2015)

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.


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## 10K Pete (Sep 16, 2015)

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

Pete


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## Swifty (Sep 16, 2015)

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

Paul.


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## gus (Sep 16, 2015)

10K Pete said:


> 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.


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## gbritnell (Sep 16, 2015)

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


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## Brian Rupnow (Sep 16, 2015)

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


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## Cogsy (Sep 16, 2015)

Brian Rupnow said:


> 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.


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## gbritnell (Sep 16, 2015)

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


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## gus (Sep 17, 2015)

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.


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## Brian Rupnow (Sep 17, 2015)

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


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## gus (Sep 18, 2015)

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.


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## Swifty (Sep 18, 2015)

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.


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## gus (Sep 18, 2015)

Swifty said:


> 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.


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## Swifty (Sep 18, 2015)

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.


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## johnny1320 (Sep 21, 2015)

Is there any info on making hobs?


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## crankshafter (Sep 21, 2015)

Jonny1320
Have a look : 



johnnyhttp://www.metallmodellbau.de/GEAR-CUTTING.phpttp://www.metallmodellbau.de/GEAR-CUTTING.php320 said:


> Is there any info on making jobs?


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


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## johnny1320 (Sep 21, 2015)

crankshafter said:


> Jonny1320
> Have a look :
> 
> 
> ...



Thanks for the info


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## johnny1320 (Sep 21, 2015)

Found this on centering thanks to crankshafter


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## techonehundred (Sep 21, 2015)

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]


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## gus (Sep 23, 2015)

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.


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## gus (Sep 28, 2015)

Alrighty. Got over the goofy stretch of hobbing 48 Pitch Gears. 

One reject to redo and the tail shaft 16T gear to cut and I am done with thw timing gears for Howell V-2 Engine. Paul's Gear Hob stood up to all unfair treatment. The gear case will be mind boggling. The centre distance between gears will be done using a tram. Gear mesh gap will be judged by eye ball. Gear hobbing using direct indexing is best and fast over the conventional method using Indexing plate and DH. With direct indexing there no need to count holes.  Direct index plate rules out indexing error which may produce 1/2 tooth .


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## Swifty (Sep 28, 2015)

Looks like a great set of gears Gus, I'm glad that the hob lasted the distance.

Paul.


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## gus (Sep 28, 2015)

Gear Hob made by a Master Tool&Due Maker will last forever. Model 0.5 and 0.6 from CTC is about to arrive. I was about to give up on poor skills at gear hobbing. Its obvious I was treating the hob like a Involute gear cutter and getting bad results. Taking my sweet time to finish up some remnant work. The V-2 seems to have an endless list.


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## gus (Sep 29, 2015)

Gear Hob packed shop and the 16T pinion gear is short of the 45 thou tooth height.  No worry . Hob is usable if I move up or down 2 digits to use the other cutting teeth. The tooth profile of pinion resembled E.T. Fingers. The worned cutting tooths on the hob can be seen.


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