Chronos gear making DVD

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It's crap, in fact it's worse than crap it's crap, crap.
Not worth the plastic it's written on.
In no order,
[1] Out of focus.
[2] Crap.
[3] Using a home made mill from Taig and Sherline parts that hast the tensile strength of pre stressed licorice so everything moves but not all in the general direction.
[4] Crap.
[5] Boring.
[6] Crap.
[7] Uses the wrong value of Pi in all the calculations so every calculation is out.
[8] Crap.
[9] Only works with TPI pitch hobs and never mentions DP or Mod so no way to calculate for these even if he'd got Pi right in the first place
[10] Every shot of a finished gear is that bad you can't see whether it's correct, good bad or crap - suspect crap.
[11] Covers two types of hobbing, one with annular hob teeth where you take a cut and it cuts one rack tooth and a couple of part teeth, you then index round and repeat and the action of the part teeth leaves a tooth with 3 flats on. Many use this method and it's passable for some work.
Second method is with a helical hob, or in his case a worm as he's on TPI and using a pre gashed blank he free hobs it and relies on the hob to drive the blank.
Due to backlash, movement etc this leaves a rough finish to the teeth.
[12] In the latter free hobbing method he tilts the blank and not the hob so it will cut a wider tooth space than standard due to the helical angle of the hob. No reason to do this as his Bassets Allsorts machine can tilt.
[13] He's clueless.
[14] Crap.
Reply to
John Stevenson
Hmm, not your favourite DVD then John? or is it that Gert is still giving you earache about all that extra flooring you had delivered? Never mind think of all the machines you can store on 360 sq m.
Reply to
Don't hold back John
Is this from that Jose Rodriguez chap, whom I seem to recall you've mentioned before in a similar vein?
Reply to
Peter Neill
Yes that's the one. Don't know about any of his others as I only bought the gear hobbing one and at about 30 quid I'd like to stop others wasting their money - unless they want to buy mine if it hasn't been used instead of the RS one as a coaster.............
Reply to
John Stevenson
"Awfully complicated set of clanging clattering and clicking rotors cams belts and wheels" possibly doesn't have the same marketing attraction? On the other hand the alternatives might have been _really_ complicated.
Reply to
Peter Parry
IIRC those vids were part of the owners efforts to sell the gear making machine on Ebay.
Great work on his part.
Don't recall what the machine sold for, though.
Cheers Trevor Jones
Reply to
Trevor Jones
Try the following links to see one mans tutorial on gear cutting. Yours in the workshop John
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Reply to
Interesting that 1 minute 40 into the first video he mentions making a quick change gearbox for his CNC lathe ????????????
I thought the whole idea was on a CNC to do away with the gearbox ?
Besides this though watch these 6 video's because they show exactly the same as Jose Rodriguez does but in more detail and better.
Reply to
John Stevenson
Yes, but that chap is quite wrong about how he thinks he's getting the right profile (that he doesn't get). With this kind of hob (it is not a spiral hob) he would have to make different passes to get the profile. He thinks he gets it be feeding in in small steps. Actually, he could feed the whole depth of cut and then will have to make several passes. These passed would look like this: Make first cut. Rotate (to keep with his example) by a fraction of the angle between teeth -say 2°- *and* lower the Z-axis "a bit" (math required) and make a pass. Only this will give him a involute profile.
Reply to
Nick Mueller
Now strictly speaking are those hobs? A conventional hob with a helical track generates the gear by rotating the hob and blank together. That form of 'hob' is really a rotating form of Sunderland Gear Planer.
Reply to
Andrew Mawson
True it's not an involute but has a series of steps on it, the larger the number of teeth the more the steps are due to interference with the cutting teeth above.
In all fairness this type of gear is passable for the machinery it's done on as even using a true spiral hob and gearing the blank will not achieve a true involute due to machinery restrictions, flex, etc.
This is obvious in the video where he takes small 5 thou cuts. Nick says cut in one pass but if you look and listen to the spindle those 5 thou passes are slowing it down. This is bound to have an effect on finish and the true shape.
Moving the cutter up and down whilst rotating the blank will only serve to cut a gear with more steps. A true involute can only be produced by hobbing if it's generated, i.e. constant movement.
. Regards,
John Stevenson L Stevenson [ Engineers ]
Reply to
John Stevenson

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