Zyto Gear Comparison Advice ?

Hey guys, Would like to hear your thoughts on this comparrison. We have here the 40 tooth Zyto gear on the left and a 45 tooth replacement for one of the gears I'm missing. The bore seems accurate and the thickness too. Both are a match. The keyway also is fine. However the tooth profile, sorry if that's not the correct term, differ somewhat. The new gear is slightly broader and thicker at the tip and has a slight chamfer. I'm ok with the chamfer as I know its to prevent teeth from chipping however while the new gear does have curvature on the tooth face its very slight and much more flat in comparrison to the Zyto gear. I fear the pressure point will be different and that will lead to premature wear on one or both gears. Advice on my best course of action is appreciated.

Thanks

Paul

**LINK**

http://www.homemetalshopclub.org/news/10/pressure_angle_anamation.html

I suspect that one is 14.5° and t'other 20°

MichaelG.

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I suggest you image them on a flat-bed scanner for a better representation than the camera gives.

Edited By Michael Gilligan on 12/01/2019 18:27:04

Thanks for the advice Michael,

The scan is sharper and the tooth profile is far clearer. Hope this helps.

Regards.

The zyto is almost certainly 14 1/2 degree pressure angle.

All HBM gears on their advertised lists are, I think, 20 degree pressure angle. How well they might mesh for a low power, slow speed application, I don’t know. Likely be noisy but do the job? A cutter, to make the proper gear would be about twenty quid.

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It does indeed, and I'm happy with my original estimate.

... I would not mix them.

MichaelG.

What DP are they? If they are 20DP you could probably use Myford change-wheels.

Brian my gears are 20 DP or so i have been told but the HBM are, or i thought were, for the Myford and are also 20 DP its the Pressure Angle I think thats the issue. I've raised a return and will post it back tomorrow. I need to find another supplier of the right gear for the Zyto now but its likely i will have to make it myself as I doubt they are manufactured by anyone. I will talk with a few of the engineering suppliers like Myford/RDG, Chronos, Arc etc next week to see if anyone can supply them. I had hoped the ML4 gears would be suitable but it seems not. Almost but not quite.Also I know im being fussy bit id like a gear, if possiable, without the recess in the face just so it matches my existing gears.

Right now though I cant really attempt to make them myself. Ive no dividing head or plates and lack a lot of the equipment to do so. I have an ML7 in the garage but its not fully kitted out yet and the yto dosn't even have a countershaft or motor so is currently inoperable. Im hoping someone will sort the countershaft issue for me at some point in time, preferabally by the end of the month but Im loosing faith slowly. Ive found a really clear photo of the Zyto countershaft last night so am now considering what it will take to replicate it. IE Fabricate it myself. I have most of the tools i need for fabrication just need to collect the materials.

Im sure you understand the amount of work involved in that though. The frame, Buses, pins,pulleys,collars,cone pulley,grub screws, taps, welding> it would be fun but also given my present circumstances money and time i could use elsewhere. I still need to buy a motor for instance but i might just rig something up with some Plumbers Bearings. Im lacking pulleys as well and how to do keyways etc . Ive a few ideas but again tools!

Edited By Paul Kennedy on 12/01/2019 22:18:32

Edited By Paul Kennedy on 12/01/2019 22:25:09

Hi, Myford series 7 change wheels are 20 DP, 14.5 pressure angle **LINK**. I bought some years ago from the original Myford company for my late fathers RandA lathe, which is in the same band as Zyto etc. and they fit spot on to the original RandA wheels, just had to drill a little hole for the drive pin.

Regards Nick.

Edited By Nicholas Farr on 13/01/2019 07:43:22

Hi Nic, Thanks for the link but that looks suspiciously like an exact match to the HBM gear I'm returning. The Zyto Gear tooth are much more elongated and pointy in comparison.

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It should not match the HBM gear, Paul ... Unfortunately, the illustration is poor, but the description is clear.

MichaelG.

I'll order one beginning of the week to see. Thanks for the link. Sorry if I came across as insolent.

UPDATE !!!

Hey guys the HBM was supposed to fit the Myford and I was worried that the Myford Gear also was similar albeit the photo was maybe not clear as Michael pointed out. So I went up to my garage and sought out an original Myford Gear from the ML7 and it appears to be the same pressure angle as the HBM and also the Myford photo that Nicholas kindly linked me to. The Zyto gear is different.

The Myford Gear is on the left. It appears obvious to me but the Zyto teeth seem longer and sharper. The base width of the teeth appear to be the same but the zyto tooth point narrows quicker than the Myford. Perhaps a pressure angle of 10 degrees ? There's very little in it and im fairly sure the myford gear would work but Im curious now how i can confirm my suspicions about the zyto tooth pressure angle ?

I've since put the gear teeth under x60 magnification and the tooth point on the Zyto gear is most definately narrower than that of the Myford. All other dimensions such as bore diameter, thickness and keyway depth and breadth appear the same.

Edited By Paul Kennedy on 13/01/2019 14:07:36

Edited By Paul Kennedy on 13/01/2019 14:17:49

... Thanks for the update, Paul

[he said, bewildered]

MichaelG.

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I posted just before you showed the photo.

.... I will try to respond this evening, if no-one beats me to it.

Edited By Michael Gilligan on 13/01/2019 14:12:33

Some x10 Photos.

Myford gear is on the bottom.

Edited By Paul Kennedy on 13/01/2019 15:53:59

I vaguely recall that some gears on a Myford are 20 degree and only the change gears 14.5 degree.

Yes! I am not going insane (yet), however it seems all ML7 gears are 14.5:

Posted by John Stevenson on 24/02/2012 22:40:23:

Jim,

I can't comment on the rack or it's mating pinion as I don't have any details on these but could get them if I wanted.

However as regards the screw cuting gears they are all 14 1/2 degrees PA with the exception of the first 4 on the Super 7 and like family.

The first 4 being spindle gear, the two tumblers and the gear the tumbler drives. These are 20 degrees PA.

Outboard of this they are all 14.5 degrees.

The ML7 are all 14.5 including back gear but the backgear on the S7's is special and requires a special hob as the tooth form is modified.

John S.

May be worth reading Bubble's posting near the bottom of that thread on the longevity of mis-matched change gears:

www.model-engineer.co.uk/forums/postings.asp?th=65580#replybox

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No problem with that ... provided that you don't care what the new 'Average PA' might be when they've bedded-in, and that [until then] the varying velocity gives results within your tolerances.

MichaelG.

Edited By Michael Gilligan on 13/01/2019 18:03:01

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Very useful photos, Paul

Something certainly doesn't look right ...

This may be worth a look: **LINK**

https://khkgears.net/new/gear_knowledge/gear_technical_reference/involute_gear_profile.html

MichaelG.

Thanks Neil, I've not done the necessary calculations as yet but I'm leaning towards a 20 degree pressure angle looking on the website the tooth profile matches my teeth perfectly. I will fire up autocad at some point to confirm this however..

You might enjoy this: **LINK**

https://geargenerator.com/

MichaelG.