By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale May 23

Myford 33t and 34t gears for metric threads

All Topics | Latest Posts

Search for:  in Thread Title in  
Mike Donnerstag27/01/2019 09:44:24
avatar
48 forum posts
4 photos

I’ve just read the article in MEW August 2018 on metric overlays for the Myford gearbox. This uses 33 and 34 tooth gears to replace the existing gear, to enable most of the common metric thread pitches.

Can anyone tell me how this compares with using the metric conversion set, as it certainly seems simpler and cheaper.

Can anyone tell me where I can source the 33t and 34t gears?

Many thanks, Mike

norm norton27/01/2019 09:57:38
90 forum posts
5 photos

Mike

A google search for Myford 33T, Myford 34T comes up with lots of links.

Read this past thread for more information as well

https://www.model-engineer.co.uk/forums/postings.asp?th=125630

Norm

Edited to add that the John Stevenson mentioned in that thread is now no longer with us. But the gears are now made by others.

Edited By norm norton on 27/01/2019 09:58:32

Edited By norm norton on 27/01/2019 10:00:52

Thor27/01/2019 10:13:47
1070 forum posts
28 photos

Hi Mike,

It seems the 33T is available from RDG.

Thor

Brian Wood27/01/2019 10:20:33
1895 forum posts
37 photos

Mike,

The results are almost equivalent to the values you would get using the expensive conversion set, in practice you will see no sensibly measurable errors. However, the metric and BA pitches you can get with just these two gears is rather limited in extent.

Regards

Brian

Mike Donnerstag27/01/2019 10:44:30
avatar
48 forum posts
4 photos

That's great Thor - I'll buy a 33T from RDG.

Does anyone know where I can get the 34T?

Mike

ega27/01/2019 10:53:47
1159 forum posts
95 photos
Posted by Mike Donnerstag 1 on 27/01/2019 10:44:30:

That's great Thor - I'll buy a 33T from RDG.

Does anyone know where I can get the 34T?

Mike

Widely advertised on eBay.

Brian Wood's book Gearing of Lathes for Screwcutting is a good read.

peak427/01/2019 10:59:37
avatar
743 forum posts
65 photos

Can't see any on ebay at the moment.
Try HPC Gears, who offer 34t 20dp in metal and Delrin.
OK would need modifying to fit, but probably easier than making from scratch.

Bill

Roderick Jenkins27/01/2019 11:08:12
avatar
1736 forum posts
442 photos

Mike,

Just for interest I calculated the actual pitch achieved using the official Myford metric conversion set for the gear box. The actual figures are in the right hand column:

myford gbox metric.jpg

A similar calculation for the 33/34 option is shown below

metric approximations.jpg

So, the official set is an order of magnitude more accurate but for practical purposes the difference is negligible. For the finer metric threads some additional gears to the 33 and 34 are useful. I have the metric conversion set, it came withe my S/H lathe but when I needed to cut a 16mm x 2 thread last week I broke out the 34T gear. Much more convenient.

HTH,

Rod

Rod Renshaw27/01/2019 11:11:25
41 forum posts

Hi

I bought both 33 and 34T gears from the present Myford brand owner last year at one of the shows. I don't have any information about current stocks.

Rod

Mike Crossfield27/01/2019 11:13:53
186 forum posts
10 photos

Take care if buying gears from HPC. Most of their standard gears are 20 degree pressure angle, whereas Myford change gears are 14.5 degree pressure angle.

Roderick Jenkins27/01/2019 11:15:09
avatar
1736 forum posts
442 photos
Posted by peak4 on 27/01/2019 10:59:37:

Can't see any on ebay at the moment.
Try HPC Gears, who offer 34t 20dp in metal and Delrin.
OK would need modifying to fit, but probably easier than making from scratch.

Bill

We need to be a little careful here, Myford change gears are 14.5 degrees pressure angle.

Rod

ega27/01/2019 11:21:29
1159 forum posts
95 photos

Roderick Jenkins:

Thanks for the comparison; I regularly consult your stud gear table.

Neil Wyatt27/01/2019 23:05:07
avatar
Moderator
15980 forum posts
674 photos
73 articles
Posted by Roderick Jenkins on 27/01/2019 11:08:12:

So, the official set is an order of magnitude more accurate but for practical purposes the difference is negligible. For the finer metric threads some additional gears to the 33 and 34 are useful. I have the metric conversion set, it came withe my S/H lathe but when I needed to cut a 16mm x 2 thread last week I broke out the 34T gear. Much more convenient.

Some of those Myford errors are pretty huge, approaching the wavelength of light...

And one of the other lot is almost six microns out!

Lean on the lathe while you are screwcutting and it may introduce a bigger error

Neil

Peter Spink27/01/2019 23:59:42
avatar
56 forum posts
14 photos

Hmm, was thinking of going this route but 33T and 34T changewheels not on the Myford or RDG site anymore.

At £263 for the metric conversion kit I wonder why 🤔

Thor28/01/2019 05:12:04
1070 forum posts
28 photos
Posted by Peter Spink on 27/01/2019 23:59:42:

Hmm, was thinking of going this route but 33T and 34T changewheels not on the Myford or RDG site anymore.

At £263 for the metric conversion kit I wonder why 🤔

33t.jpg

The 33T seems to be available.

Thor

Edited By Thor on 28/01/2019 05:12:40

ian j28/01/2019 09:08:16
avatar
264 forum posts
228 photos

When this subject came up in the past(10/2016) I bought a pair of gears from the late John Stevenson for £25 inclusive of UK postage. I'm sure John would have produced a "stick" of gears and parted them off to width. Maybe worth an email to Adam to see if he can lay his hands on any.

Mike Donnerstag28/01/2019 09:23:25
avatar
48 forum posts
4 photos

Hi Ian,

Is Adam related to John? How can I contact him?

Many thanks,

Mike

Roderick Jenkins28/01/2019 09:30:50
avatar
1736 forum posts
442 photos

I don't think 33 and 34 tooth gears were ever part of the old Myford inventory. I got mine from the late, great John Stevenson. Shortly before his sad demise Sir John mentioned on this forum that he was making a batch of gears - I wonder if these were for RGD Myford? If so it seems that they are running out. Perhaps there is an opportunity for a little entrepreneurship here.

Rod

Lambton28/01/2019 09:32:19
avatar
674 forum posts
2 photos

Mike,

No lathe with an imperial lead screw can cut a truly accurate metric thread unless a 127 tooth gear is used. Despite this fact both the official Myford conversion set and the 33, 34 toothed input gear method are capable of producing metric threads accurate enough for all practical purposes.

The Myford conversion kit is both very expensive, is inconvenient and time-consuming to set up and then take down. The 33, 34 method only takes a few moment to set up.

I cannot understand why anyone would find the need to screw cut BA threads as a good set of taps and dies together with a tailstock die holder will do a very good and accurate job. In almost 60 years of model (and full size ) engineering I have never known anyone screw cut a BA thread.

Eric

Roderick Jenkins28/01/2019 09:37:47
avatar
1736 forum posts
442 photos
Posted by Mike Donnerstag 1 on 28/01/2019 09:23:25:

Hi Ian,

Is Adam related to John? How can I contact him?

Many thanks,

Mike

Adam runs the homeworkshop.org.uk website. A request on there for 33 and 34 tooth Myford change gears might do the trick.

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Support Our Partners
Eccentric July 5 2018
ChesterUK
Warco
TRANSWAVE Converters
Ausee.com.au
Eccentric Engineering
Sarik
Allendale Electronics
emcomachinetools
Subscription Offer

Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest