Drummond vs Myford change gears

I've never come across proper Drummond change gears until recently and they are absolutely massive compared to the Myford gears I have been using over the last 10 years

About 50% thicker than myford ones they look more like the gears out of a gearbox from a car and have a very solid run-all-day industrial look about them

The small Drummond lathes (apart fron the Roundbed) were military spec industrial lathes . The Myford ML 1,2,3,4, series were all hobby machines built to a price. The Myford M Type being the exception because it was a Drummond design. The M Type is built like a brick s/h compared to an ML7 and the cost of manufacturing the M was what prompted the introduction of the more more versatile but built to a price ML7.

I've never come across proper Drummond change gears until recently and they are absolutely massive compared to the Myford gears I have been using over the last 10 years

Ady, in 10 years you've never seen genuine drummond gears? Unusual to buy and own a drummond with no standard gears? There are usually a few in tow.

Totally agree with Lee's comments. The Myford/drummond M type has 3 faults, 1 and 2 the spindle and tailstock barrel are too small, the spindle bore is too small and both have 1 morse tapers and 3 the rack feed with the single gear is operates the "wrong way". (CR*P) The last one is easy to remedy but 1 and 2 requires some serious engineering. Other than that it beats the ml7 hands down, but of course that is not reflected in second hand lathe prices

When I was looking for changewheels for the Smart & Brown model A lathe, I bought a single Myford one to see if they were similar, as they are relatively easy to get hold of. Unfortunately, a 127 tooth Myford gear would have been much too large in diameter to fit. The S&B gears are very fine pitch, visually similar compared to a Myford gear as the Myford compares to the Drummond. I have replaced all of the S&B change wheels with MOD1 metric pitch wheels as they are easy to get hold of, and also because I got hold of a 125-127 MOD1 gear cheaply which was for some Chinese lathe.

Changewheels do not have much power going through them, so there is no need for them to be huge.

Drummond gear teeth are that big because if they were any smaller they'd lose teeth. They come from an era before advances in cast iron metallurgy made it as versatile as it is today.

I'm not saying they couldn't do it for higher-end machines etc but I think that the £5 lathe budget stretched to more iron but not more technology. It's common to see busted teeth on lathes of this era, these days not so much.

Something to remember is that if your compounding gears you can mix them up . I have a 16t gear that is smaller than the smallest Drummond 20t , I match it to a gear of the same dp that is compounded with a Drummond gear, great for a fine feed.

Are they not different pressure angles ? I thought Drummond was 14.5 degrees and Myford 20.

regards Martin

Some more details on pressure angles:

https://www.sciencedirect.com/topics/engineering/pressure-angle

Looks like 20 degrees is more 'modern' and 14.5 is more relegated to replacement parts.

Indeed - be careful not to mix Drummond and Myford change-wheels. Basically, they won't!

I don't pretend to unsertdnad the trigonometry of gear design but do know from various reputable sources as well as simple logic that even if the DPs match, gears of different pressure-angles will not mesh properly.

"The Myford ML 1,2,3,4, series were all hobby machines built to a price."

The ML1,2,3,4 must have been military spec too. Mine has an RAF "War Department" plate on it!

I would never claim that the ML1,2,3,4 were high quality lathes, mind you.

I think the Ministry of Supply would buy anything in those desperate days.

According to the myford Ltd website all their lathes are 14.5 degrees Pa.

.

You might get something from this 2017 thread, Nigel : **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=125474

… it includes some good animations.

MichaelG.

I believe that the Drummond gears are 14DP whereas the Myford 7 series ones are 20DP.

As Lee stated above you can compound gears of different DP on the same shafts and indeed take advantage of the reduced diameter of higher DP gears if the banjo is of limited size.

The above is shown clearly in Martin Cleeve's book 'Screwcutting in the lathe' on page 44, where he used a 30 DP 127T 'translation' gear for cutting a metric thread on his imperial lathe.

HTH

Dave

Edited By David Davies 8 on 03/01/2022 09:37:52

Myford say that they are all 14.5 degree across their range.  Would make sense for stockholding, plus it locks their customers into Myford spares when most commercial gears are made to 20 degrees.  Helps to explain why their accessories are so ridiculously expensive.

Edited By John Haine on 03/01/2022 10:31:57

I would think that most machines made in the ‘40/‘50s (and likely all machines pre-WWII?) would have used 14 1/2 PA. Little point in Myford having a mix of otherwise interchangeable gears on their inventory/spares list. One could imagine the mixtures of gears fitted by the un-knowing hobbyists.

My lathe make, that was produced in three guises from the 1940s, are all 14 1/2 degree PA, even though the DP was changed during the times of production (until the early ‘70s).