Myford Backplate tapered thread size

[Adrian SherlockParticipant @adriansherlock43605]

I inherited many years ago a small myford lathe

I tried to get some information on it from Myford themselves but they had no record on this Myford D1 No. D3571 saying it must be pre war

The problem I am having is that the thread on the chuck backplate is totally shot and no longer runs true

The taper that it screws onto starts at about 1" up to just under 1 1/16" at the top of the taper and is 12TPI

The diameter of the 3 jaw chuck is 4 3/16, the backplate fits into a 3" recess and is secured by 3 bolts

I have seen some backplates on the internet but they do not have any bolt holes so cannot see how they would attach

Threads on the internet appear to be listed as 1" or 1 1/16", mine tapers between the two so cannot figure out which is correct

Any help would be appreciated

Cheers Adrian

(P.S. Cannot figure out how to attach photos that are on my PC)

[Adrian SherlockParticipant @adriansherlock43605]

[Adrian SherlockParticipant @adriansherlock43605]

Just measured the diameter of the shoulder at the top of the thread and it measures 1.12"

So think that I have answered my own question and it is actually a 1 1/8 that I need, that seems to be google'ing as the Myford standard.

[Grindstone CowboyParticipant @grindstonecowboy]

How to post photos

[Brian HParticipant @brianh50089]

This may help;

**LINK**

Brian

[GeorgineerParticipant @georgineer]

Adrian,

A lot of what you need to know was covered recently in this thread:

https://www.model-engineer.co.uk/forums/postings.asp?th=171047

George B.

[John HaineParticipant @johnhaine32865]

What do you mean by "tapered"? The standard Myford thread is 1 1/8" 12 tpi. There should be a 1 1/8" plain "shoulder" near the main body of the spindle, normally called the "register" which makes the backplate run true (if the latter is accurately machined). If your nose actually tapers in diameter you have a problem! It would be seriously worn.

[Adrian SherlockParticipant @adriansherlock43605]

Posted by John Haine on 14/04/2021 16:53:24:

What do you mean by "tapered"? The standard Myford thread is 1 1/8" 12 tpi. There should be a 1 1/8" plain "shoulder" near the main body of the spindle, normally called the "register" which makes the backplate run true (if the latter is accurately machined). If your nose actually tapers in diameter you have a problem! It would be seriously worn.

Definitely tapers at the end on the 'spindle', the backplate thread also tapers from 1.2" for the shoulder then down to 1.03"

Mates got a Super 7, time to remove his Chuck I think

[HopperParticipant @hopper]

The tapers don't sound anything like Myford chucks. Something weird is going on.

Before you can get any kind of meaningful advice, you really need to identify from lathes.co.uk what model of Myford you have. And posting some pics of the tapered spindle and threads would be most helpful.

[Howard LewisParticipant @howardlewis46836]

Any chance of pics?

Are you certain that it is a Myford? Is the name cast into the bed anywhere?

If the thread is 1.125 x 12 tpi with a 1.250 register the Mandrel sounds like a Myford 7 Series.

The 7 Series has mounting foot under both Headstock and Tail;stock

The last Myford ML 3 and 4 had a 1.125 thread (See lathes UK ) But they were cantilever beds, with no mounting under the Tailstock.

Howard

[old martParticipant @oldmart]

Here's a picture of a myford thread, it is not tapered.

**LINK**

[Lee RogersParticipant @leerogers95060]

I'm leaning towards the thought that you have an ML in the series 2–3 or 4. Notorious for the variety of meaningless foundry numbers cast into the bed . Add to that a few decades of user mods and upgrades and you have a puzzle on your hands. There is no such lathe as a Myford D1. A picture or two would help .

[Adrian SherlockParticipant @adriansherlock43605]

Here is a picture of my lathe

I will get a photo of the tapered spindle hopefully tomorrow

[HopperParticipant @hopper]

Looks like one of the ML1 to ML4 series. Maybe a late ML4 with the V belts but has the earlier side-plate tailstock. Plethora of info on lathes.co.uk on the subtle variations **LINK**.

Apparently no serial number records survive today. D1 is some kind of casting identification code used by the factory/foundry and not indicative of the lathe model nomenclature.

But the ML1-4 over the years increased spindle thread size from 7/8" to 1-1/8". All were parallel threads with a parallel plain register collar behind the thread.

They are a useful old lathe capable of good work with a bit of care and understanding.

There are quite a few ML1-4 owners on the forum who will be able to provide more detail.

 

Edited By Hopper on 16/04/2021 03:40:34

[Lee RogersParticipant @leerogers95060]

Yes I'll go with the ML 4 as a best guess so far . The identifying detail is in the headstock and leadscrew attachments and the tailstock. The foundry patern numbers are as Hopper says a constant blind alley when identifying the 1234 series of lathes. Don't expect it to take off huge chunks with an insert tool and you'll find it does a tidy job when set up. The thing with these very light lathes is that everything takes twice as long to do , I recon that means they're twice the fun.

[Adrian SherlockParticipant @adriansherlock43605]

Just took the spindle out, no step from the shoulder, shoulder is 1 1/8" 12tpi

Think it maybe worn (as suggested) and not a chamfer as the bottom thread are rounded and the top almost square

Might be enough thread a shoulder to still be usable, old backplate was completely shot, couple of threads left only

Assuming a standard 1 1/8" backplate will be what is required

[HopperParticipant @hopper]

If you mean a standard ML7 backplate, no it is not quite the same. The ML7 register collar is slightly larger diameter than the thread, maybe about 1-1/4" or so. Tony at lathes.co.uk does sell a range of backplates, he may have one suitable for the ML4 spindle.

The thread in your pic looks well used but still useable. The chuck is located by the register collar and the face on the shoulder behind it, so a sloppy thread is not the end of the world.

[old martParticipant @oldmart]

The spindle thread shows a lot of wear, but with a new backplate, the joint will be satisfactory. The front of the backplate will have to be trued up by skimming in situ.

[Howard LewisParticipant @howardlewis46836]

It looks like a ML3 or 4.

A Ml1 or 2 would have a centre height of m3.125" where the 3 and 4 are 3.5"

The ML3 is 15" centre distance, where the 4 is 24" (Confirm with Lathes UK website )

Yours appears to have the optional Tumbler Reverse and the side hinged cover for the Changewheels.

The Leadscrew is 8 tpi, but the Leadscrews for the Cross and Topslide are 12 tpi. The dials for these have 80 divisions, which means that each division is not 0.001" but 0.00104"

Chagewheels are driven by driving collars (secured to the Mandrel and Leadscrew by 1/4 BSF grub or capscrews.

(Virtrually all threads, except possibly the gib adjusters, will be BSW or BSF )

To transfer the drive between the collars and gears, or to compound gears, there is a 3/32" pin in a blind hole in each part.

If you are short of Changewjheels, those from the 7 Series will fit. Dimensionally they are the same, but have a keyway instead of the 3/32 hole.

So you will need to drill through one original gear to use as a template. Fit both gears onto one of the changewheel studs, and drill though into the 7 Series gear, keeping away from the keyway..

With additional gears, you can set up a fine feed, 20:60/20:65/20:60. This will give a fine feed for turning of 0.0000427" / rev. You may need to fettle the inside of the Mandrel end of the Banjo to enable the first stud to move far enough to set the correct mesh for the gears.

My advice is to set the mesh, starting from the Leadscxrew, and working your way to the Mandrel. Just run a piece of paper about 0.003" thick between the gears.

HTH

Howard

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