Another ML7 question. Bull gear locking screw

This topic has 18 replies, 13 voices, and was last updated 18 March 2026 at 01:35 by drnewcomb.

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12 March 2026 at 20:45 #840934
drnewcomb
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@drnewcomb
To engage and disengage the bull gear from the pullies on a Myford ML7 there is a small recess hex (Allen) screw on the bull gear that needs to be tightened or loosened. I can’t get a standard hex key to fit in the space allowed. I think I need to cut off about 5/8″ from a key to get it to fit. The problem is that without disassembling the spindle it’s hard to know exactly what size key to modify.

Can someone tell me what size hex key fits that screw? Or is there some secret way to turn that screw with an unmodified hex key? Thanks.
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12 March 2026 at 21:07 #840936
Charles Lamont
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@charleslamont71117
According to the manual, it is a 2BA, so that will have a 5/32″ socket. A 4mm key will almost certainly also fit.
12 March 2026 at 21:12 #840938
howardb
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@howardb
I have an old ML7 – the arrangement for disengaging the bull gear from the pulley is a PITA.

I seem to remember that the socket capscrew is 2BA and the hex key AF size for that screw is 5/32″ – 0.15625″
13 March 2026 at 00:22 #840949
drnewcomb
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@drnewcomb
Yes. I recall the manual saying it was a 2BA screw but I’ve never seen that notation in the US (where the lathe and I are located). We just use fractional inches or mm for metric. I’ve got a shoebox of odd hex keys. I think I can find what I need. Thanks again.
13 March 2026 at 01:20 #840950
howardb
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@howardb
Glad to help – hope it goes ok for you.
13 March 2026 at 07:58 #840955
DC31k
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@dc31k
On 13 March 2026 at 00:22 drnewcomb Said:

…I’ve never seen that notation in the US (where the lathe and I are located).

Is that not the beauty of the internet? Everything is just a search term away. If you touch anything old and British, you will encounter BA fasteners, so having a working knowledge of them is important.

You acquiring that knowledge will balance someone over here learning about UN series threads and the world will be a better place.

Start looking for a 46t chnge gear for the machine in case you need to cut US pipe threads.
13 March 2026 at 10:57 #840980
drnewcomb
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@drnewcomb
Unfortunately, a Google search for “2BA hex key” leads to a .324” (~5/16”) bolt head. I have yet to locate a table of British Association hex (Allen) keys on the Internet.

I will keep an eye open for the 46t change gear. I’ll go back and double check that one of the two 45 gears I inventoried might not have been a 46. (Some of the stamping are very faint.)

One advantage of our Myford is that it came with a pretty complete kit. Three and four jaw chucks, drive plate, live and dead centers, collets, milling attachment and some tools I only recently identified with this group’s kind assistance. (i.e. collet extractor)

Speaking of chucks, since they screw on and off, how does one avoid unscrewing the chuck when running the lathe in reverse?
13 March 2026 at 11:09 #840981
Andrew Crow
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@andrewcrow91475
You don’t need to look for BA Allen keys, they always have the normal fraction inch sizes ie 1/8, 5/32 etc.

As for running in reverse on a Myford, not to be recommended for heavy cuts. You will get away with light cuts or using smaller left hand taps and dies as after conventional machining the chucks are usually on pretty tight.

Avoid running in reverse as much as possible.

Andy.
13 March 2026 at 12:34 #840998
noel shelley
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@noelshelley55608
The BA socket head is an ordinary imperial allen key size – in this case 5/32″. As for a table, I would think that any good, old machinery handbook would give them. The Workshop Practice Series, No 42, Metalworkers Data Book, gives them. Noel.
13 March 2026 at 13:36 #841012
Michael Gilligan
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@michaelgilligan61133
Please just get a high quality 5/32” Allen key, preferably made by Unbrako

https://unbrako.com

Yes, they are better than most

MichaelG.

.

https://unbrako.com/wrenches
13 March 2026 at 13:45 #841014
Nigel Graham 2
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@nigelgraham2
You will need shorten the business end of the key.

I’ve just measured mine – finding I’d cut it to about 5/16″ inside length, leaving just enough straight for the depth of the socket.
13 March 2026 at 15:54 #841028
Nick Hughes
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@nickhughes97026
The key originally supplied with my fathers new ML7 in 1955, was not just a shortened allen key, the bend angle was less than the standard 90Deg (from memory around an 80 ish Deg bend), to give more clearance between the key and the Bull Gear face.
13 March 2026 at 18:07 #841040
Howard Lewis
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@howardlewis46836
To avoid the risk of the chuck unscrewing, avoid running in reverse.

To cut left hand threads, use the tumbler reverse, so that the saddle moves away from the headstock.

For parting of, mount the parting tool inverted in a rear toolpost. This makes life easier, since the swarf tends to fall clear of the groove, reducing the risk of clog ups / dig ins.

Howard
13 March 2026 at 18:12 #841042
Dave Halford
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@davehalford22513
My lathe just has a spring loaded pin. You get a fat washer to pull on and twist
13 March 2026 at 19:56 #841057
Kevan Shaw
Participant
@kevanshaw32462
I swapped mine for a hex head bolt 2BA. now any spanner or even a crescent gets on easily and quickly. You can get access by removinf bearing caps
13 March 2026 at 21:29 #841068
howardb
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@howardb
On 13 March 2026 at 19:56 Kevan Shaw Said:

I swapped mine for a hex head bolt 2BA. now any spanner or even a crescent gets on easily and quickly. You can get access by removinf bearing caps

Good idea – I had thought about doing that in the past when it was my only lathe – why Myford didn’t do it is a mystery.
14 March 2026 at 12:15 #841081
drnewcomb
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@drnewcomb
Thanks for all the help. I noticed the ML7 book is available in the US from Amazon for US$14 with free shipping. One will be in my next Amazon order.
14 March 2026 at 13:50 #841100
cedric 1
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@cedric
On 13 March 2026 at 21:29 howardb Said:

On 13 March 2026 at 19:56 Kevan Shaw Said:

I swapped mine for a hex head bolt 2BA. now any spanner or even a crescent gets on easily and quickly. You can get access by removinf bearing caps

Good idea – I had thought about doing that in the past when it was my only lathe – why Myford didn’t do it is a mystery.

Possibly because the leverage provided by a common ring spanner on such a tiny screw would result in snapped screw or rounded off hexagons over time.
18 March 2026 at 01:35 #841490
drnewcomb
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@drnewcomb
Done
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