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Myford Quick Change Gearbox Disassembly

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Chris Taylor 722/02/2019 23:10:21
2 forum posts

Hi All. I have been lucky enough, although through unfortunate circumstances, to acquire my late Uncles Myford Super 7 with quick change gearbox.

The lathe was very well used and covered in swarf and had been in a shed at the end of his garden for sometime. In order for me to move it, I had to basically dismantle it into one person manageable blocks and figured that it would be worth stripping it down to component parts and then stripping all the chipped paint of and repaint and do a complete rebuild on it. I bought all the manuals but am stuck dismantling the gearbox so would appreciate any help.

I have the gear box dismantled down to what on a motorbike box I would call the selector drum. On this rides the selector handle and on the opposite side of the handle is a gear which is is on a shaft dowel pinned to the selector arm. The gear sits proud into a hollow on the bottom of the drum which allows it freedom to move up and down the drum as the selector is moved. I am sure many of you know this.

However the hollow in the drum does not run full length so I cannot see an way of withdrawing the drum without removing the gear on the selector arm but that requires trying to remove a 1/8'' dowel pin on a moving arm. Am I missing something? How do you remove a dowel pin on an arm you cannot hold still? Have looked over and over at the parts list but cannot see any solution and the Myford store could not give much info.

Next, any recommendations for stripping old paint? I was thinking of tapeing the machined surfaces of the iron parts ie the bed and getting them sandblasted to avoid any risk of water rusting those critical parts as paint stripper would involve water rinse. Equally, as the surface finish of the bare metal other than the ways is not critical I could tape the ways with aluminium tape and use paint stripper. Just paranoid bout protecting the machined surfaces.

Thanking you all for any info.

Hopper23/02/2019 08:38:21
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3304 forum posts
65 photos

Sounds like you've fallen for the common beginner mistake of "strip it right down to the last part and rebuild and repaint it".

Don't.

Most stuff on most of these old lathes does not need total rebuilding. Just a bit of cleaning and adjusting. Unless you are an experienced machine tool rebuilder you are likely to cause more problems than you solve by pulling every last piece apart. You can use masking tape to cover the selector arm while your repaint the gear box.

And don't strip the paint.

Myford used a lot of "bog" putty to fill casting holes and then laid on lots of thick undercoat to get a nice smooth finish to their rough castings. You don't really want to strip all that off. The best approach is to scrape and wire brush and sandpaper the existing paint down to a good surface then paint over top of it. Remember, this is a piece of industrial equipment, not a Brough Superior petrol tank.

Brian Wood23/02/2019 09:29:18
1831 forum posts
36 photos

Wise words Hopper

Brian

JohnF23/02/2019 10:36:54
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747 forum posts
82 photos

Chris, try this link it has a manual of the QC gearbox

**LINK**

If it does not work message me and i will copy mine for you

John

ega23/02/2019 11:37:34
1103 forum posts
90 photos
Posted by Hopper on 23/02/2019 08:38:21:

... Myford used a lot of "bog" putty to fill casting holes ...

Standard practice for many, I believe, yet when I stripped and refinished my 1960s Super Seven I don't recall any filler being present.

I agree about the gearbox: it is easy to make a mistake in the order of the gears when re-assembling. As to the OP's query, the only guide I needed was the Myford manual.

Scrumpy23/02/2019 11:57:34
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147 forum posts

I fully agree with Hopper on this my next door neighbor went along the same root as you are going before he stripped the lathe down it was a workable machine only needed some adjustments but after he’d done his strip clean and paint and removed so much filler the castings were ruff it was a dogs dinner of a lathe his answer sell it and start again without stripping it

Chris Taylor 723/02/2019 12:05:00
2 forum posts

Gentlemen, thank you for your prompt replies and advice.

Hopper, yes you are probably right regarding “beginner mistake” but it seemed the obvious next step after breaking it down to manageable blocks which basically meant the bed was bare, to strip and repaint but your comments are noted and a good clean will probably suffice for most of it and I have no desire to dismantle the carriage!

John F, thank you for your post and offer-I am already in possesion of both the lathe and the gearbox manuals and parts list which I purchased promptly from Myford along with appropriate oils. It shows the dowel pin on the end of the selector arm.

Now if I had a lathe, maybe I could turn up a collar to go over the bushing with a long grub screw and could press out the dowel pin. Hmm. I think having already bent a pin chisel, Mr Hopper’s suggestion is looking like wise words to be followed.

Thank you again.

Chris

KWIL23/02/2019 12:10:06
3058 forum posts
56 photos

A good clean and general flatting of the existing paint, followed by a primer followed by selective filling, followed by repaint if you must. This will give a good overall finish, removing the chips which started you out in the repaint trip.

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