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Colchester Triumph 7.5" (Round Head) Lathe

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James Cliff06/04/2019 13:17:21
2 forum posts


I have a Colchester Triumph 7.5" Mk1 (Round Head) which is used every day in our machine shop. It's an old girl, but it is priceless to our business and is still used just as much as the other lathes.

Today however it's given up. We can still select all gears on top (two levers) but the main high / low gear lever on the front is the issue. In low box all is fine. In high box when running the spindle slowly moves in its correct direction. But it doesn't pick speed up and I can stop it by hand.

I've removed the head off the gearbox and noticed that the high speed driving gear (drives spindle tube through selector) is spinning freely on the shaft. See attached pictures and video.


I can’t find any tech drawings for this lathe. There is no grub screw, roll pin or bolt to hold the gear onto the shaft so I can only assume its fixed to the shaft through splines. And subsequently the splines have worn off? However, it went from working fine to not in the space of 5 minutes with no grinding or typical gearbox failure sounds.

Does anyone have any experience with these lathes, and would be kind enough to advise?


Chris Evans 606/04/2019 18:09:01
1625 forum posts

Have you looked on .uk (might have that wrong but should get you there)

Michael Gilligan06/04/2019 18:40:18
15427 forum posts
665 photos
Posted by Chris Evans 6 on 06/04/2019 18:09:01:

Have you looked on .uk (might have that wrong but should get you there)


This should be a good 'landing page' for you, James : **LINK**

Happy browsing ...


Clive Foster06/04/2019 18:48:40
2131 forum posts
73 photos

Unfortunately thats a manual I don't have. Never managed to find a downloadble copy either.

Re-mastered (?) copy of the manual and parts list on E-Bay right now for £ 7.50. Seller is fazerblazer (Premier Machine tools). Gotta be worth it.

I've bought from him before, albeit tooling not a book, and found him a decent man to deal with so would be confident that quality is OK.


Phil Whitley06/04/2019 19:25:49
1142 forum posts
142 photos

first thing is that the gear lever is in the wrong position, it should face upwards, and move from the 10 oclock position to the 2 oclock position, there is a pin through the second shaft which I think keys the gear to the shaft. I have a pdf manual for a roundhead student, which is essentially the same gearbox, I will see if I cam PM it to you.


Clive Foster06/04/2019 19:39:30
2131 forum posts
73 photos


Are there two different headstock gear set-ups for the roundhead Student? The Student manual I have shows a very different gear arrangement to that Triumph.


Phil Whitley06/04/2019 19:56:23
1142 forum posts
142 photos

Clive, as far as I can see the layout in the parts list for the mk1.5 student is the same, as is the lever layout on the outside of the box. The ratios might be different, but I think it is essentially the same as mine. There appears to be a pin 5649 that anchors the gear to the second shaft, and also a double key, and a single key on the spindle which anchor the gears to the spindle. I would suggest that the failure of either would cause the sudden onset symptoms he has. At any rate, it looks like the second shaft at least will need to be removed. I have a pdf student manual, but it is resisting my attempts to send it!


peak407/04/2019 02:01:04
1075 forum posts
124 photos

Might This Link be of any use gentlemen.


Phil Whitley07/04/2019 12:28:12
1142 forum posts
142 photos

Yes it might! that one is different to the student, but it does show a key which holds the gear in question to the second shaft, which may well be the cause of the failure! edit, just looked and I have a copy of that manual as well, but it is 11meg so it would be best for the op to download it himself!!


Edited By Phil Whitley on 07/04/2019 12:32:05

James Cliff08/04/2019 07:44:38
2 forum posts

Thanks for the replies all.

There is practically no room either side of the gear to get a pin though, so I think your right. The shaft will need to come out.

Phil do you have a copy of the manual? Or a link to download?


larry phelan 108/04/2019 15:27:18
647 forum posts
22 photos

Since there is no grub screw or no roll pin,it has to be a key [this would also account for the sudden death ]

Sad to say,looks like the shaft will have to come out,but then,it has had a good innings !

Do let us know what you find.

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