Colchester Bantam Lathe

[Nigel McBurney 1Participant @nigelmcburney1]

Colchester users may find this useful,some years ago I bought an all metric Student lathe,one feature which i had never seen before was a dial fitted on the saddle handwheel ,one rotation of the dial was exactly 25mm and it was accurate and useful. It was also fitted with variable speed and was short bed,it was a pain to use so I then bought a master 2500, which was imperial with dual dials,out of curiosity I checked the saddle travel against one turn of the saddle wheel, it moved 25mm so I came to the conclusion that they must be fitted with metric module racks so I took the dial off the student and it fitted my master, so I now had an imperial lathe with metric reading dial for saddle travel.I then sold the student minus dial, Most of the time I work imperial on the cross and topslide and metric on the saddle and it is so useful despite the imp/ metric mix. I then looked at my all metric triumph 2000 the rack was module so I went along to G & m tools and found a suitable metric dial which could be converted to fit the triumph hand wheel. I have Colchester bed stops but they are not reliable as they do slip and never use them now that I have saddle dials. One thing on my ex naval triumph is a 2ft long engraved sign stating "this machine is fitted with a metric threaded leadscrew" I have often wondered if someone made an expensive cock up confusing 0.2inch imperial with 5 mm metric pitch leadscrew. Going back to the student ,the mechanical vari speed and the phase converter was a useless combination ,I asked a machine tool dealer if he had experience with variable speeds ,his comment avoid if possible any variable speed powered by 3 phase conveters.

[MuzzerParticipant @muzzer]

My Bantam has metric threads and dials on the cross and top slides and the tailstock but is otherwise an imperial machine ie has imperial leadscrew and gearbox. It seems this was quite common and is most likely something to do with the number of machines that were supplied to schools and colleges. I'm ashamed to say I've owned this machine for nearly 20 years now and it was only recently that somebody pointed this out to me….

BTW, there are various Bantam / Colchester owners active on the homeworkshop.org.uk forum. It's good to check in there from time to time.

Murray

[Marcel JolinonParticipant @marceljolinon76204]

Mr Trevor Wright,

Did you post dimensions for the carriage stop? if so whereabouts.

As these things are about as rare as hens teeth I am making one. Currently producing drawings.

Some dimensions would be helpful, Overall length, diameter, and the bolt size. I am planning on making the thing metric although it would appear that the bed on my metric machine is imperial. By my reckoning the V should be 3/4" having filed out a template.

If I have got it right the picture should be my initial design done with CREO

[Trevor WrightParticipant @trevorwright62541]

Marcel,

Started to dimension the stop but the angles were too difficult to measure accurately, was waiting for someone to ask…..looks like I will have to now lol.

Give me a couple of days to dismantle and measure.

Trevor

[Marcel JolinonParticipant @marceljolinon76204]

Trevor,

I have made a template of the lathe bed and taken dimensions from that. The measurements were taken in mm as being a metric machine I assumed that the bed dimensions would be metric. Not apparently so as my conversions bring it out at 3/4" on the slope. I am afraid that my drawing did not go to a jpg very well, the angles appear to be 90 deg and 135 deg. which would make sense from a manufacturers point of view along with 3/4". These are the key dimensions for the stop.

The main problem areas for me are hoe wide the is the brass clamping piece, as I guess this to be critical, too narrow and it is likely to slip, and the diameter of the bolt. I was working on 5mm but the one in your photo appears to be about 5/16" (8mm) and quite coarse (Whitworth?)

[Marcel JolinonParticipant @marceljolinon76204]

Try as I might I cant get a decent copy of my drawing to upload. Any suggestions?

[Trevor WrightParticipant @trevorwright62541]

Marcel,

Have added dimensions to photos of the Stop-block, the perspective of the pictures is confusing but the faces the dimensions are attached to are true.

Edited By Trevor Wright on 19/10/2014 16:04:43

[Trevor WrightParticipant @trevorwright62541]

There are more images on my album, no doubt there are dimensions missing and someone will inform me, but post and I will supply the missing information.

Have added this as I cannot add text below a picture.

Trevor

[Neil WyattModerator @neilwyatt]

> Have added this as I cannot add text below a picture.

Click on picture and hit right arrow, should work.

Neil

[Trevor WrightParticipant @trevorwright62541]

Thanks Neil…..too late to edit now though.

trevor

[Marcel JolinonParticipant @marceljolinon76204]

Thank you Trevor.

I guessed the diameter to be about 2" I will now do some working drawings and make one from that. If all goes OK I can post the drawings. Unless there is a way to allow for others to download files.

Marcel

[David Barnes 9Participant @davidbarnes9]

Hi everyone,

I'm probably posting this in the wrong place, but go easy as I am a newbie!

I have a Colchester Bantam, and I what to do some general machining and would like to use the auto-feed for a traverse cut.

But the layshaft is going to fast, which is fine for thread cutting.

The gear train I have is as follows: 120B 127B 35B 30B .

What gear combo would I need to slow the layshaft down to a sensible speed.

Sorry but I am just learning all about machine turning hence the ignorance!

Thanks

Dave

[mtrehy mtrehyParticipant @mtrehymtrehy33968]

On my imperial machine it's 21/120, 100/60 which I think gives 0.001" per revolution.

On yours changing the 30 to 60 (assuming this is gear Y) should reduce the feed 50%

[MuzzerParticipant @muzzer]

I think most of the std feeds assume 35t on the top (spindle) position and 30t on the bottom (gearbox) position. The intermediate gear (120t) is just an idler and doesn't affect the overall ratio. I leave those in position but at one time I changed the 30t to a 60t to half the feed rates.

If you select range A and gear 6 on the gearbox, you end up with something like 1"' per rev, which is pretty much what you need? Mine has an imperial leadscrew.

Do you have the plate showing the feeds, ranges and gears – it's riveted to the front of the machine.

Murray

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