Colchester Bantam lathe lead screw

A while back, I bought a Colchester Bantam metric lathe - the chap had changed the lead screw and lower sadle in order to have the thread dial lacking on the metric lathe.

He assured me that the lead screw was identical on the metric and imperial versions of the lathe, I was skeptical but thinking about it why would Colchester make two different threads at extra cost and surely he would have checked by measuring them first.

Now looking in the manual I see the Eagle and Condor have 4tpi and 6mm threads respectively.

I was wondering if somebody could be kind enough to measure the thread on the Eagle and presumably somebody else (unless you have both) the Condor to clear this up?

I dread the answer that they are in fact different (head ache tablets on the ready...

Why don't you measure the length of 10 pitches of the thread? Then it will be obvious what leadscrew you have.

its in storage at the moment but if both Eagle and Condor have 4tpi I still would not know I might wrongly assume its incorrect expecting mine should be 6mm. I'll try to measure it as soon as I can get to the lathe anyway.

Edited By Pence on 25/06/2019 19:44:57

Pence.

My imperial Bantam leadscrew is 4tpi.

Keith.

okay thanks that's very useful. Now all I need is somebody with a metric bantam to measure the leadscrew to see if its 4tpi too or disaster 6mm!

Edited By Pence on 26/06/2019 11:37:58

I would expect a metric lathe to have a metric leadscrew. The guy I bought my 7 x 12 Chinese lathe from bought it from Warco and took it home in his car. He had pre-ordered a metric version, but by an oversight, Warco only had an imperial one. They gave him a metric leadscrew and nut. I have them, still greased and wrapped up.

You obviously don't have a Myford!

Or inversely, some Chinese-made imperial lathes.

the thing is if he did measure them for 6mm pitch there would be 4 in 24mm as oppose to 4 in 25.4mm a noticeable difference surely nobody could make such a mistake?

I have a 1984 Mk2 Bantam 800. It is a metric machine. According to the owners maunual that came with it, it has a 6mm leadscrew, whilst the imperial version has a 4tpi leadscrew.

The Hawk, Eagle and Condor models were earlier. Looking at the info on Lathes.com it isn't clear whether they had identical leadscrews and just relied on different gearboxes or whether they had metric and imperial leadscrews.

I think it's fairly reasonable to say that the lathe had a metric screw and now it has an imperial one. Why would Colchester go to the trouble of making both types of screw then fit the imperial one to a metric lathe and have to rely on translation gears for metric threading?

A couple of things the seller said don't ring true. If he claimed that the metric and imperial screws were identical why would he find it necessary to change the screw and the apron? Either he didn't realise until he bought them that the threading dial and half nuts he got were useless to work on the metric screw or (more likely) he knew full well what he was doing and just wanted to produce inch threads with the dial but didn't want to spoil the sale by letting on it was not the standard item for the machine.

Luckily for you it's not a total disaster and cutting metric threads with the screw you have is only a matter of getting hold of the requisite gears for the end cluster. What you need will depend on what machine you actually have.

yes looking at the boxfthreadp program using the 127/120 gears to compensate the box will still produce all the threads without different gears than calculated in the handbook except modular ones. But they probably will never be used anyway. But I think this would certainly put somebody off if I decided to sell so I think I'm stuck with it unless I sell as spares and repair for much less than I paid.

Nevertheless I came across this thead where this user rohart claims "My Colchester Bantam runs a 6mm leadscrew, and contrary to all the factory specs it is fitted with an indicator. " very puzzling maybe the 6mm thread will drive the dial gear after looking in the spare parts manual.

I will soon get to my Bantam and measure that thread that assume is 4tpi - surely 4 threads in 24mm is easy to distinguish from 4tpi!

Thread dials will work with metric leadscrews, you just need the correct drive gears for them.