Cowells Lathe question

[Jo]

Can anybody help me?

I have just purchased a new "house lathe" in the shape of an early Cowells lathe. In amongst the hoards of goodies it came with was a set of thread cutting gears which I have the thread chart for and a 40 and 16 tooth gear plus an extra idler.



Does anyone know what extra threads these let you cut?

Jo

[goldstar31]

Unless you get a better answer, I'd suggest that you get a copy of Martin Cleeve's Screwcutting in the Lathe.

He quotes Professor Dennis Chaddock that 25 change gears CAN be set to give 750, 000 different pitches- but only if they are not tied into a gearbox.
If you add a transposing gear- well, who knows?

Good Luck

N

[rodwilson]

A Smith's book "Cowells 90 Lathe" shows three set-ups using the 40 tooth on the leadscrew and gives 50.8, 33.87 and 29.63 TPI. No mention of a 16T. PM me if you want a scan.

Was your lathe one of those made in Norwich? Norwich is famous for a few things other than me...........

[ettingtonliam]

I'm not particularly familiar with the cowells lathe, but from the photos on www.lathes site, it doesn't seem to have a tumbler reverse on the screwcutting train. in which case the extra idler has to be inserted into the train to reverse the leadscrew if you want to cut a left hand thread. Drummond round bed lathes had the same arrangement.

Richard

[Jo]

Looks like progress... If an additional idler is added then it would seem logical that the 64 tooth leadscrew gear would need to be replaced with something smaller to allow for the extra space.

Thanks Rod, I have the book. For info she was made at 95-101 Oak Street, Norwich back in 1979.

Jo

[billyboiler]

My Cowells screwcutting chart does not have a 16 listed , 20 is the smallest and 64 the largest.

It also states that as the leadscrew has a 1mm pitch, standard TPI ( imperial pitches ) cannot be cut perfectly. but many pitches very close to these are obtainable.

There is a Cowells 90 forum on Yahoo which you may find useful.

[rodwilson]

Feb 2, 2012 15:40:10 GMT Jo said:

For info she was made at 95-101 Oak Street, Norwich back in 1979.

Jo

The Oak Street Shop was where my interest in model engineering started. I would go there in a lunch break and look at the lathes and models on display. My Myford was the last lathe sold from that address and I went to the Cowell's clearance sale shortly after. Unfortunately I'd spent out on the Myford but was pleased to add an ME90 to the workshop some years later. My machine has the 'Norwich' dials but was assembled after the move.

[Jo]

Thanks Billy.

I had looked through the list of threads she can cut. As far as I am concerned all she needs to be able to cut is 26, 32, 40 and 60 tpi. After all BA is only metric...... ;D

I will look out the yahoo forum.

Jo

[phil1001]

Jo,

The range of threads you can cut will depend on the leadscrew pitch as well don't forget. The cowells lathes were fitted with a few different leadscrew and nose threads over their lives. Mine is actually a Perris lathe (the forerunner of the Cowells 90) but it has a mteric leadscrew pitch. I attach a copy of the thread chart that came with the lathe and you ncan see metric pitches OK but TPI just a little bit out. The chart may help you till you get something better.

Phil.

Attachments:

[Jo]

Thanks, Phil,

It looks like I need to cut myself a couple of new gears add to the chain to enable the standard ME threads (26,32,40 & 60).

Jo

[Boadicea]

Feb 2, 2012 13:25:31 GMT rodwilson said:

Was your lathe one of those made in Norwich? Norwich is famous for a few things other than me...........

Sorry to defocus the debate but I suppose you just cut the mustard. The cole man cometh. ;D
Sorry Jo - back to the prologue!