C2 thread cutting ratios

[KBs PensNmore]

I have a copy of Seig C2 Mini Lathe.
I started to set up for the thread cutting of a 1.5 pitch, following the recommended set up A 30 t B 40 t C 50 t d 40 t, the trouble is that the D setting doesn't connect with the rest of the drive train. If that is incorrect, I wonder what else is wrong. Could someone who has one, give me the correct gearing, for the metric and TPI, please.
Thanks in advance,
Kryn

[slhouetteV8]

Can't really help but...


I would have thought one of the idle gears was on some kind of banjo arrangement?


The only gears that matter here are the input and output gears. Assuming 30t @ A and 40t @ D are correct you may be able to get another gear to mesh. There should be some kind of adjustment though.

[slhouetteV8]

Just had a quick look at my lathe...

Metric 1.5 pitch thread uses 45t as driving gear and 60t as driven gear. Ratio 1:0.75

Your lathe uses 30t as driving and 40 as driven. Ratio 1:0.75

Guessing we have the same pitch lead screw those gears should be correct.

[Steamwhisperer]

Hi Kryn,
I may be talking out the back of my head here but...
Would A mesh with B, (B and C are keyed together on the idler shaft) then C meshes with D?

Phil

[mahgnia]

Kryn,

Does the gear not reach to mesh with the C gear, or is it in the wrong plane?

The Grizzly manual for a C2 gives for 1,5mm pitch: A 40, B 60, C (nothing), D 40.
This means that a spacer bushing behind the D gear is removed, and the D gear meshes directly with the B gear.
The quadrant plate behind the gears should have enough adjustment to allow proper meshing of the gears.

By this, I am guessing that the leadscrew pitch is also 1,5mm, and the spindle to leadscrew ratio should be 1:1.

Andrew.

[KBs PensNmore]

Thanks for the replies. I've set it up with 40/60/40 and end up with a pitch of about 1.6,( discovered that "B" is adjustable) the nut won't screw on. I'm making an ER 25 collet chuck, so I can't get a die for that size, probably could, but I don't want to buy one, not for just a one off.
Kryn

[mahgnia]

Kryn,

It sounds like your lathe may be an imperial one with a 16TPI leadscrew.
You will need to check the leadscrew pitch before you can work out the change gears that should be used.

If you can give the exact leadscrew pitch, and all the change gears you have, we may be able to come up with a combination that will work. If the leadscrew is imperial, this will not give an exact pitch of 1.5mm, but it may be close enough.

Andrew

[KBs PensNmore]

I'll go and check it now, thanks. The shaft is 16 TPI, and the gears I have are 20 X 2 of, 25, 35, 40 X 2 of, 45, 50 X 2 of, 55, 57, 60, 65, 80 X 2 of.
TPI is not Totally and Permanently Intoxicated, sometimes I wish I was though. This bl*#dy lathe is driving me to it.
Kryn

[mahgnia]

I have a copy of Seig C2 Mini Lathe.
I started to set up for the thread cutting of a 1.5 pitch, following the recommended set up A 30 t B 40 t C 50 t d 40 t, the trouble is that the D setting doesn't connect with the rest of the drive train. If that is incorrect, I wonder what else is wrong. Could someone who has one, give me the correct gearing, for the metric and TPI, please.
Thanks in advance,
Kryn

Kryn,

Working back from the gear train suggested from your original post, the leadscrew is metric with a 1.6mm pitch.
If so, we may find a better combination of cahange gears to use.

Andrew

[KBs PensNmore]

Thanks Andrew, I found some info that appears that some lathes imported into Australia, came with an imperial lead screw, guess which one I got. NOT METRIC The listing I found has from 8 TPI / 3.175 mm pitch to 52 TPI / 0.4885. with all the gear settings, and errors per in and cm
I hope this helps others, http://lathenovice.wordpress.com/cutting-imperial-and -metric-threads/
Thanks to everyone that replied.
Kryn

[mahgnia]

Thanks Andrew, I found some info that appears that some lathes imported into Australia, came with an imperial lead screw, guess which one I got. NOT METRIC The listing I found has from 8 TPI / 3.175 mm pitch to 52 TPI / 0.4885. with all the gear settings, and errors per in and cm
I hope this helps others, http://lathenovice.wordpress.com/cutting-imperial-and -metric-threads/
Thanks to everyone that replied.
Kryn

Kryn,

Good link that should help those with this lathe and imperial leadscrew.

The gear change combination suggested on this page for 1.5mm pitch should work fine for your ER25 collet chuck.
May be worth testing on some scrap before committing to your final workpiece.....

Andrew

[mahgnia]

Kryn,

After a bit of fiddling with my C6 gear program to give suitable results for your C2 with a 16TPI leadscrew, the following are some change gear settings that may work for various metric pitches, to a reasonable degree of accuracy.

The actual pitch can be calculated using the formula:

1.5875 x A/B x C/D mm

1.5875 is the actual pitch of your leadscrew in mm

Andrew.

Pitch mm	A	B	C	D	Actual Pitch mm
0.4	20	55	45	65	0.39965
0.45	25	55	50	80	0.45099
0.5	25	55	45	65	0.49956
0.6	35	57	40	65	0.59986
0.7	35	55	45	65	0.69939
0.75	35	65	50	57	0.74983
0.8	40	55	45	65	0.79930
1.0	35	50	45	50	1.00012
1.25	35	40	45	50	1.25015
1.5	65	55	40	50	1.50091
1.75	40	35	55	57	1.75063
2.0	35	50	45	25	2.00025

[KBs PensNmore]

Thanks for that Andrew, I'll print it of so that I can have a permanent record of it. I've finished my ER 25 collet chuck, and now in the process of trying to load the pics on here.
Kryn