Gears for RDG 250VSL lathe

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Gears for RDG 250VSL lathe

This topic has 11 replies, 4 voices, and was last updated 6 February 2015 at 12:14 by Ian Richardson 4.

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2 February 2015 at 17:30 #178198
Ian Richardson 4
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@ianrichardson4
Folks I have a RDG 250 VSL lathe which is very similar to the Warco 250VSL but sadly not exactly the same.

I want to cut a M12 x 1.75 thread but my chart on the lathe only goes to 1.5.

The Warco 250 does have gears for 1.75 but comparing 1.25 and 1.5 on the Warco and mine shows different gears, so I assume that the Warco gear selection won't give me 1.75.

Does anybody know the correct gears Z1, Z2 etc for 1.75 on a RDG lathe?

Or could anybody explain how I can work them out for myself?

Thanks

Ian
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2 February 2015 at 17:30 #12416
Ian Richardson 4
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@ianrichardson4
2 February 2015 at 20:20 #178211
JasonB
Moderator
@jasonb
Is it a metric or imperial lathe?

If you post a photo of the chart on the front of the machine we can try and work it out for you.
2 February 2015 at 23:19 #178239
Ian Richardson 4
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@ianrichardson4
Many thanks for the offer of help.

Here is the machine label with the relevant info.

Ian
3 February 2015 at 07:28 #178254
JasonB
Moderator
@jasonb
So its an imperial machine, the metric ones either RDG or Warco will cut 1.75 but its not easy on teh imperial with teh supplied gears. I'll see what I can work out this evening.

If anyone else wants a stab then the spindle has a fixed 40T driver, ABC on the gearbox alters the ratio by 2:1, 1:1 or 1:2 and gears are in 5T steps from 20T to 80T plus a 63T & second 80T. No 35T, 8tpi leadscrew

Edited By JasonB Note no 35T availabl;e I think

Edited By JasonB on 03/02/2015 09:09:18
3 February 2015 at 08:06 #178259
Ian Richardson 4
Participant
@ianrichardson4
Jason thank you so much.

If I knew what gears were needed I could buy a set or the odd spare from Warco maybe?

I think I'm correct in saying that Amadeal sell spare gears that are suitable for my lathe.

One thing about these Chinese lathes is the commonality of parts which could help me to achieve this.

I'm also regretting not buying a 4 jaw independent chuck as I could really use one now!

Warco can sell me a 4 jaw and backing plate that means I should be able to correct that one!

Thanks again

Ian
3 February 2015 at 08:41 #178263
mahgnia
Participant
@mahgnia
Ian,

Try one of these combinations with the gearbox in A position:

Spindle-Z2,Z1,Z4,Z3,Leadscrew

01.750 mm, 40 – 40 : 35 – 80 : 63 – 50 Error 0.012%
01.750 mm, 40 – 40 : 63 – 50 : 35 – 80 Error 0.012%
01.750 mm, 40 – 50 : 63 – 40 : 35 – 80 Error 0.012%

01.749 mm, 40 – 35 : 45 – 40 : 30 – 70 Error 0.029%
01.749 mm, 40 – 35 : 45 – 70 : 60 – 80 Error 0.029%
01.749 mm, 40 – 35 : 45 – 80 : 60 – 70 Error 0.029%
01.749 mm, 40 – 35 : 60 – 70 : 45 – 80 Error 0.029%
01.749 mm, 40 – 35 : 60 – 80 : 45 – 70 Error 0.029%
01.749 mm, 40 – 40 : 45 – 35 : 30 – 70 Error 0.029%

Some combinations may not mount or reach.

You can play with the ABC positions by selecting a gear out of these combos and replacing with a half or double size gear.

Andrew.

Edited By mahgnia on 03/02/2015 08:42:54

Edited By mahgnia on 03/02/2015 08:44:34

Edited By mahgnia on 03/02/2015 08:47:34
3 February 2015 at 08:43 #178265
JasonB
Moderator
@jasonb
Had a bit of time so best you can get with the supplied gears would be 1.764mm pitch which is a 0.79% error, should be OK for a short engagement .

Easiest way to calculate is to use the nthreadp programnme, just enter all the gears you have and pick one that uses a 40T driver as that is fixed on the spindle. I had to add another 40T idler but if the gears don't mesh you may have to go 40T spindle, H & 80T, 70T & 80T, 63T & H. You will need the front dial in "A" . Just run a scratch cut first to make sure its all ok.

I don't think you have a 35T in the set but if you do you could get a lot closer at with a 0.01% error. I think Amadeal etc only supply spares for the standard set but worth asking if they have a 35T if its not in your set

Yes there are a couple of suppliers who leave off the faceplate, 4-jaw and steadies which may make the initial machine price more attractive but in the long run its better to spend a bit more and get the bits which you WILL need in the end

Edited By JasonB on 03/02/2015 08:49:29
3 February 2015 at 09:08 #178268
JasonB
Moderator
@jasonb
QUick thought as I should really be working but it may be poissible to substitute the 35T with an available 70T spare and then use the gearbox to bring it back down to the correct movement. try the programme I linked to but enter two 70T gears and a pitch of 3.5 or 0.875
3 February 2015 at 09:54 #178274
Les Jones 1
Participant
@lesjones1
Hi All,
This is my possible solution. 40 T spindle gear driving an 80T. 63T (On the same shaft as the 80T) driving the second available 80T 70T (On the same shaft as the second 80T) driving a 50T on the gearbox input. The gearbox set to 1:1 ratio. I THINK the gears will clear each other but if not an extra shaft would have to be made to fit a spcer gear. (If the spacer gear was used it would reverse the sense of the leadscrew directon control.)

Using the same codeing as the chart on the lathe Z1 = 63, Z2 = 80, Z3 = 70, Z4 = 80, L = 50
These settings would give a 0.012% error (1.75021875 mm pitch)

Les.

Edited By Les Jones 1 on 03/02/2015 09:55:13
3 February 2015 at 11:52 #178297
Ian Richardson 4
Participant
@ianrichardson4
Hi Everybody,

Many, many thanks!

Now the sun has come up and warmed the workshop I'll go out and have a play.

Thread length I am going for is less than 25mm so no worries about a small error.

I am mightily impressed as to how quick you all came up with an answer!

I'll let you know how I get on as it could be useful for somebody else.

Thank you all again.

Ian
6 February 2015 at 12:14 #178697
Ian Richardson 4
Participant
@ianrichardson4
Hi All,

Many thanks again for all that info.

I rang Amadeal and spoke to Edward who was very helpful.

I have ordered a 35T and a 40T which have to come from China to get a better set up.

For the moment I went with Jason's 1.764mm pitch as Les' set up sadly wouldn't fit. There isn't room to introduce another gear train.

When the 35T and 40T arrive I'll try a closer match.

To get over the slight error I turned a fairly deep scratch cut and then used a die o finish it off.

The material is 8.8 high tensile bar.

I've included a photo to show what it looks like in case anybody has a brainwave!

Best

Ian
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