HELP? G4003G

TakeDeadAim said:
My lathe is a G4003G which has a different gearbox, the combo of 40 up top and 60 below in position 2A is finer than 3.0
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So I am a little confused. I thought I had used the gear box plate for the G4003G, but maybe it was the G4003 (which I cannot see in the manual). So your are saying that these two have different Norton Gear boxes??? The manuals that I downloaded were not clear. Please post a picture of the gear plate that is on your lathe so I can check and tell me what the upper and lower gear tooth numbers were to get this plate.

The manual for the G4003G says that you should have the following gears and it shows the plate for TPI in the screen grabs below. Are these not what you have on your lathe? The plate that is shown indicates that the gear box I built into the spread sheet should work. 40 top, 40 bottom, A-1 yields 4TPI. Likewise for all of the other numbered lever positions. The A, B, C, D, E are just factors of two so that would be all that is necessary to check out the gear box.

And if I understand your statements then you can have a the following arrangements of gears:
Gear box axle: 40T, 60T (two gears)
Spindle axle: 26, 27, 35, 40, 50, Missing 45. Plus the 86 and the 91 gears fit here also, but do they separate?
Exchange gear axle: 86, 96 Plus the 26, 27, 35, 40, 50, Missing 45 gears will fit on this axle.

I will run the gear arrangements show at the bottom for you. Please let me know if these conditions apply.




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The photos you posted are correct but the gears are not universally interchangeable. The 26,27,35,(one of the 40) and the 50 will fit in position F as shown in photo 0033. Only the other 40 and the 60 will fit in position G. The 91/86 are one piece and get flipped around to reach the TPI or FPR as shown on the charts. All mesh adjustment is on the bracket for the 91/86 gear and is limited, not by the adjuster but by the space between the F and G gears. The Metric threads are achieved by following Figure 34, (photo 0032)

The quick change gearbox is similar to a South Bend quick change box with the addition of a shaft to allow the shifting of the drive from the feed shaft to the lead screw and another to change the direction of either. I can't exactly tell you what this part is for but it is a tight tolerance piece and the thread must be a hand fit so it's smooth but not loose.
 

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I understand, but it is almost impossible for me to measure which arrangements will fit or not fit the spacing without having the lathe. It is indeed a shame that the 91/86 are one piece. Never the less, it brings up another issue. Will the 91/86 even fit on the upper position or is there a clearance issue. Also, can you put two separate smaller gears on the exchange gear axle? I did run the program for the gear set up I posted just above. It yielded a few 3.00 TPI values and lots of approximations. Many of these I assume are impossible. If you can live with even a close approximation you might make it work. For example is 3.02TPI or so good enough?

This is a portion of the results that yield exactly 3.00TPI or very close, but I fear that few of them are physical. Would row 98 or 99 work? For example row 99 requires that the 91 gear be at the spindle and that the 50/35 be the exchange gear and that the 60 be at the gear box. From the photo of the end of the lathe it looks like the 91 (91/89) would fit at the spindle.

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Here is the corresponding sheet for that search. It lists all of the TPI values and approximations.
 

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B2 said:
I understand, but it is almost impossible for me to measure which arrangements will fit or not fit the spacing without having the lathe. It is indeed a shame that the 91/86 are one piece. Never the less, it brings up another issue. Will the 91/86 even fit on the upper position or is there a clearance issue. Also, can you put two separate smaller gears on the exchange gear axle? I did run the program for the gear set up I posted just above. It yielded a few 3.00 TPI values and lots of approximations. Many of these I assume are impossible. If you can live with even a close approximation you might make it work. For example is 3.02TPI or so good enough?

This is a portion of the results that yield exactly 3.00TPI or very close, but I fear that few of them are physical. Would row 98 or 99 work? For example row 99 requires that the 91 gear be at the spindle and that the 50/35 be the exchange gear and that the 60 be at the gear box. From the photo of the end of the lathe it looks like the 91 (91/89) would fit at the spindle.

View attachment 465420

View attachment 465421
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Both the shaft size and the location, would not allow the placement of the 86/91T gear onto the F location. Gears that mount there are the 10mm thick 16mm ID (26,27.......) size gears. The 60 will likewise not fit there, it and one of the 40s only fit in position G. IF you start moving things around much the ability to get even tolerable mesh is difficult.

I'd never buy a machine from them again but I have this and in the 10 years I've owned it this is the first metric thread I have had to cut. This is not common in my business even foreign products usually use an SAE or industry-standard thread.

All and all the lathe has been a problem child with parts hard to get and tech support rarely knowledgeable of their product. The extra $5000 to $8000 is worth it.
 
Got it. I still may post the spread sheet. I will eliminate all of these gear positions that I think you just said would not fit. This means that your number of choices goes down significantly. Looks like your only approximation would be to use the values listed below. It would be the smallest TPI value you could make. What is surprising to me, given your search for a 45T gear is that even with the 45T gear you do not get 3.00TPI in the spread sheet ! Are you sure that 45T will work? If so I must have something else wrong.
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Good luck.
 
These are the gears that I made available to the spread sheet.

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Per the chart it is 45 at position F; 60 at position G; 91 engages the 45; 86 engages the 60 and the box is at A6.
 
I just experimented a bit. I think the gear that you need is 80T at the spindle not a 45T. Then 60T at the gear box and a setting of A-6 for the Norton and any gear at the exchange position. This will get you to 3TPI exact. Will an 80T fit?
With 80T at the spindle then you can use the 40T at the gear box and A-1 to get 3.00TPI exact. If you want small TPI values you need to have a big gear at the spindle.
 
@TakeDeadAim - I have the 45 tooth gear if you want to borrow it; would just need to pay shipping round-trip.

You are looking to make a 3.0 pitch, not 3TPI, right?
 
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