How do you convert your threading gear change chart to speed/feed rates?

[mac1911]

Complete new to this. Still reading up. I see all the speed and feed calculations but how do you figure out the feed rate by pitch rate pn the gear chart

 

[ddillman]

there should be a separate chart for feed rates on the machine. You should post what machine you have

 

[graham-xrf]

Ahh.. a little picture would be so great!
Once the folk here know what the machine is, and what the gears are, you are guaranteed to get your answers, and you will be given the method.

There is a way to get at it from first principles. The pitch of the leadscrew, the speed of the motor, and the numbers of teeth on each gear in the train. The gears can be arranged in so many combinations, which is why we have table charts.

 

[mac1911]

Ahh.. a little picture would be so great!
Once the folk here know what the machine is, and what the gears are, you are guaranteed to get your answers, and you will be given the method.

There is a way to get at it from first principles. The pitch of the leadscrew, the speed of the motor, and the numbers of teeth on each gear in the train. The gears can be arranged in so many combinations, which is why we have table charts.

Smithy 1220XL
I will go through the manual again but only seen charts for thread pitch.
There are charts for speeds and speeds for different materials i will up date my first post soon

 

[graham-xrf]

Smithy 1220XL
I will go through the manual again but only seen charts for thread pitch.
There are charts for speeds and speeds for different materials i will up date my first post soon

OK - I did not quite get your intention the first time around. Here you are after a chart that will give you SFM (surface feet per minute) speed to get satisfactory cutting, for different materials, and an internet search will yield some recommendations ..
BUT
There are some factors that mess with it.
1. What type of tooling is assumed for the table. It might be carbide insert tooling with deep cuts in floods of coolant.

2. The SFM that is going to happen depends on the diameter of the part at the time. The next cut will be on the smaller diameter, so in theory, you need to go faster. This is why CNC cutting has the chuck start at one speed, and then get faster and faster (within limits), as the tool gets nearer the centre when facing. You are saved by the fact there is a range around the recommended speed which will do as a starting point.

3. You need to invoke π = 3.14159, the easy constant (pi). The SFM will be the diameter (at the time) x π. Only do remember to divide also by 12 to get the diameter in feet before you multiply by pi.

If you are working metric, it will be metres/min, so divide the diameter mm by 1000, then go for pi.

Best way is to consult the charts, figure your way back to the RPM you need, and try a little test cut. What happens is not all about the speed. It also is affected by how deep you cut. Carbide inserts work with a deeper cut. Consider also that the one cut may be the last before the tool starts rubbing, if the material was unkind enough to work-harden under the heat of those nice blue chips.

 

[mac1911]

OK - I did not quite get your intention the first time around. Here you are after a chart that will give you SFM (surface feet per minute) speed to get satisfactory cutting, for different materials, and an internet search will yield some recommendations ..
BUT
There are some factors that mess with it.
1. What type of tooling is assumed for the table. It might be carbide insert tooling with deep cuts in floods of coolant.

2. The SFM that is going to happen depends on the diameter of the part at the time. The next cut will be on the smaller diameter, so in theory, you need to go faster. This is why CNC cutting has the chuck start at one speed, and then get faster and faster (within limits), as the tool gets nearer the centre when facing. You are saved by the fact there is a range around the recommended speed which will do as a starting point.

3. You need to invoke π = 3.14159, the easy constant (pi). The SFM will be the diameter (at the time) x π. Only do remember to divide also by 12 to get the diameter in feet before you multiply by pi.

If you are working metric, it will be metres/min, so divide the diameter mm by 1000, then go for pi.

Best way is to consult the charts, figure your way back to the RPM you need, and try a little test cut. What happens is not all about the speed. It also is affected by how deep you cut. Carbide inserts work with a deeper cut. Consider also that the one cut may be the last before the tool starts rubbing, if the material was unkind enough to work-harden under the heat of those nice blue chips.

Ok let me try to re ask with pictures
I get the calculation

Here is the machine 1990s Midas 1220 XL


Here is the FPM to RPM chart


Here is the FPM chart with the HSS and carbide list.Then a more detailed alloy type chart Then the gear change thread gauge. Now this gear set runs the lead screw so I assume the FPM is dictated by the change gears and RPM selection.
I could not find any other info in the manual or related info to my search on this question
Right now the lathe change gears are set up per email from smithy as it left the factory
.003 on LO and .005” HI
Heres the thread chart
So example

By these charts with 1/2” plain low carbon steel HSS Cutter has a FPS of 80-150 for numbers sake lets meet in the middle at 120
The RPM chart says 917 RPM
Now being limited to 160-1600 with 4 speeds in between
I can get 1000 rpm

So I guess my question is how do you determine your cutting at 120 FPM ?

 

[Jim F]

You get to choose .003 or .006 for the feed rate.
those are in. per rev. numbers.

 

[T Bredehoft]

Those (.003 or .006) are feed rates, the cutter advances that much per revolution. Disregard speed in this. Well, don't disregard it but it doesn't affect the movement. Too much speed will destroy the tool.

All the others are threads per inch of travel. 10 pitch equals .100 per rev, thread pitches are not for turning but for threading. The "feed rates" are for turning.

 

[mac1911]

You get to choose .003 or .006 for the feed rate.
those are in. per rev. numbers.

So how do you factor FPM
With .003 - .006 gear setting?
Am I doing this right or is there another way?
1000 rpm x .003” = 3” a minute ?

 

[mac1911]

Those (.003 or .006) are feed rates, the cutter advances that much per revolution. Disregard speed in this. Well, don't disregard it but it doesn't affect the movement. Too much speed will destroy the tool.

All the others are threads per inch of travel. 10 pitch equals .100 per rev, thread pitches are not for turning but for threading. The "feed rates" are for turning.

10 tpi on the lead screw is correct.