# PM 1340 Feed Rates



## bretthl (Jan 31, 2019)

Are the carriage and cross feed equal at a given gear setting?  In other words if the gears are set to say D1 (0.010"/rev) will the this be true for both the carriage and cross feed?


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## Bob Korves (Jan 31, 2019)

Depends on the machine gearing, but I have always found smaller radial feeds than axial feeds for the same feed screw setting on lathes I have used.  The ratio between them stays the same.  That gearing is by choice of the designer, and could be made any way that is desired at the factory.  I have never seen the same feeds for both axes in any lathe I have used.  Look at the feed charts to see what you will get.  The manuals should be viewable online...


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## bretthl (Jan 31, 2019)

Bob Korves said:


> Depends on the machine gearing, but I have always found smaller radial feeds than axial feeds for the same feed screw setting on lathes I have used.  The ratio between them stays the same.  That gearing is by choice of the designer, and could be made any way that is desired at the factory.  I have never seen the same feeds for both axes in any lathe I have used.  Look at the feed charts to see what you will get.  The manuals should be viewable online...



There is no mention of this relation in the manual.  On this particular lathe one revolution on the cross feed is 0.200" however the depth of cut is 0.100" (I think there is a term for this?).  So would the cross feed rate be 1/2 of the carriage rate?  The rates given on the chart do not differentiate between the two.







It is interesting that progressing from A to E halves the feed rate for each step.  That is why I suspect that the cross feed is half the carriage feed.  If one were running the carriage in D1 then to attain the same feed the cross feed should be run in C1.


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## mksj (Feb 1, 2019)

Cross feed is 1/2 the carriage feed rate per top of the feed diagram 1/2 cross feed to 1/1 feed. So 0.004" feed would be 0.002" cross feed. This is pretty typical for most the lathes I have seen, it is also indicated in the front of the 1340GT manual (see below). Most of you cutting feed rates will be in the E1-8 and maybe D6-8 (~0.008-0.003) for this size lathe, the rest of the gearing is primarily for threading. The ratios probably have more to do with threading increments. On this lathe the deepest I typically went in a DOC was around 0.1" (diameter of up to 0.2" in softer materials), steel was typically 0.1" for removal). It all depends on the material and the tooling you are using. (looks like the picture links are broken)


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## bretthl (Feb 1, 2019)

mksj said:


> Cross feed is 1/2 the carriage feed rate per top of the feed diagram 1/2 cross feed to 1/1 feed. So 0.004" feed would be 0.002" cross feed. This is pretty typical for most the lathes I have seen, it is also indicated in the front of the 1340GT manual (see below). Most of you cutting feed rates will be in the E1-8 and maybe D6-8 (~0.008-0.003) for this size lathe, the rest of the gearing is primarily for threading. The ratios probably have more to do with threading increments. On this lathe the deepest I typically went in a DOC was around 0.1" (diameter of up to 0.2" in softer materials), steel was typically 0.1" for removal). It all depends on the material and the tooling you are using. (looks like the picture links are broken)



I completely missed that little notation, thanks!  I will make it my new avatar to remind myself to read the fine print.

I'm running a Seco WNMG in 4130 and 416 and it refuses to break chips at < 0.020" DOC and feeds < 0.008".


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## mksj (Feb 1, 2019)

So some materials it is hard to break a chip, might try a deeper DOC, certainly your feed is up there. The 1340GT is a fine machine, but you start getting into rigidity issues if trying to push it much harder. Also insert type and style play a large factor. I typically used CCMT tooling for steel/SS and my WNMG for aluminum and softer materials. You should look at your SFM and insert recommendations. I have done some machining of 4140 and 8620, but primarily with CCMT 32.51 insert made by Iscar (IC907) covers a wide range.

On 416 SS, I did check some other recommendations and you are in the ball park, this was for barrel work so assume around 1" diameter. Your feed rate is where I would wnat to be for SS, but may need a bit more DOC. On finish work I would switch to my WNMG with a sharp ground edge (Korloy insert). See attached  document with various inserts (that worked for me on the same lathe). Final pass is often done with a ground sharp edge, DCGT or WNMG at a lower feed. DOC is often dictated by the nose radius and sharpness of the insert edge to achieve cutting as opposed to pushing the material out of the way.
SS 416
CCMT09T304HF (Iscar IC907) in a 5/8 inch SCLC holder, 800 rpm,  Feed of .008/rev, DOC 0.03"
CNMG431 F3P (Iscar IC8250) Feed of .007/rev CSS 725 DOC,  .070"
Iscar Sumo Tec WNMG inserts. Specifically WNMG 080408-M3M
Seco TP2500 or TP2501, TM2000 with the MF4 chipbreaker
Cactus Tools sells a lot inserts/machine tooling on eBay may be worth emailing them to see what they recommend. This insert may be worth trying for rough/bulk material removal, note the nose diameter. Then switch to a ground edge for finishing.








						ISCAR Carbide Inserts WNMG 332 F3p Grade Ic8250 Pack of 10 for sale online | eBay
					

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416R SS and 4140 CM with carbide inserts
Tennon Turning and Facing with Indexable Insert Tools and Carbide 800 rpm
Feed of .007" for Rough and .002" for final pass

4140 recommendations, the DOC is not achievable with a smaller lathe and I would use cutting speed and feeds similar to 416 maybe with a slightly lower SFM.


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## pacifica (Feb 1, 2019)

A cxa toolpost , remove compound ,build an indexed,robust non t-slot  toolholder with a grade 8 bolt attached to compound will make a big difference with the 1340gt(see _*solid tool post mount*_ from mar.1 ,2018). Plus all the things Mark recommended. I also reinforced the stand with steel and added 500+ pounds of weight to the stand.


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## bretthl (Feb 1, 2019)

I have been running WNMG 331 FF2 TP3500 SECO at 0.050" DOC without issue in 3140 and 416.  I should try the Iscar 332's as you suggest.  I bet I would get an even better surface finish.  Upping to 3 hp (as well as 3 phase) has been a huge improvement with insert performance.



pacifica said:


> A cxa toolpost , remove compound ,build an indexed,robust non t-slot  toolholder with a grade 8 bolt attached to compound will make a big difference with the 1340gt(see _*solid tool post mount*_ from mar.1 ,2018). Plus all the things Mark recommended. I also reinforced the stand with steel and added 500+ pounds of weight to the stand.



Oh man I can't live without the compound!  I did read David Best's presentation on rig up and it looks very solid.   https://flic.kr/s/aHsm1cKjPB


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## ptrotter (Feb 3, 2019)

I'm still trying to figure out the feed rates on my 1340GT.  The table only shows feed rates for the left (A-D) gear lever. For example, the table shows .005-.0027 inches per revolution for left gear lever on "E" but says nothing about the effect of the right gear lever (1-8).  Can someone enlighten me?


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## mksj (Feb 3, 2019)

The left hand letter gear selector sets the gear set range, the right one is the fine adjustment within that letter range. So 8 being the slowest and 1 being the fastest within that range (corresponding to the TPI). So E1 (64 TPI) feeds at ~0.005 IPR, E8 feeds at ~0.0027 IPR, so E4 would be ~ 0.004 IPR, E7 would be ~0.003 IPR. Cross feed would be 1/2 the carriage feed. On the D range, everything is doubled, and for each successive letter range. Pretty much for feeding you pretty much using an IPR range of 0.0027-0.010 (typically 0.008 probably for this size machine except with softer materials), so the Range of E8-E1, and D8-D1.


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## ptrotter (Feb 3, 2019)

mksj said:


> The left hand letter gear selector sets the gear set range, the right one is the fine adjustment within that letter range. So 8 being the slowest and 1 being the fastest within that range (corresponding to the TPI). So E1 (64 TPI) feeds at ~0.005 IPR, E8 feeds at ~0.0027 IPR, so E4 would be ~ 0.004 IPR, E7 would be ~0.003 IPR. Cross feed would be 1/2 the carriage feed. On the D range, everything is doubled, and for each successive letter range. Pretty much for feeding you pretty much using an IPR range of 0.0027-0.010 (typically 0.008 probably for this size machine except with softer materials), so the Range of E8-E1, and D8-D1.



Thanks Mark, nice to hear from you. I thought that was the case but wanted to make sure.  I really love the proximity stop you built for me.  I have been practicing threading with it after watching your video.  I'm starting to get the feel of this machine.  Thanks again for all your help.


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## P. Waller (Feb 3, 2019)

In the past many lathe manufacturers used a cross feed lead screw 1/2 the pitch of the longitudinal feed screw,
Therefore a .005 inch per revolution feed in the Z axis results in a .005 inch feed per revolution.

The X axis (Diameter axis) moves at 1/2 the feed rate for obvious reasons.


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## INTJ (Feb 16, 2019)

mksj said:


> Cross feed is 1/2 the carriage feed rate per top of the feed diagram 1/2 cross feed to 1/1 feed. So 0.004" feed would be 0.002" cross feed. This is pretty typical for most the lathes I have seen, it is also indicated in the front of the 1340GT manual (see below). Most of you cutting feed rates will be in the E1-8 and maybe D6-8 (~0.008-0.003) for this size lathe, the rest of the gearing is primarily for threading. The ratios probably have more to do with threading increments. On this lathe the deepest I typically went in a DOC was around 0.1" (diameter of up to 0.2" in softer materials), steel was typically 0.1" for removal). It all depends on the material and the tooling you are using. (looks like the picture links are broken)



Thanks Dr. Mark!

I have had my 1340GT for nine months and guessed it might be something like that.  I was disappointed that there wasn’t a feed table in the manual that showed the actual rate at each setting.  I searched and searched on the internet but couldn’t find anything.  I also have not been able to get Matt on the phone for months.  No one else at PM really knows these details so I just gave up.  I can’t remember if I e-mailed my question, but I guess Matt is just too busy to answer technical questions anymore.

I think I could make a chart for feed rates assuming the mathematical relationships stay the same between 1 and 8.  That may not be necessary as I have found when working in 416 Stainless rifle barrels, slower is better, so I cut tenons and shoulders on E-8 and 135 RPM—which is max speed in the lowest gear range. (I have Dr Marks control setup.)  I chamber at 60 RPM and go slow.  

The proximity stop doesn’t work too well for me when trying to get a smooth shoulder.  I might be doing something wrong, but I get better results by disengaging the power feed with the lathe still turning.  The next time I thread I will try the proximity stop, as it should work great for that.  

A word of caution.  I would not put any weight on anything I have posted.  I am still a total newb to machining, though I did get the chamber of my firefroming barrel and the chamber of my match barrel (long range benchrest) virtually identical.


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## mksj (Feb 16, 2019)

Won't get a smooth shoulder because you are cutting sequential diameter passes and the cutter tip is at an angle (not 90 degrees to the face, there is always a relief backwards) so you will get ridges with each pass. Also you are cutting to a stop postion while the cutter is advancing as opposed to dissengaging the feed and allowing the spindle to continue rotating. I always take passes just short of the final face dimension then use the cross slide to face to the final face dimension. Alternative is to face with a cutoff blade and then take passes just shy of the cutoff face. It is a bit of a learning curve, I have changed a lot of my techniques when using the P sensor.


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## INTJ (Feb 16, 2019)

I actually thought of doing that way and might try it.  I am much interested in threading with the Prox stop.  Your video shows the process well as I REALLY like the idea of not having to frantically disengage the half nut and pull back the compound each pass.


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## bretthl (Feb 17, 2019)




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## INTJ (Feb 17, 2019)

You rock!  Saved me from having to do it....


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## szenieh (Feb 21, 2021)

bretthl said:


> View attachment 287934


Hi,

I know this is a very old post, but do you mind sharing how you calculated this table? Mark mentions above that the TPI will directly correspond to the feed rate which makes sense. However, it is not the reciprocal of the TPI. There is some other ratio involved (approximately 3). I tried to verify your table but I am not able to. Maybe Mark can chime in and explain how this is calculated.

Salah


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## szenieh (Feb 21, 2021)

mksj said:


> Cross feed is 1/2 the carriage feed rate per top of the feed diagram 1/2 cross feed to 1/1 feed. So 0.004" feed would be 0.002" cross feed. This is pretty typical for most the lathes I have seen, it is also indicated in the front of the 1340GT manual (see below). Most of you cutting feed rates will be in the E1-8 and maybe D6-8 (~0.008-0.003) for this size lathe, the rest of the gearing is primarily for threading. The ratios probably have more to do with threading increments. On this lathe the deepest I typically went in a DOC was around 0.1" (diameter of up to 0.2" in softer materials), steel was typically 0.1" for removal). It all depends on the material and the tooling you are using. (looks like the picture links are broken)


I am trying to figure out what the calculation is. It is not the reciprocal of the TPI. I seem to be missing a ratio of some sort to get from the TPI to the feed rate. Can you help?

Salah


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## zmotorsports (Jul 23, 2021)

szenieh said:


> Hi,
> 
> I know this is a very old post, but do you mind sharing how you calculated this table? Mark mentions above that the TPI will directly correspond to the feed rate which makes sense. However, it is not the reciprocal of the TPI. There is some other ratio involved (approximately 3). I tried to verify your table but I am not able to. Maybe Mark can chime in and explain how this is calculated.
> 
> Salah



I know this is an old post but I've wondered this myself.  

Can someone explain to an idiot like me how the feed rate is calculated?

I have always just divided the TPI into 1 to find the decimal equivalent but the chart above shows completely different results.

For example I was machining last a part last night using D-6 on the Norton gearbox.  The chart on my PM1340GT indicates that D-6 is the gear position for 48 TPI (Threads Per Inch).  If you calculate that out isn't is  1/48= .020833 or roughly .021"?  Yet in the chart above for D-6 it shows .0068".

Can someone please explain?

Thank you.


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## darkzero (Jul 23, 2021)

zmotorsports said:


> I know this is an old post but I've wondered this myself.
> 
> Can someone explain to an idiot like me how the feed rate is calculated?
> 
> ...


I haven't read the entire thread so forgive me if I'm totally missing the question but TPI is not the same as feed rate. TPI would be teeth per the distance of an inch so you can caluculate the travel but the feed rates listed on the chart is when using the power feed rod instead of the leadscrew, feedrate is Inch Per Revolution. So if you set your gearbox to say .005", the carriage should travel .005" for one complete revoution of the spindle. You can somewhat verify this with an indicator or DRO with the power feed engaged & turn the spindle by hand.


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## mksj (Jul 23, 2021)

TPI is carriage moved by the lead screw, feed is fed by the feed rod, the ratio of lead screw to feed rod carriage movement is something like 3.1:1.  So D-6 is 48 TPI or 0.0208 IPR, divide by ~3.1  to get the feed rod IPR of the carriage which would be ~0.0067 IPR.
Mark


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## zmotorsports (Jul 23, 2021)

Awesome.

Thank you Will and Mark, I really appreciate that.  Been using this lathe for several years now and know what settings work well for various materials and RPM's but never really calculated the feed rates out until I started playing with calculations the other night and simply couldn't come up with what others were stating for feed rates.

Thank you very much.

Mike


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## xr650rRider (Jul 23, 2021)

I just finished Clough42 Electronic Lead Screw on my PM-1340GT and the feed rates just didn't match the front of the machine.

This is the actual feed rate chart, one on machine is incorrect. I put Norton gearbox on D-6 and use 1:1 pulley ratio and 1:1 ratio to encoder. I used a Servo that is rated for 1.2 NM @ 3000 RPM, so using 6:1 ratio I have plenty of torque. I used a JMC 400 watt Servo and changed internal stepper pulses to 500 using servo software.

Code changes
#define LEADSCREW_TPI 8
#define STEPPER_MICROSTEPS 6
#define STEPPER_RESOLUTION 500
#define STEPPER_MICROSTEPS_FEED STEPPER_MICROSTEPS * 4.2405

Using the example above D-6 being a 48 TPI, the feed rate would be 1/48 = .0208"/Rev, when you change to feed ratio, the feed would be .0208/4.2405 = .00491"/Rev which matches the updated worksheet on Precision Matthews website.


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## parshal (Jul 24, 2021)

If I'm reading that chart correctly it's quite a bit different.  Is the IPR graph for carriage or cross feed?

The chart shared earlier (attached) has D-6 at .0068" for carriage and .0024" for cross.


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## xr650rRider (Jul 24, 2021)

It's for carriage, verified using DRO and turning by hand.  4.2405 is the constant ratio between threading and feeding.  Not sure if earlier PM-1340GT had different gear ratios or not.  I thought mine must be a unicorn, then found the spreadsheet on Precision Matthews website and it's been there for a while.  Using the gearbox, what I thought I had been feeding, turned out to be completely incorrect.


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## mksj (Jul 24, 2021)

One is the carriage movement off of the lead screw, the other is the carriage movement with the feed rod, cross slide would be 1/2 the feed rod. That is a pretty gross discrepancy,  had I known that when I had my 1340GT I would have been more aggressive on my feeds.


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