lathe, multi-thread starts

[TFesta]

I need to groove this part. It's 16 equal grooves along the OD like 16 thread starts.

It will run at 15 deg. and the OD is 16.150. How do I calculate the feed? I'll be using a threading cycle and telling it that it has 16 starts.

[TFesta]

From what I got. The length of the cut is 50.737 for 1 revolution.

So the z-distance will come out to 13.1316 and that will be my feed.

At that rate I can only go 15 RPM max to keep my feed rate under

the 200IPM max feed rate for the machine.

[kh012]

if you are using a threading cycle the the feed is based on theads per inch. you have to figure that out first.

but since you have multiple leads your "TPI" is greater per lead.

say your cutting a 1/2-20 thread then the tpi is .050, but if the thread has two starts then the lead is .100 per start.

with 16 starts you have figure the advance for one revolution then multiply x 16 to get the lead for one thread.

then convert this to the tpi that you need.

 

HTH Ken,

[JerryBenoit]

You also want to check if your tool you choose to cut this feature will clear the flanks of the thread. I once had a job we needed to cut with 60 starts on the O.D. of a part that required us to modify the holder to angle the insert so there was clearance with the flanks. Simalar to a laydown insert and its use of the shim.

 

Jerry

[TFesta]

You also want to check if your tool you choose to cut this feature will clear the flanks of the thread. I once had a job we needed to cut with 60 starts on the O.D. of a part that required us to modify the holder to angle the insert so there was clearance with the flanks. Simalar to a laydown insert and its use of the shim.

 

Jerry

 

 

Yes Jerry, I had to do that one other time too. If we get the job we'll have to alter the tool holder.

[TFesta]

if you are using a threading cycle the the feed is based on theads per inch. you have to figure that out first.

but since you have multiple leads your "TPI" is greater per lead.

say your cutting a 1/2-20 thread then the tpi is .050, but if the thread has two starts then the lead is .100 per start.

with 16 starts you have figure the advance for one revolution then multiply x 16 to get the lead for one thread.

then convert this to the tpi that you need.

 

HTH Ken,

 

 

Ken, I did get it to thread. On this Okuma the feed it called out just like any other feedrate. Some do go by TPI. Thanks for your help.