Getting taper with Geo die head

[Philip]

Hello everyone,

I didn't know where else to go so I figured you swiss wizards might be able to help. Here's the situation. I am running a job of 17-4 s/s threaded studs. 5000pcs. They are 1" long, and have a 4mm x 0.7 thread. They are slotted at one end. I am using a Geometric 9/16 D self opening head. This is being done on a turret lathe. The chasers are new Quality Chasers, 45 deg. chamfer 15 deg. hook. I ran 1500pcs. for the first release with one set of chasers no problem. For the second release, I switched to a new set of chasers and started having immediate taper problems. Over the length I was getting a .006" taper, smaller at the beginning of the thread where the die head started. No idea what is going on. Contacted Quality and they had me send them the chasers. No problem with them. They did change the chamfer to 33 degrees, and honed the hook. Put them in and they worked. Ran about 350pcs. and am starting to have this problem again. Taper is less, about .002-.003 but I still don't know why this is occuring. Any ideas? Thank you in advance for any help.

Regards,
Philip Confalone
PC Machine Works

[ProProcess]

You ran the first 1,500, did you break off and reset up?

It certainly sounds like setup issue but take a look at ...

is the Pocket line-up (indicator)
is the Pocket straight (indicator/ z travel)
is the Geo head on center (some of them have their own adjustment)
does the head open/close "freely"
are all the chasers converging on the same center
is the turret stop set propperly (if mechanical)
is the z feed propper(if CNC)
is the material from a different lot
has the blank changed or is the blank tapered
does the major and minor taper the same amount

These are jus a few.
Good Luck

[Philip]

No, setup stayed the same. Just changed out chasers. Like I said, the first 350pcs. ran fine. Why would it suddenly change? I was thinking the clamping pressure on the collet might be doing it, but then again that really doesn't make any sense. If I had any hair I'd be pulling it out! LOL

Regards,
Phil