Citizen Swiss Machines

KaptainKajun · Jan 7, 2022

Hey I'm having trouble with a Citizen Swiss style lathe. I am using an A20 Swiss style lathe of which we have 6 in my shop. I am trying to cut 316 stainless steel and the guide bushing keeps getting trashed but I cannot figure out why. I've checked my speeds and feeds and checked my main spindle pressures to make sure that it was not scarring the bar before it even reaches the guide bushing. The order of operations is 1.Facing the material. 2.Drill with 5.9 mm carbide drill with through tool coolant. 3.Put a chamfer on the ID. 4.Tap the hole with 1/4-20 right hand tap. Then a bunch of other stuff, but my problem falls in those steps. I kept getting excess error alarms while drilling and breaking drills so I changed up the speeds and feeds and that problem stopped but now its happening during the tapping cycle and when it happens it trashes the guide bushing and I cant figure it out.

Tom Lg · Jan 7, 2022

KaptainKajun said:
Hey I'm having trouble with a Citizen Swiss style lathe. I am using an A20 Swiss style lathe of which we have 6 in my shop. I am trying to cut 316 stainless steel and the guide bushing keeps getting trashed but I cannot figure out why. I've checked my speeds and feeds and checked my main spindle pressures to make sure that it was not scarring the bar before it even reaches the guide bushing. The order of operations is 1.Facing the material. 2.Drill with 5.9 mm carbide drill with through tool coolant. 3.Put a chamfer on the ID. 4.Tap the hole with 1/4-20 right hand tap. Then a bunch of other stuff, but my problem falls in those steps. I kept getting excess error alarms while drilling and breaking drills so I changed up the speeds and feeds and that problem stopped but now its happening during the tapping cycle and when it happens it trashes the guide bushing and I cant figure it out.

I use a Citizen A20 every day. Please describe what you mean when you say "...trashes the guide bushing...".

Can you send me a sample of the code for the operations?

Booze Daily · Jan 7, 2022

5.9 hole for 1/4-20 tap? That's too big even for a roll tap.
Just wanted to point that out before you make a whole pile of scrap.

wmpy · Jan 7, 2022

It sounds like your material is binding in the guide bushing. Maybe the diameter of the material is inconsistent? I'd try loosening up the GB a bunch to see if the problem goes away.

chad883 · Jan 7, 2022

What size of stock? Is your tap dull and bulging the O.D. of your material? What speed and feed for the drill? Might be work hardening some and making tap push material not cut. Is your face operation kicking a burr on the O.D. of your stock?

mhajicek · Jan 7, 2022

Are you using "Swiss ready" ground stock?

KaptainKajun · Jan 7, 2022

yes

mhajicek said:
Are you using "Swiss ready" ground stock?

yes I do use swiss grade materials

KaptainKajun · Jan 7, 2022

When I say trashes the guide bushing I mean that it causes the guide bushing to get messed up to the point that even outside the machine it binds up on the material and leaves scars. I could send you a copy of the program if you send me your email

KaptainKajun · Jan 7, 2022

weve been using this size drill for years on other parts and have performed strength tests and the result are always better than expected.

KaptainKajun · Jan 7, 2022

chad883 said:
What size of stock? Is your tap dull and bulging the O.D. of your material? What speed and feed for the drill? Might be work hardening some and making tap push material not cut. Is your face operation kicking a burr on the O.D. of your stock?

Stock is 5/16" 316 stainless steel. The speed and feeds are 500 RPM and F.050 going 1.375" deep using a right handed forming tap in a rigid tap collet. The material is getting bulged up somehow although the tap doesnt appear to be dull considering its brand new.

BGL · Jan 7, 2022

You have answerd your own question - been there making removable dowel pins, I changed to cutting tap. You only have some 0.04" wall. The nature of a form tap is to displace material.

Nerdlinger · Jan 7, 2022

BGL said:
You have answerd your own question - been there making removable dowel pins, I changed to cutting tap. You only have some 0.04" wall. The nature of a form tap is to displace material.

Even if you have been making the part with this process (form tap) for a long time it would be easy enough to switch to a cut tap and see if your problem goes away. Good luck!

KaptainKajun · Jan 10, 2022

Nerdlinger said:
Even if you have been making the part with this process (form tap) for a long time it would be easy enough to switch to a cut tap and see if your problem goes away. Good luck!

I switched materials, now I am using a 3/8" bar and it did the exact same thing, Bound up in the guide bushing leaving massive scars and burrs. I was able to run a full part today but when I tried to get it to repeat, all hell broke loose. The probem definitely seems to be in the drilling or tapping cycles.

Nerdlinger · Jan 10, 2022

Hmmm, what if you skip past the tapping op and start just making a few parts with the drilling op to see if it survives. This is on-center, right? So you were getting a main spindle overload alarm? Does the load spike during the drilling/tapping ops? So the lands of the guide bushing are getting galled up?

DPM · Jan 12, 2022

Been there done that.. Your OD is expanding during drilling and or tapping. The material OD binds in the bushing when you suck the material back. Quick and easy fix is to turn the od down a little so that any OD expansion will not affect the bushing and then perform your drilling and tapping. Just ensure the distance you turn the OD doesn't exceed the bushing land.

Tom Lg · Jan 21, 2022

Just saw your PM earlier this week, and responded.

Nerdlinger · Jan 21, 2022

I hope the OP carries this thread through resolution. I’m interested.

TeachMePlease · Jan 21, 2022

Nerdlinger said:
I hope the OP carries this thread through resolution. I’m interested.

Uh oh, he made the nerd linger.

KaptainKajun · Jun 14, 2022

Hey sorry for disappearing I was busy solving this problem. The issue turned out to be in the drilling process. The drill was going too deep and building up heat while at the same time not allowing the chips to evacuate properly. I switched to a peck drilling operation and went up a stock size to turn the OD a little more so that we dont have the guide bushing issue. All is working great now and I appreciate everyone that tried to help.

SWYooper · Jun 14, 2022

You were going 1.375" in 316 and not pecking at all? I love me some coolant-thru drills as well but that just seems like asking for trouble.

Anyway, glad you got it figured out!

Citizen Swiss Machines

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