Problem- guide bushing range

[hacdlux]

i am curious what my adjustment range is on a td32 gb


i have a job im setting up in 1.25 316 ss

i have a aluminum trial bar at 1.2501
i have a stainless trial bar at 1.251
and the customers special stainless bar is 1.2491

.002 variation between the three

i have a .0004 tolerance on one feature but it is before the back turn

i am using the full land because of back turning operations

should i lap the bushing down for the final part?

[DCogswell]

Originally Posted by hacdlux i am curious what my adjustment range is on a td32 gb i have a job im setting up in 1.25 316 ss i have a aluminum trial bar at 1.2501 i have a stainless trial bar at 1.251 and the customers special stainless bar is 1.2491 .002 variation between the three i have a .0004 tolerance on one feature but it is before the back turn i am using the full land because of back turning operations should i lap the bushing down for the final part?

If the mfg of the GB did their job (.1250") then, the only prob you may encounter is the $$ trial bar and trying to hold .0004". However, if the material is just used for set-up purposes then you'll be fine.

The fun starts with the 316$$! I hope that customer supplied material doesn't have any surprises in it!

[hacdlux]

The fun starts with the 316$$! I hope that customer supplied material doesn't have any surprises in it!

customer provided qualified, double heat treated, metalographed,ground material

we already did proof of concept in regular 316 ss i was tought many lessons

[DCogswell]

Sounds like you did your homework. Hope you're running oil instead of that tap water...

[hacdlux]

no way, we run soluble drawing compound

way better than the old tap water stuff

we had this nasty little stainless part that we kept having problems with
been running this ever since

although water has cost alot in maintainence lately

[gizmo_454]

Blaser's Swisslube works well for most things. In any case, the material is "double heat treated." I would be careful with this. Just because the normal 316 worked, does not mean the special stuff will. I have run "strain-hardened" 316 before, and also implant grade 316 @32HRc. Neither run like normal 316. Just be careful.

Good luck!

Mike

[hacdlux]

im sorry, double anneal

[lukehonor]

You're probably going to fight the job a little bit, no matter what size guidebushing you have. I run some Tsugami SS32's and I've had bar stock similar to what you're explaining. You should be okay, but you're looking at an .0008" difference between guide bushing and bar stock. If it's a long running job you may have some problems because your guide bushing is going to actually be over-tightened to compensate for the .0008". Personally, I wouldn't run it like that.

I like to have my barstock ground +/- .0005" of the guide bushing diameter. I've ran some very complicated jobs with ground bars +/- .0005" with no problems. I pull in and out of the guide bushing 5+ times during one cycle and I don't have any problems. BUT, i've ran the same job with not-ground stock and a difference of .0003"-.001" from guide bushing to stock and the job simply wouldn't run.

You may be okay, but you may have some serious issues. Good Luck!

[SirDenisNayland]

No issues here running plus or minus two thou cold finish stock through regular carbide bushings.

Just have to make sure the bars are all the same and adjust for different lots. As long as you're not shearing the material and the main collet isn't slipping let'r rip. You'll be surprised at the leeway you really have when you start experimenting for yourself.

In the ideal world you want perfectly onsize centerless ground material, but its not do or die like a lot of people make it out to be.. plus sending out thousands of pounds of bars for grinding really eats into your profit... Only time ill send something out for centerless is when I have to hold less than half a thou across all aspects, and even without grinding, once the job has warmed up its not uncommon to hold a tenth all day long. Call me crazy if you will, but I come from the production world, not the single tube bar feeder ten minute part then check it then run another piece and make twenty pieces in my entire shift world.

Another thing, if you're truly asking these questions there are likely other variables at work contributing to your problems if you're still stuck on guidebushing nuances. It'll come in time. I don't even feel bars anymore, I know its where it should be by the feel of my guide bushing wrench.

Cheers.

[hacdlux]

stepping up in the world
moving from .002 tolerances to .0002

my ss just turned 3 years old and my mori is almost 4
before that i was a mill operator for a year

i got three days of apps training on both machines then had to figure the rest out myself with the assistance of this forum,

half the machinists i know dont even know what a swiss is much less have any advice.

i also am moving from 1 minute unatended parts that run for day on end with just emptying the parts catcher to 15 minute parts tying up almost every tool in the machine and holding tolerances in the micron range

thank you to every one for their advice and critiques