Need Help!- rough turned stock through guide bushing

[hacdlux]

i have an upcoming job in 4340-m i am having problems tracking down cold drawn or ground stock

one supplier has the stock in hot rolled and turned condition but i've never ran this before and am woried about it jamming in the gb

stock dia .750 and ive got +-.002 tolerances on this side of the part

machine is a tsugami ss32 with a std- td32 guide bushing

all else fails i'll send the bar out for grinding and run it that way

[MikeMc]

It is going to depend on the OD tolerance of the bar itself, if it is too far off it will stick in the GB. The other concerns will be the straightness of the bars and out-of-round conditions. You could have the vendor send you a sample bar to check, or just have it ground.

[elsanch]

use a sand collet and gb...it wont "stick"

[Doctor Tsugami]

I know its late in the game but your machine can be put into a guide bushing less mode, might this work , many customers are using this method for short parts that don't need to be supported.

[houstonsamuel]

Don't get the hot rolled. The scale on the bar sucks! The turned stock is not all that bad. I have done many jobs with turned stock. Just make sure the bars are the same all the way down and not bent to bad. Also depending on your guide bushing it may not like the bar if its on the high side of the turned tolerance. If you are getting a bar or two, turned should get you by. If this is a major production or a tight tolerance part you should get it ground. Nice mahine you there

[cncserveng]

Qualifed bar stock is always the best way, but good quality bright drawn from the same batch of material might be ok, if you can set the guide bushing for the tightest diameter you might just get away with it.

[hacdlux]

We actually managed to find ground bar from another supplier(not very consistent) i just pulled that job off the machine this morning.

the ss32 is not convertible (guide bushing only)

the second part in the group has a 1/4 broach and it spiked the load meter on my z2 axis t0 180% so i am going to put the second part on my mori

thanks everybody for the replies

[houstonsamuel]

Have you tried a 3 point broach or two point broach? I think the chucking on the SS is an upgrade.

[hacdlux]

i was wobble broaching, i'm fine with doing it as a secondary were having problems with the boring bar before the broach and it gives us a chance to inspect the parts before we broach them

the 2 point intrigues me. i take it that it would be a straight punch with indexing the c axis,

still not sure if it would reduce the thrust low enough, it is a 12 pt broach

going to have to look into it

there is no chucker kit for the 32mm machine, only the 20 mm. they do make the ss32l which is chucker only( they came out with that about 6 months after i bought mine)

[houstonsamuel]

Well I guess Im not up to date with the SS32. Yes, you are right about the 3 point or 2 point broach. You will have to index the spindle and straight punch it. If you get a chace to do try it out.

[polygon]

Did you end up trying the 2 or 3 point broach? I'm just curious about how it turned out. You could also do a rectangle and rotate that right? Thanks.