Hey, finally a section for one of my favorite lathes.

[groovemixer]

yeah finally!! have to say hardinge is one of top lathes, we have a t42sp about 7 to 8 years old, had some very bad crashes and she still holds to 5 microns!!! trying to purchase another with live tooling this time.

[g-codeguy]

TARIQ08 , A little more information would be helpful. O.D. or I.D. thread? How are you threading now? RPM, DOC, lead in, etc. I use the G76 thread cycle almost 100% of the time. Do a lot of threading, but it's been years since I did an acme thread. Are you re-turning & re-threading?

[DOA]

Originally Posted by TARIQ08 I am trying to thread aluminum tubes on a conquest 42 lathe and i am getting a lot of burrs. I am doing acme thread form, 4tpi. What are the best possible G code

I've not done ACME as big as 4 on my Hardinge, but I have done a bit of 6-8 & 10 tpi's. Your feeds and speeds are very important aa well as the condition and/or style of insert. The best results I got was from using a smaller gauge insert and doing 2 "cycles" with the second pass altered or moved in Z- to widen the profile and minimize the burring. It's virtualy impossible to do the ACME in one "cycle" without burring.

[TARIQ08]

I am doing OD threading to aluminum tube 1.32Dia., ID of pipe 0.940, depth .1 and rpm of 900 and using G76 cycle.

[DOA]

Originally Posted by TARIQ08 I am doing OD threading to aluminum tube 1.32Dia., ID of pipe 0.940, depth .1 and rpm of 900 and using G76 cycle.

The .1 DOC seems to me to be pretty large, especially for the 4 ACME. Back it off to around .02 to .05 to start and experiment with a slower rpm, say around 500 . You can increase your DOC and RPM's to get the best results and you can always consult your tooling supplier for the recommended DOC and RPM too. The 4 ACME is taking quite a load at .1 DOC. You may want to take another "cycle" with the Z moved -.005" or so, but this will widen the thread form, so adjust the depth of thread accordingly.

I am not familiar with all of the threading cycles from the programming manual, I usually read up on a particular function when I need to apply one. I do know there is a threading cycle for "compound" feeding the angle of the thread form, in your case 29.5 degrees, but you'll have to consult the programming manual or wait for a reply from someone that has. I'll do some checking, but I'm not near my manual.

[turnandburn]

Your best bet would be to thread using a g76.

The first G76 block:
G76 Ppppppp Qqqqq Rrrrr

Ppppppp - the first two digits are the number of finish passes, the second two digits are thread pull out chamfer amount, the third two digits are tool nose angle.

Qqqqq - specifies the minimum depth of cut per pass

Rrrrr - specifies amount of stock to leave for the finish pass

The second G76 block:

G76 Xxxxx.xxxx Zzzzz.zzzz Ppppp Qqqqq Rrrrr Fffff

Xxxxx.xxxx - specifies the X end point of the thread.

Zzzzz.zzzz - specifies the Z end point of the thread.

Ppppp - specifies the single depth of the thread.

Qqqqq - specifies the cutting depth of the first pass.

Rrrrr - specifies the taper angle of the thread.

Fffff - specifies the thread lead.

You might want to leave .002-.005 on your od after roughing , then thread, follow with finishing tool to final od, then duplicate your g76 line and give a first pass equal to your single depth and take one spring pass to remove any burr rolled in to threads by your finishing tool.

Hope this helps,

Pete

[TARIQ08]

Thanks a lot Pete, I will try the program.

[Rodney Wallace]

We have a 1993 Hardinge T42 (bought new)......Has anyone else had problems with the subspindle belt breaking??

We have had this problem starting in 2000.

It was breaking at least 6 times a years (with constant use)...We would replace the belt with the manufactures suggested belt,but it would still break soon after(I can tell you as an operator I got to know the sound of the belt breaking and usually could save it from crashing the subspindle...otherwise the results of a tool hitting an unmoving part was disasterous)

FINALLY... We replaced the (last) belt with one from Gates (of highest quality and price...lol) and havent had a belt breakage in over a year now.

Its been a great machine other than the belt troubles.

Just wondering if anyone else had a similar problem???

[DOA]

I can't relate any belt problems on the lathe, but had a vertical mill that frequently roke thr drive belt, It got a LOT more dependabla and life when we started using the Gates top of the line belts. Ya know what they say...
"You get what you pay for"