Turning Finish

Great response! All the right questions.

Thank you Mr. Brain

we are using constant speed command. we will try to put extra relief on edge of the tool. tool is also on centre height. do you have any idea about some standared tool bit for facing purpose.

i will wait for your reply.

Thank you again

HS

HS, tip geometry depends on the material you are turning. If you are using indexable tips, then contact your supplier for information regarding which tip for which material! If you can chip the swarf into tiny chips instead of long strings this will help due to the fact that the chip is easier to wash out of the way! We need to know the material really to be able to help more! I hope this helps.

Truman

Dir Mr.Hinashu Sharma,

You used constant surface speed command is correct.

And if allowed, you can centre drill and then finishing the surface to correct the tool height. Or calibrate the tool height first and then finishing surface without centre drill.

My personal preference for a tool to only face would be an 80deg diamond, positioned to ~ 10-15deg lead angle; giving 20-25deg clearance angle.

This usually gives enough room so that chips do not get caught.

I had a similar problem with turning 4140 steel.

The job required facing a 2" shaft, cutting a shoulder and thread it, then drill a 1/4" hole down the centre for 8" length, finish with a #1 morse taper.

Facing and drilling was problematic. I actually dulled drills in some pieces, and others cut like butter. I had to discard a number of pieces and buy new shafting. The problem appeared to be batch dependent, so I assumed it was the quality of the raw material and the heat treatment. I found "aircraft" carbide tipped drills cut the cleanest, and different carbide inserts faced better.

But some pieces would never finish properly, hard, soft, tear etc.

It would help if you stated what material you are machining?

Hi Garth

we are maching the Mild Steel. It is a 150.0mm diameter plate and we can't do drilling in centre of the plate.

Thanks

HS

Do you mean plate steel or a piece cut from 150mm shaft.

Mild steel shafting can have a fair bit of variability in tensile from the outer diameter metal to the center, usually due to the forging process the outer section will be a higher tensile than the center and will machine smoother at a higher surface speed than the center section, as mentioned before increase the surface rate if possible.

Plate steel has a better tensile than shafting due to the rolling process and is more consistent you would find it would generally machine smother than shafting.

You should try a different tip geometry for finishing cut instead of tip approach try flank approach.

Yes, Mr. Grath we are using plate steel arround 50.0mm thick. Do you know any standared about tool bits geomatry for different machining operation speaciely for turning purpose.

Thanks

HS

Please tell me what material of work piece was.

You use only face turning or longitudinal/facing turning, don't you?

You can use sandvik tool and insert, it is not cheap but too stable in machining.

They are: tool is PSSNR 2020K 12 or PSKNR 2020K 12

Insert(bite) is SNMG 120408-PF 4015 for steel.... Detail is page A30 of Sandvik main catalogue.

Best regard.

Dear HS,

I would suggest to go for a finish cut using a uncoated cermet insert in CNMG120408 style and a chip breaker especially for MS as Mitsubishi Carbide has got one which they name as FS breaker,run at 250m/min constant speed and you would like the regular finish on your part.You can cut dry or wet whatever.

Just try if you can.

Rajnish Dhawan

Try roughing it out to about 0.2 over size then taking a finishing cut! Is that free cutting mild? Some of that cheap mild steel tends to rip if you get a bad bit, so there is only one option and that is use a better quality free cutting mild steel if you want to solve the problem!

Hi Brain

we are using exceatly the same method as you suggested. Now only thing is remaining that tool bit and raw material quality. so that we need to work on that.

Thank you

HS

When the cutting tool approaches the centre during facing the surface speed of the part becomes slower. Increasing the speed of the part would be ideal. Some CNC machines allow this if you opt for surface speed feeds. As for some pieces ok could be the quality of material.