# I need RPM settings please



## muscleflex (Oct 15, 2014)

Hi, I need rpm settings please for the below material and usage if anyone can help?

FACING:
aluminum rod: 6mm diameter
mild steel rod: 5mm diameter
stainless steel rod: 3mm diameter

PARTING:
aluminum rod: 6mm diameter
mild steel rod: 5mm diameter
stainless steel rod: 3mm diameter

I have a 7x14 mini lathe. It has a digital readout.
 For facing.. I started using between 400-600rpm for the aluminum rods
I have not parted yet. I just got the parting tool last week: http://www.ebay.co.uk/itm/141031590854?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT

Any help pls would be greatly appreciated. Thanks


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## chuckorlando (Oct 15, 2014)

well you need to find the cutting speed for the material. Then calculate the rpm and such. (CSx4)/Diameter. Then your feed is  number of teeth x rpm x feed per tooth

http://www.southbaymachine.com/setups/cuttingspeeds.htm#Feed Rates


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## chuckorlando (Oct 15, 2014)

When I part I run it as slow as it goes which is about 100rpm. Thats to fast some times on my 9x20. Go very very slow on the feed.


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## muscleflex (Oct 15, 2014)

Thanks - I have looked at this in the past and it just really confused me! 
so... for example for my 6mm aluminum rod (just a tad smaller than 1/4"), is it 250rpm or is it 400-700? there's two columns which I don't understand on that link. One is Ballpark CS and the other is Cutting Speed.




chuckorlando said:


> well you need to find the cutting speed for the material. Then calculate the rpm and such. (CSx4)/Diameter. Then your feed is  number of teeth x rpm x feed per tooth
> 
> http://www.southbaymachine.com/setups/cuttingspeeds.htm#Feed Rates


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## chuckorlando (Oct 15, 2014)

Let me do th mathe real fast. I know off hand 200rpm is way to slow for 1/4


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## muscleflex (Oct 15, 2014)

Is this right?
Ballpark CS for aluminum is 250. and if my rod is 1/4" then using the formula (CSx4)/diameter will give me
250x4 = 1000
1000 / .25 = 4000??? that can't be right? 4000rpm?


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## chuckorlando (Oct 15, 2014)

Seems to me on steel be about 1500rpm. Now cut that in half and work up towards it till you find the right finish.

http://www.custompartnet.com/calculator/turning-speed-and-feed

The real trick to these things is knowing the cutting speed for the material. Not the rpm or your feed rate. Use the CS to calculate the rpm

http://www.custompartnet.com/calculator/turning-speed-and-feed

This site has all the info you need to figure out all this stuff. I just open a window for the info's needed and a window for the calculator


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## chuckorlando (Oct 15, 2014)

I believe I gave you milling calc first..

Cutting speed (100) x 12/.25 = 1528rpm


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## muscleflex (Oct 15, 2014)

Wow I never thought it would be so complicated!!! 
Thank you for the help tho. I have something to go by now.


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## chuckorlando (Oct 15, 2014)

It's not complicated so much as alot to learn at one time. This is the page I was really looking for here in the link. It has everything you need to know. Use the chart to find the cutting speed(sfm). For your machine I would start at the lower number in each given range.

http://its.fvtc.edu/machshop2/Speeds/RPMcalc.htm

I have to go over all this every time I do it so dont feel bad


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## muscleflex (Oct 15, 2014)

Thank you - I shall give this a run tonight when I get home.


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## Rbeckett (Oct 15, 2014)

As Chuck aluded to the formula is not really difficult, but a lot to learn on the beginning.  If you do the calculations correctly you will get a good surface finish and a quality piece of work.  How far is the 6MM rod extending from the face of your chuck?  If it is sticking out pretty far you might want to use your follow rest to prevent wobbling and vibration in the material too.

Bob


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## muscleflex (Oct 15, 2014)

Hi and thanks. I'm actually not turning it down or anything. The work I do on the rods are just mainly facing (to clean the ends as I handcut them using a hacksaw).
Then I thread them using a threading die in a die tail stock holder.

The parting tool, I was thinking of using it to create a shallow channel or groove on one end of the rod.. kinda like this:


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## chuckorlando (Oct 15, 2014)

Can you get the stock through the head stock? If so why not skip the bandsaw and just part each one. Save you on facing and sawing


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## muscleflex (Oct 15, 2014)

That was the plan originally but I don't know how to use the parting tool. I'm a bit scared as I might break the HSS tool...
Do you recon I should run at around 100rpm for parting then? I could give it a go tonight and see.
also do I need lube?


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## chuckorlando (Oct 15, 2014)

I'm no expert on parting but I ran mine as slow as It went. Thats about 100. And just hardly feed it. Let the machine talk to you. You can feel when it struggles or is not happy. Feel and hear it. Mine rolled off like butter though it struggled in a few spots. It was not scary though. Just be easy man.


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## Wreck™Wreck (Oct 15, 2014)

muscleflex said:


> That was the plan originally but I don't know how to use the parting tool. I'm a bit scared as I might break the HSS tool...
> Do you recon I should run at around 100rpm for parting then? I could give it a go tonight and see.
> also do I need lube?



Coolant or cutting oil is usually required when parting. I was parting 1" Dia. 304 SS to center this morning, .090 wide carbide insert (right handed), 530 RPM, .001 IPR, flood coolant. I didn't want to turn it faster because I had to catch a 4" long part that came off by hand (-:


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## chuckorlando (Oct 15, 2014)

I have to assume your machines a wee bit larger then a 7x14 ahahaha.


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## Wreck™Wreck (Oct 15, 2014)

chuckorlando said:


> I have to assume your machines a wee bit larger then a 7x14 ahahaha.



14 X 36 Romi/Bridgeport CNC, last week I parted off 800 small aluminum parts, very boring as you can imagine.


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## janvanruth (Oct 15, 2014)

dont try and learn parting on a real part.
take a piece of scrap rod and try on that.
as close to the chuck as possible, if possible with tailstock support, exactly 90 degree, exact centre hight, to low will first cut then break the cutter,way  to high wont cut but wont break cutter a little to high will cut but will give problems at the end of the cut , feed agressively!, lock carriage, tighten gibs, tool not reaching out further than necessary, cutting oil

i can grind a parting tool with my eyes shut( nearly) nowadays, you guess how come...

but i finally did a lot of parting this week with no problems what so ever.


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## Cadillac STS (Oct 15, 2014)

I got one of these and it has been great.  A tachometer that can give RPM or SFM (Surface Feet per Minute).  Like you said you need speeds for the different diameters.  This tachometer tells you exactly what speed you are turning by measuring it from the spindle and you look up the SFM from a chart based on the metal and diameter.  With the tachometer going and data from the chart you know for sure you are optimal speed.

I think it would be helpful especially for someone new to machining.  With experience people will tell you that you can just know and feel what the speeds should be.  

http://www.machtach.com


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## muscleflex (Oct 16, 2014)

I had a go last night on a scrap 6mm diameter aluminum rod. it worked ok at 100rpm. Altho I couldn't seem to part it off completely. I got to about 75% in but it wouldn't cut anymore. I'm guessing my tool is not aligned and either too high or too low. Also I was using just a cheap 3 in 1 oil..and my lathe doesn't seem to like it. I was parting off better when it was dry.

Can anyone please tell me what cheap oil I could use?


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## chuckorlando (Oct 16, 2014)

wd40 would work. Dark tap fluid from a box store. You are likely to high. As the OD gets smaller you are running out of material to cut as your cutter is over center. If you were to low it would part through the work but it would leave a square tit holding the two.


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## muscleflex (Oct 16, 2014)

Thanks. I only gave it a quick go last night as I was in between helping my wife with out 7week old baby.
I'll give it a try again tonight and will make sure the pointy end of the parting tool is at center.

I'll keep you guys updated.


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## chuckorlando (Oct 16, 2014)

congrats on the child bro


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## muscleflex (Oct 16, 2014)

Thanks! She's definitely a joy but definitely taking up most of our time!
Thanks for all the help so far!


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