Gallery, Projects and General > How do I??
Milling tool steel
SPiN Racing:
Hi Guys!
I think I already know the answer.. and its Carbide..... BUt I want to run this by you all first.
SO.
I decided to get started on the Tool holders for the QCTP tonight.
I had previously purchased a chunk of steel... grade zero tool Steel I gather. It was a drop.. and it is 3" wide by 1" thick, and 26" long. Sooo I will be cutting a Slot down the length of it.. then dovetail it... then flip it. Cut 1/2" slots across it. Then into the band saw to lop off the individual tool holders... then back into the mill to get holes drilled and tapped.
SO
I tram the head of my mill. 1 thou over a 24" sweep.. I think thats gonna be ok.
I lock this beast of a slab of metal down onto my CLEAN (yes I spent last weekend cleaning the area around the mill and lathe of swarf... 5 Gallon bucket of packed down swarf) Mill surface.
I make sure to get it perfectly square and true with a dial indicator as I traverse the mill.
I chuck up a .75" SIDE MILL... (two flutes GOLD colored cheapy titanium coated Fleabay brand new cutter)
I bring it down with a piece of paper under it, till it JUST touches the work piece.
I adjust the mill stops so the powwer cross feed stops with the end mill JUST outside the work piece on each end.
Move the 5 gallon bucket that is the coolant pump and resevoir over to the mill.. hook it up, so it floods the milling bit nicely.
Hook a drain from the mill table to another clean bucket to catch the used coolant.
Fire up the mill around 1150 RPM.
Bring it over the work... raise the table so it just barely cleans the metal.
then I turn on the coolant, and crank that thing the length of the work. SMoothly and slowish.
I end up with a nice smooth clean evenly cut "channel" in the metal. maybe 2 or 3 thou.
I then raise the mill about 30 thou. ANd decide to see how well its going to cut this steel if I move slow and have flood cooling.
Soooo It cuts... tip gets hot.. little smoke from the WD-40.. but not too bad.. I can still see the tip, and the spray etc. It SOUNDS ok.. nice smooth uniform cutting noise.
I get into the work about 1.5 inches and the sound changes... it begins to go higher pitched.. no chatter.. but it begins to go higher pitched and starts to squeal.. So of course the ultra slow manual feeding I was doing.. I slowed down and backed off.
I attempted to re-start the cutting twice.. and it just squealed and smoked once I very carefuly brought the cutter to the work piece.
I decided 30 THou was too much so I backed off to 15 Thou. Tried again.. and it squealed a TINY bit when I started.. but only a tiny bit.
I slowed down my cut even more so I was barely turning the handle... and I was getting little 1mm chunks of steel uniformly coming off the part, with a small amount of smoke from the coolant.
I then put the power feed on its slowest setting (which isnt moving) and then turned up to the super slow crawl of a speed I was feeding it at.
The table ultra slowly crawled across under the cutter.. uniform sound.. uniform chips, and a tiny tiny amount of smoke from the coolant. The tool bit was bathed in coolant, and staying cool.
Now
The work had a odd shape to the cut.
It had a real smooth center.. and on each side of the cut it had a... prolly 1 or 2 thou step. -----_______-----
Knowing this wasnt right.. I thought about it as it slowly crawled along... and realised it wasnt the head out of tram.. because that would just cut funny.. leaving a swirl mark of some sort... this wasnt.
After the cutting was done I pulled the tool bit.
Looking at the end.. it had eaten 1/3 of each flute back about 2 thou, but the stronger center was unblemished.
I changed to the other 3/4" cutter I had... a END MILL (4 flutes.. but center cutting also) and moved that baby over to the work.
I tried to make a 5 thou cut.. and it screamed at me like it was going to explode soon as the tip touched the work. Also followed with a HUGE plume of smoke.
I sped the mill up to 1750.. it screamed louder, and more instant smoke.
I slowed it to the slowest speed and it chattered and squealed and smoked.
And yes I am talking move it to the work and ever so slowly slowly slowly slowly touch the work. (I learned to be careful with a smaller cutter when I started by moving into the work too fast and the small cutter exploding..... so I am very very very careful now... and lucky too thanks)
SOOO
My question.
Should I buy a carbide Side Mill?
As this is a bar of tool steel.. from what I read about Mills.. the Gold colored TiN ones are fine for brass and aluminum.. but once you move to stainless and or tool steel they are complete crap.
Carbide 3/4 Hogging Mill... (Needs to be run at high speed.... high speed being how many RPM?)34 Bucks..
http://www.wttool.com/product-exec/product_id/31610/nm/Carbide_End_Mills_WT_Import_
A Solid Carbide 2 Flute (picture shows 4 flutes) is a bit expensive at 50 Bucks!
http://www.wttool.com/product-exec/product_id/32044/nm/2_Flute_Solid_Carbide_Single_End_Mills_Import_
Or should I simply buy a Indexable tip tool such as this? 16 Bucks, plus inserts..
http://www.wttool.com/product-exec/product_id/33787/nm/Indexable_Carbide_Insert_End_Mills_WT_Import_
Or a set for 50 Bucks
http://www.wttool.com/product-exec/product_id/33822/nm/Indexable_Carbide_Insert_End_Mill_Sets_WT_Import_
Thoughts and opinions appreciated :D
sbwhart:
Hi Spin
Sounds like you're harding the job up with the heat generated from the cutting action, did you have a good flood of coolant on the work.
Coolant does three main things 1:- Keeps the job cool, 2:- Lubricates the cutting face of the tool,
3:- washes away the swarf.
With some material No 1 is the key thing with others its No 2 with other applications its No 3 It sounds like you got a No 1
You should be able to machine tool steel with good quality HSS cutters unless its something special you are trying to cut. With your mill that I know is a quite a good size the depth of cuts you've been taking you should have no trouble, in fact small cuts can be worse that large cut. Cuts of 2 or 3 thou can result in the tool rubbing and generating heat, you have to be bold and go for a deeper cuts.
There's no harm trying a TC cutter but even these will cause trouble if you're not using the right technique
Hope this helps
Stew
SPiN Racing:
Thanks for the input!!
Yes I moved my coolant over to the mill.. and elevated it, and am dispensing from a 3/32 opening and it has a LOT of coolant coming out. It is WD-40.
Hmm.
More food for thought. hardening it as I try to cut..... /nod
sbwhart:
Spin
WD40 may not be the best coolant to use in this application its good for ally and none ferrous stuff but for steel its more usual to use a water soluble cutting oil something like this
http://www.chronos.ltd.uk/acatalog/Chronos_Catalogue_Oils__Lubricants___Adhesives_etc
Cheers
Stew
bogstandard:
Spin,
Stew is perfectly correct, WD40 is definitely NOT the one to use.
Not only is it no good for ferrous materials, because of the temperatures reached during cutting, it just might burst into flames on the job, and with it being continuously fed with even more WD40, you run the risk of not only your workshop going up, but god forbid, yourself with it.
A good water soluable oil is much better for what you are trying to achieve. One pint of cutting oil, depending on the water/oil ratio mix can give you up to about 100 pints of cutting/coolant fluid. So much cheaper as well.
John
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