A screw up in using a slitting saw

[ieezitin]

Lads

In the shot below is a set up on the milling machine of me trying to Slit-saw a taper pin expansion rod i am making. The saw thickness is .007 thou x 1 1/8th od, i ran the mill at 150 rpms the part is made out of 304 stainless.

In this shot you see the work in front of the slitting saw, i centered the saw blade to the pin center and i plunged cut in (moving the part away into the blade) .075 thou. that worked fine, i bathed it in Kroil and slowly fed the part onto the blade.

I then needed to slit the other side of it so i just raised the quill and moved the table 180deg, lowered the quill to center height and started to slit this side.

The device you see poking into the end of the collet block is a stop for the pin up in the hole, my thought was the blade may want to throw the pin out. That will become clearer on the next photos.







Here is a shot of the first side i successfully cut.






Well!!!!!!!!! here is what happened when i did the other-side, i got to about .050 in the cut and the thing turned to Shite, the blade snapped and at the same time gouged the piece which is now ruined.





Here is the shot of the part with the pin included, i installed a sacrifice pin into the arbor for the machining process in slitting, the wall thickness on the taper tube end is around .032 thou






I figured that what i am trying to explain may be a little hard to do in words so i can show you my drawings for you all to get a better perspective.


Linear drawing showing taper reamer and drill, this is to scale.





Detailed drawing.








And a shot of the pin installed before being turned down.










What i shall do now is re-make another one and this time just index the pin, as i know it worked in that location.

if anyone has any experience in using very thin slitting saws i would appreciate the advice, i have never slitted anything this thin.

Happy days Anthony.

[tekfab]

So if i've got my head around this when you were doing the second cut you were climb milling it with the slitting saw ? yes ?

Mike

[PixMan]

I'm also a little confused. When you state that you "moved the table 180º" does this mean you raised the quill and cranked the Y axis (the in-out, not left right) movement of the machine so that the cutter was now on the opposite side of the workpiece from what we see in your photo?

The best thing to do, especially since the first side of the slotting operation went so well, would have been to simply flip the collet block over the 180º and repeat the operation. If I get it right, your first photo is of the second side before crashing. If that's true and it's a right hand cutter, you definitely had that work "hog in" to the cutter and that's the reason for failure. As long as you had a reasonably firm clamping of the collet, the .007" thick saw would have been in multiple pieces long before it ever moved the piece back in the collet.

BTW, your saw looks a lot bigger than 1-1/8" in diameter. If true, your speed of 150 rpm may be too high for HSS in 304 stainless steel.

[TomG]

Yup, climb milling was one of the things that did you in. The other is a lack of proper cutting oil. Stainless likes to stick to cutters and requires a good grade of sulfur based cutting oil, Kroil is not cutting oil. I would also recommend using aluminum for the sacrificial pin and don't forget to take the backlash out of the feed screw before taking a cut.

You had the right idea using a sacrificial pin and the set-up for the first cut, it's just that with some machining operations, all it takes is one factor to make the whole thing go awry.

Tom

[ieezitin]

Gents.

The cutter od is 1.740 x 17 teeth per inch x .007 my mistake, but my rpm i said was correct.

Yes i cut the first cut as you see it in the first photo I pushed the Y Axis away from where the operator stands, i plunged it.

The sacrifice taper pin is a store purchased N03 steel pin.

The bed was locked on the Y axis anticipating climb-milling, but correct me if i am wrong if your not feeding the part to the cutter how would climb milling take place?

Indexing the collet block 180D was the right move next, for the life of me i do not know why i did it doing this i had to re-set the clocks and other stuff i just made my life harder.

Kroil is a rust / nut-breaker product but its very slippery and i use it on Ali all the time with good results. I agree the coolant had a major roll in busting the blade.

Well since we now have the full picture i am going to make another one and attempt this again, i have another blade identical to the original, i will purchase some water coolant product and give this another go, all suggestions are welcome.

Thanks to all for the comments so far.

Anthony.

[stevec]

(08-11-2013, 02:34 PM)ieezitin Wrote: Gents.
correct me if i am wrong if your not feeding the part to the cutter how would climb milling take place?
Anthony.

While you were not actually "climb milling" feeding on the Y axis.
The X axis feed you used created a similar interaction of the cutter and the material. Flipping the block would eliminate the difference.
Also, if you plan to use a slower cutter speed you have to use a slower feed.
Good luck, I hope your next post announces success.

[TomG]

If you have the cutter in front of the part and feed it in with on he Y axis, you are conventional milling and the cutter will push the part away. If the cutter is behind the part and you feed it with the Y axis, you are climb milling and the cutter will tend to pull the end of the part into it, which is what happened on your second cut. The climb milling thing would be more apparent if your cut was shallower on the X axis.

I use these slitting saws all the time and would highly recommend using ordinary cutting oil over coolant. Coolant will only work on a slitting saw if you flood it. Oil sticks much better and it only takes an instant of no lube for the saw to seize in the cut because there is so little clearance.

Tom

[ieezitin]

Tom.

what cutting oil would you recommend?

I can buy from all the usual places..

Thanks a million..

Anthony.

[EdK]

Here are a few sources of dark cutting oil.

http://blackswanmfg.com/index.php/black-...egory_id=5
http://www.veritassupply.com/valona4984s...4sgal.aspx
http://www.faucetdepot.com/prod/Oatey-He...153334.asp
http://diamondtool.net/p/cutting-oil/rid...ailed_desc

Ed

[dallen]

plumbing supply its what most plumbing supply houses sell.

and the stuff that say's Ridgid on the jug is over priced