Parting tool question

[chucketn]

I have been busy making aluminum QCTP tool holders for thoseonce in a while tools that we hate to take another tool out of its holder touse.

Last night I was making the knurled wheels (mat’l aluminum)for setting tool height. I drilled a piece of al bar and tapped for the heightscrew, sectioned off 4 wheels, chamfered the edges, and finished parting themoff. The picture shows the burr left by parting. My question is, can I grind aparting blade with a slight angle on the tip to cut the parted piece clean? Howmuch angle?


Chuck

 

[Woodster]

Yes you can. About 5-10 degrees should be ok, but be careful of tool deflection and don't forget to stone the corner off.

 

[deverett]

It looks like you may already have a slight angle on the end of your parting blade. What is happening is that the headstock corner is cutting deeper than the tailstock corner, giving you the burr on the parted pieces.

You would only need a slight angle of perhaps 1 or 2 degrees so that the tailstock corner of the parting blade cuts slightly deeper than the headstock edge. Continue feeding in after parting off and the burr will be removed from the stock material.

Keeping the angle as small as possible will help prevent the parting blade wandering giving you a convex face to the parted item.

Personally, I find it difficult to grind the cutting edge truly perpendicular to the length of the blade, so I don't have your problem!

Dave
The Emerald Isle

 

[chucketn]

Uh, I think I should take that as a compliment Dave, maybe? Before I regrind, I'll work the tip of the cutting tool on my stone. I did find that running the parted wheels onto the tap again cleared off most of the burr, and I could clean the rest easily with a fine file. just trying to improve overall quality of my work.

Chuck

 

[gus]

Hi Chuck,

When parting Try dobbing with small brush Tapmatic Aluminium Tapping Fluid. I get clean finish and good parting and good swarf flow. Slight angle helps minimise burr on the tail stock side.I am stuck with lathe running at 600 rpm.
I use LMS parting tool.

 

[Lew Hartswick]

I've tried the "taper the front" of the cut-off tool many times and it still leaves a bit
of the ring. I think it's about impossible to get it clean. The cutoff part starts to swing
before it gets clear off and tears a bit with it. This has all been with aluminum, may be
a bit better with steel.
...lew...

 

[gus]

Hi Chuck,
The Webster Engine require 4 pcs 6 mm ID x 12 mm OD x 3 mm thick Aluminium Spacer Washers.
The first two pcs were clean parting while the last two had a wee bitty left but was easily peeled.
Use LMS "T" Parting Blade with DIY holder. Use JIS Aluminium Bars. Coolant was Tapmatic Tapping Fluid for Aluminium. Turning speed 600 rpm.Notice the clean free flow of chips curling out.The sharp inside corners were chamfered with a countersink tool by hand. Quite happy with finishing.

 

[Forestgnome]

Since those are threaded they should have a chamfer on them anyway, so just put them under a countersink tool on the drill press. It'll bite off the burr and put on a chamfer at the same time.

 

[Mechanicboy]

Tools for aluminum and aluminum alloys should have larger relief and rake angles than tools for cutting steel. For high-speed steel turning tools the following angles are recommended: relief angles, 14 to 16 degrees; back rake angle, 5 to 20 degrees; side rake angle, 15 to 35 degrees. For very soft alloys even larger side rake angles are sometimes used.

High silicon aluminum alloys and some others have a very abrasive effect on the cutting tool. While these alloys can be cut successfully with high-speed steel tools, cemented carbides are recommended because of their superior abrasion resistance. The tool angles recommended for cemented carbide turning tools are: relief angles, 12 to 14 degrees; back rake angle, 0 to 15 degrees; side rake angle, 8 to 30 degrees.

For best finish, use kerosene or soluble cutting oil.

 

[Engineeringtech]

When I have something like this I use a flush cutting diagonal cutter to clip off most of the burr. Then I take the rest of the burr off with a countersink at the drillpress. Helps to set the part on a piece of rubber to keep it from rotating. McMaster sells some rubber that really grips.

 

[tornitore45]

If the final approach is delicate the burr band is usually a few thouseands thick, I use a utility/Xacto knive to cut it off. It cuts like paper.

I also have 3 drill bits 1/8; 1/4 and 1/2 mounted on permanent handles to use as deburring tools for small holes. The bits are dressed for zero rake like you do for brass so they do not dig.

 

[Engineeringtech]

I'd like to know how you dress the bits for zero rake. Are you just doing it freehand on a bench grinder?