Question On Milling A Slot

[kizmit99]

Hi All - I'm making a part and have a need to mill a couple of slots into a piece of CRS. The feature I'm asking about is circled in pic below...



The slot is .125" deep and .125" tall.
I was thinking I'd have to buy a slot-cutting end mill, but when I go to look for them, I can't seem to find anything appropriate. I can find 3mm and 4mm metric cutters. 4mm is too tall, but I guess a 3mm could work, would just have to run it through at two heights. I can also find T-slot cutters, that are in english units, but they don't go down to 1/8" (instead I found something like 9/64ths)...

If I went with the metric cutter, the shaft size is 12mm... Which (I assume) means I would also have to spring for a 12mm R8 collet (or mill holder) to hold it? Or, is 12mm "close enough" at .472" that a 1/2" collet would hold it firmly enough? My guess would be no.

I *think* another option would be to take a normal 1/2" 4-flute end mill to the grinder and grind off most of the side cutting flutes to form my own slot cutter. Bad idea?

Also, I've got about 20 inches of slot to cut -- should I expect a single cutter to last long enough for that, or should I assume I'll need a couple of cutters?

Is there something obvious I'm missing? Thanks!

 

[mosedawg56]

Try keyway cutters.

 

[Uglydog]

Woodruff
Be sure to carefully calculate cutting speed and feed.

Daryl
MN

 

[kizmit99]

Thanks! Searching for keyway cutters I was able to find something of the proper profile (at a reasonable price)...

Daryl -- is there anything "special" regarding cutting speeds with a cutter like this? (beyond a standard 400/dia RPM)

 

[Terrywerm]

Yup, woodruff key seat cutters. Run them at the standard SFM for the material you are cutting and use plenty of coolant. Make sure you don't overdo the feed rate and you should be fine.

 

[4GSR]

One thing to keep in mind, woodruff key cutters do not have side cutting abilities. They also do not unload chips very good when doing a tee style of slot like your doing. But that's ok, people do it all the time in industry. I know of several parts we used to do years back that has a similar tee slot to them and they were done with woodruff key cutters. Like Terry said, use plenty of coolant, but most important, use a pressurized coolant if you can. Running a spray mister wide open will work, too. Just be sure to use some guarding to keep from getting hit by the chips and coolant if you can. IF you don't have a coolant system at your disposal, a blast of air at a low pressure, say around 10-20 psi will work too.

The key to milling the tee slots is clearing the chips as you mill. Once you clog a flute on the cutter, it's all over with. Cutter will knock eventually hang up and break.

Ken

 

[kizmit99]

One thing to keep in mind, woodruff key cutters do not have side cutting abilities.

Not sure I follow this?

Thanks for the idea of using air to clear the chips (although I've heard not to use air to blow off the table/etc, I'm assuming that would be geared more to towards 'don't use 100psi air to clear chips'. What you suggest is what I'll probably have to do, as I don't have flood coolant (I usually just use a squirt bottle of WD40).

Terry - thanks for confirming the cutting speed question!

 

[brino]

Not sure I follow this?

I believe Ken is saying when using a woodruff key cutter in a vertical mill do NOT feed with the z-axis (up/down).
Feed can only be in the X and Y-axes. Basically treat it like a non-plunge or non-end cutting milling cutter.

For cutting steel, WD40 is not a great choice. Instead try some pipe-threading oil from your local hardware store. Save the WD40 for cutting aluminum.

-brino

 

[rock_breaker]

Question for the group; Would a fly cutter properly ground be advantageous for a first pass then finish with a key cutter?
Ray

 

[astroracer]

You wouldn't have to mill a slot if you made the gib a separate piece and simply bolted it on. I just rebuilt a milling vise with bolt on gibs.
Before reassembly to the slide.

Bolted on

Sure would simply things.
Mark