Milling machine - End Mill Vs Slot Drill

[LandyManLuke]

I'm looking at getting some tooling for my milling machine. It's all new to me so I have been reading abouting end mills and slot drills etc.

I think I understand that the more flutes/teeth, the more material you can remove, and that a 4 flute cutter can't be used for plunge cutting, as the teeth don't cover the entire end of the tool. Is that correct?

Does tool selection come down to deciding whether I want to plunge cut Vs a faster sideways cut? are the two mutually exclusive?

Thanks,

Luke

[SmasherWebbs]

A cutter is as the name says for cutting and not drilling as a milling tip will have a cutting edge on both side and bottom. And yes the more teeth the higher the speed/feed you can use ( make sure you use lots of coolant!). If your drilling blind holes a slotting tool will do the job but you can get 2,3 or 4 flute bits that fit in many chucks for cheap.

And with a solid milling tool don't bother trying to re_sharpen if chipped. It will only end up with you wrecking a tool or going insane trying to get it too cut smoothly. Just by a new one!

[SmasherWebbs]

If your serious about doing a lot of machining getting a adjustable milling and slotting tool with replaceable carbide tips is worth every penny.

[SmasherWebbs]

http://www.iscaruk.co.uk/Products.asp/ProductId/686/CountryID/16/MenuItemID1/25

[longlandy]

Iscar good, I use iscar and wnt and can recommend both.

[vulcan bomber]

4 fluted cutters will move more material per rev but with a full cut on you will be more likely to get vibration.

2 fluted are the opposite of above to a degree.

3 fluted are some where between the others, we use mainly these at work.

Its not wise to plung with any with out a drilled hole first you'll get an over size hole at the start of your slot, your best plunging on a 2 fluted cutter, but if you have drilled a hole 1st, you can plunge with any of the above, make sure the cutters center is cleared.

[LandyManLuke]

Would you use standard twist drills for drilling first then?

I'm probably going to get a set of centre drills for starting holes and marking out etc with the DRO.

[Warthog]

HSS 2 or 3 flute slot drills can be used to create perfectly acceptable slots and holes. Using a twist drill generally is just adding another tool change into the equation. (Wasting time on conventional Mill) All the keyways i cut are milled using a 2/3 flute slot drills. (Always start with a plunge cut to depth to start the keyways, slot drills dont like edge cuts)They produce good holes and keyways within acceptable tolerances.

Material removal is paramount for cutting keywaysand slotting requirements. An end mill will/generally choke up if used on keyways and slots (Poor surface finish and tool wear) whereas a 2/3 flute slot drill will clear more easily.

End mills are the generally for facing and edge cutting.

Long Series Hss slot drills and Ends, however are a pain in the arse......But a neccesary evil.

Carbide tip tooling is good, but not the be all and end all. HSS tooling can be picked up pretty cheap in comparison.

In all fairness, a Couple of HSS Endmills say a 20mm and 50mm Dia. With a few slot drills and some twist drills will see the conventional miller in his shed good for most applications (Drill, Slot, Surface and Edge profiling)

Hope that there is some sense in what i have written?

[vulcan bomber]

Would you use standard twist drills for drilling first then?

I'm probably going to get a set of centre drills for starting holes and marking out etc with the DRO.

yep a bog standard drill its what you want.

[vulcan bomber]

Would you use standard twist drills for drilling first then?

I'm probably going to get a set of centre drills for starting holes and marking out etc with the DRO.

yep a bog standard drill its what you want.

[zoltan]

4 fluted cutters will move more material per rev but with a full cut on you will be more likely to get vibration.

2 fluted are the opposite of above to a degree.

3 fluted are some where between the others, we use mainly these at work.

In my experience I've found less vibration with more flutes but with a full cut on I wouldn't be too greedy with the feed. Thing I like about an end mill is the better finish versus a slot drill

[Warthog]

Would you use standard twist drills for drilling first then?

I'm probably going to get a set of centre drills for starting holes and marking out etc with the DRO.

No point really(in most applications) Even if you are just drilling a hole. Set your tool offsets on the DRO, put the slot drill in and move to your location. Plunge to depth and cut.

Cant see any reason why you would take a single action routine and add Centre Drill and then Drill to the routine?

[LandyManLuke]

Sorry, centre drills were for general use, rather than cutting a keyway. I can imagine situations were it would be advantageous to centre-mark locations using the DRO on the mill, then drill them on the pillar drill, rather than mark them out by hand. At least, it's something I will try.

Would you expect to cut a keyway in a single pass with a slot drill then? Plunge to depth at one end, and feed all the way along? I would have tried perhaps plunging at each end, then taking the middle out in layers?

[pete3000]

centre drills useful for sizing holes accurately for tapping, endmills seem to be imp or metric in few std sizes.

Have found using hss is ok on aluminium/plastic. Use carbide or carbide tipped on steel. Unless you have decent cooling suds pump setup your hss cutters wont last long on steel without stopping or shallow cuts and fine feeds.

Pete

[ejparrott]

Would you expect to cut a keyway in a single pass with a slot drill then? Plunge to depth at one end, and feed all the way along?

No, absolutely not. Contrary to other advice, although acurate, I always drill each end nearly to depth, plunge each end with a slot drill, then mill down in steps. With the addition of NC, you would be able to use a small cutter - say a 6mm for an 8mm keyway - then ramp mill down to depth anyway, that is plunging gradually over the whole length of the keyway, and forming the rads at each end rather than using the rad on the cutter. The final cut then is at depth and flattens out the bottom. This way you use the tool offset option to produce a slot to an accurate width too, rather than hoping that the cutter cuts size, and then trying to make an oversize key to fit what was produced.

[Warthog]

_{Would you expect to cut a keyway in a single pass with a slot drill then? Plunge to depth at one end, and feed all the way along? I would have tried perhaps plunging at each end, then taking the middle out in layers?}

_{Coming from a Conventional Milling POV. No NC...}

_{Yes i would expect to cut the Keyway in once pass. Plunge to depth and feed to end location in one hit. This i would do for Keyways upto 25mm. If larger then i would do 2 passes. One with a smaller slot drill and then finish with the specific slot drill size. (I dont neccesarily follow that 2 pass rule, its what you sense will be a comfortable option for your Mill size and material type etc)}

_{(General rule of thumb is that a Keyway wont be pass the depth of 1/2 the cutter diameter)}

_{Slots drills will produce Keyways to within tolerance range, using this procedure.}

_{If you do repeat passes, you find the keyway will have poor surface finish and have a step finish on the edges. This will impede key fit and fitting. Unless you you have NC and do as said above.}

_{Milling is all about Job set-up, and tool selection. Get those 2 areas nailed and the cutting procedure is a breeze.}

_{Having been trained up on the HSS tooling. I praise it for its value for money and availabilty. IMHO, Carbide tooling is good though but not essential. Yeah you gotta use Suds, but even with carbide, start smashing of lumps of material at speed, your work piece wil be scorchio!!}

_{Hope that helps? There will be differing opinions on how to do stuff, im sorta trying to see it from a home workshop scenerio. Where your tooling will be second hand and need to be cheap.}

_{What mill you running? Bridgeport.....?}

[LandyManLuke]

All useful info, thanks all.

Yup, Bridgeport, rescued from the scrap man - it had a duff spindle motor, but I'm working on sorting that. Overall, it's an old, but hopefully not too worn machine, the quill and spindle seem solid, but there's plenty of backlash in the X & Y screws. Fortunately, the DRO still works so I'm not too bothered about the backlash, and I plan to replace the screws one day.