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2.45" hole through 2" Nylon

Pathfinder20

Plastic
Joined
Dec 25, 2016
Location
Port Saint Lucie Fl USA
Currently making 2.45"(-.0 + .01) hole by drilling 3/4" thru hole then using G13 can cycle with 5/8
carbide reduced shank endmill in .52 steps. Considering full depth G13 at .1 woc. Only
plastic grind 3/4 endmill was carbide at $277 with 2.25" flute length. Maybe a 3/4" 2 flute
hs endmill? Have Hass VF4SS 12000 rpm spindle.

Thanks,

Pathfinder20
 
Punch a much bigger hole, then get after it with a 2” flute length YG-1 Alu Power or Destiny Viper, full depth.

Regards.

Mike

What he said plus make sure you're hanging on to the part well, .....aggressive end milling can pull plastic up out of vise jaws, and if you're unlucky - throw it at high velocity :eek:
 
Punch a much bigger hole, then get after it with a 2” flute length YG-1 Alu Power or Destiny Viper, full depth.

Regards.

Mike
I'm a bit cornfused here.

A 2 flute HSS should be center cutting ?

Why not just spiral down thru (helical interpolate)
Once and done, start down in, right at the 2.45 dia.
 
Spiralling down with a two flute end mill will most likely throw the workpiece before you are halfway through. Unless, as Limy says, its seriously strapped down. Chip evacuation doesn't look much fun either.

Last time I had a similar issue, only 35 mm hole similar diameter / depth ratio, I tried a Forstner bit from the wood mangling department. Worked well once I'd sussed the right combination of feed and speed to get a nice ribbon chip peeling out and quite respectable finish. Manual machine in my case but no reason it shouldn't work on a CNC. If your spindle can run slow enough.

Clive
 
Spiralling down with a two flute end mill will most likely throw the workpiece before you are halfway through. Unless, as Limy says, its seriously strapped down. Chip evacuation doesn't look much fun either.

Last time I had a similar issue, only 35 mm hole similar diameter / depth ratio, I tried a Forstner bit from the wood mangling department. Worked well once I'd sussed the right combination of feed and speed to get a nice ribbon chip peeling out and quite respectable finish. Manual machine in my case but no reason it shouldn't work on a CNC. If your spindle can run slow enough.

Clive
How can you make these assumptions ? OP has said nothing of part configuration.

Feeds, speeds, & depth of cuts can easily changed with the tap of a keyboard.
Making all loads applied to the workpiece whatever the OP desires.
 
I'm a bit cornfused here.

A 2 flute HSS should be center cutting ?

Why not just spiral down thru (helical interpolate)
Once and done, start down in, right at the 2.45 dia.

Plowing a deep slot in nylon, IME, can be trouble due to no coolant to flush chips out owing to nylon absorbs water and grows. Without coolant blast to clear chips, you get recutting and a mess, even fouled endmill.

Big drill, with chip-break cycle, can shed its swarf without it wrapping up on the drill. Might need to play with feeds, speeds, and chip-break increment.

Big drill hole gives room for the endmill chips to at least maybe self-evacuate, mostly.

That's how I'd do it :).

Regards.

Mike
 
^ Its what air blast was made for! Along with larger low flute count tooling. IMHO you don't need to go 3/4" cutter, hell 3/8" or 1/2" is plenty for 2" deep in nylon. I too ike the YG cutters, they work awesome in the stuff and are cheap enough to use unlike some of the competition. My experiance carbide is optional on most plastics, only really a must on glass or fibre filled plastics.

Fostener bits do work well, but they need to be sharp like all plastic cutting tools,

I second the grip comment, doing the above helical plunge and HSM out spiral, a 1/4" step on soft jaws is plenty to grip a large block of mild steel just fine, the same in nylon and it will be outta there in a heart beat! Its not just slippery to grip, but it also tends to relax - take a bit of a set at higher clamping pressures, ergo what was a tight grip 5 minutes ago may now nearly fall out! This is made all the worse if you do some high heat machining and then have the part cool off then come back again aggressively.
 
And if you want a quick and cheap large roughing hole on most plastics - a wood spoilers flat bit works a treat, .....only FON'T go for those with a screw point!
The best I've found is the DeWalt Extreme like this DeWalt Extreme Flat Wood Bit 32mm | Wickes.co.uk dirt cheap and does the job.
Keep the speed low (say 200 rpm for 1 1/4'') and feed up, n the jobs a goodun.

FWIW 1, IME Forstner bits are okay on thin stuff, but they have next to no back taper so will rub and heat plastics very quickly.

FWIW 2, if you have to grip pieces of plastic by only a ''little bit'' use dovetail jaws and m/c a matching dovetail in the plastic, .that way you have a good hold without any danger of slip.
 
i remember 6" round nylon i had on a lathe and i drill 2" hole through it and when i go through it cracks like a wood log with radial crack.
.
i tried 2nd piece and it did same thing. nylon is famous for being under stress from water absorption and drying out. just saying you might want to expect piece of nylon just cracking in middle of putting big hole through it.
.
somebody suggested i put nylon in 5 gallon bucket of water overnight and try the next day drilling a 3rd piece. i didnt bother and threw out the 3 foot long piece i had as bad nylon
 
Sami, old wood workers trick with the fostners, pean the cutting edge near the od, so its just a nats larger than the body, its a small step, but none of the commercial ones come sharpened that way as you don't need it in softwoods, some of the really hard oily hard woods and its a must! Cuts a hole thats a nats bigger than its body that way.
 
Adama

Must remember that trick if I ever get some decent Forstener bits. Mine are a LiDL £5 (ish) set and must be a touch oversize at the end as they go through thick plastic with no trouble. Hafta say I'm very impressed with the finish and hole size accuracy from these uber cheap bits when I've used them in plastic.

Clive
 
Adama

Must remember that trick if I ever get some decent Forstener bits. Mine are a LiDL £5 (ish) set and must be a touch oversize at the end as they go through thick plastic with no trouble. Hafta say I'm very impressed with the finish and hole size accuracy from these uber cheap bits when I've used them in plastic.

Clive

LIDLs eh Clive? ;) did you get any of the digital calipers they ran a few years back, ...about 14 quid rings a bell, word spread like wildfire, every bugger had em :D.....mine were amazingly good, and lasted 3 or 4 years before giving up the ghost, ...........but that might have had something to do with being dropped 2 storeys on to a hard concrete floor :scratchchin:
 
I don't think its just you i have had real mixed luck with fostner bits, had some realy nicely ground looking ones that barely cut, then had a cheap one i had to get whilst working on site that did not cut at all till sharpened with a angle grinder + thin cutting disc then proceeded to cut lovely!

Am glad to be out of the high end wood work game pain in the ass working on site all the time!
 
Limey

Yup. Well sort of, got given a set in payment for a years worth of little jobs at mates rates (free). Mine were not up to machine work accuracy and batteries lasted about 3 months. Word on the street round here is that quality was very variable. Guy who gave them to me says his are still fine and batteries last over a year.

When it comes to calipers I like the Moore & Wright ones with the double length vernier covering 2 inches instead of the usual 1. So much easier to read. Took years but I eventually amassed a full set.

Tend to find LiDL a good source for "cheap one to try" when undecided about whether its worth splashing out on proper quality gear. That said some of their stuff is more than good enough for all reasonable use. Some is rubbish tho'. But they refund without blinking if you take things back which is nice.

Clive
 
Update:drilling with .75 hss drill through. 5/8 3 flute reduced shank endmill.
spindle 10000 rpm. G13 can cycle Q.2 Z.525 L4 F170. Two holes complete 1:30 minutes.
Still think can improve some more.

Pathfinder20
 








 
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