Boring 1/2"X14" hole in nylon rod

challenger · Aug 3, 2020

I have 2 2"X14" pieces of nylon rod that need a 1/2" hole through them. My only thought is to start each side as accurately as possible so they meet in the middle as accurately as possible. My lathe headstock is only 1-3/8" but my four jaw will grab a good portion of the rod and I'll use a rest as well.
Any other tips are appreciated.
Thanks

Limy Sami · Aug 3, 2020

As you say I'd use a rest etc etc and use drills (preferably bright ground / polished) that are new or have only been used for non abrasive plastics and are razor sharp, .....but with the cutting lips dubbed (as for brass) to stop self feeding, ......keep the speed right down and feed up, withdraw frequently using plenty of cold coolant ''up the hole'' ............if you can't use coolant (it does taint for food use ???) use dishwashing liquid in water.

Oh yeah, if your fixed steady isn't the roller type, turn a up steel ring to fit over the nylon for the fingers to run on.

ratbldr427 · Aug 4, 2020

Good advice Limey.The trouble with deep holes in plastic is heat.The material is a good insulator so expansion can close the hole and stick the drill or even split the material.

So don't get greedy, clear the hole often and use coolant.Just because the material is soft and cuts easy dosn't mean it cant stick a drill and wring it off.BTDT but only once!

1953chevB · Aug 4, 2020

I would be curious how this works out. being it's 28D depth of hole, did you quote with deep hole drills?

Limy Sami · Aug 5, 2020

ratbldr427 said:
Good advice Limey.The trouble with deep holes in plastic is heat.The material is a good insulator so expansion can close the hole and stick the drill or even split the material.

So don't get greedy, clear the hole often and use coolant.Just because the material is soft and cuts easy dosn't mean it cant stick a drill and wring it off.BTDT but only once!

As has a certain PMer from Norfolk UK, only to top it a few weeks later, when one winters morning chuffed to bits that the nylon rod that had just come off an overnight delivery truck and had to deep drill ONLY JUST fitted up the lathe spindle.

Magic, leave a couple of inches out of the chuck to end work, then deep drill, draw out from chuck and finish the OD then part off, rinse and repeat for umpteen bars.

Well, he got the hole drilled without a problem (he'd BTDT and learnt his lesson) ............ and then the job ground to a halt, ...............and he took a lot of crap from his workmates.

camscan · Aug 5, 2020

Limy Sami said:
As has a certain PMer from Norfolk UK, only to top it a few weeks later, when one winters morning chuffed to bits that the nylon rod that had just come off an overnight delivery truck and had to deep drill ONLY JUST fitted up the lathe spindle.

Magic, leave a couple of inches out of the chuck to end work, then deep drill, draw out from chuck and finish the OD then part off, rinse and repeat for umpteen bars.

Well, he got the hole drilled without a problem (he'd BTDT and learnt his lesson) ............ and then the job ground to a halt, ...............and he took a lot of crap from his workmates.

Would you recommend a 'D' bit dad?

Limy Sami · Aug 5, 2020

More fundamental than that son

camscan · Aug 5, 2020

Limy Sami said:
More fundamental than that son

But would you recommend it? IE,have you ever tried it?

Limy Sami · Aug 5, 2020

Deep drilling plastics with a D-Bit? .....yes many times, .........did several 1'' dia x 12'' deep in PEEK (with a ''profiled end) with a D bit, ............and 15mm dia x 8'' & 10'' deep in both Nylon and PTFE, again with shop made D bits.

KMoffett · Aug 5, 2020

limey,
"use drills (preferably bright ground / polished) that are new or have only been used for non abrasive plastics and are razor sharp, .....but with the cutting lips dubbed (as for brass) to stop self feeding"

What's the point of "razor sharp" and then "dub"ing it.

1953chevB · Aug 5, 2020

KMoffett said:
limey,
"use drills (preferably bright ground / polished) that are new or have only been used for non abrasive plastics and are razor sharp, .....but with the cutting lips dubbed (as for brass) to stop self feeding"

What's the point of "razor sharp" and then "dub"ing it.

yes please define, razor sharp is what I was taught, but Dubbed?

Limy Sami · Aug 5, 2020

Dubbing'' is reducing the rake angle on the cutting edge ,,,,,,,,,the rake angle being defined by the helix angle.
With brass and some other soft metals, drils tend to grab on break through causing the flutes to act like a screw thread ???

On brass, by reducing the cutting edge helix angle to zero - with an oilstone - no need for the grinder, for about 1/16'' (like a lathe tool for brass) turns the drill in to more of a scraping action, and all but eliminates the grabbing and self feeding action.

I've found doing the same (dubbing) with drills for plastic, works very well, ...for believe me, in soft nylon drills with a helix angle / raked cutting edge will ''over feed'' and jamb the flutes.

Hope this helps.

challenger · Aug 5, 2020

1953chevB said:
I would be curious how this works out. being it's 28D depth of hole, did you quote with deep hole drills?

It's for a personal project.
Thanks
I'll let you know how badly I screw this pooch.

challenger · Aug 5, 2020

Limy Sami said:
Dubbing'' is reducing the rake angle on the cutting edge ,,,,,,,,,the rake angle being defined by the helix angle.
With brass and some other soft metals, drils tend to grab on break through causing the flutes to act like a screw thread ???

On brass, by reducing the cutting edge helix angle to zero - with an oilstone - no need for the grinder, for about 1/16'' (like a lathe tool for brass) turns the drill in to more of a scraping action, and all but eliminates the grabbing and self feeding action.

I've found doing the same (dubbing) with drills for plastic, works very well, ...for believe me, in soft nylon drills with a helix angle / raked cutting edge will ''over feed'' and jamb the flutes.

Hope this helps.

I suspect the bit would then have to be reground if one wanted to use it for steel?
There is actually a really good video on YouTube by Joe Pizynski (yes I did ef up the spelling). He is drilling some SS with a small hole of about. 250 IIRC. He stresses starting the hole perfectly. Or as straight as possible using a center drill, small drill, bigger drill, tiny boring bar and then a reamer. All the above for only about 1" I think. Once the hole is started straight he uses a pecking method as described by a few here. Just a couple of cuts, back out and clear and repeat. He then swaps the stock end for end and repeats. The results are very impressive in my inexperienced opinion. Now this is steel, not plastic and it is a total of maybe 6" long but the length he used is as much for illustration as it is for application I believe.

dian · Aug 6, 2020

i guess the question was why razor sharp when you dull it.

Limy Sami · Aug 6, 2020

dian said:
i guess the question was why razor sharp when you dull it.

That's the point, you are not dulling the edge, merely changing the angle, ........ the actual cutting edge remains just as sharp.

I agree that ''dubbing'' is probably a bad word to use to describe the operation, but it's what I was taught over 50 years ago.

camscan · Aug 6, 2020

dian said:
i guess the question was why razor sharp when you dull it.

You are not dulling it, you are just removing the helix angle.
The drill should be as sharp as ever.

Milland · Aug 6, 2020

Limy Sami said:
More fundamental than that son

So the material got a little CuTE, huh, Limy?

Limy Sami · Aug 6, 2020

Milland said:
So the material got a little CuTE, huh, Limy?

The bastard stuff expanded and jammed in the spindle

...........and had to be drilled out - wasting well over an hour :rolleyes5:

dian · Aug 7, 2020

camscan said:
You are not dulling it, you are just removing the helix angle.
The drill should be as sharp as ever.

i doubt it will be very sharp if done by hand. often "bubbing" is called "dulling the edge".

Boring 1/2"X14" hole in nylon rod

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