Threading PR - a trick

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watch_art

watch_art

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Dunno if this has been done before - or if this is old news and I'm just discovering it all over again - but I'm turning some PR tonight that I got from Scott at the Central Arkansas meetup today, and as I was threading the 10mm threads that go into the barrel, it started to crunch - so I pulled the die/die holder off and looked at it. It's nice and warm with the 120W lightbulb inches above it - it's got a nice layer of oil on it....

DUH!!!
I put the tap for the nib unit all the way in, so the tap supports the thin tenon, and I cut the threads front to back no problem!

YAAAAAY!!!!


007 by snennewton, on Flickr


008 by snennewton, on Flickr


Any questions I'd be glad to try to answer.

:biggrin:

I'm so excited b/c when I turned a section from a Brooks blank of PR, it SHATTERED. Twice. AND I blew up a cap. Ugh...

So... lots of heat helps, and for tiny parts, leave the tap in there.
 
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It looks like you use the collet method, so you could also put collet, blank and all in the toaster over at about 140 degrees for about 15 minutes after drilling, but before using the tap and die. Add a little PAM and PR gets a LOT easier to thread.
 
Did this in the 4 jaw chuck - once parted off I put it on a holder in the collet chuck. Finished drilling, then turning down. Polish - and here it is!!
I don't have a toaster oven - but I bet that would be a good investment.



010 by snennewton, on Flickr
 
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watch_art said:
Did this in the 4 jaw chuck - once parted off I put it on a holder in the collet chuck. Finished drilling, then turning down. Polish - and here it is!!
I don't have a toaster oven - but I bet that would be a good investment.



010 by snennewton, on Flickr
Click to expand...


If you got a Good Will store near by, you can have your pick of about 30 different toaster ovens for about $5
 
I wrecked 2 sections when I tried to tap the external threads after the inner ones. :eek:

Then the lightbulb went off and I started cutting the outside thread first, then drill and tap the smaller inside threads. :rolleyes:

It is just a matter of getting the sequence of operations figured out to minimize rejections. :wink:
 
Yes that's how I do it, in addition I usually make up a spare threaded collar from PR to fit the outside thead and put that on to support the thin wall.

IMG_4194.jpg


IMG_4195.jpg
 
I have always found that the courser a thread the earlier it should be done
I do the M10x1 for the grip first
the turn the outer diameter to 14mm insert the M10 tap and tap the M14x).8 tripple start

fine threads require less torque to cut as they are not so deep..

I do like the coller idea - as I do have a few bodies with off centre cut threads and wondered what to do with them..
 
has anyone thought of putting the screw for the lid on the grip section - Had to do it this way as I wasn't sure the timber would stand up to the on-off threading of the lid

Even placed a sleave inside the lid to ensure the thread would last
 

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Awesome pen

And great idea, I really enjoyed meeting you at the Central Arkansas IAP Chapter meeting yesterday. You certainly added alot to the group and I look forward to our next meeting.
 
043Turning said:
has anyone thought of putting the screw for the lid on the grip section -
Click to expand...

Yep, I do almost all of mine this way. The bulb filler tutorial shows how I do it. There are advantages and disadvantages to each way of doing it, but I like the threads on the section so that I can do a CA finish on the body without getting it on the threads - I like to use materials other than pure acrylic.
 
like others mentioned, I too first cut the outside threads, then the inside.
since the taps used are usually taper taps, the cutting edge engages slowly, over 4-5 revolutions, which stresses the plastic less. the die, on the other hand, have a short taper of only 2-3 revolutions = more stress on plastic.
 
I've seen people cut outside first, but even with a tapped support piece screwed on, I ve had lucite crack doing this. I've done better with inside first - still screw a support piece inside. I used the tap too, but if you ever get to larger inside threads, you would need to make a piece for the support if the tap wont fit inside the die holder.

Alex, you are completely correct about Dies being more agressive than taps, but there is also the consideration that a circle with even pressure all around it from the outside is much stronger than pressure from the inside. Most materials are much stronger in compression than in tension. Think about how strong an arch is in architecture.

Bottom line - try both ways and do what works for you!
 
I like the idea of making threaded inserts to put inside the piece being cut with die. Hadn't thought of that - even after using the tap on this section. It's funny how the answer is right in front of me and it doesn't click sometimes. :)

Thanks!
 
Today I Learned (TIL) in the "notes for self" section:

1- Need a toaster oven: for PR threading and for the PR casting I don't often do

2- Make tapped thread support collars (and, threaded posts to internally support)

2a- Really need to make sure I buy BOTH a tap and die (and drill) together - not just the tap or just the die.
 
Yeah - I'm gonna start searching for a thrift store toaster oven pretty soon. I'll need some heavy duty electric in my shop though - the lathe and my little floor heater threw the breaker yesterday. :(
 
BTW, as an alternative to the toaster oven, I set up a hair dryer and let it blow over both the blank and die for 5 min or so.

This will warm things nicely - probably in less time too due to air movement - just like a convection oven is faster
 
Dustygoose said:
I love your kitless pens. I will try it one day... now that I have seen it up close, prolly sooner. Thanks for the tip and great pen!!!!!!
Click to expand...

Thanks! Can't wait to see what you turn out.

Knucklefish said:
And great idea, I really enjoyed meeting you at the Central Arkansas IAP Chapter meeting yesterday. You certainly added alot to the group and I look forward to our next meeting.
Click to expand...

Was great meeting you all, too. I felt very welcome and can't wait for the next meet up.

Robert111 said:
watch_art said:
Nice tips! I love that 3 jaw. Where do I get one?
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PSI $59.95
Woodturner's 3-Jaw Micro Chuck at Penn State Industries
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Thanks! Adding that to my shopping list. This will fit the 1x8 TPI on the 46-460 right? Or is it a MT fit? I don't see the details listed.
Thanks!
 
My talon chuck w/spigot jaws just doesn't hold close enough for what I want to do.

So, I was looking at that also (me = Delta LA-200, 1x8 TPI / 2MT)

If 2MT, then we need to stick a draw-bar to hold it in place.
So, I want to get the 1x8 TPI micro chuck.
 
IMHO you would be better off with a Beall collet chuck that screws over the 1"x8tpi spindle thread. I twill allow you to use the full internal diameter of your lathe and allow much longer work to be mounted.

The drawback with morse taper mounted is that your internal spindle is not available.

The Beall comes with ER32 collets allowing you to grip up to 20mm diameter in 1mm steps.

PSI also sells a version.

Ideally one would buy the Beall chuck on its' own and then a full range of ER32 collets, 2-20mm, from Ebay.
 
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I wish that last post was two days earlier. I have the Beall collet chuck and it seems like I'm always running into my piece being slightly too large for one insert and too small for the next one down. So I ordered the 4 in-between sizes to go with it from the Beall website and it was about $80 for 4 collets. And now you show me 19 collets for $65....someone please tell me I'm getting better quality....lol.

Thanks,
Gil
 
Is anyone in California doing these? I'd really like to stop by and see this done in person...it's my next evolution. Been eyeballing CL and Harbor freight for a metal lathe. is that the best option? Currently using Jet's 1014 and 1642.
 
Gilrock said:
I wish that last post was two days earlier. I have the Beall collet chuck and it seems like I'm always running into my piece being slightly too large for one insert and too small for the next one down. So I ordered the 4 in-between sizes to go with it from the Beall website and it was about $80 for 4 collets. And now you show me 19 collets for $65....someone please tell me I'm getting better quality....lol.

Thanks,
Gil
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Well that wasn't the first post on ER collets and Ebay on this forum, so if in doubt always do a search before purchasing something.

In fact I'm amazed how often the same questions get asked on this and other forums, people don't seem to search much.

That is a real shame because there is a wealth of knowledge here.
 
Well I think I got my answer...they just arrived today and came in these individual blue plastic cases with a big "Made in China" sticker. ;(
 
Made in CHina doesn't mean poor quality. Seagull watch is a great example.

-SeaGull USA

There are lots of high quality things made in China - you just pay more for them. The cheap stuff is just that - cheap. Maybe quality control isn't top notch so more duds make it through to the customer - or maybe finishing isn't as good so it doesn't look or feel as nice. But great stuff does come out of China - for sure.
 
Gilrock said:
Well I think I got my answer...they just arrived today and came in these individual blue plastic cases with a big "Made in China" sticker. ;(
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Sounds like the ones I got from Ebay, I have 2 sets, one at the wood lathe and one at the metal lathe.

Both are excellent quality, couldn't ask for better.
 
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