casting threads

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glycerine

glycerine

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Have any of you ever cast threads directly into your PR, or do you cut them later? What I mean is taking an existing pen part or bolt with the right threads, coating it with some type of release gel and then casting your blank around it. Is that feasible, or not worth trying?
 
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G,
I thought about it, but I find it is easier to cut them directly into the material. Funny you should post this now, last night I threaded some PR and it was a bit brittle for the die and thought about revisiting that idea. I do all this stuff on a wood lathe and am always trying to keep my center problems at a minimum, and adjust, adjust, adjust.
 
cnirenberg said:
G,
I thought about it, but I find it is easier to cut them directly into the material. Funny you should post this now, last night I threaded some PR and it was a bit brittle for the die and thought about revisiting that idea. I do all this stuff on a wood lathe and am always trying to keep my center problems at a minimum, and adjust, adjust, adjust.
Click to expand...

Ok, so what do you use to cut the threads? a tap and die set? I only have a wood lathe as well and was thinking casting the threads might be the only way I could even make any until I get some better equipment.
 
glycerine said:
Ok, so what do you use to cut the threads? a tap and die set? I only have a wood lathe as well and was thinking casting the threads might be the only way I could even make any until I get some better equipment.
Click to expand...

Yes, I use a tap and die. I believe the set I got is on sale at HF for like $35. It has the M10x1.0, and I started with the 1/2x20 then upgraded to a 1/2x36.

As far as casting threads is concerened, I think better after I eat, so here is my idea:
There was a tutorial a few years back when casting your own blanks became more feasible. I can't remember who it was, but he used a 1/2" copper pipe as a mold. You could create the mold with whatever you have available and insert a threaded rod, bolt or whatever inside. Must keep it true with the mold using a bolt or washer or drilled end cap. Pour in resin, and screw out when cured. I suppose one of the glitches will be screwing out the thread when cured. You can always clean up the threads with the proper tap. Now for the section which needs to be cut with a die, a reverse mold would work, but it is probably easier with a tap and die.
 
glycerine said:
Have any of you ever cast threads directly into your PR, or do you cut them later? What I mean is taking an existing pen part or bolt with the right threads, coating it with some type of release gel and then casting your blank around it. Is that feasible, or not worth trying?
Click to expand...

Certainly worth trying. Let us know how it turns out.


YouthMinisterDan said:
I cast my first resin blanks and they are still tacky on the outside, it has been 48 hours. Did I not use enough catalyst?
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Holy thread high jack batman!! :eek:

They should be fine. PR will be tacky on the outside unless you use an additive to prevent it.
 
I was thinking , if you used Alumilite the shrinkage problem is almost eliminated . You would have to be careful with the mold release you use because it could change the dimensions of the threads and could cause the threads to be very rough , the alumilite will reproduce whatever the thread surfaces look like .
 
YouthMinisterDan said:
I cast my first resin blanks and they are still tacky on the outside, it has been 48 hours. Did I not use enough catalyst?
Click to expand...

What type of resin did you use? Most casting resins are laminating resins and are "air inhibited" meaning the top will remain tacky so you can add another layer of resin to the casting, and the 2 layers will bond. Letting the cast sit for a few days in a warm place or post curing will solve the problem. However when you turn the casting down the tacky layer will be turned off, so no worries.
 
glycerine said:
Have any of you ever cast threads directly into your PR, or do you cut them later? What I mean is taking an existing pen part or bolt with the right threads, coating it with some type of release gel and then casting your blank around it. Is that feasible, or not worth trying?
Click to expand...

I cast at times for my own use bottlestoppers with a nylon 3/8 x 16 bolt. I spray down the bolt with Ease Release 200, then mount the bolts in the molds, coat the bolt with resin, that has just had the catalyst added, then do the thickening wait, before adding the rest of the resin, then set under pressure.

The resin will shrink down to the bolt, so you must let the resin fully cure and then post cure, so the resin will not shrink any more. The only downside is that the threads on commercial bolts are a looser fit than threads on a machine cut "bolt." You will have to chase them with a tap to make them fit properly, unless you make a casting directly from a spare fitting, you will still have to let it fully cure, or you will get some shrinkage.

See these photos as I can't get them to link as thumbs:
http://www.penturners.org/photos/index.php?n=10554
http://www.penturners.org/photos/index.php?n=10555
http://www.penturners.org/photos/index.php?n=10556
http://www.penturners.org/photos/index.php?n=10557
 
ldb2000 said:
I was thinking , if you used Alumilite the shrinkage problem is almost eliminated . You would have to be careful with the mold release you use because it could change the dimensions of the threads and could cause the threads to be very rough , the alumilite will reproduce whatever the thread surfaces look like .
Click to expand...

Yes...but alumilite threads pretty darn nice and easy, so why bother building a mold for casting the threads when you can tap them out in less than a minute?

Threading is not rocket science. Get yourself a Beall chuck. Spin your blank to fit in whichever collet you are going to use, basically matched to the finish size of the pen your making. Wrap some tape around the end of the blank to add some structural strength. Mount a drill chuck in the tail of the lathe. Drill the blank to size according to which tap you will use. Now install the tap into the drill chuck. shoot some cooking spray in the hole and on the tap. Slide the tail up to the hole. using two hands, slowly push the tail into the pen as you turn the live side by hand. Make 1/2 a turn or so then back off to clear the threads then in again..in and out till you are deep as you wish to go :rolleyes:

The pen section is done basically the same way, but this time you use the die. You can purchase a die holder from someplace like Enco, they are not too expensive. The die holder allows you install the die in your drill chuck. All this easily accomplished with any wood lathe. Unless you are confident with the threading tools on a metal lathe, then on a metal lathe you would do it the same way too. Especially the tapping part..I see people with metal lathes tend to use a tap rather than the threading attachment because it is probably quicker and easier is my guess.
 
Glass Scratcher said:
I cast at times for my own use bottlestoppers with a nylon 3/8 x 16 bolt. I spray down the bolt with Ease Release 200, then mount the bolts in the molds, coat the bolt with resin, that has just had the catalyst added, then do the thickening wait, before adding the rest of the resin, then set under pressure.

The resin will shrink down to the bolt, so you must let the resin fully cure and then post cure, so the resin will not shrink any more. The only downside is that the threads on commercial bolts are a looser fit than threads on a machine cut "bolt." You will have to chase them with a tap to make them fit properly, unless you make a casting directly from a spare fitting, you will still have to let it fully cure, or you will get some shrinkage.

See these photos as I can't get them to link as thumbs:
http://www.penturners.org/photos/index.php?n=10554
http://www.penturners.org/photos/index.php?n=10555
http://www.penturners.org/photos/index.php?n=10556
http://www.penturners.org/photos/index.php?n=10557
Click to expand...

Great info, that's exactly what I am talking about! Thanks for the pics.
 
workinforwood said:
Yes...but alumilite threads pretty darn nice and easy, so why bother building a mold for casting the threads when you can tap them out in less than a minute?
Click to expand...

I'm gonna side with Jeff here. Alumilite is the most enjoyable material I've used so far to thread. No problems, it really stands up to all the hype. Taps and dies with ease.
 
workinforwood said:
Yes...but alumilite threads pretty darn nice and easy, so why bother building a mold for casting the threads when you can tap them out in less than a minute?

Threading is not rocket science. Get yourself a Beall chuck. Spin your blank to fit in whichever collet you are going to use, basically matched to the finish size of the pen your making. Wrap some tape around the end of the blank to add some structural strength. Mount a drill chuck in the tail of the lathe. Drill the blank to size according to which tap you will use. Now install the tap into the drill chuck. shoot some cooking spray in the hole and on the tap. Slide the tail up to the hole. using two hands, slowly push the tail into the pen as you turn the live side by hand. Make 1/2 a turn or so then back off to clear the threads then in again..in and out till you are deep as you wish to go :rolleyes:

The pen section is done basically the same way, but this time you use the die. You can purchase a die holder from someplace like Enco, they are not too expensive. The die holder allows you install the die in your drill chuck. All this easily accomplished with any wood lathe. Unless you are confident with the threading tools on a metal lathe, then on a metal lathe you would do it the same way too. Especially the tapping part..I see people with metal lathes tend to use a tap rather than the threading attachment because it is probably quicker and easier is my guess.
Click to expand...

Is Alumilite a polyacrylic resin? How is it different from other acrylics?
I am still fairly new to pen turning and would be afraid of cracking a newly turned blank trying to use a tap and die set, because of the walls being so thin, so I thought casting them in might be an option. I figured if the cast doesn't come out right, at least I'd know I screwed up in the beginning and not the end.
That and the fact that I still don't have a real lathe. I have a drill press with a lathe attachment laid down on it's side. So I don't have a tail stock to attach the die to.
 
glycerine said:
Is Alumilite a polyacrylic resin? How is it different from other acrylics?
I am still fairly new to pen turning and would be afraid of cracking a newly turned blank trying to use a tap and die set, because of the walls being so thin, so I thought casting them in might be an option. I figured if the cast doesn't come out right, at least I'd know I screwed up in the beginning and not the end.
That and the fact that I still don't have a real lathe. I have a drill press with a lathe attachment laid down on it's side. So I don't have a tail stock to attach the die to.
Click to expand...


Alumilite is a PolyUrethane.

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PR is polyester resin, and alumilite is urethane resin. Both products are awesome, but they have different properties that make each one better at certain tasks. Although technically Alumilite is harder than PR, PR is harder in texture and performance, Alumilite has elastic properties which allow it to have some stretch and give to it. This is why Alumilite doesn't quite reach that super shine like PR does. The new Crystal Clear Alumilite is far better than the original, as they have removed a bit of the elastic property, but by no means removed all of it. PR doesn't have stretch, therefore it is somewhat brittle. You take a piece of PR and a Piece of Alumilite and whack them with a hammer 1 time only and the PR will be 50+ pieces, the alumilite might break into 2 or 3 pieces. There are other similar products that have some stretch to them, like ebonite as just one example, but most of the other products are not feasable to pour your own. I'm not saying you can't tap PR either, I'm just saying that you will have far easier and better success rates with Alumilite in this situation.

Thin walls and then tapping..yes, that is where it gets tricky. This is why I said to tape the blank real good. If you wrap some electrical tape around the end of the blank a half dozen times or more..now the walls are not so thin anymore.

A drill press is not much different than a lathe and will work just as good. You mount the drill bit in the drill press. Maybe you already drilled it before you spun it, maybe not, it doesn't matter, you should still mount that same drill bit in the press. Put the blank in a vise, no need to tighten the vise very much either, just enough to hold the pen. Pull down the press and seat the bit into the hole, then clamp the vise down. Now you have the center of the hole lined up with the drill chuck. Remove the drill bit, install your tap. Pull down on the drill press with the power off of course! Enter the pen and turn the chuck by hand as you pull down, back off to clear hole, re-enter etc etc. Be sure and use a lube of course, cooking spray works good...actually I prefer you use a cooking spray and be sure the spray contains no silicone. WD 40 has silicone in it. Silicone contamintes wood. You get it on your tools, eventually you get it on your hands and on your wood, it's guaranteed, so just dont have any silicone in the shop...junk it all, buy cooking spray for threading, or use a non silicone lubricant, like the Bostick products for lubing your table saw and other tools. That's my advice..no silicone ever !!! <no wire hangers either:wink:>
 
workinforwood said:
Snip

Be sure and use a lube of course, cooking spray works good...actually I prefer you use a cooking spray and be sure the spray contains no silicone. WD 40 has silicone in it. Silicone contamintes wood. You get it on your tools, eventually you get it on your hands and on your wood, it's guaranteed, so just dont have any silicone in the shop...junk it all, buy cooking spray for threading, or use a non silicone lubricant, like the Bostick products for lubing your table saw and other tools. That's my advice..no silicone ever !!! <no wire hangers either:wink:>
Click to expand...

According to the makers of WD-40, it does NOT contain any Silicone.

"What does WD-40 contain?
While the ingredients in WD-40 are secret, we can tell you what WD-40 does NOT contain. WD-40 does not contain silicone, kerosene, water, wax, graphite, chlorofluorocarbons (CFCs), or any known cancer-causing agents."
http://www.wd40.com/faqs/

.
 
Glass Scratcher said:
According to the makers of WD-40, it does NOT contain any Silicone.

"What does WD-40 contain?
While the ingredients in WD-40 are secret, we can tell you what WD-40 does NOT contain. WD-40 does not contain silicone, kerosene, water, wax, graphite, chlorofluorocarbons (CFCs), or any known cancer-causing agents."
http://www.wd40.com/faqs/

.
Click to expand...

That's cool to know. Thanks!
 
A lot of good thoughts here so here are mine.
Yes you can cast the threads as fine as you wish. If you use RTV mold material you don't even need a release.
Now the questions to ask is should I cast the threads. Butch pointed out shrinkage issues, while someone else mentioned possible fit problems. You also run the rist of an air bubble in the thread.
In my opinion, if you cut your threads with tap and die you have much more flexability and control. Your threads will alway be clean and crisp regardless of what you cast with. You can change where and how long you decide to thread. If you bugger up the end you can shave off 1/16" and turn one more thread without a problem. I think you get my point.
Again, just my opinion.
JJ
 
Having made dozens of pens requiring threads to be cut for caps, front sections or nib feeds, I have faced many obstacles.

I think the problem is not so much whether one can actually cast the threads or not but can they be cast precisely enough! Take a lower body for example, with threads in one end allow the blank to be mounted in such a way as to drill out and turn the blank to size? How about the cap, you would have some internal threads but again, how would you mount the blank to further drill and shape the blank then hold it to add a clip? When I make a fountain pen front section for example, the threads are the last thing I do once I get the section to exactly the right size.

Just something to think about.
 
JJturns said:
I forgot to add that the pen I have currently posted made of M3 was threaded with tap and die on a Wilton mini wood lathe that cost $99.00 on sale. You don't have to have the best equipment to thread with tap and die. Check out this terrific thread by George.
http://www.penturners.org/forum/showthread.php?t=51646
Click to expand...

Here is a friendly suggestion; Use your pen a while before making more as I believe they will not hold up. I made two pens from m3 material and while both threaded like a dream, neaither lasted for more than a few months of use.

I gave one pen to a friend and kept the other for testing. My friend used his more than me and his Cap threads wore down within a month of daily use to the point his cap would not even engage threads. My threads broke where the nib section screws into the lower body. I have done identical designs in acrylic and none have cracked or worn down yet so the material was the problem.

M3 may thread easily but in my opinion is a very poor candidate for making a pen where threading is required.
 
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