Well, let’s begin at the beginning shall we. I started my build with the controller box and drives. I used a surplus enclosure from a company that makes printing equipment. I picked up my drivers and steppers from a yard sale for $50 and only one drive is a bit flaky.

The motors are Power max II and the drivers are PacSci-6410 (micro stepping) from Pacific Scientific, very nice for the money.

The power supply is one I striped out of a telecom equipment rack I spotted at the dump. It’s 50 volts at 10 Amps, and the price was right……FREE!

Photos soon…

altogether folks.. photos, photos, photos, photos, been waiting on this for a while now......

This is too good to be true. Keep going!

Sorry guy’s I know I have been delinquent in my duties, but living in New England means some times you have to put your hobby on hold and go sand 800 feet of driveway.

I’ll try and get a few photos up to night…..if I’m not too sore.

I love the title of this thread "Chronicle of a Geek". Now show us just how Geeky you are. :) It's really hard to be geekyier then me.

Ok, time for the long-awaited first photos…

1 & 2 are the driver box and drives there is a small power supply from a scanner in there too, to run the fan and for limits and anything else that might need +5 or +12 volts.

3. is the main supply 50 Volt ,10 Amp. I added circut breakers, the two little black squares on the end closest in the photo.

You remind me of myself, sometimes using the table saw as a workbench, then you got to get it all off, what sort of driver are you using that you are powering it with 50V?

Hi Tjord,

Yes, although I have counter space, things just gravitate to the table saw…. I don’t know why, they just do.

The drives are from PacSci-6410, micro stepping. Full step down to 1/50,000. I have work with these drives in the past so I snapped them up when I saw them.

Some of the futures are adjustable:

Step Size
Damping control
Idle current reduction
Settable current.

And they run at up to 75 Volts....

Wow, i'm not familiar with that board but it sounds cool, 75 volts you say, I'm probably not gonna even run half that, I'm wondering what performance you'll be getting when you're done.

For software I am using, AutoCad, Ace, and TurboCNC. I check my code by running it on MicroTech CNC Simulator.

What are you guys using? Or going to use?

Say... what are you gonna be cutting with your cnc?

For software I am using, AutoCad, Ace, and TurboCNC. I check my code by running it on MicroTech CNC Simulator.

What are you guys using? Or going to use?
I use TurboCAD and Mach3. I plan to try the CNC Simulator and ACE soon. At work I have Catia too.

I'm using Autocad, NC Plot and Mach3, used acad since 2000, but now learning the other two, can turboCNC be used stable within XP or will i have to find a copy of win98? :confused:

I plan to use my router to cut body parts for robots…. I said I was a Geek! But I want to build the joe2006 using this router to cut what I can. I might do some signs too. What are your plans?

TurboCNC runs under DOS. I have been running it on an old or should I say very old laptop (486-75) in DOS mode under Win95.

Ok a little more info on the controller,

The enclosure has a few more cut outs in it than I need but it was free and its stainless steel. I had to add a few holes to mount the drivers.

1 is the back
2 is the front
3 is with cover
4 Driver test setup, yep its on wood…
5 Installing drivers
6 Drivers in
7 Drivers still in

I too would like to build the joe2006 with my router, i'm thinking about making small furniture pieces and intricate details for larger custom woodwork pieces, maybe some signs and try some craft items for my wife to try her hand at, i'm thinking about getting a copy of mach3, but i still want to see how turbocnc works, i even dl linux ubuntu 6 which has in EMC2, i hear it's really good, want to try this out too, but that requires a little more time than i have right now, but i'll get to it eventually.
Seems you are gonna have a real "detailed" looking enclosure there.

I to have been trying out Ubuntu. I like it. I am looking for an old laptop to run it on. I run it from CD right now. I thought EMC had its own flavor of Linux, is EMC2 a new version? I think I’ll stick with TurboCNC for now at least until I get my machine running the best it can.

A Few more photos from the build.

Lower T box, Ends, and together, also a couple shots of bench mayhem with some parts I experimented with.

Your parts are looking great. I like the JGRO design because its something we can cut with a table saw, and hand tools. The Joe2006 is better, but I notice that a lot of guys just buy the kit from Joe because its so complicated. I wanted the pleasure of cutting and building the router myself. I don't regret it either. Seeing others build the JGRO is fun too.
Dave

I to have been trying out Ubuntu. I like it. I am looking for an old laptop to run it on. I run it from CD right now. I thought EMC had its own flavor of Linux, is EMC2 a new version? I think I’ll stick with TurboCNC for now at least until I get my machine running the best it can.


Yeah, linux seems a lot simpler i think, didn't really figure out EMC yet, didn't have the time, i think i'll partition the hard drive on the other PC and install linux there and take a crack at it again, it's running XP right now and i'm using mach3 demo, i'd also try turboCNC but might need another PC for that, we'll see, you can try ebay for old laptops, they sell dirt cheap there.


Your parts are looking great. I like the JGRO design because its something we can cut with a table saw, and hand tools. The Joe2006 is better, but I notice that a lot of guys just buy the kit from Joe because its so complicated. I wanted the pleasure of cutting and building the router myself. I don't regret it either. Seeing others build the JGRO is fun too.
Dave


I agree, i guess that's why alot of us make the jgro with intentions of building joe's with it, joe's look like quite a bit of work, but it does look like a nice sound design don't yah think?

Photo time again!

1. This one has the Gantry installed.
2. And with the upper T box installed.
3. Finally the Z axis is on!

Wow....you're really pickin' em up and puttin' em down!
Keep it up!!
I *really* need to get my table saw cleaned off...

Cheers!

Hoskald,

Good luck cleaning off your table saw. I find every thing in my shop gravitates to the top of the saw… (I think it’s one of Murphy’s laws)

trust me you are not alone my friend, it's like a magnet, and if you're like me and don't have much space, it's almost a waste of time trying, i guess all you can do is organise as best you can.

Hi V&B,
Do you have a thrust bearing on the bottom of your z axis threaded rod? At the top it looks like you have a hose and clamp connection. I also have the hose and band clamps on my z axis, and I found that a thrust bearing a the bottom is needed pretty bad. The weight of the motor cause the tube to slip down off the shaft, slowly but surely.

Your build is looking great. It won't be long now before you're cutting.

Hi V&B,
Do you have a thrust bearing on the bottom of your z axis threaded rod? At the top it looks like you have a hose and clamp connection. I also have the hose and band clamps on my z axis, and I found that a thrust bearing a the bottom is needed pretty bad. The weight of the motor cause the tube to slip down off the shaft, slowly but surely.

Your build is looking great. It won't be long now before you're cutting.

No hose on x y or z. I'll get you a better pic. Yes I uesd thrust berings on all x,y,& z axis, (from McMaster-Carr 6655K33) I realy think you need them.

Ok hear are the Z axis coupler and thrust bearing. I have a bearing on each side of the end away from the motor. I did X & Y this way too. Each axis has a different style coupler, I used what ever I had in my parts collection (junk box)

Ever wonder what would happen if you drive your Z down in to the table top wile X is moving and your spindle is not running…. Well the cause was me vacuuming the table top off, with the vac sitting on top of the machine. The vibration from the vac caused the cable from the PC to the control box to work lose, and a rapid make and brake on the X and Z step pins causing the machine to drive X in the + direction and Z down. By the time I realized what was going on the drill bit had stabbed into the table and had a nice curve to it, check how the gantry is leaning back.

My advice to you is……don’t do this. :(

wow, do you normally have a lot of flexing issues with your machine, i'm worried about that seeing how these are made out of wood, just want to get an idea of what to look forward to or prevent as much of it as possible, i've extended mine to 60" which should gave me about 45" or so on the X axis, so my cutting bed is a little flexxy, i'm reinforcing it with two pieces of 1 1/4" x 1 1/4" angle screwed along the sides under the edges, hoping this will solve that problem, though it's not too bad i just want it as stiff as possible.

Yes the jgro can be a little flexy. a lot of what you see in the last photo is the long (Y on my machine) axis. The single unsupported pipe can and will flex a bit. Especially if you abuse it. Some support on that pipe will help a lot, or using the double rail on each side. There are ways to stiffen up the jgro, and I need to search the threads to find them.

I shot a couple of short videos I'll post tonight if I get a chance.

Thanks for the info, can't wait to see those videos.

I wonder,…am I the only guy running a Dremel as his spindle? I have got to get the mounts made for the router….anyone have some extra time I can have…

I drew this up and was thinking of giving it a try, has anyone seen anything like this?

I drew this up and was thinking of giving it a try, has anyone seen anything like this?

yup been done a few times already. here are samples of one like yours and abother with longer threads using rubber washer as keepers.

I like that, elegant and functional…

Shocking!

Ok, this is the info that Tjord and Dan dimock asked about in Tjords thread, I thought I would post it hear too. I recommend you do a little research on the net to find the right SSR for your needs. Use the info at your own risk. If you aren’t electrically inclined find someone who is….Please.

Now that I have worked out most of the backlash and lost step issues, It’s time to cut something. I drew up a mounting plate to fit a #23 motor and ran it. Here are a few pics of the setup, cutting and the part. The part came out good. And fit the boss on the motor perfectly. :banana:

The part was made with, Acad, Ace, TurboCNC.

I made some video clips but they are huge.

Very cool, I really like your build. FWIW, Im using Mach3 and V-Carve Pro.

So are you going to thread your anti-backlash nuts for your screw yourself?...How is this done for flat threads as on ACME/BallScrews, is there an off-the-shelf tap, or do you need a cnc lathe?

Hi V&B,
Great test parts. That's great and the perfect fit is icing on the cake. Thanks for the pics.
Dave

Thkoutsidthebox,

Yes I believe you can buy an Acme thread tap, but I think a lot of guys make one from a cutoff of the lead screw.

Last night and this evening I cut the mounts for the router I am going to use. There glued up and clamped, and I took off the Dremel I have been using. Hopefully in the next day or two I’ll get the router mounted up and do some test cuts. Plus post a few more picks.

Here's a photo of my ACME Tap.
http://flickr.com/photos/41267292@N00/398429536/in/set-72157594505361068/


So are you going to thread your anti-backlash nuts for your screw yourself?...How is this done for flat threads as on ACME/BallScrews, is there an off-the-shelf tap, or do you need a cnc lathe?

I finally had a free minuet to post the photos of the router mount.
Here it is…

Don't ya just love that CNC? Good looking parts.

Tonight I had an hour to spend in the shop and got the router mounted. It took 32min to cut each clamp (remember I was cutting with a Dremel, can you say “multi pass”). I am also going to try a cheap-O speed controller from Harbor Freight. So for now the Dremel is off and the router is on. Now I need to redo my drawings with a new offset for a ¼” cutter.

That's really looking good. You are going to love the stronger router. Multi-multi-pass days are gone. Now it's a couple-o-pass ahead.

Looking good there VB, all this tweaking and modifying you guys are doing, I just can't wait to get mine done, little envious here(nuts) j/k about the kicking knee thing, let us know how the new router's working out for yuh.

I know I’m over due for an update, been very busy at work this past week. I did get a chance to stop in at Home Depot and pick up a set of router bits. I’ll try and test them out by Sunday (Easter)

Hoppy trails…….sorry I couldn’t resist.

I haven’t run the router bit yet, but I did get a chance to try the new router with a ¼” end mill. I cut a sweeper shoe (not sure if it has a real name) for attaching the vacuum to the bottom of the router. And I let Jane pick the color to paint the machine….Bright Orange! I tried the paint out on the shoe. I’ll post a pic soon.

The pics of the Orange shoe... I'm looking for something to make a skirt for it out of. Any ides?

Now that my machine is all but done (is it every really done?) I need to add limit switches, plumb up the vacuum line, and get a coat of paint on it. Then maybe change out the ¼-20 lead screws for some acme rod….

It’s hard to believe is been a month senses my last post… but with winter gone I have been trying to catch up on out door projects.

I guess I need to put up a few more pics….soon.

voltsandbolts-
How about some brush-type weatherstripping for around your "orange shoe"?
www.mcmaster.com item 1131A45

Neatman

I tried two different brushes and I settled on a drafting table brush. The brissels are pliable. I cut the handles off each brush and mounted them around base of my shoe.
http://www.draftingsteals.com/catalog-pencil-sharpeners---erasing-supplies-drafting-brushes.html

I tried two different brushes and I settled on a drafting table brush. The brissels are pliable. I cut the handles off each brush and mounted them around base of my shoe.
http://www.draftingsteals.com/catalog-pencil-sharpeners---erasing-supplies-drafting-brushes.html


LOL, have not used one of those in years, I Work for Civil Engineering and surveying company, don't even have any K&E drafting tables anymore, all Autodesk Civil 3D now, my desk has a dell with dual monitors to replace all the drafting suplies.

sometimes you think of the old days of stabing yourself with an e-xacto knife or a K&E 000 leroy pin. (self tattoo), parallel bars, etc.

Joe

Hey, I'm a Civil by degree too. But I've worked in the Mechanical field most my career. I miss the inside-outside work and the calculations for ground water runoff. Now I'm getting sad just thinking about it.

Here's a picture of my drafting table brushes mounted. The nearest brush has only one screw holding it, so it can pivot for good visibility.

I know there are better collection systems. I just got fixated on this design and went with it.

Dave

Thanks guys for the brush tips. My only concern with the bristle stiffness of the brush. I don’t want the Z axis pole-vaulting over stiff bristles in a direction reversal. The drafting brush may be the ticket! I haven’t seen one of those sense I took drafting back in High School (1980), or those little metal erasure shields….

The drafting brush if you go downward in a vertical direction and when it hit the table they do give a bit of resistance, I remember that from the old days, and hitting it on the desk while talking on the phone. LOL

Joe

Another source of drafting brushes is your local art supply store. I tried some broom brushes before settling on the drafting brush. I choose the softest broom in Lowes, but it was to stiff and I ended up trashing it. The drafting brush is not noticeable in resistance to the Z stroke. The vacuum bends it inward slightly too, so Z resistance is impossible as its already bent slightly.

:idea: Last evening wile pondering what to do about attaching a brush around the curved front of my Vac shoe, the word skirt popped into my head, so I made a skirt out of some old denim rags in the shop. Its three layers thick so I hope the Vac doesn’t suck it under too bad. I’ll try to post a pic later.

Ok, the pic's of the skirt. I may have to add a stiff wire reinforcement to help it keep it's shape, but I think It will help to keep the dust down in the shop.:)

Hey VB,
Look out for the belt and suspenders! :)

No really, its looking great. My only real comment, is visibility. I have the capability to swing some of my shield away for visibility. I can't stand cutting blind.

You might consider the ability to swing some of your fabric open for visibility. If you already have it, outstanding.

I can just lift one side and put a closepin on it to hold it up...

It is functional if not fashionable, and has been working satisfactorily..

Well I guess I have been a real CNC slacker, but its summer and I have been doing out door projects. Fall will be hear soon and I will return to my in door hobbies…

My new thread on motor heating is just getting warmed up, stop in and leave a comment if you will.

http://www.cnczone.com/forums/showthread.php?p=341085#post341085

Here's a related thread on hot motors. Its pretty new and there's some good info too.
http://www.cnczone.com/forums/showthread.php?t=43243

Well, it’s finally starting to cool off a little here in the North East, and I think is about time to blow the dust off the jgro and start with a few mods. Any suggestions for a (almost) stock setup?

Things I’m thinking of are: (What would you add to the list?)

Convert to ½” Acme
Stiffen the gantry
Automate the dust collection (on/off in the Gcode)
Get a cote of paint on it
Try some other software (been using TurboCNC)

Any suggestions as to what to do first, or other mods?

I’m all ears…

how about, cut a Joe2006.

Hi Dave,

That's on my to do list. I have been thinking of a scheme to cut the over sized parts. Are you cutting a Joe2006?

I was thinking about doing the joe's, but i think i've decided on lionclaw's as all i'll need to get order is 1/2 bearings, the Z axis bushings, and i'd like to get 1/2", 8 2 start threaded rod, i've seen a video of his jogging with the same motor kit that i have at 250 ipm i think it is, really cool speeds, plus the machine seems a bit sturdier than my jgro and has a greater cutting area with more or less the same footprint.

Here's the video link: http://www.youtube.com/watch?v=meZBUQbGDqA

I too have been trying to figure out how to tackle the oversized parts, my theory is this, cut the blanks to exact length or size needed, set up a home position for the corner of the blank maybe with some sort of stop/fence, let the machine do half of the cut process, afterwards flip it over and repeat, this of course is provided both ends are identical or you'll have to adjust you file to suit.

The Lionclaw design is a nice variation of the Joe2006. The gantry rides on the outside of the rails, which adds about a foot of Y axis cutting area.

Regarding the parts that are too long to cut on your cnc, the critical cuts are the half moon pipe guides. The spacing and location being critical. I think a hardware stop as you suggest would make that job pretty simple and accurate.

I was thinking about doing the joe's, but i think i've decided on lionclaw's as all i'll need to get order is 1/2 bearings, the Z axis bushings, and i'd like to get 1/2", 8 2 start threaded rod, i've seen a video of his jogging with the same motor kit that i have at 250 ipm i think it is, really cool speeds, plus the machine seems a bit sturdier than my jgro and has a greater cutting area with more or less the same footprint.

The snow has melted finally and I can get back into the shop! It will be nice to get the old jgro up and running.

hey VB, good to see you're back at it again, what's new?

I have been spending time working on my trucks.

http://www.supermotors.net/users/VoltsAndBolts

But I'm ready to start up the old CNC. Time to look for a better software combo than what I have been using. (ACAD, Ace converter, TurboCNC) What are you guys running now?

Rob.

Rob,
I only use VcarvePro and Mach3 for 2.5D designs. No other drafting package is needed. VcarvePro has a great little 2D drafting program embedded into it's system.
Dave

Well it’s time for me to get back in the shop after a long absents, normally
I work on my indoor hobbies during the winter months here in NH, but last winter my shop (unheated garage) actually had a car in it all winter with no room for me to work, it was a long winter…

When spring hit I was thankful to get that car out of there, but I turned to my warm weather hobby My FJ Cruiser and 4Wheeling!

Well winter is here again but this year no car in my shop and I now have heat! WooHoo!
When I got up this morning it was 15* and I started reading up on the Zone, so much has happened over the last year. Some of you guys that were at or near the same level I was at have progressed so far, I have a lot to do to catch up (if I ever can) I guess its time to get the jgro up and running finished tweaking it out and choose the next machine to build. I know I’m getting a bit long winded, but it’s good to be back and starting to experiment again.

Rob Wms.

Welcome back. Heat up the garage, and get your machine running.

Much like my table saw my jgro seamed to collect quite a lot of stuff on it since its last use. Step one. Clear off and open the area around the machine. I am also switching from an old lockup prone 486 laptop to a old P1 (75MHZ) desk top. It should run DOS at a blinding speed! :tired:

Ok, I got every thing cleared and cleaned off, Checked the machine over, gave the controller box the once over fired up the computer, plugged in the 50V supply to the controller box and POW! Curls of smoke and that old familiar smell. It’s been a long time sense I have seen the magic smoke.

I found a blown transistor on one of my drivers. I switched over to the back up driver and fired it up again, no pop this time. Good news the back up driver is working ok, bad news, the other two drivers that showed no damage seam to be dead. I guess I’ll pull them and give them a close inspection.

Oh man, that's the pits. I hate the smoke and the pows, and most of all the lost curls of magic. Hope it gets well quick.

The component that suffered catastrophic failure is a International Rectifier IRF530 MOSFET. I have some IRF540n on hand an will try one on the unit with the obvious failure. If that fixes the drive I will try running each axis from it to verify the other drivers are in fact dead.

I swapped in the IRF540 and the drive lives! I did some troubleshooting and have narrowed it down to the 25 conductor cable from the PC to the controller or the printer port is fried. More to come…

Did a pin to pin check on the cable, it's good, Now to verify it's the printer port on the PC I will pull out a very old laptop and see if I can get movement...

Received the 1/2-10 Acme and thrust bearings I ordered from McMaster-Carr. I fabed up some taps and started experimenting on making Acme nuts. I have started to break down the jgro for the lead screw upgrade, wile its down I will also take the opportunity to paint or poly it. After it's back together I'll finish checking out the controller.

The power was out in a good chunk of New Hampshire this past week because of a major Ice Storm. I have a generator but it’s not enough to run the house necessities and my shop, so I worked on designing some parts for my next machine.

I pretty much worked out the base and some of the Z axis.


http://i285.photobucket.com/albums/ll75/VoltsAndBolts/CNC%20Stuff/BaseTBoxAssy.jpg

Machine Base

http://i285.photobucket.com/albums/ll75/VoltsAndBolts/CNC%20Stuff/ZAxis003.jpg

Some Z axis views.

http://i285.photobucket.com/albums/ll75/VoltsAndBolts/CNC%20Stuff/ZAxis003a.jpg

http://i285.photobucket.com/albums/ll75/VoltsAndBolts/CNC%20Stuff/ZAxis003b.jpg

I have a lot of work to do, including getting the jgro going so I can cut the parts for this machine.

now this looks interesting, got any idea what your cutting area will be yet, or is it too early to say?

I'm working on the lionclaw build for the main reason i'll get greater cutting area with basically the same footprint, this one looks like it's going to be made up on a similar basis of of it or the "joe's", which is good as it maximizes it's width (most's y axis).

keep the pics flowing.

The skin on the base is 26 x 60 in, I will adjust the size if needed. I want to fit a 1/4 sheet in the machine (2 x 4 ft) I have discovered I really enjoy the design process, and am sort of following the same them as LionClaw and Joe.

I too like the idea of a 1/4 sheet fitting on the machine, cutting area i think on mine is 26" x 50" if i remember correctly, which if so will allow for a 1" border for clamping outside and still maintain the 2' x 4' if need be.

You bring up a good point, I haven't thought about the area needed for clamping along the edge...

Just a little update on my Z axis.

http://i285.photobucket.com/albums/ll75/VoltsAndBolts/CNC%20Stuff/ZCage002.jpg

Wow I have been away longer than I thought! I have no excuse other than life just gets too busy sometimes...

Well I did get a coat of poly on the jgro, it gave it a nice warm color, and started redoing the skirt on my vac-shoe. I couldn't stand the orange color my wife picked for it any longer, so I painted it hammer tone gray and ditched the cloth skirt, it's being replaced with clear plastic from a 2 liter soda bottle.

I got the dust collector shoe reworked and back on the machine, I was surprised to find there was just enough material in the straight section of the 2 ltr bottle to go around the collector. I drilled & taped for 6-32 BHCS ¼” deep every 1” around the perimeter but only used every other hole. How to you think it looks?

I am trying my hand at making some ½-10 ACME AB nuts I fabed up a couple of taps. One 3 and one 4 flute.

Wow, very nice.

When I made mine, I reduced the lead-in diameter a bit more. But give it a try the way it is now. If you have trouble getting it to start with the current configuration, then try tapering the lead-in some more. You have plenty of cutting surface, so adding some more reduced lead-in won't hurt anything.
Dave

Hi Dave,

Sounds like your recommending a little more taper… :stickpoke

So far they seam to cut ok (with a power drill), but the thread is a little tight. An old timer told me to freeze the plastic before cutting the thread and there would be less spring back of the material. I think I’ll give that a try. It can’t hurt.

I agree on the taper, I modeled the taps after metal cutting taps and I think adding some more taper would help. Boy do they get hot when you crank them through the plastic!

Here's one for 1/2-10 one start I made that worked pretty well. The end was turned down to fit into the starter hole and it acts as a guide to insure that the threads start on center. The shank end goes into a cordless drill. The slots were milled with a regular four flute end mill. I think I would do it with a round nose end mill next time.

CarveOne

Now, that's what I'm talking about. Great lead-in and you still have 7 or 8 full sized cutting teeth.

Did anyone try freezing the plastic? Interesting idea.

Now, that's what I'm talking about. Great lead-in and you still have 7 or 8 full sized cutting teeth.

Did anyone try freezing the plastic? Interesting idea.

Didn't try that, but it should contract when near frozen and if you can tap it quick enough it should be less tight on the lead screw when it warms up. The theory is good if the material can shrink enough.

CarveOne

One more way to make a tap cut oversize to give you some clearance is to have it nickel plated. It increases the OD just enough and cuts it slightly oversize. This was a common practice when tapping acme threads in plastic (Delrin AF and acetal) anti-backlash nuts at my last job. They even had a couple different thickness plated taps to get the drag torque just right.

An alternate suggestion may be to make one more tap, drill a tapered hole in the end of it, and saw slots in it like a collet. When you drive a tapered pin into the tapered hole, you can enlarge it slightly to cut a little oversize to get the exact fit you want. An alternate method is a tapered thread, like a pipe thread, or in a really small part (like a 1/2" tap) perhaps a tapered self-tapping screw could be the wedge.

Keith

One more way to make a tap cut oversize to give you some clearance is to have it nickel plated. It increases the OD just enough and cuts it slightly oversize. This was a common practice when tapping acme threads in plastic (Delrin AF and acetal) anti-backlash nuts at my last job. They even had a couple different thickness plated taps to get the drag torque just right.

An alternate suggestion may be to make one more tap, drill a tapered hole in the end of it, and saw slots in it like a collet. When you drive a tapered pin into the tapered hole, you can enlarge it slightly to cut a little oversize to get the exact fit you want. An alternate method is a tapered thread, like a pipe thread, or in a really small part (like a 1/2" tap) perhaps a tapered self-tapping screw could be the wedge.

Keith

A finishing tap of slightly enlarged dimensions as you mention would be a good possibility. It would only need to follow an existing ACME threaded hole.

CarveOne

Freezing the plastic really worked for me. The tap cuts a whole lot better.

Jason

I agree freezing before taping seamed to help in my testing too.

Drill it, Chill it, Tap it, Test it. :cool:

Just checking in to see if anyone else has tried the freezing before taping... Well have ya?

I am in the process of moving my 3D work from SolidWorks to Alibre.