Threading problems - at my wits end

[watch_art]

I have been having a problem with my M10x.75 threading lately.

The problem seems to be just with acrylics and lucite.

I turn a section and create a tenon that's about 9.7mm with the threads mentioned.

I drill a hole in a barrel blank with a U, or even up to a 3/8", and thread it, and the damned stupid section WON'T screw in! It might go in about 2/3 of the way, but the last bit won't go in without force. It will screw in but it's VERY difficult. I don't know what the hell I'm doing wrong.

I took an old PR section and it threaded into my new barrel perfectly.
I took my new lucite section and tried to screw it into the old PR barrel and NOTHING!!

AAAUGHGGGHHH!!!!!

I feel like Charlie Brown trying to kick that stupid football.

Why is it binding up??

Could it be that the temperature has changed and the material is all contracted?

Could it be my tap is messed up?

Could I REALLY be that stupid???

....don't answer that...




Thanks

 

[firewhatfire]

:biggrin::biggrin:I wish we could answer.:biggrin::biggrin::biggrin:

 

[firewhatfire]

not really as I dont really know

 

[mredburn]

Are you using the die to form the threads on the tenon. Run the die up as normal than reverse it and run it on the threads again. Some dies are tapered so that the starting side is not as it should be. Runnig it on backwards cuts the threads deeper on the back side. I have had that problem. Also if your tap isnt going in very deep it may be a tapered tap and you wont get complete thread depth on short threading distances. I have to use a bottoming tap or make one and chase all the threads I make.

 

[Dalecamino]

Shawn, since you have other pieces that thread in, it may be your die needs adjusting. The little set screw may have backed off, and is not cutting deep enough. The way you adjust this, is to turn that screw maybe 1/8th of a turn, I think it's COUNTER clockwise. Mike Roux told me this last year sometime. So I've slept since then Mike Redburn is also correct, but as I said, you've had other pieces thread in OK. Good luck!

 

[plantman]

Are you using the die to form the threads on the tenon. Run the die up as normal than reverse it and run it on the threads again. Some dies are tapered so that the starting side is not as it should be. Runnig it on backwards cuts the threads deeper on the back side. I have had that problem. Also if your tap isnt going in very deep it may be a tapered tap and you wont get complete thread depth on short threading distances. I have to use a bottoming tap or make one and chase all the threads I make.

:befuddled::befuddled: A lot of times when this happens, you thread pitch is off not the size. The farther you screw the piece on, the farther off the threads get, the harder it is to turn on. I agee with Mike. Most , if not all, dies have an inside bevel to make starting easy. Run the die, numbers faceing towards the blank first, than reverse the die to cut threads all the way to the end. Make sure you have a small releaf at the end of the threads, and a little champher at the beginning. Also as Mike says, use bottoming taps to finish threading holes, or drill your holes deeper if you have tapered taps and the room to do so. You could also use a little Chap-Stick on your threads. If you are holding a "adjustable" die ( not all dies are ) in your left hand, and the set screw is on the right side of the die, turning the screw clockwise will tighten the die and make a smaller OD thread. Counter clockwise will force the die open and make a larger and tighter fitting thread. Your tap and die sizes all depend on who at the factory set up the machine that day to begin with. They all are not exactly made to US standards. Most are in MMs. The difference betreen a 8 X 24 and a 8 X 23 thread won't be noticed until you thread it on for a ways, if at all. The same also holds true for fittings. Thats why we always measure everything, even drill bit sizes!! Jim S

 

[watch_art]

HA!

Thanks everybody.

Well - I think I figured it out - and I'll tell you what I did.

I started off by reading this:
http://www.penturners.org/forum/f56/tight-threads-100250/
and got lots of ideas that I hadn't thought of.

First I ground the tip off of my tap so it would act more like a plug tap rather than taper tap.
Okay cool.

Then I took the set screw out of my round die - yeah one of those dumb adjustable dies - and squished it a little bit in my table vice to close it a bit - then ran it over my lucite section and tried it again in the barrel and it worked in perfectly.

 

[Dalecamino]

I guess the long way around works too then. Those set screws are there for the purpose of adjusting. But, your way worked for you. That's all that matters.

 

[joefyffe]

Shawn, since you have other pieces that thread in, it may be your die needs adjusting. The little set screw may have backed off, and is not cutting deep enough. The way you adjust this, is to turn that screw maybe 1/8th of a turn, I think it's COUNTER clockwise. Mike Roux told me this last year sometime. So I've slept since then Mike Redburn is also correct, but as I said, you've had other pieces thread in OK. Good luck!

Is this an indication of CRS disease?:biggrin: