Author Topic: Leadscrew  (Read 2480 times)

Offline Neil-Lickfold

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Re: Leadscrew
« Reply #15 on: March 25, 2019, 08:27:26 AM »
With the toolmakers tap you can make them with 2 or 3 flats.
I make them with 4 flats, and then do a relief grind up the side if it needs
any positive cutting.
Unless it is a large diameter tap, then I just make a series of cuts up the tap, and relieve
the od of the tap off the high point to reduce the drag.
I like using the full form inserts for the tpi or the thread pitch.
Very nice and thanks for the pics.
There is no point in putting in a lot of time if it is only a 1 time only thing as well.
Sometimes depending on how long the nut it etc, it can be viable to screw cut the thread than to make a tap.

Neil

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Re: Leadscrew
« Reply #16 on: March 25, 2019, 10:04:45 AM »
 I usually do 3 flats on a 20 degree angle.  This one might need a longer taper..  I milled this taper in on this one, but if it needs lengthening, ill just grind it.
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Re: Leadscrew
« Reply #17 on: March 26, 2019, 02:28:35 AM »
Productive night on the leadscrew front!    I tapped the nut, and it cut like buttah!   On to the screw.

I started bringing the 5 inch long screw to size, and it was bowing pretty bad, even with a left side turning tool to put the cut force along the axis of the part.  So I needed a follower rest.

Problem is the stock SB one is far too big for a part this size, and it is also far to wide.   So I mounted a angle plate to the T slotted saddle, and mounted up a scrap piece of bronze with a notch cut in it.

I have to readjust the follower rest for every cut, but I'm only chasing the last 0.020.   There's a little taper I'm dealing with  about 0.002 over 5 inches...I'll take that out with the TS...but I'm done for tonight.

Dave
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Offline Neil-Lickfold

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Re: Leadscrew
« Reply #18 on: March 26, 2019, 04:54:46 AM »
I always try and have the follower on the fresh cut material. But it is a 2 way thing. The chips can easily get in the way.
Its a pain, but running a vacuum cleaner to draw away the chips works really well.
I put my compound on an angle, Normally 30 deg, so that  the value on the cross slide, now becomes the diameter of the cut.
But it gets worse as you have to reset or bring into the job the steady.
I find that the Myford travelling steady often just gets in the way.
Sometimes it is also easier to cut a longer blank, to give room for the tools etc, and then set up and cut the excess off later when
the end detail is being finished,
It is small jobs like this that I think I should make up a roller box.
But like you have just persevered and made do with what was available at the time.
Neil

Offline simplyloco

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Re: Leadscrew
« Reply #19 on: March 26, 2019, 09:44:34 AM »
Very interesting and very small! When I did the 1.00 mm pitch reverser on my Britannia I gave myself a challenge and screw cut the LH thread bronze nut in the lathe! If anyone is interested here is a link to a couple of pics.
John
http://modeleng.proboards.com/thread/3571/brit-progress-screwcutting-reverser

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Re: Leadscrew
« Reply #20 on: March 26, 2019, 11:28:59 AM »
This one was a challenge.....the tool clamp screw is 4-40.    0.354-10 LH ACME

http://www.modelenginemaker.com/index.php/topic,1192.msg15322.html#msg15322
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Re: Leadscrew
« Reply #21 on: March 26, 2019, 11:44:17 AM »
I always try and have the follower on the fresh cut material. But it is a 2 way thing. The chips can easily get in the way.
Its a pain, but running a vacuum cleaner to draw away the chips works really well.
I put my compound on an angle, Normally 30 deg, so that  the value on the cross slide, now becomes the diameter of the cut.
But it gets worse as you have to reset or bring into the job the steady.
I find that the Myford travelling steady often just gets in the way.
Sometimes it is also easier to cut a longer blank, to give room for the tools etc, and then set up and cut the excess off later when
the end detail is being finished,
It is small jobs like this that I think I should make up a roller box.
But like you have just persevered and made do with what was available at the time.
Neil

I leave my compound at 29, but the tool aligned.   They both get it done in my book
I don't want to turn this project into a tool making exercise...I just want to get it done.  So I'll leave the tooling crude...but effective.

The original screw is cut long, I suspect for the same reason...to have some travel for the follower rest before the tool gets to the TS center.  Mine is also.

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

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Re: Leadscrew
« Reply #22 on: March 27, 2019, 11:24:57 AM »
I"m done!

Here's the family shot, new one mounted, and old one next to it

I've got some more in process ones...but I have a job to go to.....perhaps later

The screw was a bit of pain in the rear, as it has a very long nut, and any pitch error was immediately apparent.     So it was slow going with light cuts to bring it in.

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
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Offline b.lindsey

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Re: Leadscrew
« Reply #23 on: March 27, 2019, 01:09:05 PM »
Well done Dave. Hope the boss appreciates all the effort that went into it!!

Bill

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Re: Leadscrew
« Reply #24 on: March 27, 2019, 01:11:22 PM »
Well done Dave. Hope the boss appreciates all the effort that went into it!!

Bill
Well   me too.   But I doubt it.
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Online Vixen

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Re: Leadscrew
« Reply #25 on: March 27, 2019, 01:47:26 PM »
Nice one Dave,

"The jobs a good 'un"

Mike
It is the journey that matters, not the destination

Offline Don1966

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Re: Leadscrew
« Reply #26 on: March 27, 2019, 01:52:06 PM »
Love it Dave!.... :ThumbsUp:


 :cheers:
Don

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Re: Leadscrew
« Reply #27 on: March 27, 2019, 04:53:10 PM »
If I ever do this again .   Ill use hardened steel for the follower.Bronze wore too fast.
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Tennessee Whiskey

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Re: Leadscrew
« Reply #28 on: March 27, 2019, 06:41:32 PM »
You go boy: damn good job 👍

Cletus

Offline stevehuckss396

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Re: Leadscrew
« Reply #29 on: March 27, 2019, 07:43:13 PM »
I"m done!


Never doubted you for a second. Way to go sir
Do not be like the cat who wanted a fish but was afraid to get his paws wet.