Finishing it up (spindle adapter)

[Deanofid]

Hello all;

Worked on rigging up the Atlas to take Taig chucks today, and thought a few folks might like to see.
It's mostly straight forward lathe work, but is a bit more than just turning.

What I'm working on is a spindle adapter to let me use Taig chucks on the Atlas. It will have a 1"-8 TPI
internal spindle thread on one end, to fit the Atlas spindle, and a 3/4"-16 external thread on the other,
to fit Taig chucks, or others of that size. Should be very handy for transferring work between the two
lathes, while leaving the work piece undisturbed in the chuck.

I made one of these gadgets for my Craftsman 109 lathe a while back, and it worked out well. I no
longer use the Craftsman, but would like to retain the same convenient chuck swapping set up for the
Atlas.

Starting out with a piece of suitable sized stock from the indespensable "left overs" tub, it's chucked up
and drilled to a suitable depth for the Atlas threads, plus a little extra for threading tool run off. Then
bored as deep as I can with this type of boring tool. This tool won't bore to a flat bottom, but it's stiff
enough to cut fairly fast.

The piece is in two diameters here, but that isn't for any purpose. It's just the shape of things as it
came out of the tub.
I'm not sure what this stuff is, but it's a pretty good guess to say it's some type of leaded CRS.
It machines pretty nice.

Here's the piece bored for thread diameter, plus the needed free bore for the unthreaded part of the
Atlas spindle. The smaller diameter is where the threads will be cut, but it needs some relief down at
the bottom of the hole for the threading tool to run off after cutting the threads.

To do that last bit of run off down near the bottom of the hole, I used this tool that has a small hook
kind of thing ground on its end. The run off area is made the same diameter as the spindle free bore at
the start of the hole, and .300 long, so the end of the threading tool doesn't bump up against the
bottom. This tool was barely long enough to reach, but it did the trick.

Now the bore is ready for threading, and the pick-off gears on the lathe have been changed for 8 TPI.
Since I can't really see very well inside the bore to run a test scratch, I just ran it on the outside of the
piece. It's only about .0005" deep, and will be turned off after the internal threading is finished.

The scratch shows I have the change gears set up properly. Time to set up the threading tool to cut
the threads in the bore.

A 60 deg threading tool is ground up from 3/8" HSS, and set to cut square. The compound is set to 29
deg, same as for cutting external threads, except the 29 deg is set on the other side of zero on the
scale. It works the same way as outside threads, except the feeds on the dials of the compound and
cross slides are done in reverse. In other words, the compound is cranked toward the operator to feed
the tool, and when backing out to take another cut, the cross slide is cranked away from you, to clear
the threads that have been cut when returning to your starting point.

With the lathe off, the tool tip was set at the starting point for the threads, (inside the bore), then
cranked in toward the headstock where the threads are meant to end. The DI holder on the lathe is set
so the needle starts to move just as the thread ends. This is done so I will know when to disengage
the halfnut after taking a cut.

Everything was going along great, thread about half way done, no chatter, and BAM... Lathe locked up
tight and belt started to squeal. I knew what had happened.

The small tumbler gear had given up. I knew this gear was going bad, but hadn't got around to cutting
a new one yet. The gear was missing a bit of one tooth when I got the lathe. It was on the "to do"
list, but it looks like it will get done sooner rather than later.
It's the smallest gear in the train, and that bad tooth couldn't quite take 8 TPI. The way the other three
teeth came off, it looks like it may have been in worse shape than I thought.
Luckily, the broken teeth had jammed in a larger gear and stopped the works before they could do
more damage.
(I know these parts look really dirty, but they're not. They're made of Zamak, and turn any oil black.)

I had another gear of this tooth count on the stowed away Craftsman 109, so pinched it to get this job done.
All the gears in the train were cleaned and checked for stray bits before continuing.

That was the easy part. I had now lost the cut on the lead screw.

After what seemed like quite a while messing around, rocking the chuck back and forth and trying
different starts on the half nut, I found the cut, and finished up the threads. They came out fairly well.

Picking up a lost cut on threads isn't usually that difficult, if the threads are external. You can look at
them straight on and judge pretty well when you've got it by trying a few different places on the
leadscrew/halfnut. When they're inside threads, you can only see them from an angle, and it takes a
while, for me, at least.

After a few more cuts, and a few tries having a go on the spindle by removing chuck and all, this part of
the thingy is done.
That's it for today. Next time, maybe Monday, the outside of the piece will be finished off, and the
external threads can be cut for the Taig chucks.

Thanks for looking in.

Dean

 

[1hand]

Dean that's going to be a real nice add on for your lathes. Nice that your lathe will cut the threads you need. I've just been checking and mine won't cut its own spindle threads. Didn't realize that til now. You would figure that a lathe would be able to cut its own spindle threads. A M39-4 Die is $80.

 

[SBWHART]

Hi Dean

Nice bit of work on your interchangeable tooling, and a good recovery from the broken gear tooth.

Have fun

Stew

 

[Blogwitch]

Dean,

Very nice work, and a good recovery. I had the same sorts of problems with my Atlas lathe when cutting slightly heavier threads than yours. Actually it was the bolts for the changewheels that sheared on mine, the changewheels remained undamaged, even though they were only made out of Mazak.

But please, don't give up now.

Both Stew and myself have extended the idea to include the mill as well. In fact, maybe I will look at my small surface grinder next.
It pays to only live walking distance away, when one of us comes up with an idea, the other can pick up on it straight away and get to work.

With a little thought, and some scrap bits of metal, you can easily transform the way you machine, and it saves hours of setup time between the machines.

The main basic is a lathe nose fitting accurately centred on your RT.

With a little imagination and time, you can get total interchangeability between your machines.

You get to a stage that when a new bit of equipment comes into the shop, say a spindexer, the first thing you do is look for ways to incorporate it into the 'system'.

Keep up the good work.


Blogs

 

[gbritnell]

Dean, I had the same problem with my 6" Atlas. I had bought mine new so I know there was no damage to anything. That small gear has a weak spot where the keyway and tooth are located and if too much pressure is put on it, pop, there she goes. Mine just broke in half. I made a replacement from 12L.
gbritnell

 

[Deanofid]

Thanks for chiming in, guys.

Matt, I don't know what kind of lathe you have, but you may be able to use alternate gearing from what your lathe charts suggest for doing something like your spindle thread. Many lathes will cut a lot more threads than what is shown on the chart that comes with the lathe.
There is a neat program on www.lathes.co.uk/ called NthreadsP that will use your computer to calculate all kinds of different thread gearing. I use it to cut metric threads on the Atlas for use on my milling machine spindle, which has an ER-16 nose.

Stew, thanks!

Blogs; I haven't given up! The hard part is done, and the part of the adapter that threads onto the Atlas nose fits perfectly.
A false nose for the RT and an ER collet chuck are on the "make it" list too, and I have some scratch drawings made up that are just waiting for me to get greasy fingerprints all over them.

George, 12L might just be the thing for that smallest gear. Maybe even hard brass. It's the one on the banjo, so it has no keyway cutouts. Just a plain bore, which should strengthen it a bit.

Thanks again for the suggestions and encouragements, everyone!

Dean

 

[1hand]

Dean,

Thanks, them are some neat programs. Wish I knew more on how to use them. I think I need both of them. Because my 9x20 Grizzly lathe has a quick change gear box. When I click save to down load the gearbox one, and go to use it it says file not found. Basically I want to cut a M39x4 with my 9x20 if anyone could help me out with whats got to go where. I sure would appreciate it.

Matt

 

[Deanofid]

Matt;

I've never used the program for lathes with a QCGB, ask about the thread program in the "Questions and Answers" section of the forum, near the top of the board. This particular thread may not get much exposure, but quite a few people read QandA. There may be someone who has done just what you want to accomplish.

Dean

 

[Maryak]

Matt,

Start with the pitch of your leadscrew. 8 tpi is close to 3mm, (8.466666667 tpi). These are fairly common smaller lathe leadscrew pitches.

Go from there.

Attached is my lathe's change wheel spreadsheet. Over to the right is a continuous/continued fraction routine which may help you resolve which gears will work from those you have available.

Hope it helps.

Best Regards
Bob


View attachment Hafco Change wheels.xls

 

[1hand]

Thanks Bob, I think I got the right setup now. :big:


Matt

 

[Deanofid]

Time to finish this up.

Skimmed off the threading scratch from the test run earlier in the process, and drilled a hole for a
breaker bar so I can get it off the spindle.

Faced off the end, which had a great big divot in it from some other project long ago. Then turned
down the end to .750" for the needed 3/4"-16 threads. Then thread it!
Same procedure as that already outlined earlier, so I won't go through it all again. The only difference
is these threads will go on the outside, and they're a different size.

After a bunch of back and forth with the carriage, I end up with some decent threads to take the three
and four jaw Taig chucks.

This is how it fits up with a chuck. A DI on a test rod shows up under a thou. Not bad for a scroll chuck
with soft jaws. Better than what Taig says it will do, actually.

I put a 3/8" bore down the center, so I can run smaller stock through it.
That's not the only reason for this hole. I'm going for a twofer on this adapter, because I can.

My Taig lathe uses a 15 deg collet system, (30 deg inc.). No reason not to have the same setup on
this thing. The Taig collets aren't super precision, (and they aren't made to be), but they're okay.
All of mine run out to less than .001" when in my Taig lathe.
So, anyway, got a small boring bar and cut the taper in the adapter for the collets.

I worked on a nice finish in the taper bore. Wasn't as easy as it could have been, with Ol' Stumpy,
here. It's sometihng that will have to be fixed before I make my collet chuck for ER collets. I used up
my last bit of Hi-Spot to check the taper before I had it cut to completion. Hit it on the first try from
the look of things, though Taig collets are a somewhat "textured", so it's a little hard to tell.

And there we go. These ran out to just what I expected from Taig collets, which is, again, less than
.001". That's all you can expect from them.

This thing is done. Nothing else to see here.

Thanks for having a look.

Dean

 

[joe d]

Looking good there, Dean.

Is there a long sad story behind Ole Stumpy, or did he come that way?

Joe

 

[doc1955]

I know what you mean when you say picking up ID threads aren't fun. I try to get there with a mirror but the smaller the dia the harder it is.

But I see you are back on track again and looking good.

 

[hobby]

You make realy nice tooling.

Next tool project , fix, OL Stumpy.

And don't froget to post the pictures and procedures.

I enjoy reading your documentaries, you go into nice detail, that keeps the interest going.

Keep up the great work...

 

[1hand]

Dean you said to set the compound at 29deg. Then the tool post at 90deg to the work piece right? Then each pass for external threads you would turn in on the compond instead of the crosslide? If that's right, I totally screwed up when I cut them First threads on my lathe. I was 90deg with the compound and 90deg with the tool bit to the work piece, then I was doing my depth of cut with the crosslide. It was a 1/2 20tpi, and the nut did work, but I think I had the work piece a bit undersize to begin with. I spouse my engagement wasn't very good, that's why the nut went on. So if you could set me straight, I'd sure appreciate it. Now when I make my spindle mounts, Would anything change being that's its Metric? Or is it still 29deg and 90 to the work?

Thanks a million,

Matt

 

[Deanofid]

Looking good there, Dean.
Is there a long sad story behind Ole Stumpy, or did he come that way?
Joe

Hi Joe, and thanks.
That handle has been like that since the lathe came to me. Someone was probably swinging a hammer, and missed.


Doc, I can usually pick up a lost thread, but I've left a share of valleys in the peaks, too. Sometimes, I just goof.


Hobby, thanks for the nice comments. Before that ball handle gets fixed, gotta make a ball turner.
Make a tool, to make a tool, to make.... You know how it goes.


Matt, the compound is set to 29 degrees, yes. That's generally accepted thread cutting practice, mainly to let the cutting tool do most of it's work on only one flank of the thread.
Yes, you dial in successive cuts using the compound.

If you do a practice set up on your lathe, and set your compound like this, you will see that when you dial it in, it will push the cutting tool mostly toward the head stock against what will be the right flank of the thread, and not straight into the work. Less work for the lathe, and easier on things in general.

The part I mentioned about 90 degrees was for the tool bit, and not necessarily the tool post. You want a threading bit to be pointing straight at the side of the shaft. Not canted one way or the other. If it's not pointing straight in, the threads will not have a proper form. They will look kind of like they are leaning to one side. So, use a fishtail tool to set the cutting edge of your bit, and you'll be good.

You can cut threads by dialing the cross slide in, too. The threads will still be okay. You have a much bigger chance of the tool chattering this way, though, because the tool is trying to cut both sides of the thread at one time. The thread you did was probably fine. Tool chatter will really show up on large-ish threads if you dial in your cut using the cross, instead of compound slide.

The same setup works for metric threads, since they are a 60 degree V form.

Ask again if I didn't make it clear. We all have questions about something!

Dean

 

[ksouers]

Dean,
Nice job. Thm:

A great way to add some flexibility to the shop.