Single point or Die head

[deek]

hiya all,

I've got a SB1001 8k lathe. To get different thread pitches this machine requires changing three gears. It's a pain to do single point threading.

I'm thinking about a die head. It seems like a great idea, but I'm still fairly new at machining, so I don't want to spend money unwisely. Anyone have any input on single point vs die head threading.

thanks,

deek

 

[Cogsy]

I used to single point on my 7X12 all the time, even though it also required 3 gears to be changed, but realistically I normally stayed around the same size fasteners so it was normally set up for the correct pitch. I did usually just get them close with the lathe and finish with a die though.

Now however, I don't have a speed control knob on my new lathe and the slowest speed is 160 Rpm. I used to thread at about 40 Rpm and I consider 160 too fast for my abilities, so now I just use dies. I still don't have die head though, so you can probably get away without one for a while if there's more important tooling you need first.

 

[Blogwitch]

Deek,

A die head is just fine, but can become rather expensive.

There are different sized ones for different sizes of threads. A 1/4" one (for real small modelling stuff) will only do up to a certain size, then you have to step up to another one, say a 5/16" die head, then a 3/8" and so on, up to really large ones, plus you have to buy full die sets for each size of thread you need.

I single point a lot of my threads using a swing up toolholder that I perfected a few years ago, and when used with a holder for single die head dies gives perfectly formed threads (but you would still need to change gears if you don't have a gearbox on your lathe.

This product holds the diehead die in your toolpost instead of single pointing

http://www.tracytools.com/thread-chasers/thread-chasers2

A bit boring but this is how my swing up toolholder works, much faster than normal single pointing.

[ame]https://www.youtube.com/watch?v=8JFdNaBD5GM[/ame]


Bogs

 

[kvom]

Die heads can take a while to set up each time, so the gear swap may be just as efficient for a small number of threads. But if you need a lot of the same a die head is hard to beat.

 

[Cogsy]

That swing up tool is excellent Bogs - are there plans available for it?

 

[toolznthings]

Hi,

If you are new to machining I would change gears and get good at single point threading. This will be a plus to your skill level. Die heads are costly and can be a challenge to use. Great for lots of parts, but one or two parts not so much.

 

[Wizard69]

hiya all,



I've got a SB1001 8k lathe. To get different thread pitches this machine requires changing three gears. It's a pain to do single point threading.

I think we need to clear up what you mean by die head. Do you mean a holder for a conventional threading die of something more involved? Or do you mean something like this: http://www.mscdirect.com/product/details/82604950 ?

I'm thinking about a die head. It seems like a great idea,

That costs a good fraction of the cost of your lathe.

but I'm still fairly new at machining, so I don't want to spend money unwisely. Anyone have any input on single point vs die head threading.



thanks,



deek

It is your money but I'd learn single pointing first and then build some tooling to use standard threading dies. You will eventually need the hand dies anyways for something you are working on. As for a threading "head", if you mean what the common terminology means that is a lot of money, especially for a small shop.

 

[Tin Falcon]

Geometric die head do a fine job and are fast.
A new die head is fairly expensive used ones are not bad in price. The dies themselves can be expensive and only do one size and pitch.
single point threading can seem daunting but is a basic skill that should be learned by all machinists.

Tin

 

[deek]

Thanks for the input. I guess I'll keep working on single point for awhile and maybe get a die head for only for the threading I do a lot of.

 

[Blogwitch]

Cogsy,

This is an abridged version of the original post I did.
As mentioned in the first part of the post, almost at the very bottom, there is a rough sketch showing how to build an easier to make version that I made. But you need to read the whole post as there are bits in it that explains why certain things were done the way they were, like the mounting hole for the swing up part, it is lower than centre so that when the swing up occurs, the tip of the tool is automatically pulled back slightly. Just things like that make the tool work efficiently.

http://www.modelenginemaker.com/index.php?topic=858.msg9461#msg9461

I hope this satisfies your needs and explains things enough.

Bogs

 

[Tin Falcon]

Deek I think someone already mentioned Hand dies .
these too can be a little tricky as they are more for chasing but you can cut a thread with them on the lathe.
A few tips and tricks.
One option of course is to buy or make a tail stock die holder.
Another option is simply hold the die in a regular die handle and guide it keep it square by nudging the tool post against it of course 1st making sure the tool post is square.
if you are threading a hollow,cut the thread first then drill the hole as a die can rip the nipple right off the work DAMHIKT.
And of course do not be afraid to single point thread to rough it out and finish with a die.
One of the trick parts with single point threading is measuring. IIRC a good fish tail gage will have a chart of depth of cut. You can measure with thread mics , wedges on mics , use the 3 wire method. or in a pinch use a nut and cut and try.

Like I said earlier this is basic machining knowledge. In USAF tech school in the lathe section we learned to do an external thread single point. then made a matching internal thread and used the first piece as a go gage. Lter in the mill section the male threaded part was turned into what looked like a tap. I say looked like because it was aluminum.
A well trained first year machinist should be able to make a tap or die in a pinch.
And no pressure here I realize most folks here are self taught and have limited time and money to spend on there hobby. and we often have several hobbies. I was very fortunate to be able to spend an an entire summer 40 hours a week learning machining and welding and get paid to do it.
In a home shop you get to pick what you need to /want to learn and set your own pace.

Tin

 

[Nick Hulme]

Die heads can take a while to set up each time.

But the heads have micrometer markings so you only set up each set of chasers once and take note of the +/- setting and only need to change it if the chasers are sharpened or the material is different.

Die heads give you a full form thread, most non-carbide single point tools do not give the specified form for the thread peaks.

If single pointing with a simple tool it is advisable to first turn the work slightly under size to allow clearance at the peaks where the tool would otherwise generate a sharp point, with a die or die-head nominal size or .001" over size will yield a full, correct profile.

Split dies are designed to create a full thread on a blank bar, to suggest otherwise is utter bunkum, correct use with a tailstock die holder will produce acceptable results, especially if a first (slightly over-size) and second finishing (Chasing? ;-)) pass are used, dies for thread cleaning or "chasing" only are easily identified as they are not split and are often supplied as Die-Nuts for use with spanners.
Die head inserts are referred to as "chasers" because chasing was the historic term for cutting threads and not just for cleaning or repairing them,

- Nick

 

[Nick Hulme]

In USAF tech school in the lathe section we learned to do an external thread single point.
Tin

How did they teach you to generate the correct profile on the peak of the external threads?

 

[Tin Falcon]

How did they teach you to generate the correct profile on the peak of the external threads?

I do not remember a lot of focus on the crest.
We started by turning the propper major diameter, as found in the Machinery's handbook. Then ground the tool and set up with a threading gage aka fish tail gage. pretty much followed the details in TC 9-524 page 7-44.
Tin

 

[abby]

I have to say that if you find setting up change wheels for screwcutting "a pain" why are you using a lathe at all ? model making is a hobby and all aspects should be pleasurable.
There is such a thing as a screw-cutting gearbox which will cut down on the number of change wheel swaps necessary , these are expensive though , and not available for all lathes .
The amount of screw cutting most model engineers require would hardly justify the expense of anything other than single point threading or split die/tap.

 

[1dbweldor]

Deek
I have a die head like the one pictured from MSC in the earlier post. I don't remember the brand off hand, but I can pull it out and read what it is if you're interested. I used this die head years ago when I was making spokes for the wheels of racing motorcycles. I haven't touched this thing in years so I think it would be safe to say I could let it go and not miss it.

 

[mcostello]

There is something not addressed as of yet. I have only used 1 or 2 different kinds of die heads, but this may be a universal fact-- a die head needs adjusted and fiddled with. It is not a 1 and done type of deal, unless it happens to be the size that You just used the last time. Then You get into sharpening chasers, swapping them around to get rid of taper, etc. For a dozen or two their great, everything else, not so much.