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Internal Spiral Cutting

adh2000

Titanium
Joined
Dec 21, 2005
Location
Waukesha, WI
In another thread I talked about the spindle speed reducer I picked up for my lathe in order to cut long lead spiral threads, both internal and external threads and nuts with a single rotation in 2" for example. Today I came across this german manual on ebay that seems to describe a way of cutting these threads on an FP1 with the spiral milling attachment. For the nut they appear to put a boring bar in the slotting head. I assume they disable the up and down motion somehow and then what? Advance the slotting head a few thousandth's with each pass? How would you do that with any control? Maybe I'm totally missing something here. Does anyone think this would work?

Deckel FP1 / FP2 Frasmaschine Beschreibung zur Innen - Spiralnuten zu Bearbeiten | eBay

Not great scans. Maybe one of the german speakers here can translate and explain what is going on.

What manual is this? I haven't seen this in any of my FP1 literature. I wish the price was a bit lower, I might buy it just to read this.
 
I do think it will work but it seems like a slow process all done by hand. I did an oil groove in a bushing once using the corner milling head and a ball end carbide rotary file, there was a learning curve to get the gearing and timing reversing the direction so the ends met properly.
Not sure but think I saw that in the Deckel technical bulletins, there was a set on ebay a while back but I think there were actually 2 sets total.
Dan
 
Yes, this document is from an early issue of the Deckel Technical Bulletins.

Basically, the process is a very slow slotting operation (relying on the x carriage motion).
The depth of cut is controlled with the z (or y) axis and yes, the slotting head is still during the operation (only here to provide a way of holding the tool).

I suppose that with some calculations and the right set of gears, one could cut long lead threads using this method.
Probably extremely tedious though...

The reason to use the Deckel over a lathe for that operation is probably only the easiness of "driving" the whole mess from the spiral milling spindle reducer.

Technical Bulletin 1.jpgTechnical Bulletin 2.jpgTechnical Bulletin 3.jpgTechnical Bulletin 4.jpg

You're welcome ;)
 
In another thread I talked about the spindle speed reducer I picked up for my lathe in order to cut long lead spiral threads, both internal and external threads and nuts with a single rotation in 2" for example. Today I came across this german manual on ebay that seems to describe a way of cutting these threads on an FP1 with the spiral milling attachment. For the nut they appear to put a boring bar in the slotting head. I assume they disable the up and down motion somehow and then what? Advance the slotting head a few thousandth's with each pass? How would you do that with any control? Maybe I'm totally missing something here. Does anyone think this would work?

Deckel FP1 / FP2 Frasmaschine Beschreibung zur Innen - Spiralnuten zu Bearbeiten | eBay

Not great scans. Maybe one of the german speakers here can translate and explain what is going on.

What manual is this? I haven't seen this in any of my FP1 literature. I wish the price was a bit lower, I might buy it just to read this.

It's a bit pricey indeed, but seems like a very interesting read!

Isn't there another source for the Deckel Technical Bulletins somewhere?
 
Alan aka "Wrench" on this forum used to sell a very complete and informative compilation of Deckel litterature on a CD.
It's been a long time since I read a post of his, but may be you could try to send him a pm.
 
Thanks to TNB for posting quality scans, in French but oh well. What is the item in Fig 4? Looks like a twisted piece of flat bar. Where does that go? What is it for?

How are you expected to keep the slotting head stationary? Pull it forward so that the gear doesn't mesh with the machine gear? There is no provision for locking the slide, I guess that could be figured out along with a dial indicator to measure how much to advance each time.
 
OK, the slotting head can be used stationary by simply setting the gearbox for the spindle in "Neutral"....
As to keeping it stationary on its slide, think snugging the slide gib screws would suffice.


The item in figure 4 and figure 3 as well is a dedicated "boring tool....could use an old end mill with all but one flute ground off if the cutter (end mill) had the proper hand to its flutes.
Because of the helix angle of the long lead thread shown you must have some support to the cutting edge and it has to more or less follow the cut so as not to drag on the sides.....

For short run work you could make this sort of tool from drill rod, forge out the cutting edge and then shop harden (heat till it goes non magnetic, and quench in oil) then sharpen...Note this tool will be
cutting on its end face like a slotting tool, not on the sides like a conventional lathe tool....

Of course all this can be done using about 6 lines of code on a CNC lathe....(i cut figure "8" grooves for oil or grease in bushings all the time on my Romi....leads of 2" are no problem)

Cheers Ross
 
Thanks to TNB for posting quality scans, in French but oh well. What is the item in Fig 4? Looks like a twisted piece of flat bar. Where does that go? What is it for?

The item in question is refered to by the author as a spindle for injection molding machines.
I'm totally ignorant of the way a die-casting die works, but it seems that there are (or was, back in 1955 !) multi-start long-lead screws involved.

This cheapo solution made from a twisted flat bar and a bronze nut was offered for short runs applications where keeping the costs low was mandarory.
Note that the author also states that in most cases, that emergency solution won't give satisfying results.
 
It's a bit pricey indeed, but seems like a very interesting read!

Isn't there another source for the Deckel Technical Bulletins somewhere?

Hi Deckeleers,

Thanos

The technical bulletin in English is 1/1955. I`m just going out to the workshop and will scan and post later today.

Alan
 
cutting internal spiral grooves accurately .. we made ballnuts

As a customer app demo, we once made a tool to cut accurate ballnuts with internal grooves.
A simple basic steel broach, with single tooth carbide cutter.

Using a HAAS ST30 lathe with C axis, we back broached the grooves from the spindle towards the TS.
Using custom ground carbide toolbits from another customer of ours, bits cost about 20€ each, and would last for hundred+ ops.

The operation was simple, easy, and pretty fast.
It took about 3-6 minutes to make a ballnut, by memory.

Cuts were 0.01 or 0.02 mm deep, each, iirc.

Groove accuracy was about 0.01 mm, or better, quite a bit better than the customer expected, and their go / no go gages confirmed very good results, much better than needed or expected.
Customer was extremely impressed.

The thrust force was very low, certainly much lower than the 1200-1400 kgf permitted on the z axis and the spindle.
Perhaps 40-100 kgf or so.
Zero risk of brinelling or spindle bearing wear.

Material was bronze.
On steel I would expect the thrust to be about double.
 
Hi Deckeleers,

For those that can`t or don`t want to read those minority languages, herewith the scans of Deckel Technical Bulletin !/1955 in English.

Deckel Spiral 1.jpg

This Technical Bulletin is contained within the excellent reproduction of the FP1 operating instructions in English produced by Tony. You can buy it from his website lathes.co.uk. It costs around 40 GBP but it`s worth it.

Deckel Spiral 2.jpg

Deckel Spiral 3.jpg

Deckel Spiral 4.jpg

Deckel Spiral 5.jpg

Enjoy,

Alan

CURSES! ALTHOUGH I ROTATED THE IMAGES ON MY COMPUTER THEY HAVE BEEN RE PRODUCED HERE AS THEY WERE SCANNED. IF YOU ARE GOING TO DOWNLOAD THESE YOU CAN ROTATE THEM YOURSELF.
 








 
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