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Drive rings, to fit SK40 DIN69871 to a 1964 Deckel FP2 S20 x 2 spindle

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Diamond
Joined
Sep 25, 2011
Location
Garbsen, Germany
Today's project was making a couple of drive rings that will fit SK40 DIN69871 tooling to the spindle of my 1964 Deckel FP2. I only need one, but figured it was not much more work to make two.

The rings are thinner (3.2mm) than the normal drive rings used with SK40 S20x2 tooling, so I put the drive dogs directly across from each other, rather than offset by 90 degrees. The drive dogs on the spindle side are symmetric (left hand side below); the ones on the tool side are asymmetric (different inner radii, right hand side below).

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These are made of carbon steel (C45). I'm probably going to harden them, is that the right thing to do?

Cheers,
Bruce
 
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Today's project was making a couple of drive rings that will fit SK40 DIN69871 tooling to the spindle of my 1964 Deckel FP2. I only need one, but figured it was not much more work to make two.

The rings are thinner (3.2mm) than the normal drive rings used with SK40 S20x2 tooling, so I put the drive dogs directly across from each other, rather than offset by 90 degrees. The drive dogs on the spindle side are symmetric (left hand side below); the ones on the tool side are asymmetric (different inner radii, right hand side below).

attachment.php


These are made of carbon steel (C45). I'm probably going to harden them, is that the right thing to do?

Cheers,
Bruce

Those things look like a pain in the ass to make, so far yours are looking good. I had the luxury of finding factory ones for my use so I didn't have to bother. I think I would harden them or at least a case harden, they will get banged up on the corners if you don't. I bought some SK 40 tooling from a non Deckel machine and noticed the ring wouldn't fit, seems they forgot to turn a little step for them at the large part on the taper.
Dan
 
Those things look like a pain in the ass to make, so far yours are looking good. I had the luxury of finding factory ones for my use so I didn't have to bother.
Yep! I have one in-progress. Bruce I would like to see how you held them to mill the flats? I have a factory one but needed one with smaller lugs to fit some of my other tooling. I got to the point of thinking about machining the lugs.
 
One way to hold them would be on 4 jaw chuck with support under the thin part of the ring. I was lazier, and just clamped them in a vise.

(1) Turn a ring, 63mm OD, 11.4mm thick, 44.8mm ID
(2) Turn a step on one side, 60mm OD, 4.1mm wide. This is for the machine side.
(3) Clamp vertically in vise, with slightly less than half protruding
(4) Nibble from both sides, leaving 3.2mm in the middle.
Cut height 4mm maximum to avoid bending ring.
(5) Repeat approximately 5 times, each time removing 4mm vertically.
Total removed about 23.5mm
(6) Flip ring 180 degrees in vise. Clamp the thicker "drive dog" part, not the thin part.
Use a thin parallel under drive dogs for support and to line things up.
Top of parallel should be 15mm or less below top of vise.
(7) Repeat steps 4 and 5.
(8) Remove ring, clamp horizontally on spindle-side dogs in vise.
Tap down with hammer while clamping to be sure it's seated well.
(9) Mill non-symmetric reliefs for tool-side dogs
(10) Turn 45-degree chamfer on tool-side ID

File to deburr and remove tool rash from steps 4,5 7.

Dimensions are from memory, should be checked.

[EDIT]
Heated cherry-red with a torch, dropped into a pan of oil, sandblasted. I first experimented on a thin slice of the same steel. This heat treatment left it too hard to file easily, but still flexible enough that a 1mm slice will bend rather than break.

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Cheers,
Bruce
 
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Reason for offsetting by 90* the drive tangs from side to side is that it gives the ring a more "universal" effect...that is the ring can move to adjust to
differences between drive and driven ....Sort of like a pump drive coupling.....
May not make any difference if everything is perfect...but you know how that goes...
Cheers Ross
 
Hi Ross,

Reason for offsetting by 90* the drive tangs from side to side is that it gives the ring a more "universal" effect...that is the ring can move to adjust to differences between drive and driven

Thanks, that makes sense, I wondered about it. In making my drive rings, I left about 0.1mm = 0.004" of slop in the dogs. It fits the spindle and all of my tooling nicely, so meets my needs. I can't say for sure that it would fit every Deckel SK40 S20x2 machine out there, but don't see why not.

My main concern was to ensure that the ring itself was thin enough and had a broad enough chamfer on the tool side, so that tooling sits completely in the SK40 socket and does not bear on the drive ring. The gap was about 3.4mm = 0.126, so I figured leaving 0.20mm = 0.008" of free play here was enough.

Cheers,
Bruce
 
A short update to this thread. I originally made these drive rings to fit a tool holder that I needed to use. For that holder, a 3.2mm thickness was thin enough that the drive ring did not interfere. But a few months later, when I wanted to use this drive ring with a different holder, the ring was too thick. This means that it prevented the tool holder from seating completely in the spindle taper.

The drive rings that Singer sells are just 1mm (0.040") thick. I needed to reduce mine to about 1.4mm before it would work with all of my tooling. Although I had hardened the drive ring, fortunately I now have a surface grinder. So with a few minutes of work I thinned both of my home-made drive rings. A side benefit: it improved the appearance by removing all of the machining marks!
 








 
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