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Oil grooves and Deckels

TNB

Stainless
Joined
Aug 18, 2002
Location
France
A few days ago, I had to make a new bronze bushing for the piston axle of my vintage bar-cutter mower...

I was in a hurry because grass is growing incredibly quick now and I need that machine back together and running again asap, before I can't even open the door and get out anymore ! :D

Since the lubrication of the original bushing was only relying on three holes with inside chamfering, I decided to simply mill some kinds of oil pockets in the new bushing with the FP1.

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Anyway, that lead me to think about how I'd do to cut "real" oil grooves in a bushing and thought I'd share my experiments. ;)
Here's the *very* quick and *very* dirty reality check I did Yesterday, to see if I could do it on the deckelS11 .

You need a combination of a circular and a linear motions, but unlike what's going on when you thread on a lathe or grind an helix on a tool grinder grinder, the linear movement must change its direction every half-revolution of the spindle...
So the idea is to replace the spiralgrinding attachment with a simple cam, and a fixed stop. The cam is circular, but features a slot allowing to de-center it.
It is mounted on the gear that drives the workhead spindle when spiral grinding and rests on a fixed stop attached to the sine bar of the spiral grinding attachment.
Of course, since the S11 is a tooland cutter grinder, its table is free to move axially.
Therefore when spinning the workhead spindle while applying the cam on the stop, each revolution of the spindle generates a linear motion equal to the cam offset.

The pictures are from the quick test I did with a sharpie, to see the groove path the circular cam would generate.

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Some tweaking left, but already quite good !
 
Excellent Tien,

this task has always interested me since the first time I ever needed to make one (I ended up with two grooves near the faces and a shaped axial groove connecting both and the feed hole).

For us that don't (and might never will) have an S11, what would an alternative be? I was thinking two grooves near the faces and a very fast thread connecting them, passing over the feed hole as well. But, I fear that oil would end up in the edge grooves and stay there.... Not sure

Again, great work!

BR,
Thanos

edit: there are some very interesting lathe attachements for this kind of work...maybe some day...
 
Or you could just keep your eyes open for one of these,,,,Old school, works well.

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Small bushings like that i cut "figure 8" grooves in all the time on the Romi before fitting to the rod...Yes i know its cheating but it works quite well.
G33 allows programming a distance of cut along with a pitch.
Gives a helix....you can reverse the Z move without retracting the tool the result is the opposite helix.....
If you move the tool into the part them plunge to make a cut while starting the helix you will get a blind cut that starts inside the bushing,,then reverse the cut and withdraw the tool before it exits.

I use a round shaped tool in the boring bar with it cut flat half way through like an engraving tool. Flat side towards the direction of the spindle rotation....

Backwoods method is to simply mark out the shape on the ID using a "sharpie" and cut offhand using a Dremel......Of course a bit more clearance in the bushing works too.

Thanks for showing your setup....Cool.
Cheers Ross
 
Here is another easy way to make a oil groove

YouTube

Ramush, that is pretty cool, thanks for that. This looks like a few-hour project. A reamed bronze bushing for the shaping "ram", a pair of sealed ball bearings for each of the gear shafts, a body with a dovetail that locks onto a tool-post, and a ground HSS cutter. Gears and bearings are off-the shelf parts. One question: is the gear tooth ratio 2:1 or 4:1 ?
 
Very cool too !

Taking my experiments a little further, I discovered that the ratio between the spindle of the S11 index head and the gear for the spiral grinding attachment is... almost 1:1...

Would you believe it ???!?

I was wondering why the groove path I had with my setup was not perfectly symmetrical !!!
After checking and double checking everything such as the height of the fixed rest relatively to the axis of the gear, I finally saw the light and tripled checked the ratio of the workhead heating.... BUMMER !!!!

Almost, but *not* 1:1. More of something like 0,98 or so...🙄

I must admit that this is something I had clearly overlooked because the ratio is so close to it, I would never have thought it would not be 1:1....
 








 
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