Cutting an inside dovetail oil groove on a manual Deckel FP2

Hi All,

I haven't posted much work here recently, thought I would show my FP2 in action. This makes good use of a cool 3-axis vise that came with my machine:



The problem is to cut an oil groove on an inside dovetail. This is the auxiliary swiveling cross slide of my Studer cylindrical grinder, it's about 480mm (19") long and the groove is about 250mm (10") long. The pros like Peter do it with a hand grinder in 15 minutes. But I lack the experience and confidence so did it with the mill.

The tool is a 4mm HSS ball cutter stuck into a long extension holder.



Here is clocking in the vise to hold the part so that the path I need to cut runs parallel to X.



Here is the long cut partway completed:



The groove is shaped like a Z, and the short legs of the Z do not run parallel to any of the axes. So to cut these I needed to advance Y and Z together. I did this by interpolating in 20 steps, using a spreadsheet to get my coordinates.



Here is the finished groove:



Just in case anyone is wondering, the other side of the dovetail has a tapered gib, so that was easier. I clamped it to an aluminium "lifting table" which I could tilt along one axis (you can see the shim sticking out on the left). Here is that oil groove:



Cheers,
Bruce

A well planned and executed work. Kudos !

As usual, nice job, Bruce!

I do have one question: what prevented you from cutting the short segmentss of the oil grooves perpendicular to the long one, instead of being perpendicular to the axis of the way.gib?

Paolo

Paolo_MD said:

What prevented you from cutting the short segments of the oil grooves perpendicular to the long one, instead of being perpendicular to the axis of the way.gib

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You've got sharp eyes to notice this from the photos!

I don't see any reason why these short legs of the Z-shape need to be exactly perpendicular to the long axis of travel. So I did what was convenient.

In the case of the oil groove in the gib, since the long stroke of the Z-shape was along the X axis of the mill, the convenient thing was to cut the short legs perpendicular to that X direction, along the direction of the Y axis of the mill. This means that the short legs of the Z-shape are perpendicular to the long stroke of the Z-shape rather than to the long axis of the gib.

In the case of the groove in the internal dovetail, the convenient thing for the short legs was to leave X fixed and only interpolate Y and Z. In principle I could have interpolated all three axis or rotated the vice and reclamped, but that would have taken more time and introduced more possibility for errors. The same is true for the gib: after cutting the long path of the Z I could have rotated the clamping table. But that's more work for no return, as far as I can tell.

Bruce:
I like the work and your execution of same. Nice approach. Love the vise!
I am a bit confused! Is the oil groove in the slide side your idea, or is this something that the factory did?
The reason i ask is that most adjustable tapered gibs work in a relatively narrow position......and most machines i have seen only need to have a small pocket to communicate to and feed the gib proper...
Looking at the photos seems that there only two holes in the gib.....just curious why you thought you needed the long groove.

Cheers Ross

Hi Ross,

AlfaGTA said:

I like the work and your execution of same. Nice approach. Love the vise!

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Thank you!

Regarding the vise, I was surprised to find that fifty years later Kesel is still making the same vise https://www.kesel.com/wp-content/uploads/2017/08/USS-Datenblatt-1.pdf in 80 and 100mm wide versions (mine is 125mm). Am also shocked to see how much they sell for (thousands).

I am a bit confused! Is the oil groove in the slide side your idea, or is this something that the factory did?

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As delivered by the factory, the slide has oil distribution (in ring-shaped grooves) only to the flats of the dovetail, not to the diagonals. But the oiling point for one of those rings is hidden behind the wheel guard and unusable. So I first drilled a set of passages so that that flat could be properly oiled. See here: https://www.practicalmachinist.com/...-rhu-450-1960s-343863/index5.html#post3204053

After that was done, I decided it also made sense to oil the dovetails. So I made additional drillings to connect the oil passages which fed the flats to also feed the dovetails, and added the oil grooves shown in my first post in this thread.

While it's not factory, it's also not my idea. It was suggested by Richard King and others in the machine rebuilding forum here, and seems like a good idea.

The reason i ask is that most adjustable tapered gibs work in a relatively narrow position......and most machines i have seen only need to have a small pocket to communicate to and feed the gib proper...

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That is also the case here. The gib has a 1:100 taper, so moving it by 10mm (0.4") in length closes the gap by 0.1mm (0.004"). To ensure that the gib gets oil even after being adjusted, I made a 20mm long slot on the back of the gib, so even if the gib is moved to tighten the dovetail, the oil will still reach the sliding contact surface and groove.

Looking at the photos seems that there only two holes in the gib.....just curious why you thought you needed the long groove.

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The oil groove on the dovetail and the oil groove on the gib are both fed by a single oil hole. The design of this groove (slanted Z-shape) was suggested by Richard King, and it's one that makes sense to me. When oil is pumped in, it goes uphill along the short leg against gravity under pressure. Then it enters the long downward sloping leg, and stays there for days, slowing creeping out into the sliding joint.

I'm not sure why you mention two holes in the gib, as it only has one. But in one of the photos you can see the two oil rings on one flat, each fed by a separate oil hole. Richard suggested joining those two rings with a diagonal groove, but I'm not sure if that's needed as the flats are getting plenty of oil. The only wear on the flats was in the vicinity of the oil circle groove whose oiling point was hidden behind the wheel guard, and now that's fixed.

Cheers,
Bruce

Bruce:
Thanks for the explanation...
Cheers Ross

Very nice looking. I did something similar with my lathe's cross slide after seeing a video by Stefan Gotteswinter. By hand with a dremel.

Nice post and photos, for some reason I find it particularly interesting to see Deckels used to modify other machines (especially Teutonic machines) and enjoy seeing your thought process and methodology. Cool vise, never seen that one before, looks much more solid than anything comparable I've encountered.

Oil grooves into CDA954 bronze liner for my FP2-NC with galled up ways:
FP2 NC Fuhrungsschaden - Seite 2 - Zerspanungsbude

DeadMahoDude said:

Oil grooves into CDA954 bronze liner for my FP2-NC with galled up ways

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Nice repair. I see that I am not the first person to use a long extension to cut oil grooves on inside surfaces .

DeadMahoDude said:

Oil grooves into CDA954 bronze liner for my FP2-NC with galled up ways:
FP2 NC Fuhrungsschaden - Seite 2 - Zerspanungsbude

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Hi DeadMahoDude,

would it be possible to share that repair here as well? At least the basic details. I got the rough concept from Google translate (since my German are suffering) but it would be great if you could share details here.

Seems like a serious repair that might interest many with 'not so perfect' machines here.

BR,
Thanos

thanvg said:

Hi DeadMahoDude,
At least the basic details.

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Got the machine in Sept. 2017, was very cheap and advertised as electrically broken. Bought it, since I was more into fixing electronics than machine rebuilding back then.

Fixed the electronic fault, was only a broken transistor inside the electric cabinet. But when I tested it, I realized it had backlash of about 0.08mm in X. Investigated the fault and found that the nut on ballscrew that preloads the axial bearings on ballscrew had unscrewed, which caused the table slide to wiggle on ballscrew. Further investigation revealed that box ways on bottom of X were toast. So I decided to rescrape and began gathering scraping equipment.

Since the galling on both sides were too deep to simply scrape them out, I first milled down the gouges on the sliding piece. About 0.3mm on the backside and 0.5mm on bottom (red). The box ways on top were also milled (blue, on the slide side & pink) to keep them on the same level than the box ways on top. The dovetail was left unchanged. All previously milled way surfaces were then scraped flat and parallel to within a few micrometers.


The inside of fixed box ways had deep gouges as well. Initially considered to use turcite, but quickly decided against, due to price and the squishyness of turcite and decided to use reasonably priced CDA954 Al-bronze from ebay instead. CDA954 is nice to scrape and cuts well with sharp HSS tooling but has a horrible tendency to distort when machining. Probably the best way to to cut it into sheets is to narrowly cut both sides with slitting saw on mill as reference/guide slot and then use bandsaw/handsaw to finish the cut.

The sheets and the milled surface inside the box were then thoroughly scratched with a piece of sharply ground HSS parting blade and glued on with (really old leftovers) of 3M Scotch Weld DP 490 epoxy. Cotton fibers were added for extra strength.

The bonded bronze liners were then cut flat on the shaper, scraped and oil grooves were cut. As I test fitted the pieces back together I found that the ballscrew wasn't in center with the endpieces, so the ballscrew socked was rebored with an offset towards top/back of about 0.8mm. Threads on top of the ballscrew mounting screws were turned down to get some extra wiggle space. Pink mounting surface was shimmed with 2x 0.02mm brass sheet so that everything would move smoothly. Oil tubing/distributors/dose pumps were cleaned as well. The number on top is the amount of oil they keep, btw, so connect them accordingly.


I now have reassembled the machine and the reworked ways move smoothly. Need to rewire some switches however, before I can power it back on.

Galled up ways as I started the rebuild

New bronze liners

Cutting relief on top to scrape more easily

DeadMahoDude said:

Cutting relief on top to scrape more easily
View attachment 253170

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Could you also have done this with a thick (say 2mm) slitting saw? That's what I've used in the past for relieving inside corners for easier scraping.

ballen said:

Could you also have done this with a thick (say 2mm) slitting saw? That's what I've used in the past for relieving inside corners for easier scraping.

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Slitting saw probably works just as well. Only problem I see with that are the sharp corners that it leaves, which may act as stress/crack starting points.

DeadMahoDude said:

Slitting saw probably works just as well. Only problem I see with that are the sharp corners that it leaves, which may act as stress/crack starting points.

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I've only done small parts where the forces are small enough that this isn't a concern. Roughly speaking steel or cast iron can resist forces of order 100 Newtons per square mm. For example the part below has many square cm of cross section, and should be able to endure many tons of force without damage. The actual forces are at least a hundred times smaller.

DeadMahoDude said:

Got the machine in Sept. 2017, was very cheap and advertised as electrically broken...

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Very interesting read, many thanks