cutting a rack on a Deckel
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    Default cutting a rack on a Deckel

    Hi to all,

    since long I have considered how one could cut a gear rack on a Deckel (my FP2 in particular). Currently, we (along with my friend Kyriakos) have started repairing two HLVHs, the rack being one of the things that need to be replaced.

    We got a competitive quote from a gear cutter guy, so we'll outsource the part. However, for the sake of completeness, I still would like to have a way to do this on the FP2.

    The thing is that, I can't find a sane way to set the work up. The optimal approach would be to use a rack cutting attachment, like this Brown-Sharpe item shown here:

    fig-246-rack-cutting-attachment-milling-machine-courtes.jpg

    This thing has a very low profile casting so that the spindle ends up very close to the table, enough to be able to fit a gear cutter that could clear the head and actually be able to cut.

    On the FP2, this is not easily accomplished. Regular vertical head is fat enough, fatter than the cutter. The angular spindle head fits perfectly in terms of dimensions, however I don't think it should be assigned such a task, due to the sensitive MT1 spindle. Doesn't feel right to put a gear cutter on a MT1 arbor and cut a rack on steel, but I might be wrong.

    Horizontal spindle is not an option for anything but very short racks.
    Working along Z also doesn't provide any gains, still the clearance issues with the vertical head.

    If I HAD to run such a job, I would prepare a fly-cutter type tool that would clear the OD of the vertical spindle (cut a tooth off a gear cutter and braze it onto a shank, and fit it on a fly cutter). Then flip the vertical head 90 deg and work exactly like in the Brown-Sharpe image. I would not feel very comfortable running this cutter and, I guess, it would also wear out rapidly (since there is one cutting edge only), but if the arbor is short it might work. Can't think of anything else though...

    (indexing is another story, actually I had thought about indexing the new part off a fixture that would employ a small, unworn, portion of the original rack to be copied. Would not rely on the DRO, but, as I said, this is another discussion).

    Would really like to see how the forum has done (or has considered doing) such an operation, I might be missing something.

    BR,
    Thanos

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    I opted to go with angle heads from Werkzeug- und Maschinentechnik | Holz- und Metallindustrie : BENZ GmbH Werkzeugsysteme to solve similar problems, this is for my FPS 300M (Deckel FP1). The advantage of these angle heads is that you get a full SK40 attach to the mill and standard ER tool holding so its pretty solid.

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    Quote Originally Posted by thanvg View Post
    On the FP2, this is not easily accomplished. Regular vertical head is fat enough, fatter than the cutter. The angular spindle head fits perfectly in terms of dimensions, however I don't think it should be assigned such a task, due to the sensitive MT1 spindle. Doesn't feel right to put a gear cutter on a MT1 arbor and cut a rack on steel, but I might be wrong.

    If I HAD to run such a job, I would prepare a fly-cutter type tool that would clear the OD of the vertical spindle (cut a tooth off a gear cutter and braze it onto a shank, and fit it on a fly cutter). Then flip the vertical head 90 deg and work exactly like in the Brown-Sharpe image. I would not feel very comfortable running this cutter and, I guess, it would also wear out rapidly (since there is one cutting edge only), but if the arbor is short it might work. Can't think of anything else though...
    The tooth profile on a rack is not the same as on a gear.
    Much simpler in fact, since the tooth will have plain straight flanks, and not the involute shape found on gears.
    So no need to butcher a gear cutter. A Deckel SO or SOE and a simple drillbit is all what you'd need to make a suitable tool.

    Still, totally clearing the vertical head casting would call for a very large diameter fly cutter...
    My angular head has an MT2 spindle. Beefier than MT1, but nothing to rave about rigidity wise.

    In an emergency situation, where I where I'd have to make do with what I have on hand, I suppose I would consider machining a small pitch but long rack with the slotting head.

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    Oh my....

    E.g. Angle head Mono WSX, angle head size 4, ER32, perfect.

    How do you secure the angle head on your regular vertical head. I mean, to keep it from rotating. Custom holder for that spigot?

    If I may, could I ask how much it cost? Not that I could ever afford it....

    Still, I would like to see how this was done (if somebody ever tried) back in the day, with Deckel accessories.

    BR,
    Thanos

    PS. To my understanding, this a solution that differs from that B-S attachment I showed or a BP angle head. There, the machine's spindle only provides drive. Loads and geometry are controlled by the extension housing. In the Benz case, it seems like the machine's spindle handles both drive and machining loads. So, you still can't go crazy on a cutter down there, but it is WAY stiffer than the Deckel's MT1 angle spindle head...

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    when I got my HLV-H and tore it down for rebuilding, I gave this problem some thought as well, but my final (theoretical) solution however was a bit different, I would have used the Y axis as a shaper ram, as TNB said, the gear profile is just a simple V, easy enough to make a cutter to even cut more than one notch at a time, the cutter would have been bolted rigid to the Y axis (not utilizing the spindle), if I would have ended up doing this, Mikron WF41 would have been used, it is CNC so I could have stepped down the table for the cutter return path - so wouldn't have to build a clapper box

    I said the rack solution to be theoretical because since my HLV-H was missing the feed motor, and they seem to be very scarce, and the gears in the apron don't look so good, so far I decided to do away with the rack and the gears altogether and use a zero backlash ball screw + servo, same for X axis and use manual pulse generator wheels for manual controls and maybe even install a cnc controller to finish that off, it is still in planning, and the idea is to do this without having to modify/machine original parts, like a complete bolt on setup, I figured the ball screw + servo approach will cost me about the same as to rebuild it as it was from the factory, and the CNC would end up far more useful to me, this project however isn't near the top or priorities for the moment...

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    Just for fun
    TNBs solution is the one with the best merrits
    Another option is to make a low profile shaft that you could clamp on the quill and drive it from the spindle with some gears
    Eighter use 3 gears or with 2 put on your cutter in revers

    But can`t you buy stock racks ???
    Even metric would do if you replace the mating gear too


    Peter

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    Quote Originally Posted by TNB View Post
    The tooth profile on a rack is not the same as on a gear.
    Much simpler in fact, since the tooth will have plain straight flanks, and not the involute shape found on gears.
    So no need to butcher a gear cutter. A Deckel SO or SOE and a simple drillbit is all what you'd need to make a suitable tool.

    Still, totally clearing the vertical head casting would call for a very large diameter fly cutter...
    My angular head has an MT2 spindle. Beefier than MT1, but nothing to rave about rigidity wise.

    In an emergency situation, where I where I'd have to make do with what I have on hand, I suppose I would consider machining a small pitch but long rack with the slotting head.
    Sorry TNB, missed your original reply.
    Yes, fly cutter would end up pretty large in OD, and the cut is interrupted as well, not so nice.

    Your angular head has an MT2??? Did they change it later? I thought they were all MT1....well, that's much more useful. It could work for this.

    Yes, slotting head would also be an option that I forgot to mention, and, it is a fact that the particular rack is relatively small pitch. What I don't like about the slotter for this repetitive operation is the Y stop. I find the angular head, set on fixed Z and taking each cut in one pass much more appealing to me.

    Quote Originally Posted by jz79 View Post
    ... and the gears in the apron don't look so good, ...
    ... isn't near the top or priorities for the moment...
    How difficult could it be to drain that apron oil when you are the owner/operator of such a fine machine? The gears would have lasted forever and save us all the trouble...

    I know the feeling, mine has been sitting for almost a year without having produced even a single chip. Variac issues (burns the feed fuse) and the apron butter gears in sorry state). But this is going to change soon (hopefully)!

    Quote Originally Posted by Peter from Holland View Post
    Just for fun
    TNBs solution is the one with the best merrits
    Another option is to make a low profile shaft that you could clamp on the quill and drive it from the spindle with some gears
    Eighter use 3 gears or with 2 put on your cutter in revers

    But can`t you buy stock racks ???
    Even metric would do if you replace the mating gear too


    Peter
    Peter you are suggesting something similar to the Bridgeport angle head approach. Hold on to the quill and use the spindle for drive. Of course is would work.

    As I said earlier, we'll get the racks made for next to nothing, the discussion is on a theoretical basis...

    BR,
    Thanos

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    Not exactly
    The subspindle parrallel to the main spindle driven by straight gears
    Then the head and subspindle both in horizontal position
    No bevel gears needed
    Peter

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    I would use the vertical spindle as i think "T" suggested.....
    Angled end mills are commercially available and since a rack tooth form is simply a straight angled face (14.5 or 20*) using a tapered end mill would give the desired cut....

    Blank set on the "X" axis. Feed across using the "Y"....


    This is a case where the American style of "Universal Dividing Head" is just a better design than the Deckel setup....
    With the Brown and Sharpe or Cinci Dividing head and spiral lead gear box one can use the change gears to allow the dividing head to drive the table lead screw (opposite of the way one would cut a helix)
    Allows very accurate movement of the table through the dividing head gear ratio (40:1) and the correct plate with the appropriate lead gearing to give a precise move along the "X" axis.....(increment for each tooth)

    Could do this using the Deckel spiral milling attachment, but leaves holding the part blank as a bit of a problem.....Doing the increment per tooth using the micrometer collars of even a DRO
    likely would induce lead errors in a rack of any length, it that was of any importance.....Here the measuring rod setup using gauge blocks would be a good solution.

    Cheers Ross

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    Just toss the Deckel and get an Aciera F4 or F5.
    img6.jpgimg34.jpg

    I have been mildly hoping to land one of those attachments for years, but never pulled the trigger. I think Greub in Switzerland had at least one. I need one with NMTB40 input. Most appear to be 30 taper with metric drawbar threads.

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    Quote Originally Posted by Peter from Holland View Post
    Not exactly
    The subspindle parrallel to the main spindle driven by straight gears
    Then the head and subspindle both in horizontal position
    No bevel gears needed
    Peter
    Got it. Would require actually putting some kind of spindle together (whatever comes with that) but it's doable.

    Quote Originally Posted by AlfaGTA View Post
    I would use the vertical spindle as i think "T" suggested.....
    Angled end mills are commercially available and since a rack tooth form is simply a straight angled face (14.5 or 20*) using a tapered end mill would give the desired cut....

    Blank set on the "X" axis. Feed across using the "Y"....


    This is a case where the American style of "Universal Dividing Head" is just a better design than the Deckel setup....
    ...
    Understood. I admit, I didn't think of the actual shape of the rack teeth. Yes, an angled end mill would work, though it would not be my favorite option due to the static point of such a tool. Not that finish down there in the valley counts....

    Regarding stepping over to the next tooth, that's how I feel as well: you need to index and even a DRO (at least mine) would not be first in the list here. Nice setup the one you described, using the indexing plates of an indexing head. I guess, even on a Deckel, you can go half way: Setup a rig with a couple of gears driving X leadscrew and index with a plunger. I think this is what the B/S sub-table does in the picture.

    Still faced with the inaccuracy of a worn leadscrew though, if we want to go totally crazy on this. The alternative I suggested earlier, with a short master rack with 3-4 teeth in a fixture that would clamp on the already cut teeth to index for the next one, X axis being locked, seems the simplest indexing approach to me.


    Quote Originally Posted by rklopp View Post
    Just toss the Deckel and get an Aciera F4 or F5.
    ....
    Well, this has been discussed with Kyriakos....in a way...

    You have to admit though, that for cutting a rack, even that head would not clear a common cutter....


    Since you all noted the gear profile, and how easy it is to sharpen a tool...I am thinking that an old large horizontal cutter, large enough to clear the vertical head when tilted 90 deg, would do just fine. Could easily be ground to the exact angles, and, due to the large number of teeth, if you go nice and slow, it's easy on the machine too. Even a quick-and-dirty custom cutter, a disk with several radial holes to accept round shank cutters, ground after all cutters are assembled, could work, without having to sacrifice a horizontal cutter.

    Thanks to all for dropping ideas!

    BR,
    Thanos

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    Quote Originally Posted by thanvg View Post
    Oh my....

    E.g. Angle head Mono WSX, angle head size 4, ER32, perfect.

    How do you secure the angle head on your regular vertical head. I mean, to keep it from rotating. Custom holder for that spigot?

    If I may, could I ask how much it cost? Not that I could ever afford it....

    Still, I would like to see how this was done (if somebody ever tried) back in the day, with Deckel accessories.

    BR,
    Thanos

    PS. To my understanding, this a solution that differs from that B-S attachment I showed or a BP angle head. There, the machine's spindle only provides drive. Loads and geometry are controlled by the extension housing. In the Benz case, it seems like the machine's spindle handles both drive and machining loads. So, you still can't go crazy on a cutter down there, but it is WAY stiffer than the Deckel's MT1 angle spindle head...
    You need a custom bracket/ring that attaches to outside of the spindle housing that in turn captures the benz-tool pin that comes up from the side to prevent the angle head from rotating. I purchased my FPS 300M (Deckel FP1) from FPS and they are fabricating the bracket on my behalf. And yes, the machines spindle handles both drive and load, the bracket is used strictly for preventing it from spinning and for interface with coolant if desired, so it is lightweight. Yes, these are expensive.

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    I did a rack on my FP1 with a horizontal milling cutter which had the right "V" angle. A lot of work since it was done manually. Worked out the coordinates on the computer and printed them out for the three cuts needed for each tooth. Left angle cut, right angle cut and then use a slitting saw to remove what was left. Had to go to the doctor two days later because all the muscles in my upper body froze because of yanking on the headstock crank so many times.

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    Talking about angled
    The head angled at 20°(from horizontal = 70° from vertical) and then a disk like cutter with the angles asymetric
    One side 0° the other side 40°
    That is with a 20°pressure angle

    Peter

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    Quote Originally Posted by bcstractor View Post
    I did a rack on my FP1 with a horizontal milling cutter which had the right "V" angle. A lot of work since it was done manually. Worked out the coordinates on the computer and printed them out for the three cuts needed for each tooth. Left angle cut, right angle cut and then use a slitting saw to remove what was left. Had to go to the doctor two days later because all the muscles in my upper body froze because of yanking on the headstock crank so many times.
    I guess a short rack, right?

    Quote Originally Posted by Peter from Holland View Post
    Talking about angled
    The head angled at 20°(from horizontal = 70° from vertical) and then a disk like cutter with the angles asymetric
    One side 0° the other side 40°
    That is with a 20°pressure angle

    Peter
    Hey Peter,

    that's an even better idea, in order to do your thing with the smallest possible cutter OD that would clear the inclined head. Thanks!

    BR,
    Thanos

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    Thanos, this is an interesting discussion. Perhaps it has already been suggested, but if not, how about getting an "end-mill" style cutter that has the correct cross section for a tooth (sides angled 20 degrees, tip width correct or a little smaller than needed. Then just use the vertical head vertical, move Y to cut a tooth, move Y back, shift X by correct amount, repeat. Or will that not work? Cheers, Bruce

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    Quote Originally Posted by ballen View Post
    Thanos, this is an interesting discussion. Perhaps it has already been suggested, but if not, how about getting an "end-mill" style cutter that has the correct cross section for a tooth (sides angled 20 degrees, tip width correct or a little smaller than needed. Then just use the vertical head vertical, move Y to cut a tooth, move Y back, shift X by correct amount, repeat. Or will that not work? Cheers, Bruce

    I think its what Ross suggested, earlier.I have done it on a special tailstock construction, where the client needed 500+mm of quill travel.The best way was the schaublin's star philosophy, so we created a rack on the quill's outer diameter with an angled endmill.It just needed 2-3 z-axis passes per tooth cause the odd cutter geometry may be facing vastly diferring cutting forces during just one pass.

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    Well, as I said, using an angled endmill for a two-sided cut (cutting down to the corner) has not been my no1 preference. When I had to mill grooves, I've opted for form milling cutter (or fly cutter). I feel more comfortable this way, with the milling cutter cutting the profile nicely, compared to the tip of the angled end-mill which is pushing and not cutting since it has zero linear speed due to zero radius.

    But again, that's just my preference, people who know what they are doing suggested otherwise here

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    Thanvg:
    Isn't it the same for any end mill?
    What you are forgetting is that the end of the cutter will have some diameter...None of the tapered end mills i have seen was made to a sharp point....so if the end has some diameter even if it is small
    the tips of the end flutes will not have zero speed and they are the first to enter the material....Just like any end cutting end mill....
    If it made you nervous you could simply cut a straight slot with a plain end mill to finish the root of the tooth , the4n follow with the angled cutter...(end mill) to finish the tooth for width. My guess is that one would
    to get the best finish do two finish cuts , one to each side of the cut to widen it and give the proper tooth thickness...but its all the same setup...direct and straight forward.

    Cheers Ross

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    Clear enough Ross, thanks for elaborating


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