Can I cut prop shaft taper w/o taper attachment? - Page 2
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  1. #21
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    Quote Originally Posted by Screwmachine View Post
    It's a nice technique but I don't see a prop shaft fitting between centers on a SB!
    There also needs to be some provision for securing the end of a prop shaft outside the little SB headstock. I have to wonder if the OP is aware of the danger associated with machining a long shaft regardless if he can cut the taper or not.

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    Likely you can make the taper with two passes if compound travel is short.. with having the shaft expose you can blue fit with not taking out of the set-up Getting .002 .005 to size you can file or crocus cloth the final fit. You might fine round file or round hone and bugs or burrs for the Id taper if needed. IMHo

    But held short in a 4jaw perhaps your through hole is not big enough to take the shaft through..
    Then between centers if the bed is long enough.

    Often you can use your bed travel to set a taper. plate check the part taper for 2" (or what) length , eyeball the taper to rough close,
    Then with using a 2" JoBlock and a test or dial indicator to the straight part or the shaft find the zero off the indicator and your in seed hand wheel, and with using 2" bed travel. One should get ,001-.002 close with this.. so much better than take a cut and measure for the start.

    I once knew a guy with a prop hole opening business. Props often come in one size, the smallest for that size prop. He did them on a big gap bed lathe.
    I always thought a Pratt vertical boring mill would be a better machine for props. mostly for an easier set-up time. Yes then need the way if having one.

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    Quote Originally Posted by Screwmachine View Post
    It's a nice technique but I don't see a prop shaft fitting between centers on a SB!
    He doesn't give the shaft length.

    As far as my opinion goes, I think he should take the shaft to someone who is in that business.

    Bill

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    Quote Originally Posted by 9100 View Post
    He doesn't give the shaft length.

    As far as my opinion goes, I think he should take the shaft to someone who is in that business.

    Bill
    Agree because if you don't know how to do something better to try it on a slug of scrap , not a good piece of stock.

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    Quote Originally Posted by 9100 View Post
    He doesn't give the shaft length.

    As far as my opinion goes, I think he should take the shaft to someone who is in that business.

    Bill
    Where's the fun in that!

    I'm with Bill - set up the compound & have at it. Practice on some scrap first.

    Worked for me and I have a $4000 prop on the end of the shaft I made. I did use a TA but that's a detail, the compound would work fine for a one-off.

    Then flip the shaft so the tapered end is outboard of the headstock, blue it up and lap it in. This isn't rocket science either. In fact Keith Fenner made a decent YouTube vid on fitting a prop.

    As for people wanting to charge a fortune for this - sure, you can. Then people like me go the DIY road and then undercut you....

    PDW

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    Kudos to want to try but the prop shop that gets all of this work in these parts just charges something like $75 to cut in the taper, key and thread the shaft.
    I can do the work but don’t bother- everything gets sent to them.

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    You know, even a novice gains experience when they practice,

    It would take less time for the OP to chuck up some nasty piece of hot rolled and set up and work out the details of remaking the "real piece" than to dick around looking for useful comments on this forum.

    Send it out! Lots to be learned there! CRIPES!

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    You can probably do it, sure. All of the good advice has been given. Don't expect to make any money on the job, probably going to just go to the prop shop themselves once you give them a quote. This smells of "I fucked someones prop shaft, can I remake it myself and not get caught?" If so, you're just looking for a liability lawsuit.

    Also what grade of stainless do you intend to use? While 316 probably is good enough, Aquamet 22 as well as a few other grades are pretty much industry standard. Pretty much 316 with a beefier price tag but it does have superior corrosion resistance as well as some other advantages. A lot of prop shops get their Aquamet directly from Western Branch (East Coast) and at a significantly cheaper price than you or I could. Last I checked from a different supplier it was somewhere in the realm of $6.99/in?

    At the end of the day, if you don't know your stuff and you cant do it economically (to yourself; them, I mean it's a boat...) then don't try and wing it. You'll either scrap some expensive stock or offer an inadequate product. I don't feel an SB 9 has the rigidity to reliably turn a 1" prop shaft as true as it needs to be to not cause some cavitation of the prop. Just get a quote from the pros and count your losses, they've got the equipment, the means, and the know-how to do this as it should be.

    One final takeaway.. Prop shaft is a precision piece of metal, it NEEDS to be true along the length. We've (family) been in the industry for 40 years now, we trash shafts over .007" run-out anywhere along the length. If you plan to use some McMaster 316 1" roundbar to turn a propshaft just please don't. You think you've felt bad vibration on a boat? just wait. That poor mechanic that has to perform that engine alignment...

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    Lot of BS flying about here......nothing about inboard ski boats is precision,cept maybe the 350 crate motor.........hey,I used to make shafts and bits and pieces for them,I know how rough they are under the pretty gelcoat........but old thermite has finally unearthed a pearl of wisdom from all the oysters he s trashed .....forget spending a fortune on a TT attach.......motorize a big compound ,and mount it in a rigid mount on the saddle of your lathe.......and for all the doomsayers.....water damps vibration,thats how boaties can run with half a blade missing and hardly notice it.

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    Quote Originally Posted by john.k View Post
    Lot of BS flying about here......nothing about inboard ski boats is precision,cept maybe the 350 crate motor.........hey,I used to make shafts and bits and pieces for them,I know how rough they are under the pretty gelcoat........but old thermite has finally unearthed a pearl of wisdom from all the oysters he s trashed .....forget spending a fortune on a TT attach.......motorize a big compound ,and mount it in a rigid mount on the saddle of your lathe.......and for all the doomsayers.....water damps vibration,thats how boaties can run with half a blade missing and hardly notice it.
    Sorry, I must’ve missed the ski boat comment, that’s my bad. My work and experience is about 90% sailboats pushing anywhere from 30 to 100 horses of Japanese cast. I forget other types of boats exist. For a 16ish” 3 blade or worse- a maxiprop hanging out 7’ from the coupling face you will absolutely notice runout. A missing blade would probably destroy your strut or tranny if allowed to run long enough.

    For a ski boat though? Aren’t they basically held together with string and Elmer’s glue with a junky English Ford jammed inconveniently in there? Couple popsicle sticks and some hot glue oughta take care of that.

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    Quote Originally Posted by FlyinChip View Post
    I want to make an inboard boat prop shaft from some 1" stainless on my Heavy 10 lathe. I do not have a taper attachment. The taper IIRC is 1:12 or 3 degrees (may have to double check that).

    Just throwing this out here and see what comes back!
    Quote Originally Posted by FlyinChip View Post
    jonok thanks, so how is that set up to do that?
    Everything the OP posted is right here. No 9" southbend, dont know type of boat beyond an inboard engine.

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    Quote Originally Posted by PDW View Post
    Where's the fun in that!

    I'm with Bill - set up the compound & have at it. Practice on some scrap first.

    Worked for me and I have a $4000 prop on the end of the shaft I made. I did use a TA but that's a detail, the compound would work fine for a one-off.

    Then flip the shaft so the tapered end is outboard of the headstock, blue it up and lap it in. This isn't rocket science either. In fact Keith Fenner made a decent YouTube vid on fitting a prop.

    As for people wanting to charge a fortune for this - sure, you can. Then people like me go the DIY road and then undercut you....

    PDW
    You need to watch that video again, because you obviously missed the part about cutting the keyway with a specially ground horizontal cutter for his K&T to produce the radiused bottom. This is a task that is unrealistic to do on his SB. I also suspect that the responders that thinks he can, have never done a prop shaft themselves.

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    Smell a lot of BS here

    But this may not qualify as a ski boatel-cid.jpg

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    Quote Originally Posted by steve-l View Post
    You need to watch that video again, because you obviously missed the part about cutting the keyway with a specially ground horizontal cutter for his K&T to produce the radiused bottom. This is a task that is unrealistic to do on his SB. I also suspect that the responders that thinks he can, have never done a prop shaft themselves.
    Really? That "impossible"? Wonder how TF the FIRST one ever got made? Of anything.

    So show me what's wrong. Beside a grand waste of time, of course. That we shall argue, NOT. A given. "Taken as stipulated", in other words.

    Mind.. I am about to cheat. Shamelessly so.

    Apologies, it's a known failing amongst those who impose their wicked ways on inanimate matter. Metals, even.

    So I have "stuff", SB or other.

    - a powered spindle.

    - a means of holding a cutting tool

    - power traverse.

    - a grinding wheel

    - a torch, coal, or charcoal.

    some HCS steel, if not also HSS

    If all else fails, a single-flute cutter can be made to produce any form as will fit the space. Horizontally applied. OR Vertical.

    The only thing I have to BUY IN .... is electricity.

    Or Diesel fuel. I did say "cheat"?

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    Quote Originally Posted by thermite View Post
    Really? That "impossible"? Wonder how TF the FIRST one ever got made? Of anything.

    So show me what's wrong. Beside a grand waste of time, of course. That we shall argue, NOT. A given. "Taken as stipulated", in other words.

    Mind.. I am about to cheat. Shamelessly so.

    Apologies, it's a known failing amongst those who impose their wicked ways on inanimate matter. Metals, even.

    So I have "stuff", SB or other.

    - a powered spindle.

    - a means of holding a cutting tool

    - power traverse.

    - a grinding wheel

    - a torch, coal, or charcoal.

    some HCS steel, if not also HSS

    If all else fails, a single-flute cutter can be made to produce any form as will fit the space. Horizontally applied. OR Vertical.

    The only thing I have to BUY IN .... is electricity.

    Or Diesel fuel. I did say "cheat"?
    I'm now really confused. I have no idea what you just said. Are you saying that he should do this job on his SB? If you are saying that he could do the job on his SB, I agree with you, he could, but it would be really bad advice. Besides, it's 09:00 here in Germany, but it's 03:00 in Virginia. What the hell are you doing on your PC at this time of day? You need to get a life.

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  19. #36
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    Quote Originally Posted by steve-l View Post
    You need to watch that video again, because you obviously missed the part about cutting the keyway with a specially ground horizontal cutter for his K&T to produce the radiused bottom. This is a task that is unrealistic to do on his SB. I also suspect that the responders that thinks he can, have never done a prop shaft themselves.
    He didn't say anything about the keyway in his posting so I didn't address that.

    Doing the taper is totally do-able with the equipment he has. Keyway? Dunno. He might have that covered, might not.

    As for mine, shrug, I *have* a horizontal mill and a T&C grinder but it was easier to tilt the table on my Deckel type to the taper angle and use the vertical head. Will I get stress cracking? We'll see. It's *my* boat, shaft & prop. I can always make another one. In fact I can make 6 before I get close to the price I was quoted for a professional to make one.

    Incidentally I used 316L instead of Aquamet22 as well. A 35mm shaft with a 36HP diesel and a 3:1 reduction transmission, total shaft length 850mm. It's quite adequate.

    PDW

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    Quote Originally Posted by steve-l View Post
    .. he could do the job on his SB, I agree with you, he could, but it would be really bad advice.
    "We" do not know anything AT ALL about his time, goals, economic circumstances, nor "level of desperation", so that "bad advice" part is up to him. METHODS, we CAN suggest, and more than one.
    Besides, it's 09:00 here in Germany, but it's 03:00 in Virginia. What the hell are you doing on your PC at this time of day? You need to get a life.
    I HAVE a life. It happens to key off Hong Kong's time zone most days. Cooler here at Chaos Court as well. Soon coming up four in the afternoon there. More to the point, wife is touring Australia this go. She - and 90'ish Mum - only touched a toe in HKG for one day, then airborne again. As is their habit. Perth is on the same clock as HKG, FWIW.


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    Thanks for all the replies. seems like they vary from "impossible!" to "sure you can".

    A few clarifications:

    This is for an antique boat of very low power (although proper tolerances for this operation would be the same)

    I have access to a Bridgeport for cutting the 1/4" keyway presumably with an 1/4" end mill. Not sure about holding the part but presumably just in the vice at the taper angle so the top surface is indicated level to the bed.

    The material would be 304 or 316L stainless 1" OD from Grainger or similar.

    The taper itself is 3.5" long

    I can make a taper attachment per video on youtube YouTube but would rather skip that if I can. It's a whole other project in itself but it is not rocket science to make one.

    Of course I can farm this out and there's a prop shop a mile from me but that's not the point. Plus it's expensive.


    1-prop-shaft-taper-20190807_110223.jpg

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    Quote Originally Posted by FlyinChip View Post
    Thanks for all the replies. seems like they vary from "impossible!" to "sure you can".

    A few clarifications:

    This is for an antique boat of very low power (although proper tolerances for this operation would be the same)

    I have access to a Bridgeport for cutting the 1/4" keyway presumably with an 1/4" end mill. Not sure about holding the part but presumably just in the vice at the taper angle so the top surface is indicated level to the bed.
    That can work. Use vee block, pivoted, plus riser shims under, clamp-down, over to maintain the angle very firmly. A vise SHOULD NOT be trusted to do that by itself.

    Modest dub to the end mill's extreme corners, you'll have "radius enough" to reduce risk of stress risers. Chamfer the key to clear, not necessarily mate. Mebbe add a low-strength Loctite as filler to keep any cavities at lower risk of corrosives build-up, and good to go.

    SB is one lathe where "finding" a TA has a fair chance, so I'd not be in a rush to make one.

    Most days, I'd far rather have a powered compound option - "long slide" most of all.

    This is not one of them, but in general, Sod's Law that tapers too steep for the TA seem to be the most common ones needed.

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    Quote Originally Posted by thermite View Post
    That can work. Use vee block, pivoted, plus riser shims under, clamp-down, over to maintain the angle very firmly. A vise SHOULD NOT be trusted to do that by itself.

    Modest dub to the end mill's extreme corners, you'll have "radius enough" to reduce risk of stress risers. Chamfer the key to clear, not necessarily mate. Mebbe add a low-strength Loctite as filler to keep any cavities at lower risk of corrosives build-up, and good to go.

    SB is one lathe where "finding" a TA has a fair chance, so I'd not be in a rush to make one.

    Most days, I'd far rather have a powered compound option - "long slide" most of all.

    This is not one of them, but in general, Sod's Law that tapers too steep for the TA seem to be the most common ones needed.
    ok-all in favor of electing thermite mayor of this site...say aye


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