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  • Lathe Spindle sizes

    Some time ago when Craftex produced their CT128 with a 1" spindle size there was considerable debate about whether it was strong enough for the swing capacity etc. etc. Now the CT128 has a 1/4" x 8 spindle and everyone seems happy. Just an example of how manufacturers do listen or look and update. Now imagine my dismay when a friend opens up the headstock on his green International lathe and the spindle size is reduced from 1 1/4" to 1" between the bearings. PLUS right behind the inboard bearing there are 3 round headed screws drilled and tapped into the spindle for the magnetic RPM reader. So I guess the moral of the story is don't be fooled by external visuals or what's written on spec sheets. There are some who think the bottom line is everything and set out to deceive. I know if it was my lathe there would be some very strong language in a letter on it's way. So once again buyer beware!
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  • #2

    Re: Lathe Spindle sizes

    Re: Lathe Spindle sizes

    I'm not sure that the design gives cause for anxiety. The maximum bending moment on the shaft is at the outer bearing. The short distance between the two bearings is going to limit the bending moment on that portion of the shaft. Once you are inboard of the inner bearing you are not dealing with any bending moment and the inserted screws would not jeopardize the integrity of the machine.

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    • #3

      Re: Lathe Spindle sizes

      Re: Lathe Spindle sizes

      I agree that it isn't a big deal. The 1-1/4 portion is only 1-1/4 at the OD of the threads and it has a MT2 hole through the middle with the MT large hole diameter at the threaded portion. To say that portion of the spindle is identical to a solid 1-1/4 shaft is a stretch.

      billh

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      • #4

        Re: Lathe Spindle sizes

        Re: Lathe Spindle sizes

        If there are no significant bending moments past the inboard bearing then there would be no need for an outboard bearing. This particular lathe has a swivel head and that allows very large chunks of wood to be mounted, possibly up to 30" in diameter. I would be a little worried about a heavy catch on the rim of a 30" piece that was hung on a 1" hollow shaft drilled through for 3 screws. Like I said, not my lathe and to each his own, but, I have to wonder why these companies can't put some good honest engineering in their products. YOMV and that's OK by me.

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        • #5

          Re: Lathe Spindle sizes

          Re: Lathe Spindle sizes

          I'm curious. How would you define "good honest engineering"? All the ads that I see set out the specs of the machine in terms of the inner bore size (mt2, mt3) and thread size and pitch. So, it would seem that the ads are accurate. Your beef is with the engineering itself, I understand. How is their engineering dishonest? There don't seem to be posts on here or anywhere else about spindles bending or breaking with wild abandon. So, it would appear, at least on the face of it, that the engineering that went into our lathes resulted in products that are reliable and do what the ad men say that they will do. So, where is the dishonesty?
          Grant Wilkinson
          Ottawa ON

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          • #6

            Re: Lathe Spindle sizes

            Re: Lathe Spindle sizes

            Grant I understand your point and maybe I should have been a bit more specific. It is normally assumed that a 1/2" bolt has the same diameter from thread to head within a few thou, or a table saw spindle is the same diameter behind the arbor or bigger and more to the point the majority of lathes I've checked out has the same or larger diameter along the spindle length as the threaded portion. So when I find the scenario I described I'm a little concerned and perplexed. As for the specs in the book unless there's an honest description of the wasted spindle or an accurate drawing a new buyer would have to do a really good under the hood inspection to satisfy the specs are indeed honest. Ads are selling tools and as such don't have to be that accurate but again it comes down to buyer beware and I'm giving a heads up that this particular lathe has a potential problem IMO. That's all it is my opinion. When the posts about the CT 128 started appearing on this forum I was of the opinion that it was OK to have a 1" spindle size. Then they changed it to 1 1/4" and maybe it was discussion on this and other forums that brought about the change. But this is another well known company trading on an established reputation and seemingly using some questionable engineering in a part of the lathe not normally looked at by a potential buyer. The owner of the lathe in question was not exactly thrilled, and has a good solid engineering back ground and when he showed me I had to agree with him. He also discussed some alternatives to the set up for the RPM display and whether the reduction in spindle size between the bearings was even a money saver considering the extra work involved. The motives for this kind of seemingly mild deception are only known by the company marketing the machine, but I don't think there's anything wrong bringing the matter to this forum and it being made public.

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            • #7

              Re: Lathe Spindle sizes

              Re: Lathe Spindle sizes

              This situation has in fact been discussed on many forums. There was also a lathe shoot out at one of the wood working mags a few years back that really criticized the GI 25-650 for doing this. Before buying my machine; used (yes I do own one of these) I was aware of this. I also see no reason for the engineers to go this route, however after ownership of about 4 years I have had no issues arising from the 1" spindle, and I have turned some good sized pieces of wood.
              Just my 2 cents worth.
              Brian; Caledonia On.


              http://lumberjocks.com/toyguy/projects/page/1

              Comment


              • #8

                Re: Lathe Spindle sizes

                Re: Lathe Spindle sizes

                Roudhead: I can understand where you are coming from. I don't see the manufacturers as being dishonest, but we can agree to disagree. I don't know of any manufacturer that goes into the level of detail in their sales literature that I understand you will like to see. That doesn't make what they do right, just standard. As for the CT128 going from 1 to 1.25 spindle, I wonder how much of that was a real engineering-related need, and how much was simply to address a PR issue that was not backed by any actual problems in the field.
                Grant Wilkinson
                Ottawa ON

                Comment


                • #9

                  Re: Lathe Spindle sizes

                  Re: Lathe Spindle sizes

                  The lathe spindle size as specified is the size of the thing that sticks out of the headstock. It tells us the diameter and thread pitch for accessories and to give an understanding of what sort of load one might afix to it. I've never presumed that it was a spec for the diameter of the whole length of the stock attached to the threaded portion. However, I do presume that there was a proper design assessment done so whatever is between the bearings is adequate to support the anticipated loads.

                  billh

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                  • #10

                    Re: Lathe Spindle sizes

                    Re: Lathe Spindle sizes

                    I believe there is not a heck of a lot of engineering done to build those lathes, rather more of a copying and than skimping and cutting corners, as why the heck would one go with a 1" spindle when every other lathe manufacturer that builds a lathe with those capacities has a 1" spindle (not the ones that ad a riser later in life) and again here specifying a 1" spindle (not spindle head) and hen supplying a 1" spindle with a larger end on it.
                    A spindle is a spindle, not a tread end on a spindle.
                    Of course that is just IMO and I was not trying to improve the bottom line, I just don't like the quality to go down to Chinese standards so to speak, like soft cast iron, sloppy fits and lousy hardware (bolts & screws etc.)

                    Have fun and take care
                    Leo Van Der Loo

                    Comment


                    • #11

                      Re: Lathe Spindle sizes

                      Re: Lathe Spindle sizes

                      Originally posted by gwilki View Post
                      Roudhead: I can understand where you are coming from. I don't see the manufacturers as being dishonest, but we can agree to disagree. I don't know of any manufacturer that goes into the level of detail in their sales literature that I understand you will like to see. That doesn't make what they do right, just standard. As for the CT128 going from 1 to 1.25 spindle, I wonder how much of that was a real engineering-related need, and how much was simply to address a PR issue that was not backed by any actual problems in the field.

                      The real issue when the Ct 128 first came out was the fact that it was advertised as a 1 1/4 spindle, only to find out it was in fact only 1 inch. I think that the bitching about this is what made them go to a 1 1/4.
                      Brian; Caledonia On.


                      http://lumberjocks.com/toyguy/projects/page/1

                      Comment

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                      • #12

                        Re: Lathe Spindle sizes

                        Re: Lathe Spindle sizes

                        This is the first time for me to write. I have a 25-650 and in Feb. I tryed turning 24"dia. x 28" lenth on the end of the lathe. What I found was that the shaft started to flex. So I reworked the tool support and reducted the cut size to very small. The drive stopped many times. Had to reset the drive. After adding outboard support with skate rollers, the flex stopped letting me make bigger cuts. Looking into the drive head to my surpise I see a 1" shaft with hole for the tec. What do I do now ? I'm looking at a new custom 1 1/4' shaft but the cost is very high, with new pully, bearing, and larger motor and controller. Maybe go for a VB36 bowel lathe?

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                        • #13

                          Re: Lathe Spindle sizes

                          Re: Lathe Spindle sizes

                          A Oneway 24-36 would handle it, no China quality there

                          Have fun and take care
                          Leo Van Der Loo

                          Comment


                          • #14

                            Re: Lathe Spindle sizes

                            Re: Lathe Spindle sizes

                            Originally posted by Ducktruck View Post
                            This is the first time for me to write. I have a 25-650 and in Feb. I tryed turning 24"dia. x 28" lenth on the end of the lathe. What I found was that the shaft started to flex. So I reworked the tool support and reducted the cut size to very small. The drive stopped many times. Had to reset the drive. After adding outboard support with skate rollers, the flex stopped letting me make bigger cuts. Looking into the drive head to my surpise I see a 1" shaft with hole for the tec. What do I do now ? I'm looking at a new custom 1 1/4' shaft but the cost is very high, with new pully, bearing, and larger motor and controller. Maybe go for a VB36 bowel lathe?
                            I doubt a 1-1/4" diameter shaft would be the answer to this problem. A 24" dia piece that is 28" long is a serious load especially if the wood is not bone dry and balanced. I wouldn't put a piece that long on any lathe without a steady rest if not tailstock is being used. Regardless of how much space you can get by rotating the headstock there are limits to what any lathe can safely handle. The fact the 2HP motor kept tripping is another indication of an overloaded condition.

                            billh

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                            • #15

                              Re: Lathe Spindle sizes

                              Re: Lathe Spindle sizes

                              Since I put my foot in the stuff early, I'll take it out now. Having read all the posts on this, and especially Leo's, I can see that my original position was wrong. Leo is right. You were, too, Roudhead. I guess I needed another point of view to see it. It is dishonest to say that a lathe has a spindle of one size, when the only part of the spindle that is that size is the threaded part on the end. I, too, would assume that if a lathe has a spindle of 1.25", it's that diameter from one end to the other. I was wrong to take the position that since the spindle didn't bend, it was ok to have a threaded part bigger than the rest of it. (Just for fun, though, I'll say that I bet none of us would mind of the advertised spindle size was 1.25", the threaded part really was 1.25", but the hidden part was 1.5". Dishonesty in advertising is all relative. :-) )

                              On a side note, I'm curious, Ducktruck. How much does a blank 24" D and 28" long weigh?
                              Grant Wilkinson
                              Ottawa ON

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