OK....I am going to look into getting additional feed screws/lead screws made for my newly acquired Presto 6N. I have a 112 lpi and a 240 lpi, both outside-in. (I can't test anything yet because I need my cutter head rebuilt....but that's another story...going to Bruce Leslie for that.)
I am starting to ask around to try to find a good machinist in the New York City area. (if you know one....post it!)
The Presto 6N feed screw seem to be one of the most coveted items around here. It occurs to me that once I get one made, I might as well get several of the same kind made....and it will probably bring down the price per item quite a bit.
SO....I'd like to get a sense of what people around here MOST WANT. And which are the best ones to get made, lpi-wise. And how many people on this board want such items. And what we all think is a reasonable price for a well-made one.
I am thinking that:
a 150 lpi (3:45 @7" 45 rpm, 14:40 @12" 33 1/3)
and a 180 lpi (4:30 @ 7" 45 rpm, 17:36 @ 12" 33 1/3 rpm)
...would be popular. Both outside in. The sense I'm getting is that above that lpi is pretty taxing and poor performing for an old Presto. Maybe the 180 lpi is even too narrow.
Any other biggies? Feedback?
Are these feedscrews the same on other Prestos?
(A very quick and crude measurement of my feedscrews seems to indicate that you can multiply the record's target lpi by .13 and get an approximate lpi of the feedscrew. For example: 112 x .13 = 14.56 lpi on the actual screw. or 240 x.13 = 31.2 lpi. I would make a more careful measurement down the line.)
Remember....this is theoretical at this point. I have not yet found a machinist.
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Steve E.
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So far I've had 3 or 4 people say they personally want them and others who say it's a great idea.
It turns out that the same feedscrews work for the Presto 6N and 8N.
The 8C ("8N turntable with the 8D overhead") uses a different screw, according to Alan Graves.
According to emorritt, the Presto 12 series and model E's had different screws as well. If I am reading him correctly, he thought the rare 14 and stationary lathes might have used the same screws as the 6N.
Respondents have reported that they have the following screws:
96 lpi (outside in and inside out)
112 lpi (I have this one)
120 lpi
136 lpi ("for 78s")
184 lpi (starts to require rolled off bass here)
200 lpi (this and higher requires reduced signal)
224 lpi (for 33 1/3....one guy says he has 226.)
240 lpi (I have this one....makes TINY grooves.)
256 lpi
One of ours supposes that the most useful screws are:
136
160 and
180
("Although the 180 is theoretical for me.") Makes sense to me, in terms of fidelity vs. running time. Alan Graves says that on his Scully, 140 to 150 was the best for loud DJ cuts.
Another is interested in:
96
150 or
240
"if the machining is of good quality."
I will keep you posted....still looking for names and contacts of machinists! Len Horowitz is looking around, but it would be nice to get several estimates.
By the way, my measurements seems to indicate that you can figure out the threads of the feed screw by multiplying its intended record lpi by .125. (or 1/8 )
For example: the 112 feed screw has 14 threads per inch, and the 240 lpi feed screw has 30 threads per inch.
112 lpi x .125 = 14 threads per inch on feed screw
240 lpi x .125 = 30 threads per inch on feed screw
so of course, the opposite holds true and the threads per inch of the feed screw x 8 will give you the records' lpi. Perhaps this is why so many of them seem to be multiples of 8.
It turns out that the same feedscrews work for the Presto 6N and 8N.
The 8C ("8N turntable with the 8D overhead") uses a different screw, according to Alan Graves.
According to emorritt, the Presto 12 series and model E's had different screws as well. If I am reading him correctly, he thought the rare 14 and stationary lathes might have used the same screws as the 6N.
Respondents have reported that they have the following screws:
96 lpi (outside in and inside out)
112 lpi (I have this one)
120 lpi
136 lpi ("for 78s")
184 lpi (starts to require rolled off bass here)
200 lpi (this and higher requires reduced signal)
224 lpi (for 33 1/3....one guy says he has 226.)
240 lpi (I have this one....makes TINY grooves.)
256 lpi
One of ours supposes that the most useful screws are:
136
160 and
180
("Although the 180 is theoretical for me.") Makes sense to me, in terms of fidelity vs. running time. Alan Graves says that on his Scully, 140 to 150 was the best for loud DJ cuts.
Another is interested in:
96
150 or
240
"if the machining is of good quality."
I will keep you posted....still looking for names and contacts of machinists! Len Horowitz is looking around, but it would be nice to get several estimates.
By the way, my measurements seems to indicate that you can figure out the threads of the feed screw by multiplying its intended record lpi by .125. (or 1/8 )
For example: the 112 feed screw has 14 threads per inch, and the 240 lpi feed screw has 30 threads per inch.
112 lpi x .125 = 14 threads per inch on feed screw
240 lpi x .125 = 30 threads per inch on feed screw
so of course, the opposite holds true and the threads per inch of the feed screw x 8 will give you the records' lpi. Perhaps this is why so many of them seem to be multiples of 8.
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Steve E.
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OK, I am moving into higher gear with this idea of getting more feed screws machined for the Presto 6N.
If you are one of the interested parties, please consider doing some research and price hunting for a machinist in your area.
It is in the best interests of us all to get an ACCURATE sense of how much it will cost per feed screw. And to do this very soon. There is evidence of some auctions coming up, and it would be silly for us to spend huge sums of money--while acting like starving sharks-- on random antique screws if we can get the ones we _really_ want for cheaper....or even, perhaps, for more money, but with far greater utility. Many of the old screws were for radio applications and aren't so useful now.
I spent much of today running around to my local machinists, and none of them would take the job. I finally found a guy in Queens who sounds like he is willing. He has not offered me a price quote yet, as he is waiting for me to bring in a sample. But I would like to get a jump on this.
Being that this is New York City, I suspect it may be pricier here than in other parts of the United States. It would be nice to get competitive quotes.
Remember that you can figure out threads per inch by dividing the target lpi by 8. So, to use the most common screw as an example, 112 lpi / 8 = 14 threads per inch on the feed screw.
The screws are 9 inches long. They are 5/8 inch diameter on the thick end, and 1/2 inch on the thin end. There is a little hole on each end, and a slot on the side of each end that a locking pin slides into.
I estimate that we would want 7-10 of each screw made. I am not sure if it is easier to make multiples or not. (I suspect not.)
If you are one of the interested parties, please consider doing some research and price hunting for a machinist in your area.
It is in the best interests of us all to get an ACCURATE sense of how much it will cost per feed screw. And to do this very soon. There is evidence of some auctions coming up, and it would be silly for us to spend huge sums of money--while acting like starving sharks-- on random antique screws if we can get the ones we _really_ want for cheaper....or even, perhaps, for more money, but with far greater utility. Many of the old screws were for radio applications and aren't so useful now.
I spent much of today running around to my local machinists, and none of them would take the job. I finally found a guy in Queens who sounds like he is willing. He has not offered me a price quote yet, as he is waiting for me to bring in a sample. But I would like to get a jump on this.
Being that this is New York City, I suspect it may be pricier here than in other parts of the United States. It would be nice to get competitive quotes.
Remember that you can figure out threads per inch by dividing the target lpi by 8. So, to use the most common screw as an example, 112 lpi / 8 = 14 threads per inch on the feed screw.
The screws are 9 inches long. They are 5/8 inch diameter on the thick end, and 1/2 inch on the thin end. There is a little hole on each end, and a slot on the side of each end that a locking pin slides into.
I estimate that we would want 7-10 of each screw made. I am not sure if it is easier to make multiples or not. (I suspect not.)
The 12 series was a very small lathe and I don't think the feedscrew was intended to be changed - it's geared on one end which would have made it a very expensive part to make interchangable. The lathes designated 'D' and 'E' were also small machines meant for educational or home use. If I remember right (will have to get it out and look) these were changable, but they weren't the same size as the transcription lathe feedscrews. Much smaller. The 14 and 8D series didn't use the same feed mechanism as the 'N' series, so the screws you're thinking of making will only work on an 'N' series lathe. Yes, the 8C is similar to the 8D machines - sort of a hybrid because it was a small lathe like the 'N' but has the variable feed similar to the 8D's. I got a brief look at Alan's 8C and it's an interesting machine and definitely a rarity in the Presto line. Finally the 'stationary' lathe is somewhat of a mystery machine - I doubt many were made and from photos I've seen of them the overhead looks longer than that of an 'N' series and while it's obviously a similar screw-type drive like the 'N' lathes, I really have no idea what kind of feedscrew was used for them. These oddballs were 'crossover' machines which could be set up for use with Presto's new lacquer disks, or they could be used for mastering in wax, either the 'cake' or a flowed blank like the ones shown in the Milton Cross film. Hope this sheds some light...
Feed Screws
Hi:
I've had good luck with 224 LPI on my 6N. I drop the level about 4 or 5 db to keep the grooves from touching is all. I've kind of thought 180 LPI might be a good compromise. I have a 136 LPI. It's fine for louder cuts but I'd like to be able to get just a little more time. Really depends on the music and type of head that is being used also I would think.
Doug
I've had good luck with 224 LPI on my 6N. I drop the level about 4 or 5 db to keep the grooves from touching is all. I've kind of thought 180 LPI might be a good compromise. I have a 136 LPI. It's fine for louder cuts but I'd like to be able to get just a little more time. Really depends on the music and type of head that is being used also I would think.
Doug
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Steve E.
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i actually used my 224 lpi screw this week--I made my mom an acetate copy of her CD album as a holiday present. First time I have cut a whole 33!
And I was impressed that it sounded OK. Her album is simple--just voice and nylon string guitar--so there wasn't much bass information.
It did come out noisy. Strangely, especially, in the first third of each side. I am not using heat, so I figure that could be a factor.
The album runs about 17.5 mins per side, and there was a LOT of extra space. I think you can fit about 26 mins per side using that LPI.
And I was impressed that it sounded OK. Her album is simple--just voice and nylon string guitar--so there wasn't much bass information.
It did come out noisy. Strangely, especially, in the first third of each side. I am not using heat, so I figure that could be a factor.
The album runs about 17.5 mins per side, and there was a LOT of extra space. I think you can fit about 26 mins per side using that LPI.
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cuttercollector
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Congrats. on cutting your first Lp!
One reason it might have more noise at the first 1/3 of the disc is that your depth of cut and cutting angle might be not be the same outside to inside. Double check how parallel your carriage and leadscrew etc. are to the disc beginning to end. If it is higher at the outside (or even at the inside) adjust it as close as possible to the same all the way across the disc. Sometimes a minor change in cutting angle with a cold stylus can make all the difference.
One reason it might have more noise at the first 1/3 of the disc is that your depth of cut and cutting angle might be not be the same outside to inside. Double check how parallel your carriage and leadscrew etc. are to the disc beginning to end. If it is higher at the outside (or even at the inside) adjust it as close as possible to the same all the way across the disc. Sometimes a minor change in cutting angle with a cold stylus can make all the difference.
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grooveguy
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Well, guys...
Good luck with having a local machinist make you a leadscrew. I looked into that once for my Rek-O-Kut and found it prohibitively expensive. The Rek-O-Kut required a mating "half nut," which the Presto may not need.
My first lathe was an RCA that was not unlike the Presto 6N. The native pitch was 96 lpi, useless for anything but '78s. The RCA leadscrew had a 'buttress' thread that would have been almost impossible to have made, so I opted for Plan B.
I removed the worm gear from the leadscrew and drove it from a separate DC motor belt-driven to the spiralling crank. The motor was off some military surplus equipment and had a tremendous speed range. At about 100 rpm it gave a pitch of about 180 lpi, perfect for 33s and 45s. Lead-in and out simply put more juice to the motor, which revved up to 3000 rpm or so. Worked like a champ, except you could hear a bit of a whine during lead-in and -out as the motor wasn't mounted with rubber shockmounts.
Good luck with having a local machinist make you a leadscrew. I looked into that once for my Rek-O-Kut and found it prohibitively expensive. The Rek-O-Kut required a mating "half nut," which the Presto may not need.
My first lathe was an RCA that was not unlike the Presto 6N. The native pitch was 96 lpi, useless for anything but '78s. The RCA leadscrew had a 'buttress' thread that would have been almost impossible to have made, so I opted for Plan B.
I removed the worm gear from the leadscrew and drove it from a separate DC motor belt-driven to the spiralling crank. The motor was off some military surplus equipment and had a tremendous speed range. At about 100 rpm it gave a pitch of about 180 lpi, perfect for 33s and 45s. Lead-in and out simply put more juice to the motor, which revved up to 3000 rpm or so. Worked like a champ, except you could hear a bit of a whine during lead-in and -out as the motor wasn't mounted with rubber shockmounts.
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Steve E.
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Well, that's a really smart idea for the more technically sophisticated among us. The whole multi-screw idea is pretty wacky, really. Am I missing a good reason they didn't just do this? cost? size of electronics available at the time? additional money to be made by selling the screws?
Since it took me a little while to grasp this....I am going to restate what may be obvious to many here:
The Presto 6N has a feed screw which always rotates at the same speed in relation to the turntable, because it is physically driven by the turntable via the flange that rests at the turntable's center. As the screw then moves the cutterhead assembly at a constant rate from the outside towards the inside of the record (or, rarely, in to out instead), this results in a consistent spacing of the groove on the record.
If, on the other hand, the feed screw turned faster or slower in relation to the TT, it would move the cutterhead assembly faster or slower along the diameter of the record and the groove spacing would change accordingly. I'm assuming this is how most or all professional record lathes work if they don't have changeable feed screws.
Since it took me a little while to grasp this....I am going to restate what may be obvious to many here:
The Presto 6N has a feed screw which always rotates at the same speed in relation to the turntable, because it is physically driven by the turntable via the flange that rests at the turntable's center. As the screw then moves the cutterhead assembly at a constant rate from the outside towards the inside of the record (or, rarely, in to out instead), this results in a consistent spacing of the groove on the record.
If, on the other hand, the feed screw turned faster or slower in relation to the TT, it would move the cutterhead assembly faster or slower along the diameter of the record and the groove spacing would change accordingly. I'm assuming this is how most or all professional record lathes work if they don't have changeable feed screws.
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Steve E.
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I don't think we need the half nut.grooveguy wrote: Good luck with having a local machinist make you a leadscrew. I looked into that once for my Rek-O-Kut and found it prohibitively expensive. The Rek-O-Kut required a mating "half nut," which the Presto may not need.
I keep hearing that various people had it done for about $100 "a few years ago", which, given the way all our memories tend to work, could mean five years or a couple decades. It may be that the needs of the marketplace have resulted in fewer machinists with those skills or that equipment, and THAT could drive the price way up. The one guy I found does medical machining...we'll see his price.
There's a guy on this board who also made some of his own in high school, but I am starting to more-than-suspect that he's a genius and routinely does things most mortals can't.
I am leaving his name out so he won't get flooded with orders.-
grooveguy
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Man, if you can get one for $100, or even $200, that's great! I guess this means that the Presto doesn't need the half-nut. I recall some sort of wedge-shaped 'blade' that rides the groove in the leadscrew, so I guess this is the same for any pitch. Sure wish I could find a 180 lpi screw for my Rek-O-Kut; 210 is too fine a pitch for most of what I do, and the other 240 lpi leadscrew I have is worthless.
Many, many years ago, I build a couple of experimental lathes, both had an infinite range of groove pitch. The first was fashioned out of an old Radio Recorders brand portable recorder, a 16" lathe-in-a-suitcase meant for remote recording. I removed the leadscrew and attached the carriage to a thin metal band. The band went around the outside of a 3" diameter drum, which was driven by a second motor through a series of clockwork gears. (Figure that one revolution of the drum would pull the carriage more than 9 inches, so to cut one side of a 12" record the drum had to turn only 30 degrees or so.) The second lathe used an aircraft hydraulic cylinder. Oil under air pressure pushed on one side of the piston, and the oil on the other side was permitted to bleed through a needle valve. This worked like a champ and gave the most evenly-spaced grooves I've ever seen. Both ideas interesting, but more work than they are worth. Do let the group know if you do find an economical source for leadscrews... best of luck!
Many, many years ago, I build a couple of experimental lathes, both had an infinite range of groove pitch. The first was fashioned out of an old Radio Recorders brand portable recorder, a 16" lathe-in-a-suitcase meant for remote recording. I removed the leadscrew and attached the carriage to a thin metal band. The band went around the outside of a 3" diameter drum, which was driven by a second motor through a series of clockwork gears. (Figure that one revolution of the drum would pull the carriage more than 9 inches, so to cut one side of a 12" record the drum had to turn only 30 degrees or so.) The second lathe used an aircraft hydraulic cylinder. Oil under air pressure pushed on one side of the piston, and the oil on the other side was permitted to bleed through a needle valve. This worked like a champ and gave the most evenly-spaced grooves I've ever seen. Both ideas interesting, but more work than they are worth. Do let the group know if you do find an economical source for leadscrews... best of luck!
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blacknwhite
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There are several cool online forums of metalworking hobbyists just like us here... you might paste your post asking for what they would say is reasonable realistic quotes for feedscrews on some of those forums, as well as of course asking forum members if any of them would be interested in the job.... they may ask you very technical details about type of metal you want to use, contours of the feedscrew grooves (may require inspection with a loupe), etc...
Of course the cheapest way for you to get the job done would be to buy solid clear virgin PVC rod stock and get that machined... you could almost build something at home to cut grooves into plastic rods and then polish the grooves w/ plastic scratch-remover on tiny high-speed V-shaped-edge buffer wheel, so they won't be noisy... then, when running the plastic feedscrew, use white lithium grease to minimize wear and see if it works.... not sure how cheap you want to do this, but that would probably be the cheapest. Not sure if a blade riding it (as opposed to a halfnut) would shred it too much or not, but that clear virgin PVC rod stock you can buy from any local plastic supplier is fairly tough stuff... If you made a setup to cut the threads yourself, it might be worth it tho...
just random thoughts
- Bob
Of course the cheapest way for you to get the job done would be to buy solid clear virgin PVC rod stock and get that machined... you could almost build something at home to cut grooves into plastic rods and then polish the grooves w/ plastic scratch-remover on tiny high-speed V-shaped-edge buffer wheel, so they won't be noisy... then, when running the plastic feedscrew, use white lithium grease to minimize wear and see if it works.... not sure how cheap you want to do this, but that would probably be the cheapest. Not sure if a blade riding it (as opposed to a halfnut) would shred it too much or not, but that clear virgin PVC rod stock you can buy from any local plastic supplier is fairly tough stuff... If you made a setup to cut the threads yourself, it might be worth it tho...
just random thoughts
- Bob
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Steve E.
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Indeed, the "blade" is the same for all lpi's, but actually Alan Graves hipped me to the fact that the supplied blade is a problem at the finer pitches: It is just too thick to ride the tight grooves accurately. He remembered making a thinner one once out of an exacto-blade material.
emorritt (hope you don't mind my paraphrasing, and do correct me) suggested that the supplied blade is actually very hard to remove. I believe he considered beveling or thinning/tapering the front edge of the existing blade instead. (hadn't tried it.)
emorritt (hope you don't mind my paraphrasing, and do correct me) suggested that the supplied blade is actually very hard to remove. I believe he considered beveling or thinning/tapering the front edge of the existing blade instead. (hadn't tried it.)
I'm going by an attempt I made about three years ago to get one out per the instruction manual. Their description is to simply 'remove the securing pin and the old blade will fall out'. Uh, yeah. I didn't try pounding on the pin that holds the feed finger blade in place, but it probably would have caused the pin to swell and then it would be stuck for good. I'm sure some are probably easier to remove then others, but due to the age of this equipment metal characteristics can change in time and some may be less tight than others. I'd suggested to Steve that in a case where you can't remove the securing pin for the feed finger blade and you want to use a high LPI screw, a dremel tool or some other method of thinning the contact area of the feed blade would be an appropriate choice. The blades made by Presto do have a specific shape to them which are closer to a feed nut (half nut) with a round surface area that will create more contact with the threads of the feed screw than a flat, straight-edged part would. Since the threads are flat-sided this may not be an issue since I've never tried something like an exacto or other precision sharpened piece for a feed finger blade, but it may work. Just my $.02
Machining new leadscrews
This thread (no pun intended) is a bit dated now, but I'm in the metro NY area and might be able to manufacture new leadscrews for record cutting lathes. First, I need to know how much of a demand there is, and secondly, the details (dimensions, thread profile, etc) of the screws themselves. Any interest?
George
George
Hi,
I made one awhile back and created a crude drawing with some dimensions. Here is a link to the original post:
https://lathetrolls.com/viewtopic.php?t=1105&start=0&postdays=0&postorder=asc&highlight=leadscrew&mforum=lathetrolls
Keep in mind that this was what I was able to come up with by looking at some examples I have here. There may be errors or details I missed. The one I made works pretty well, but it does exhbit some patterning. I suspect it is due to the thread form and the quality of my cut thread. A real machinist would be able to do much better.
Mark
I made one awhile back and created a crude drawing with some dimensions. Here is a link to the original post:
https://lathetrolls.com/viewtopic.php?t=1105&start=0&postdays=0&postorder=asc&highlight=leadscrew&mforum=lathetrolls
Keep in mind that this was what I was able to come up with by looking at some examples I have here. There may be errors or details I missed. The one I made works pretty well, but it does exhbit some patterning. I suspect it is due to the thread form and the quality of my cut thread. A real machinist would be able to do much better.
Mark
Mark,
Very nice. Your choice of leaded steel makes sense, and I agree with Mossboss that building a hardened leadscrew would probably would be overkill, especially with a buttress thread. Although I have no idea what kind of accelerations the mechanism produces, but I'm guessing not much (?) Fraggle is also right-on about having to set up and finish grind after heat-treat. That kind of grinding is very expensive.
I started thinking about getting my hands on a record cutting lathe back in the 80s when I figured they were being scrapped, but never pursued it. Then I saw one for sale the other day, and that lead me to this very interesting site. I'm thinking about manufacturing hard-to-find replacement parts for record lathes in order to finance the purchase of a record lathe of my own. I have an engine lathe at home, plus access to a cnc machines.
George
Very nice. Your choice of leaded steel makes sense, and I agree with Mossboss that building a hardened leadscrew would probably would be overkill, especially with a buttress thread. Although I have no idea what kind of accelerations the mechanism produces, but I'm guessing not much (?) Fraggle is also right-on about having to set up and finish grind after heat-treat. That kind of grinding is very expensive.
I started thinking about getting my hands on a record cutting lathe back in the 80s when I figured they were being scrapped, but never pursued it. Then I saw one for sale the other day, and that lead me to this very interesting site. I'm thinking about manufacturing hard-to-find replacement parts for record lathes in order to finance the purchase of a record lathe of my own. I have an engine lathe at home, plus access to a cnc machines.
George