Presto K-8 questions (newbie!)

[SueDenim]

Hi guys!

Long time reader of the forum, first time poster

From all my reading and searching I've not been able to answer these specific questions regarding a Presto K-8 that I've been offered (for a good price).
The unit is in great condition, has it's original cutting head and decent amp 45 tubes.

1. Would I be able to cut onto Lexan/PVC with this head provided if it was fitted with the correct stylus?
If so, what stylus would you suggest (eg. Vinylinum diamond? Adamant ruby??)

2. If required, what's the best method of heating the stylus coil?

3. Is there any way to cut a lead-in/out groove on the Presto K-8?

4. What's the typical freq. response I can expect from the cuts?

OK - I think that's everything for now!
Sorry for the multiple questions but this would be my first leap into to the Lathe Troll's kingdom and I'd like to know I'm buying the right machine for my purposes!
Primarily, I'm looking to cut 78 rpm discs for my Jukebox.

Thanks in advance!
Sue D. x

[markrob]

Hi,

To cut polycarb, you would need to get a diamond stylus with the correct shank. I don't think this is a big deal. I think these older heads used the same shank as the more modern Presto heads (.065" diameter 47/64" long). The other issue is that if you want to cut juke box 78's, you would need a 3mil stylus to make the correct groove geometry. You can probably get away fine using a standard microgoove 1 mil stylus as long as you cut deep enough to make the wider grooves required for 78 playback styli. Given the current cost of these styli and the fact that they do not last forever, the ecconomics may be also be a problem. The sound quality of the K8 should be fine for the typical 1930-40's 78 juke. You may not be able to cut quite as loud as a commercial relase, but I think you will be ok. It probably makes sense to try and cut polycarb because these boxes tended to track in force measured in pounds (I used to have a Seeberg Gem ca. 1939). They were pretty hard on shellac 78's. What model box do you have and is it using the stock pickup? Also keep in mind that you will need to factor in the cost to resore the K8 if it has not already been done. As far has heat goes, I don't think you need to do this for polycarb, but is pretty easy to add if you find the need. Just a couple of turns of nichrome wire, some cement, and a external power supply will do the trick. I you get that far, I can give you more specific details. Hope this helps.

Mark

[SueDenim]

Thanks for the quick reply Mark - much appreciated

I have a Seeburg M100A with an original Blackhead Pickering magnetic cart/stylus (rebuilt by West-Tech).
It tracks at around a much more reasonable 10-12 grams.

From what I am told by the seller, the K8 is in working condition though I suspect I may look to re-cap the amp if it hasn't been done recently.

Do you know whether it's possible to create the lead-in/out grooves that will be required on a K8?

Given the deep grooved cuts I will need to make with a 1mil stylus, how many cuts on average would you say a new diamond tip will typically last before it needs to be re-ground/polished?

Thanks again mate!
Sue D.

[piaptk]

Making a diamond work on those is not easy in my experience, and if you don't have a vacuum suction system set up (probably hard to implement on a K8), you will not have any success at all. I wouldn't use a anything but a diamond to cut polycarb... it will tear your needles up. It is possible to turn your standard ruby stylus around 180 degrees to EMBOSS the sound into polycarb, but I'm not sure that the grooves would be deep enough to play on a standard jukebox, much less a 78 player.

Also, you can't resharpen diamonds from Vinylium... unless you someone personally, in which case, please let us know!!!

You can still find NOS 78 rpm sapphire and stellite cutting needles... try Gib at West-Techservices.com or Robert Van Dyke http://www.robertvandyke.com/... I know Robert has a bunch of them, and they are only $40 each.

Good luck!

[SueDenim]

Thanks for that info Piaptk....

So basically, what you are saying is that, although I could fit a NOS 3mil cutting stylus to the K8, it would be totally trashed if I tried to cut onto Polycarb?

Still unsure whether a K8 can cut lead-in/out grooves too!

Sue D.x

[piaptk]

I have not ha any success cutting polycarb with standard needles... You could try the backwards trick, but it's tough to line up just right....

Never had a k8, but most suitcase recorders cannot cut lead in and out grooves...

[opcode66]

As has been stated, it would be tough to get this to cut plastic with diamond. Especially with no suction.

K8 does not have a lead-in/lead-out groove function. A lot of the older units would have a fly wheel with a handle on it. When you wanted to put space between tracks or when you wanted lead grooves you woul simply crank the wheel which would then turn the feedscrew faster to cause the head to travel laterally more quickly and the groove to becom a fatter spiral.

[markrob]

Thanks for the quick reply Mark - much appreciated

I have a Seeburg M100A with an original Blackhead Pickering magnetic cart/stylus (rebuilt by West-Tech).
It tracks at around a much more reasonable 10-12 grams.

From what I am told by the seller, the K8 is in working condition though I suspect I may look to re-cap the amp if it hasn't been done recently.

Do you know whether it's possible to create the lead-in/out grooves that will be required on a K8?

Given the deep grooved cuts I will need to make with a 1mil stylus, how many cuts on average would you say a new diamond tip will typically last before it needs to be re-ground/polished?

Thanks again mate!
Sue D.

Hi Sue,

That's a nice Juke! My Gem had the same mech as the 148 (Trashcan). It was a real brute of a mechanism, but reliable. Yours is the first of the more modern mechs. I have an HF100R here (45's). Given the lighter tracking magnetic pickup, I wonder if you would be better off cutting lacquers with a standard steel or saphire stylus to start. You won't get great wear out of them, but given the use, I bet they last longer than expected on this juke.

I don't know the K8, but even if it can't do lead in/lead out, you should still be ok. On my HF100R, the end of record lift off point is based on position (via a limit switch). Some consumer changers needed the faster velocity and or eccentricity of the leadout to trigger lift-off. Does you mech work the same way as mine? If you start out this way, you could always try polycarb later. If you really get the bug, you could move up to a Rek-o-Kut or Presto overhead style lathe down the road.

Mark

[blacknwhite]

Given the lighter tracking magnetic pickup, I wonder if you would be better off cutting lacquers with a standard steel or saphire stylus to start. You won't get great wear out of them, but given the use, I bet they last longer than expected on this juke.

agreed.

Also, minor note - a few uncommon 78 jukes like my 1952 Rock-Ola Fireball 120 (yes, they made this 60-disc machine in a monstrously huge 78 rpm version!) requires that records be the standard 78 rpm size (from 1935 onwards) of 9-7/8" diameter, and NO LARGER. "10-inch lacquers" are EXACTLY 10 inches diameter. This will jam up the 1952 Rock-Ola donut mechanism, locking it up & damaging it, and it's a pain in the neck to fix (but I got it done...).

I believe your Seeburg juke can also hold 12-inch 78s, so the slightly larger size of metal-based lacquers really shouldn't cause any major lock-ups.... if anything, the center hole might be 1/16-inch displaced from where it should be when the turntable mech clamps down, but it seems that shouldn't be a prob...

Also, I have never used a K-8... Is it possible to disengage the feedscrew while cutting? Do you have a very steady hand? Might be worth a try manually pushing gradual lead-ins / lead-outs that way, just engage/disengage the feedscrew real slowly while still pushing the arm forward, to avoid the arm moving backward when engaging, or "locked/circular" grooves... and you will probably get a "ka-thunk" sound at beginning & end...

- Bob

[opcode66]

You can disengage the feed mechanism on this Presto but I believe it simultaneously lifts the cutterhead...

That is how the RCA's work. They are very similar in design.

[markrob]

Hey Bob,

Before I moved and had to downsize, I had a 1436. Mine was setup for 45's. I really enjoyed that one.

http://www.pinballrebel.com/archive/rockola/r1436/r1436.htm

Your point is well taken about the size. Its not hard to trim the lacquer down. I made a jig to do that and used a router with a flush trim bit to trim my cuts down to 7" size before casting in silicone.

http://home.comcast.net/~markrob1066/pwpimages/Flush%20Tirm.JPG

This pict shows my setup for trimming the finished cast record, but I used the same basic setup to trim the laquer down before casting.

http://home.comcast.net/~markrob1066/pwpimages/Lacquer%20Disc%20Ready%20for%20Pour.JPG

http://home.comcast.net/~markrob1066/pwpimages/Silicone%20Poured.JPG

http://home.comcast.net/~markrob1066/pwpimages/Finished%20Mould.JPG

http://home.comcast.net/~markrob1066/pwpimages/Finished%20Record.JPG

BTW, the casting process is another one to consider. The drawback is that its single sided. With some difficulty, you could probably cast two sided, but I haven't tried that yet. The urethane resin is pretty tough and would be fine in a juke. I was able to play one on my R with no problem.

I like your idea to disengage the feedscrew. If it works as opcode say's, there may be some hope. Perhaps a little modification could be made to to the K8 to keep the head raise function from working.

Another option that might be possible would be to add the leadout manually after the fact. I believe this was sometimes done on 78's back in the day as the eccentric groove was not cut on the lathe (at least, I don't think so). You could probably make a hand tool using an old cutting stylus and do it at 33 or 16 RPM on a turntable.

Finally, I wonder if you would be ok to just stop the cut at the end of the track and let the pickup drift to the center on its own. Not sure if that would work, but with the Seeberg vertical style mech, the arm might just move to the center on its accord.

Mark

[Jesus H Chrysler]

with practice you can do pretty good roll outs on the k series cutters. Disengaging the drive does lift the arm, but the head stays down. You can apply a little pressure to it as you guide it by hand to the label edge and lock the groove. it takes a steady gentle hand but it can be done. I haven't done lead ins, but I don't seewhy you couldn't.

[blacknwhite]

http://home.comcast.net/~markrob1066/pwpimages/Flush%20Tirm.JPG

This pict shows my setup for trimming the finished cast record, but I used the same basic setup to trim the laquer down before casting.

You've had success with casting too, sweet! Yeah, I played the one good one I got on some pretty heavy old pickups and it seems to play great until I broke it, dough!...

I, too, just haven't had time to play with making 2-sided ones... the problem is, I don't have the time right now to establish relationships with small-time music artists of the types of music I like, in order to HAVE clients lined up, in order to MAKE MONEY from putting in the time required to build a semi-automated record-casting jig & run a short-run record label

Ah well, maybe someday, maybe not...

Nice work!,

- Bob

[SueDenim]

Thanks to all you guys for the advice - very much appreciated.

You don't find many Presto or Rek-o-Kut lathes for sale in the UK which is why I'm sorely tempted by this K8

Final question (hopefully!), anyone know the usual frequency response of the original K8 cutting head?

Sue D. x

[piaptk]

Not to hijack this thread or anything, but how are you guys that are doing casting keeping the bubbles at bay? Mine start out looking great, but as the plastic sets, it develops tons of bubbles. I spent weeks working on it, and gave up...

[SueDenim]

Hi-jack Hi-jack
I've been cast out into da cold...

[markrob]

Hi,

In my case I degassed each part of the two part mix(s) separately using a vacuum pump. Then I mixed the two parts together and avoid stirring too violently. This works fairly well, but can't say I'm totally happy with the results. I believe the silicone compound has the poorest surfaces and affects the final urethane casting the most. I say that becasue I recently got some metal 7" stampers (for my record press experiments) and did a quick pour of some urethane to see if there was any difference in the surface noise. I didn't even bother to use my vacuum setup to degass the resin and I thought it was quite a bit cleaner sounding. It was tough to demould from the metal stamper though (I did not try a release agent). Smooth-on sells some additives to allow you to play with the viscosity of the products they offer. I've considered getting some. The downside to these additives are that the physical properties of the materal is affected as you make things easier flowing.

Mark

[Jesus H Chrysler]

Sue, I think the original head (5-c) would go to about 8 khz. If you can get ahold of a 1-c they'll go to abot 10khz. I don't remember what the low end is, but I'm sure it would fall within the capacities of your jukebox.

[blacknwhite]

(offtopic)

Piaptk - about the casting bubbles: Markrob's ahead of me on this: I have not yet tried microgroove records, since it seemed to me too much of a challenge to start with; I'm a big time fan of the older coarse-groove (about 3 times as large groove tip radius) 78 rpm's, so I started with that - figured it'd be "low-hanging fruit". Guess it was; I didn't vacuum-degas, but the results were still "good enough" for large-groove 78 rpm. I doubt it would have been good enough for microgroove. Like Markrob said, stir thoroughly, but not vigorously.

That was over a year ago. Still haven't yet tried a more challenging modern microgroove disc; quite impressed that Markrob got that to work at all.

- Bob

[maniman]

Hi guys... Reading this thread some questions comes to my mind .... If I decide to get the diamond on the K8 (k8 / k10 I dont know exactly ) ... there's no problem about the stylus advance route ? Explain

As I see with the VR or the 6N , the stylus describes a linear path exactly from / to the tt center....but the K recording arm describes a curve path that finish at the tt center.... the re's not a problem ? not frequency response changes ? Really if works isnt important , I'm planning to get the K running with diamond more focused on mobility and live cutting than sound quality it self ... the question is ...

Someone operates right with a diamond on a K8 using the original recording arm ? I assume must adapt a suction tube and heat wire the stylus in a concrete way that I dont know...but is possible runs right ?

Thanks Dudes.