I may get Presto 6N feed screws made....sign up!

Post: # 8602Unread post **markrob** Wed Apr 21, 2010 10:44 am

Hi,

That's possibly the reason. There will always be some backlash in the system. However since the feed is in one direction, it should not matter once started. I think the problem is that uniformity of my screw is not so hot. So you get some slight variances on a cyclical basis that show up as pattering on the laquer cut. At 160 LPI, it doesn't take much for it to show up in the cutting process. I have a small 6" Atlas Craftsman metal lathe from the 40's with no follow rest. That coupled with my poor lathe skills resulted in the problems. If I make another, I'm sure I'll do better.

Mark

Post: # 8606Unread post **kino9** Wed Apr 21, 2010 1:27 pm

Hi again,

You may not be a master machinist, but I think you've got the right approach, especially about the follower rest. I'm assuming you held the stock between centers. I've single-pointed both 60° as well as all kinds of acme threads on engine lathes, and I have to say, the buttress threads would be challenging, being a modified square profile. I'm curious- when you made this leadscrew, did you need to make the corresponding nut, or half-nut for that particular leadscrew? I don't know how these recorders engage the leadscrew. Will have to do some research!

George

Post: # 8607Unread post **markrob** Wed Apr 21, 2010 1:45 pm

Hi,

I did hold the leadscrew between centers when turning. There is no corresponding nut. The carriage is driven by a spring loaded knife blade. I believe this blade is meant to be sacrificial over time as it is somewhat easy to change out. I think this method is used to allow for variable pitch leadscrews. If a nut were used, you would have to change it for each pitch. The pitch can vary from 12 to 38 threads per inch (corresponds to 96 to 300 lpi on the record). On my DIY lathe, I used an off the shelf threaded rod (not Acme) and modified a connecting nut into a half nut. But on this design, I created varible pitch with an external DC motor.

http://home.comcast.net/~markrob1066/site/?/home/

http://home.comcast.net/~markrob1066/pwpimages/Lead%20Screw.JPG

Mark

Post: # 8611Unread post **kino9** Wed Apr 21, 2010 3:35 pm

Hi,

Thanks for the link to your site, will read more this evening. Very interesting project. Can you play this disc with a stereo cartridge, and how does it sound?

I used to have a stack of AA back-issues, long since lost

but I look forward to reading the Reg Williamson article later.

A "knife" follower, ok.

George

Post: # 9470Unread post **Steve E.** Sat Jun 19, 2010 4:36 pm

George, I missed your offer (or forgot about it) and there certainly would be an interest!

I am having a meeting with a Queens NY area machinist on Monday to get a sense of his rates. I might not have made this meeting if I saw your offer, but since I've been going back and forth with this guy for a long time, I wanna do it. Doesn't mean I'm committed to working with him, though I do hear very good things about his work.

I'm specifically going for 6N screws. But I know there are other Presto gauges that people might want screws for. Doesn't the K8 have changeable screws? If anyone else is interested, pony up some basic info on the dimensions of their feed screws, pronto. (I have all the info needed on 6N screws.)

Post: # 9471Unread post **piaptk** Sat Jun 19, 2010 5:40 pm

I'm very interested in getting some feedscrews made depending on the price. I am aiming at getting a shop with FOUR 6ns up and running and starting a shop similar to Peter Kings in the US. So I need some 160 lpi feedscrews, which I believe (correct me if I'm wrong) seems to be the best balance between volume/depth and time per side.