Super 7 questions

Mmm Ramon - are you allowed to take a spur off of a spur ?? Ridiculous really as the spur could have been to a 4 gang socket, BUT I agree, nice clean wiring installation.

Bob

No doubt you'll receive a variety of answers to your queries !

• Which size segmented belt is correct for the Super 7?
  It appears there are no 'hard & fast rules'. I've seen on the (new) Myford stand that their belts are much thinner i.e less thick, than the Fenner or Brammer belts. I went with the thicker belt & it's hard to provide you with a dimension given its nature. However you might get some idea from this:-
  
  
  
  Advantages? # smoother running & no pattern when light turning due to orig solid belt joint running over pulleys. # can be fitted without removing the mandrel & disturbing bearings.
  Disadvantages? # provokes bad language when trying to remove a link # they stretch (mine needs 1 link removing after about 5 years - a job that is regularly put off) # they don't "bed down" into the pulleys as well as the 'solid' belt when taking a deep cut meaning they can slip when old. That's not necessarily a bad thing.
• Does one change just the belt running from the jack shaft to the lathe or the motor belt as well?
  Only ever used it between countershaft & mandrel.
• Does running a segmented belt in reverse cause problems in practice? Here I’m referencing the need to run the motor both forward and reverse for threading.
  Never experienced that, even when being forced to cut with lathe in reverse BUT work in collet not of course in chuck or on faceplate !
  
  Anyway, I’m going to hold off for the moment as the standard V-belts appear to be in very good condition. Truth to tell, I ran a few test cuts today and the machine is already so much quieter relative to the old ML-10 that I’m not sure I even need extra sound/vibration dampening.
  It's at high speed that you'd notice the benefits compared with the original hard belt.

Point taken about the high speed. Couldn't run the old ML-10 fast enough for that to be an issue.

I'll take some time in the next day or two to check what this new lathe does at high speed.

Ignatz

You say you checked the holes with some drill shanks. Be aware the core diameter of 1/4 BSF and M6x1.0 are almost the same so your hole "C" may be either.

John

John, thanks for the tip.

I've got loads of M6 screws so I'll gently try one for fit.

John, ... Once again my thanks for your tip.

I tried out an M6 x 1.0 and, yes, it seems to fit in every one of those holes (!)

Went looking on line and found that those two threads ( 1/4 BSF & M6x1.0 ) are very roughly similar although they have different thread angles (55° vs 60°. Also, the M6 isn't a 'perfect' fit and the 1/4 BSF's are probably a safer bet for anything that will take heavy strain.

Fowler,

... I tried running that lathe at the higher and highest speeds. Definitely a bit more vibration and I can see where a segmented belt might be of some use. Time will tell if this is something I will choose to invest in.

During these brief high speed tests I noticed a pronounced 'squeal' when switching on the motor... ultimately to figure out that the motor drive belt is a bit slack when placed in the high speed position. It seems to have a correct tension in the low speed position, but I could be wrong.

Does this indicate that a replacement motor drive belt is required?

An "easy test" for belt tension, Grasp belt midway between pulleys using thumb and first finger. Can you just twist the belt 90 degrees, if so.OK

As an aside, I can run my S7 at top speed without vibration being an issue. Yes it's a standard belt.!

Kwil,

... thanks for the info. I twisted the belt as you suggested and it went quite a bit further... about 135 degrees.

Actually, the belt looks pretty good, just maybe a bit too slack.

Where is the adjustment for the tension of the motor belt located?

Two grub screws with lock nuts that rest on top of the shaft that holds the belt tension lever.

Mike

Michael, ... Are you referring to the two screws that I have indicated in this exploded diagram?

Ignatz

I just checked and while a M6 screw will screw into a 1/4 BSF threaded hole (sloppily), a 1/4 BSF screw will not go into a M6 threaded hole, it's too large a diameter. So your hole "C" may be either. When I screw a M6 screw into hole"C" it's a nice snug but not tight fit whereas into a 1/4 BSF nut it's a very loose rattling fit.

John

Ignatz

Just thought, the studs holding the change wheels to the quadrant are 1/4 BSF. You could use one of them to check the hole sizes, as I said, if it won't go in will be M6.

John

Ignatz

Yes , you use the screws you highlighted to adjust belt tension.

Mike

John, ... great suggestion to use the change gear retaining studs to check the hole threading. It turns out that the holes at 'C' for mounting a quick change gearbox are indeed M6. The others are 1/4 BSF.

Michael, ... I fiddled with the tensioning screws (indicated in blue below), but ultimately had to drop the motor a bit (shaft indicated in green below) as well to get the motor belt and counter-shaft belt tensions to balance.

In the process of testing it out I discovered that the counter-shaft bushing at the clutch control arm end ( #125 indicated in yellow ) must be pretty worn since the associated oil cup (mounted at red dot) empties out in mere minutes... or sooner.

Obviously, until I take the time to disassemble the counter-shaft/clutch assembly I won't know if I just need a replacement Oilite bushing or both that and a replacement counter-shaft.

Micheal, as Ignatz has pointed out the green bolt and nuts are for the motor belt adjustment, the blue ones are strictly for the layshaft pulley (106) to spindle belt tension.

NOTE You should all be aware that in Manual S.723N dated 8/73 the Quick Change Gearbox mounting screws are given as 1/4"BSF x 3/4 (Large Head) and in Manual S723W dated 11/84 they are given as M6 x1.0 x 16mm Capscrew.

When the actual production change over was made I am not aware

I have now found the changeover points:-

Headstock hold down, changed to M8 x1.25 and Gearbox and apron to M6 x 1 from machines ML7 K125240 and Super 7 SK124461. Ref Ian Bradley

Regarding the link belts question, the original S7 uses I think "A" section but the big bore "Z" section which are actually smaller in width. Important to get the right ones, A section link belts on Z section pulleys slip. There are also link belts with links moulded from flexible plastic without reinforcement - I bought one of those from RDG and it was quite unsuitable, stretched like anything and slipped badly. Finished up with a Gates red belt made of some sort of fibre sections bought from RS.

Haven't had the time to tear into the counter-shaft assembly to assess the damage at that leaky bushing, might be a few days until I have a free moment to do so...

...but, I've a few questions about that ahead of time.

1. If I'm replacing that worn bushing (#125) should I also replace the bushing at the other end of the shaft (#126... I'm not seeing any unusual oil loss at that end.)
2. How much wear is considered normal on the end of the counter-shaft?
3. If the counter-shaft is worn are there ways to save it? Polish the end? Turn it down?
4. What is the normal running clearance between the shaft and the Oilite bushing?
5. I'm certain that I'm not the first to encounter this sort of problem. Can anyone point me at any posts on the forum or perhaps online videos that present the proper way to handle this repair?

Any extra hints or tips gratefully accepted.

Kwil

That info on the changeover to metric screws agrees with what I have with my lathe. It was bought 22 Sep 77 in central Canada and has Serial #SK127323. The manual that came with it, S.723Q (no date) shows the metric screws in the parts list. The old Myford site showed serial#s SK115830 - SK 129944 were manufactured between 1974 - 1976. ( not sure were it came from but I also have a note that #SK122657 was made Jun 75 and #SK136311 was made Nov 77). So based on that I suspect mine was made mid to late "76.

John