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Intermittent noise from clutch/countershaft

Myford S7 91-94

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Lynne16/06/2018 14:13:25
62 forum posts
23 photos

I have been machining a piece of sq. bar 32mm A/f to the round over a distance of 1 1/2" Relativly modest cut .005" or so. Heavier cuts result in a resonant clatter from the clutch/countershaft assy. Investigation reveals a fair bit of radial movement in the clutch drive, before the drive is taken up. As machining off the corners is an intermittant load this is being replicated at the clutch drive , and hence the clatter. Having looked at the exploded view of the motorising assy, it appears to me that the drive is through cone and the two projections (dogs) on the driver plate. Now this may be the norm, but I am of the view that it should not be.( the noise)

Question is, has anyone else come up against the problem, and if you have, was it resolved. Having read the threads of clutch issues, I will not be dismantling to have a look.

Question 2. The assy. drg. shows a hex nut securing the push rod. I attach picture of the assy of my lathe . No hex nut !! Has there been a mod. and it now simply screw into the drive plate?. I look forward to your comments.

Regards Lynneimgp2181.jpg

Roderick Jenkins16/06/2018 14:24:57
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1773 forum posts
451 photos

Nowadays, when I get a weird noise from the transmission on my S7, my first thought is to see whether the motor pulley has come lose. Might be worth a check before investigating other causes.

And yes, there should be a locking nut on the end of the push rod which may well be the problem, allowing the push bar to come out of adjustment.

Looking again at your photo, although hard to tell from this angle, it does not look like there is much room for a locking nut and I am wondering whether the ball has been left out of the assembly...

HTH,

Rod

Edited By Roderick Jenkins on 16/06/2018 14:42:54

Edited By Roderick Jenkins on 16/06/2018 14:51:54

Lambton16/06/2018 15:11:46
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678 forum posts
2 photos

Lynne,

I have sent you a PM

Eric

KWIL16/06/2018 15:12:17
3111 forum posts
56 photos

The two drive dogs you refer to do in fact wear with age and although you can replace them, the mating faces on the driven plate will also show signs of matching wear.

Fact of life I am afraid.

Mike Poole16/06/2018 17:14:25
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2041 forum posts
47 photos

The clutch lift is adjusted by screwing the pushrod in or out of the steel key plate, when adjusted the locknut that is missing should be nipped up to secure the adjustment. The key part of the key plate fits a key way cut across the end of the shaft and does wear giving the opportunity to rattle. The shaft and the key are hardened but there is very little area to take the loads so it will wear especially with an interrupted cut after a bit of slack has appeared. New shafts are available and key plates but they are not cheap and I doubt the cure would be long lived. There is slack on my machine but I can live with it even though it isn't nice. It wouldn't be difficult to make an oversize key plate but ideally it would be best hardened.

Mike

KWIL16/06/2018 19:11:31
3111 forum posts
56 photos

Replacement Key Plate made some time ago, heavily nickel plated, continues to work well.

Hopper17/06/2018 07:47:10
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3654 forum posts
72 photos

To minimize shake, rattle and roll on interrupted cuts, I take LH Sparey's advice and use a piece of wood held against the chuck body to act as a "shock absorber". It smoothes out the motion and eliminates drive train rattle and snatch surprisingly well.

dscn2084.jpg

dscn1046.jpg

Lynne17/06/2018 12:05:44
62 forum posts
23 photos

Good Day, Thanks for all the responses to the problem I raised.

Roderick. The slot is just below the face of the cone, and on closer inspection I can see that it has been centre popped around the edge, so there was no intention to replace the hex nut. The missing ball would appear to be a likely scenario, but to find out for sure, I am going to have to 'go in'. I cannot find the posts I read about the uncompromising spring. The 'keyword' search, I find, is pretty useless. Was it KWIL who posted a method of dealing with the the spring issue, by the use of long screws , and removal from the drive plate end. It would be usefull for me to have more detail of this approach. If it was KWIL, perhaps you could go through this method again. A PM perhaps?.

Eric. Many thanks for posting me the Myford info sheet. Cup of tea time, and a read.

Best regards, Lynne

Mike Crossfield17/06/2018 13:34:43
190 forum posts
17 photos

Lynne

If you only want to check that the ball bearing is in place and that the operating rod is intact you don’t need to compress the spring. Just remove the clutch assembly and countershaft complete. This is quite straightforward and from memory only requires a clamp screw to be released and a circlip to be expanded to allow the countershaft to be withdrawn.

Mike

Lynne18/06/2018 15:50:28
62 forum posts
23 photos

Hello Mike, Thanks for your post. The situation is that if I am to return the clutch system to its original form, I will have to extract the operating rod. As I said in my post, the screwed end of the rod has been retained in the driver plate by means of centre pops around the edge to displace metal and is locked by this , rather than the hex nut. I will remove countershaft, to investigate whether the ball is there or not. Regards Lynne

Lynne21/06/2018 12:28:13
62 forum posts
23 photos

Good Afternoon, Have got the pushrod out; threaded portion looks rather short. Does anyone just happen to have details of the overall length?, and length of thread would be usefull.

Myford do a spare. I have asked if they could supply length etc, but no response. Just looking for a sale I guess. Regards, Lynne

Niels Abildgaard21/06/2018 14:38:54
228 forum posts
74 photos

I had drive train clicking noises trying to part square 25mm steel on my rockmounted Boxford.

The solution was to drive faster.

**LINK**

https://www.youtube.com/watch?v=Sdmqk5oJ7OE

Edited By Niels Abildgaard on 21/06/2018 15:02:19

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