S7 plus to connoiseur upgrade

[Bjorn_B]

Have not been happy with a few things about my early S7 bigbore.

1: Unballance in spindle (my guess is that the cast cone pulley is to blame). The whole lathe will start a shimmy at higher spindle revs.

2: Odd prime number bullwheel (67t) not really suitable for headstock indexing (have a own built versatile dividing head so I guess you know where I'm thinking of next...)

3: Slippage in the bronze gear/cone pulley press fit, preventing use of the spindle lock for dismounting chucks.

4: Backlash between the bullwheel backgear lever/key and bronze gear creating a disturbing knock sound whenever the lathe is running

This is what I have on the bench right now..

[Bjorn_B]

There is a seal in the new pulley, propably to keep some oil of the polybelt. A small ring is turneed up and locktited to the spindle bush/spacer

[Bjorn_B]

The new pulleys are machined all over, no raw surface anywhere so perhaps some hope for a better ballance..

[Bjorn_B]

Headstock casting marked for position of bullwheel, will machine a flat and drill for mounting of a detent thingy in this area. I don't know if the detent plunger is possible to purchase yet.

[ths]

Hi Bjorn, this is an interesting upgrade. I assume that the parts were from Myford? It looks as though you have the headstock off the bed, as well as the gearbox. I seem to remember that the bull wheel was 67 teeth, did they ever go back to 60? My ML7 has 65, but 67 seems fairly useless as a dividing basis. Are the new pulleys cast iron? Hope that this works out well for you. Cheers, Hugh.

[Allen Smithee]

I'm pretty sure my Super-7B has a 60-tooth bullwheel, and does the ML7R. I was under the impression that the ML7 has a 55T bullwheel.
AS

[Stuart]

Ok

My connie has a 60 tooth bull wheel  , don't know where the 67 came from , as Allen said its the ML7 ones that had a 55 tooth one

To the OP are you fitting the correct bearing adjustment nut to the inboard side as it's got a oil seal same as the pulley note Myford think they are both the same until I took some pics for them that's why the description on the site says LH . Note when I rang them about this they said the had very little info about the connie , even Myford Chillwel supplied a S7 handbook with them

Are you changing the back gear shaft as the connie one is a different length to avoid clearance issues

Stuart

[Bjorn_B]

Thanks!

My very ealy bigbore has indeed a 67t bullwheel, they made them like this but changed later back to 60t.
(See MEW issue 108 and 109)

Parts needed for the change are bronze bushing gear, bullwheel and backgear.

Thanks allso for info on the oil seal in the bearing adjuster nut, I will modify mine to make room for a seal. Without the lathe I will have to do it on the mill with a boring head, it has slow quill autofeed for boring, that should work out ok.

Have checked the backgear/levershaft assembly in place and there seems to not be any problem. Everything seems to line up fine with the spindle gears.

Yes, the headstock is off for the moment, will make preparations for a detent mechanism for bull wheel indexing. (Mill a flat and drill for a pair of mounting holes, the detent thing will propably be home made later)

[Stuart]

It's the same style of lip seal as on the pulley, you need it to keep the poly belt dry

Mine stays nice and clean ,

Are you fitting new AC bearing ? I have fitted a matched pair of SKF ones around £180 for the pair , I measured the split shim and deducted 0.05 mm and obtaitain some shims to make up the distance and fitted these to the shaft then you are able to lock up the adjuster on the shaft tight with a known pre load no guessing involved then you can do the lateral adjustment I find one slot back from spindle locked is about right , the I build up the speed and monitor the temp and adjust if needed .

The shim idea came from Grayham Meek

Myford did not fit a matched pair when the built them and mine failed in the first week after del. from the works ( note I live five miles from the old works) so they sent out a fitter to sort it , but those failed about the time the went under so I sorted it out myself

Good luck

Stuart

[Bjorn_B]

Thanks Stuart! Ive got quite new bearings in it, old ones gave up last winter so I will use theese until knackered. Took a look at the seals, 45-55-4 are the dimensions, buggered up my sleeve on shaft bushing idea so i will machine a new shaft bushing/spacer to fit the seals when the machine is together. in a drawer i found a pair of new bearing adjuster nuts I forgot about. Ordered them when the vearings gave up because I was at the time playing around with the idea to fit taper roller bearings but gave that up and forgot about it. 

Now, what kind of tooth form/dp/module could this be? Need to machine a worm for this one day. New 60t bullwheel.. It is not clear by the picture but the diameter (across tooth peaks) is 107,2mm

[Jo]

My guess is a slightly undersized Module 1.75.

Jo

[Bjorn_B]

Thanks Jo!

measured the gears a bit more today, the bull gear and backgear mesh at a centre distance of 66,13mm (60t/16t) if this is any help to understand the pcd of the gears. Will look into this a bit later..

Meanwhile I did put the headstock casting on the mill today and machined a mounting space for a index plunger.

The headstock is back on the lathe at the moment for an alignment check. Result is that with the bed level (no twist), the spindle seems to point towards the front at about 0,02mm per 100mm (mt test bar, test indicator and precision level used). Needless to say, phone battery died, so no photo of the setup tonight. Is this acceptable or should I try to aim for zero deviation? The bed is still in quite good nick (induction hardened)

Cheers
/B

[steamer]

Hey Bjorn,

.02mm/100mm forward is a bit much.   Should be more like .02 / 300mm.     It should also....ideally, point "up" at the end by about the same amount.

It's important that it point forward by a small amount.  that way under a cut, your lathe will face concave, never convex.

Mine is about .0005"/12" or about .012mm/300mm.

It gets really hard to reliably measure that on the smaller lathes as they tend to be a bit flexible.

http://www.modelenginemaker.com/index.php/topic,369.0.html



Dave

[steamer]

http://www.modelenginemaker.com/index.php/topic,369.0.html

You can start on page 35 where I was starting to align my lathe headstock..

Dave

[Bjorn_B]

Thanks for your input Dave!

I will try to correct the front/back alignment to narrower specs (seems quite straightforward to do), have not measured up/down more than a quick traverse, but it seemed more or less level, I will verify this tomorrow.