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Myford Super 7 (with gearbox) Leadscrew Removal

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Mike Donnerstag19/05/2020 20:23:55
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181 forum posts
39 photos

I have a Myford Super 7 with a gearbox. The lathe dates from around 1982, serial number SK151723.

I need to replace two bushes in the apron and I understand that to replace these I need to remove the apron, and to do this I need first to remove the leadscrew.

To this end, I've removed the gear quadrant, the gearbox cover and the grub screw from the gear at the left end of the leadscrew. I've also removed the bolts and dowels from the leadscrew bracket from the right end, which is now hanging down from the end of the leadscrew.

I tried using a brass drift to knock the leadscrew out of the gear below, but found that, even though it is moving, it is incredibly tight. I'm just wondering if I'm doing the right thing, and need some reassurance before I use more force! Also, if anyone has done this in the past, is it reasonably easy to reassemble once I've replaced the bushes? Also, do I need any special tools to replace the bushes?

A photograph of the progress so far is below:

img_0517.jpg

Many thanks,

Mike

Martin Kyte19/05/2020 21:02:07
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1902 forum posts
34 photos

Just make sure there are not 2 grub screws in the collar (one on top of the other as locking device).

Also you may do better if you supported the right hand end of the lead screw so it's in it's normall position and aligned with the axis of the gearbox bushes.

I've never actually carried out this proceedure but I do have the manual in front of me.

You could do worse than give Myfords a ring tomorrow, they are generally helpfull people.

regards Martin

Clive Brown 119/05/2020 21:17:28
453 forum posts
14 photos

I'm not a Myford owner, so might be completely wrong, but AFAIK, the leadscrew doesn't go all the way through the gearbox. Can it be removed by removing the bearing at the RH end of the bed and pulling to the right? There's a woodruff key at the LH end of the leadscrew that connects the drive from the gearbox shaft, via  a connecting sleeve.

Edited By Clive Brown 1 on 19/05/2020 21:18:20

speelwerk19/05/2020 21:37:41
369 forum posts
5 photos

The gear is also secured with a key therefore you have to remove the gear first and than take out the key . Niko.

Mike Donnerstag19/05/2020 21:48:56
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181 forum posts
39 photos

Thanks chaps - tomorrow I'll check if there is a second grub screw and use a puller to remove the gear, as you may be right in that the key may be stopping the leadscrew from travelling any further through the gearbox.

I'll let you know how I get on.

Clive: The leadscrew on the later gearbox Super 7s definitely does all the way through the gearbox. (It'd make my life easier if it didn't!)

Does anyone have any hints on replacing the apron bushes?

Mike

speelwerk19/05/2020 21:55:55
369 forum posts
5 photos
Posted by Mike Donnerstag on 19/05/2020 21:48:56:

Thanks chaps - tomorrow I'll check if there is a second grub screw and use a puller to remove the gear, as you may be right in that the key may be stopping the leadscrew from travelling any further through the gearbox.

Mike

It should slide off very easily. Niko.

Simon Williams 319/05/2020 22:57:07
512 forum posts
80 photos

Mk 2 gearbox at this date, and the 2 : 1 reduction shown at the LHS of the gearbox confirms it, so the leadscrew does go right through the gearbox from one side to the other.

My recollection is that there is a woodruffe key in the bore of that gear, but the gear is only a light push fit on the end of the leadscrew so bashing it shouldn't be necessary.

Go looking for a second grubscrew - it's the sort of trick they'd play.

Two screw drivers behind the gear maybe?

HTH Simon

Brian Wood20/05/2020 09:22:00
2205 forum posts
37 photos

Mike,

It is such an very obvious question but you are working on the 52 T gear aren't you?

As others have said, it should come off relatively easily, that then allows you access to remove the woodruff key and the leadscrew shaft is then free to to remove towards the tailstock.

Good luck with the overhaul, I don't have the apron you have so can't help with the bushes.

Kind regards Brian.

Martin Kyte20/05/2020 09:47:55
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1902 forum posts
34 photos

You can find the exploded view here

**LINK**

The assembly instructions as per manual are:-

14S With the carriage in a central position enter the leadscrew through the clasp nut from the right hand end, and engage the clasp nut. Traverse the carriage to the left until the leadscrew passes right through the gearbox bearings.

From this I infer that the leadscrew gear No.168 needs to be removed before disassembly which allows the woodruff key to be removed. Without removing the key the leadscrew cannot pass through the bearing bush which is likely to be the source of your problems at the moment.

Once you have the gear off and the key removed use the clasp nuts to centralise the lead screw and the carriage to withdraw the leadscrew from the gearbox.

If you do not have one I suggest you order a copy of the QC Gearbox manual from Myfords.

**LINK**

regards Martin

Mike Donnerstag20/05/2020 16:24:07
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181 forum posts
39 photos

Many thanks to everyone who posted so far. I managed to get the gear off the end of the leadscrew and carefully slide the leadscrew from the gearbox. There was no second grub screw but the gear was a tight fit. Having attempted to do it by hand, I used a puller to gently pull it off in the end. I also carefully stoned the leadscrew to remove any burring around the key slot, though I couldn't see or feel any.

Does anyone have any information on how I should remove and replace the two bronze bushes in the powered cross-feed apron? I'm hoping I don't need a press. Do you think they should just drift out and the new ones back in?

Many thanks,

Mike

Martin Kyte20/05/2020 20:46:19
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1902 forum posts
34 photos

If they don't drift out then:-

Make a simple puller. Cylinder slightly larger than the bush resting on the casing, couple of suitable sized washers and a length of studding. You should be able to just wind them out. Helps if the washer on the bush is lipped to fit centrally.

regards Martin

Mike Donnerstag22/05/2020 10:30:02
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181 forum posts
39 photos

Martin Kyte: Many thanks for that tip - something I'd read in the past and had forgotten until you mentioned it. I used a spark plug socket with some studding, washers and nuts and it worked a treat.

I gave Myford Ltd. a call this morning about how to replace the two bushes holding the rack pinion assembly (LA23), but unfortunately it seems that the technical people no longer take calls. I'm hoping this is down to being short-staffed due to the pandemic.

Does anyone know how to remove the rack pinion assembly shown below, in order to replace the bushes? Is it just a case of drifting out the pin holding the larger gear? Is it tapered?

a9199 rack pinion assembly.jpg

Edited By Mike Donnerstag on 22/05/2020 10:31:08

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