Apron Removal from a Synchro 280

[steamgeek]

Can anyone advise how to remove the apron from Synchro 280VS, I am having problems with the power feed slipping and think I have some gear problems in the apron.

I have the manual for the lathe but it doesn't help much.

Was hoping that you would be able to drop the apron off from the saddle, but I think the saddle probably needs to come off before you can split them

Thanks

[Pete.]

Dropping the apron is a matter of simply un-doing the allen bolts from the top of the saddle, the hard bit is getting it off the feed rod and leadscrew. I should think that the proper way is to slide it off the end, if you can get the end block off those shafts.

[oldboyouttheback]

First, are you sure the problem is in the apron. When you state that it is slipping on auto feed, is the feed shaft still turning at normal speed. I ask this because it is possibly the feed shaft drive that is at fault inside the gearbox.
If you are sure that all is ok in that department then to remove the apron ( after a thourough clean of the machine ) you need to first remove the feed shaft and leadscrew rear support housing. The feed screw has a threaded adjuster at the end which is retained with a taper pin. make careful note of all washer and bearing locations when removing the housing, for reassembly.
Next, in order to lift the saddle to clear the cross feed gear when removing the apron you need to remove the saddle rear retainer plate and the centre safety retainer between the bedways, and accessed from the rear.
Next remove the allen bolts from the front of saddle retaining the apron, you will need to support the apron carefully to avoid it hanging on the feed shaft and leadscrew, I used wooden blocks under it.
now lift the saddle up at the front to clear the cross feed gear, and place a small wood block under it to hold it clear.
Now the apron should be free to be carefully moved to the end of the feed shaft and leadscrew, and away from the machine.

If you get this far and are going to dismantle the apron, be aware that most parts are retained with allen grub screws, but be careful because most are double screwed, so having removed one screw check to ensure that the second is removed before trying to dismantle anything.

If you get this far and want any more help please ask, I will try and keep an eye on the forum ( I don't visit often ) until I know you have been successful in locating and rectifying the fault.

Reassembly can be tricky so you may need more advice to refit the apron.

Regards

John

[Pete.]

There you go a much more comprehensive reply. I would agree that the problem is more likely to be in the feed gearbox. Last time I had a feed problem it was a sheared key in the gearbox.

[steamgeek]

Thanks for the info, the problem is in the apron, both shafts from the gearbox are turning and applying pressure to them while in motion does not cause them to slip. After further examination of the fault i would guess there is a tooth or two off a cog ( fault occurs at the same place and by applying pressure to the handle wheel the feed will re- engage for 1 revolution)

I have been searching the forum for 280VS apron drawings but not managed to find anything yet.

[Pete.]

I can supply photos but I don't recall ever seeing a working drawing for the synchro apron.

Does it happen in both sliding and surfacing modes?

[steamgeek]

Same fault in both modes, I am guessing that there is a primary drive cog(s) and that's where the fault is.

If the broken cog is steel or brass I might try to build it back up with braze or silver solder

If it's something else learn how to measure a cog and hope HPC have something close

If you have photos I would appreciate a copy,


Thanks

[Pete.]

The gears are easy to figure out. Count the teeth, add 2, divide by the diameter in inches.

[oldboyouttheback]

When you say applying pressure to handwheel will cause the feed to re engge for one revolution, do you mean the leadscrew will turn for one rev before slip occurs again, or the handwheel will turn one rev ?
I do rather doubt that a gear has lost teeth as it is more likely to have sheared the drive key before that would occur, but anything is possible as we all know, and a possible cause of broken teeth could be that the detent pin between the halfnut and auto feed levers has failed and someone has engaged the auto feed whilst screwcutting halfnut was engaged. ( be a bit like putting a car into reverse gear while moving foward at 20 mph.... BANG something has to give.

The feedshaft drives a worm gear which slides along the shaft and is driven by a key ( another possible cause if broken. ) The worm gear is engaged by the feed lever to intermediate gears which drive either the saddle or crossfeed depending which way the knob on end of saddle is turned. All the gears are steel by the way.

I am sure that the fault would be very obvious to find once the apron is removed.

John

[steamgeek]

I do like obvious faults, having played with steam locos for a number of years obvious faults are few and far between ( unless a wheel falls off )

Tomorrow is the day when I get around to stripping it down.

Whatever I find I will post some pics

[oldboyouttheback]

Good luck. Hope all goes well.

John

[oldboyouttheback]

Just in case you get to refitting the apron, I found it was near impossible to hold the worm gear whilst also trying to locate the apron, so I used the shank of a suitable size drill to loosely hold gear while sliding assembly back onto shafts. Found it worked quite well.

John

[steamgeek]

I prefer to be lucky rather than good

Thanks for the tip

[steamgeek]

2 teeth mullered on one gear,

Gear is 2" dia, with 33 teeth ( 31 at the moment ) 5/8" thick , 1" dia hole which keys on to another gear with grub screws
and the teeth seem to be set at an angle of ~3 degrees , it's the first gear off the worm drive - left handed

Let the search begin!

Any thoughts for potential suppliers please let me know

Thanks

After some further investigation, it looks like the gear picked up on the running shaft and seized up causing the teeth to strip.

Shaft is a bit of a mess, so will probably make a new one out of bronze assuming I can get the gear remade at a cost that is less than what I paid for the lathe

[Pete.]

I make that 18dp based on the photo with the ruler.

I'd have a go at pinning it and building it up with braze then hand-finish to shape until I could find a replacement or a cutter to make one.

[Andy B]

Here's the drawing for the gear.
You weren't far off with your dimensional assessment

Sorry about the colours in the pdf - that's how I got them! I haven't yet found a way to make them any more readable.

Andy

[Andy B]

A bit late maybe, but I just found that I do have the apron assembly drawing too.

Andy

[Pete.]

Andy here's the drawing as a PNG, I don't have the driver installed here to print it as a pdf.

[YouraT]

And many thanks from me to Andy B for that apron drawing - it looks identical to my 250 apron, and I was wondering exactly where the two washers I had left over had come from.....

Youra.

[oldboyouttheback]

With the drawings etc, I would contact HPC gears to enquire about having one made.