Acetal or phosphur bronze

[SteviegtrParticipant @steviegtr]

The cross slide on my S7B has a bit of axial play behind the Vernier gauge. It is an alloy casting the cross slide screw goes through , with the Vernier scale outside of it, with finally the winding handle. The play is in the casting of the alloy frame. Side to side which is annoying when winding the slide back & forth it chatters.

I have had it in bits & the screw & shaft seem unworn. But the alloy has a slight oval to it. Rather than buy a new casting nose piece, I thought of making a bronze bush for it. Then I thought I have lots of Acetal/ Delrin bar. It seems good enough for the gears on some Chinese lathes , so is it good enough to make a small sleeve bush out of. I would need to bore the casting out to accept the bush but at least it would get rid of the annoying side play. Anyone done this or similar.

Steve.

[SteviegtrParticipant @steviegtr]

Cross slide

[John OlsenParticipant @johnolsen79199]

Acetal would be fine in this sort of service, or you could consider going the whole hog and doing the mod on the Arc Euro site:

Arc Euro thrust bearing mod

regards

John

[Ady1Participant @ady1]

Delrin doesn't last long

As a quick fix I've found aluminium good

Pbronze is bestest

[SteviegtrParticipant @steviegtr]

Posted by John Olsen on 17/03/2020 00:00:46:

Acetal would be fine in this sort of service, or you could consider going the whole hog and doing the mod on the Arc Euro site:

Arc Euro thrust bearing mod

regards

John

Shame that is only for the ML & not the super 7. But given me an idea seeing that.

steve.

[SteviegtrParticipant @steviegtr]

Posted by Ady1 on 17/03/2020 00:02:20:

Delrin doesn't last long

As a quick fix I've found aluminium good

Pbronze is bestest

That does surprise me. A lot of the Chinese mini lathes have the gears made from Delrin. I am not talking about nylon.

Steve.

[Ady1Participant @ady1]

Same with leadscrew nuts

Delrin lasts a few months then fails

…or you could white metal it…what do they call it? Babbit

Edited By Ady1 on 17/03/2020 00:30:57

[SteviegtrParticipant @steviegtr]

I do have some aluminium that would do the job & just as easy to work with. Got me thinking now. Anyway seems since we have decided not to go to our motorcycle café meeting 3 times a week for the foreseeable future, I will have plenty of time to do all the jobs on the list.

steve.

[not done it yetParticipant @notdoneityet]

Same with leadscrew nuts

Delrin lasts a few months then fails

Ady1,

What pitch and diameter were these? Are these for lead, or feed, screws? I made an acetal feed screw nut but have never needed to fit it. I would expect/hope it to last better than for a lead screw. It is very tight, with zero backlash, so needs easing off a bit, methinks.

[SteviegtrParticipant @steviegtr]

Posted by not done it yet on 17/03/2020 01:00:57:

Same with leadscrew nuts

Delrin lasts a few months then fails

Ady1,

What pitch and diameter were these? Are these for lead, or feed, screws? I made an acetal feed screw nut but have never needed to fit it. I would expect/hope it to last better than for a lead screw. It is very tight, with zero backlash, so needs easing off a bit, methinks.

I am not thinking of making leadscrew nuts, just a simple bush. I cannot see how it would wear out quickly as it has no axial loads on it or any angle loads, it is just a simple guide. The only load is a the operator turning a handle.

Steve.

[HOWARDTParticipant @howardt]

It is worth giving it a go. The bearing is just a support, load on the bearing depends on the size of the hand wheel and the force you use to overcome friction and cutting forces. Nothing lost when it fails again, then use a leaded bronze.

[Ady1Participant @ady1]

What pitch and diameter were these? Are these for lead, or feed, screws? I made an acetal feed screw nut but have never needed to fit it. I would expect/hope it to last better than for a lead screw. It is very tight, with zero backlash, so needs easing off a bit, methinks.

Drummond M leadscrew lasted a week or two, I made a full wrap nut, Drum M cross slide nut lasted a month or two, I was a heavy daily user at the time, 2-3 hours

As you say, lovely and tight, with zero backlash, feels brill to start with

but alas doesn't last

Aluminium has been brill with good longevity

I was burning through original M series leadscrew half nuts at a rate of about two a year (they used a very soft bronze) and wanted something more reliable to use for spare parts

Edited By Ady1 on 17/03/2020 09:26:29

[Pete RimmerParticipant @peterimmer30576]

Stevie, it's not a vernier scale, it's a cross slide dial. Might seem like a minor thing to pick up on but a vernier has two opposing scales.

As for the bush, you could make one from acetal and it would last a good while so long as the shaft has an excellent finish on it. Also be aware that holes drilled and reamed in acetal tend to come out tight.

[SteviegtrParticipant @steviegtr]

Posted by Pete Rimmer on 17/03/2020 09:59:05:

Stevie, it's not a vernier scale, it's a cross slide dial. Might seem like a minor thing to pick up on but a vernier has two opposing scales.

As for the bush, you could make one from acetal and it would last a good while so long as the shaft has an excellent finish on it. Also be aware that holes drilled and reamed in acetal tend to come out tight.

I've been told off before talking about Vernier & the word digital. Haha. Never mind it has marks around it in thou's how's that. Now I have had some replies, maybe today it's time to take it off again to see how robust the casting is etc. Thanks for the tips.

Steve.

[not done it yetParticipant @notdoneityet]

Thanks, Ady 1. I’ve repaired a nut with a brass bush since. 1/2” diameter 8 or 10 tpi square thread. The acetal one was made by the “heat and squeeze method”.

[Nigel McBurney 1Participant @nigelmcburney1]

Leaded bronze is better than phosphor bronze and easier to macine

[SteviegtrParticipant @steviegtr]

Well that was a quick fix. There is a screw under the casting at the bush. Not a bush but where the shaft runs through the alloy casting. Not sure what it is for.

Removed it, drilled a 3mm hole up the centre. Then a made a little pad using a piece of 3mm brazing rod, which slid inside the screw. The protruding end , I burred over to create a pad. Fit it back together & it worked. No more side play. Cost, nothing.
Steve.

[KWILParticipant @kwil]

On a S7B with Power Cross Feed the small threaded hole under the casting is for a small pin which impacts with the PCF on/off knob, so that it is not possible to continue to drive the cross table beyond the inner limit.

Without this item, breakage will undoubtably occur.

Edited By KWIL on 17/03/2020 15:53:35

[SteviegtrParticipant @steviegtr]

Well you learn something every day. I wondered what on earth it was stuck there doing nothing.

Steve.

[KWILParticipant @kwil]

My Myford S7s have had their front brackets modified with a PB bearing and needle thrust washers, not a difficult thing to do.

[not done it yetParticipant @notdoneityet]

Posted by KWIL on 17/03/2020 15:53:09:

On a S7B with Power Cross Feed the small threaded hole under the casting is for a small pin which impacts with the PCF on/off knob, so that it is not possible to continue to drive the cross table beyond the inner limit.

Without this item, breakage will undoubtably occur.

Edited By KWIL on 17/03/2020 15:53:35

A point where the myford is better than the Raglan? Outside towards centre is no problem facing, as the screw would wind itself out of the nut eventually (I would have to be asleep?) but in the other direction it could be trouble.

I (nearly) always face from outside to centre but have to be careful when parting-off, under power, with the rear tool post.

[Pete RimmerParticipant @peterimmer30576]

Posted by Steviegtr on 17/03/2020 14:21:37:

Well that was a quick fix. There is a screw under the casting at the bush. Not a bush but where the shaft runs through the alloy casting. Not sure what it is for.

Removed it, drilled a 3mm hole up the centre. Then a made a little pad using a piece of 3mm brazing rod, which slid inside the screw. The protruding end , I burred over to create a pad. Fit it back together & it worked. No more side play. Cost, nothing.
Steve.

Not so much a repair as a bodge, but if you're happy with it then no-one else needs to be.

[HopperParticipant @hopper]

Posted by Steviegtr on 17/03/2020 14:21:37:

Well that was a quick fix. There is a screw under the casting at the bush. Not a bush but where the shaft runs through the alloy casting. Not sure what it is for.

Removed it, drilled a 3mm hole up the centre. Then a made a little pad using a piece of 3mm brazing rod, which slid inside the screw. The protruding end , I burred over to create a pad. Fit it back together & it worked. No more side play. Cost, nothing.
Steve.

You could have got the same result by burring over the edge of the oval-shaped hole in the casting with your hammer.

[SteviegtrParticipant @steviegtr]

Point taken. It is only a temp fix till I can get the bearings for the job to be done properly. At least it has stopped the rattle. for now.

Steve.

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