Lathe crash!

[not done it yetParticipant @notdoneityet]

Posted by ChrisB on 23/12/2018 09:19:10:

……

Machining one seems out of question.

A simple silver soldering job?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by not done it yet on 23/12/2018 09:49:25:

A simple silver soldering job?

.

That would probably depend upon the nature of the unidentified 'quite brittle' material.

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

I've wondered about replacing these, not because I've ever broken one, but because I often drop stuff on the floor and it disappears for 10 years.

If not available as a spare, NDIY may have meant silver solder as a way of making one from scratch:

1. Turn and bore the round part of the bush to size (easy)
2. Broach an outer groove. (bit fiddly, but can be done in a lathe)

Then make the rectangular key. Easy on a milling machine, a craftsman could file one by hand, and it could also be made by facing on the lathe. The main problem on the lathe is holding a small part.

Finish by silver soldering the key into the round part. (This might not be mechanically necessary but I would lose a loose key in seconds.)  Loctite might do.

Dave

 

Edited By SillyOldDuffer on 23/12/2018 10:37:34

[not done it yetParticipant @notdoneityet]

Yep, he said making or purchasing, not repairing. silver soldered because the slot might not be deep enough, but, as you say, loctite might do.

[JasonBModerator @jasonb]

No real problem to machine from solid if you have a rotary table.

No problem holding it to cut a groove if you cut teh groove while it is on the end of a big lump of bar, just start the parting cut to give the tool some runout space, plane the groove and then part off

What can't be seen in the photo is that there is not going to be much metal left when the slot is cut so in the event of a jam the solder may fail and you will split the round part from one of the internal corners down to the bore.

Should be an extra one in the toolbox anyway, there was with mine

[OuBallieParticipant @ouballie]

I use aluminium modelling tube as shear pins, following my 'episode' of Saddle meets Headstock whilst under power.

So far so good as none have sheared.

Geoff – Fingers, toes et al crossed as I do not want to go through that again.

[ChrisBParticipant @chrisb35596]

Thanks for the response, I dont have brazing equipment, but could try giving it a spot with the tig. I'll probably destroy it in the process as I don't know what the material is (could be cast iron?)

I have a spare one Jason, so for now I'm safe, but the whole set up is bugging me – the sleeve is a very tight fit, and I have to be extremely careful tapping it into the gears as the material has a tendency to crumble (if you see the end of the key in the photo you'll see what I mean). Also, the shafts on which the gears sit are not exactly the same length, so one is fine, the other is slightly shorter, so when I tighten it up the gear set will bind – fiddly to say the least!

So I'm thinking how I could make something simpler to live with. I a rotary table is on the top of my wish list but I don't have one yet so I'll either wait till I get one or thing of something else…

[Michael GilliganParticipant @michaelgilligan61133]

Posted by SillyOldDuffer on 23/12/2018 10:35:29:

… NDIY may have meant silver solder as a way of making one from scratch:

.

So it would appear, in retrospect.

MichaelG.

[not done it yetParticipant @notdoneityet]

I usually set my long travel trip to just clear the chuck. Have to remember to reset it if working a bit close to the chuck, but the option was available on my hobby lathe from about sixty years ago.

So much for progress with modern lathes, if they don’t have these simple trips which have been available for decades!

[JasonBModerator @jasonb]

The other problem you may find with soldering will be when you come to harden the fabricated part. Don't think I would want to leave them soft as they are spinning all the time at quite high speeds.

[ChrisBParticipant @chrisb35596]

Let's see if this might work. If I had to eliminate the keyed bush completely and instead put a bronze bush on each gear. Then to stick a pair together I would use two dowel pins (push fit) I reasoned that two 3mm pins will have the same shear surface area as a 2x5mm key (that's what the keyed bush has) so they should in theory hold.

I tried some sketching – the largest and smallest gears I have is 80T and 20T

[not done it yetParticipant @notdoneityet]

My 14DP 20 tooth gear was driven, or drove, by one pin of about that size. All the drive train gears were fitted with one pin – either 3/32nd or 1/8th. Little more space, but could be 3/16th, possibly – but there was not a lot of space between hole and root of teeth.

[Neil WyattModerator @neilwyatt]

Or file the underside of the key to fit the circumference before silver soldering to avoid making those stress concentrating internal corners.

Neil

[Will NobleParticipant @willnoble66529]

Posted by ChrisB on 23/12/2018 14:57:17:

……………….as I don't know what the material is (could be cast iron?)

………………..

Sintered bronze, by any chance?

If so – and I remember correctly – it can be cast/press-formed into shapes …… and also has a shear strength of something approaching cast cheese.

Will

[ChrisBParticipant @chrisb35596]

There's not much space to machine a slot for a key on the bush, Neil. The bush is 14mm od and 10mm id so with 2mm wall thickness to play with there's not much one can do…I think.

Will, it's silverish grey in colour so I'd think is something ferrous, will touch it with a grinder and see what spark (if any) it will give off, should give an indication.

I'm tempted by the pin approach, – just in case I come to need them, any one knows where I can get mod 1.5 gears at reasonable prices? Warco does not list them on their web shop but I'll ask.

[JasonBModerator @jasonb]

Beltingonline are reasonable, I've used their gears a couple of times on engines.

[Will NobleParticipant @willnoble66529]

Posted by ChrisB on 23/12/2018 19:06:32:

There's not much space to machine a slot for a key on the bush, Neil. The bush is 14mm od and 10mm id so with 2mm wall thickness to play with there's not much one can do…I think.

Will, it's silverish grey in colour so I'd think is something ferrous, will touch it with a grinder and see what spark (if any) it will give off, should give an indication.

I'm tempted by the pin approach, – just in case I come to need them, any one knows where I can get mod 1.5 gears at reasonable prices? Warco does not list them on their web shop but I'll ask.

Ah! Probably Oilite? – and unlikely to silver solder. If it does, don't think it will give up its oil, or act as a bearing surface very well afterwards.

Here's a brief description I found:

'Oilite bearings are manufactured in three standard materials. Standard Oilite oil retaining tin bronze is the generally specified material. It gives good balance between strength, wear resistance, conformability and durability in operation. Ideal in a wide variety of applications where self-lubricating properties are required over a long period of time.

Super Oilite® is an iron copper material suited to high static loads and slow oscillatory motion.

Iron Oilite® are 100% iron oil-retaining bearings which provide an ideal solution in high stress low revolution applications.'

The shear pins sound a better bet.

Will

[SillyOldDufferModerator @sillyoldduffer]

I can't look at mine until after xmas but I think they could be non-ferrous, they are dull grey, not dissimilar to Mazak. Try a magnet first.

Pretty sure they're not Oilite. The bushes freewheel on polished steel axles and are flooded with oil via ball-bearing feed points. Meant to be refreshed frequently.

Have you tried sourcing spares? Easiest solution by far. Pinning would work but will be a hassle to make and use – lots of gear combinations.

Dave

[ChrisBParticipant @chrisb35596]

It is some sort of steel as it's magnetic, and not slightly magnetic, it's like a high carbon steel – retains some of the magnetism. I've sent an email to Warco asking for spares, I'll see what they have.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by ChrisB on 23/12/2018 09:19:10:

.

Dave … Looking at the photo that Chris posted, I suspect you may be right about Mazak

The key portion [vertical face as pictured] appears to have striations typical of an extrusion, but the fracture doesn't look like aluminium alloy … I know very little about zinc alloy extrusion, but it is done.

MichaelG.

.

Ooops !! … Just seen ChrisB's latest post. 

Edited By Michael Gilligan on 23/12/2018 22:09:19

[Howard LewisParticipant @howardlewis46836]

A sinter?

Howard

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Howard Lewis on 23/12/2018 22:44:22:

A sinter?

.

Quite possibly something like this: **LINK**

https://www.manufacturingguide.com/en/continuous-metal-powder-extrusion

… if the quantity justifies it.

MichaelG.

[Chris TriceParticipant @christrice43267]

You could silver solder the key in place, then bore it out.

[JasonBModerator @jasonb]

Chris, how would you subsequently harden the soldered part?

Suppose it could be wire sparked, I'll did one of mine out later and have a look and tickle it with a file.

[Will NobleParticipant @willnoble66529]

Almost academic but my money's still on an 'Oilite'. It's a good bearing material for that situation, even if not very strong. Look at the texture and if it's grainy, most likely one of the Oilites, A N Other's version of it, or a sintered product. Many of them are iron-based.

I'd be surprised at MAZAK. It's not magnetic and has a very fine, silvery appearance if scraped with a sharp blade, like a highly polished aluminium alloy – and very soft. Old carburettors were made from it and had an awful durability on wearing surfaces.

Will

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