To silver solder or not to silver solder HELP

[David George 1Participant @davidgeorge1]

Help With a quandary.

I have a bronze casting which comes from a 1918 ish Early M Type Drummond lathe which needs replacing as the internal thread was totally shot. I have made replacement half nuts for later models which are screw cut easier as the leadscrew on the later models  are 3/4″ outside diameter where as the earlier were only 5/8″ diameter and as a closed solid nut not so easy to screw cut working down a 1/2″ diameter bore in a solid piece of Phosphor bronze is a bit time consuming but I managed to cut a reasonable thread in a bush to insert into the bronze casting which I have bored out on the mill to take the replacement bush.

I have bought some high strength silver solder and flux from Cup Alloys which they recommended and now ready to solder the bush in place with a slight clearance for the solder to flow I am in a quandary will heating the parts to solder, distort the thread or should I fix it in place with a Loctite product!

 

Just wondered if anyone who silver solders parts together may have more knowledge which may give me more information.

David George

 

 

 

 

 

 

[Andrew CrowParticipant @andrewcrow91475]

Hello David, I recently silver soldered a fabricated top slide nut for a Myford S7 it came out OK although nowhere near the size of the nut you are soldering, I also had the advantage of a tap to help with the clean up.

If you do solder it may pay to file some small grooves down the bore to help the solder flow through.

The loctite route would probably work, certainly no clean up needed, you could always fit a cross pin on the joint afterwards to give a bit more security or maybe a grubscrew vertically down the joint line.

Andy

[RobCoxParticipant @robcox]

Just use loctite, no risk of distortion and can be disassembled if needed.

I did a similar repair on my Elliott model 00 mill y axis nut several years ago, boring out the cast iron nut and fitting a bronze sleeve. I fixed the sleeve in place with loctite 603. It’s given zero problems in about 8 years of service.

Rob

[Ian PParticipant @ianp]

I suggest soft solder would be the most appropriate, although I’m sure the right grade of Loctite would be just as good.

One big advantage is that either method ‘undoable’ so in a hundred years time a future owner of the lathe could replace the bush you have made (Best leave some notes written in indelible ink on suitable paper).

Ian P

[Kiwi BlokeParticipant @kiwibloke62605]

+1 for soft solder, but make sure it’s lead/tin solder, not the horrible ‘lead-free’ stuff that doesn’t flow anywhere as readily as the ‘proper’ stuff. No worries about strength: it’s loaded in shear, and the joint area is considerable. I don’t think there would be any need to silver solder.

[David George 1Participant @davidgeorge1]

Thanks Foe all the Replies and I have decided to Locktite it as is less likly to cause a distortion and should hold with the area in contact.

 

Thanks

 

David

[Dave HalfordParticipant @davehalford22513]

I replaced my badly worn saddle 1/2″ lead screw thread tennoned into the original power section with 603. The joint area is quite small but it’s holding.

[Charles LamontParticipant @charleslamont71117]

Loctite is what I would do. If you have not already done it, beware that you will have very little adjustment time as the copper content catalyzes the Loctite cure.

[JasonBModerator @jasonb]

As it is made I would go with Loctite.

Had you asked earlier I would have said rough out the bore and silver solder in the sleeve, then bore and screwcut. I do similar when fabricating things like engine cylinders leaving the bore and flange thicknesses a bit over so they can be finish machined after soldering.

Even if planing to Loctite from the start I may have left a small coller on a longer sleeve to take the thrust as we generally feed in one dircetion for most of the time.

[Martin Johnson 1Participant @martinjohnson1]

Don’t under estimate soft solder.

Loctite quote a shear strength of 2300 psi on aluminium (the only non ferrous metal they quote) for 680 grade.

Engineer’s edge gives a minimum of 2900 psi for tin solders on steel.  My guess is that would increase on brass or bronze substrate.

Martin

[old martParticipant @oldmart]

Loctite would be effective and very easy because your joint surface is very large. I soft soldered a part thread insert into the leadscrew nut for the Smart & Brown model A lathe and have had no bother since. I tinned both parts before letting them fit together by gravity upon final heating.

 

 

[bernard towersParticipant @bernardtowers37738]

Same for the X way nut on my mill and that was eons ago

[Michael GilliganParticipant @michaelgilligan61133]

Wow … this took some finding:

Loctite 680 Technical DataSheet

https://webaps.ellsworth.com/edl/Actions/GetLibraryFile.aspx?document=13474&language=en

… or am I just having a bad day ?

MichaelG.

[JasonBModerator @jasonb]

Bad bay I think.

First result was to the pdf with Google by entering henkle 680 data sheet

Even just entering Loctite 680 the first result was the henkle page with a downloadTDS sheet at the top

[Michael GilliganParticipant @michaelgilligan61133]

Oh well … an early night for me, I think

MichaelG.

[Nigel Graham 2Participant @nigelgraham2]

I performed a similar repair on the cross-slide nut on my Harrison L5 lathe, using soft solder without problems.

However, I did give the insert a flange to take most of the thrust from the solder.

(If I use a rear tool-post for parting-off the solder will take all the stress, but the joint area is large and the axial load from a narrow parting-tool modest.)

[bernard towersParticipant @bernardtowers37738]

funny that brass coppers and bronzes are not mentioned or have I missed them?

[bernard towers]

On bernard towers Said:

funny that brass coppers and bronzes are not mentioned or have I missed them?

Don’t take my word for it, Bernard … but if memory serves me well, the ‘Accelerators’  from Loctite are mostly based on Copper Sulphate.

ergo … the resin cures to full strength onBrass, etc. … it just happens quicker !

.

See Charles Lamont’s post, above.

MichaelG.

 

 

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