Timesaver lapping compound quandary

This is the piston for my uniflow engine which I am remaking, incidentally the full assembly has 23 individual pieces of metal including  the fixings!

My question is that I want to lap the fine machined valve heads of bronze into the piston body made from cast iron . So which do I get, the type for ferrous metals or for yellow metals?  In addition for those who have used itimesaver, which grade do you suggest for this task.   The piston is 1.75” diameter

Edited By Zan on 12/12/2019 17:32:45

Edited By Zan on 12/12/2019 17:34:48

Can't answer your question but the project looks really interesting. is there any information about your engine?

See EIM from June 2015 to 2017

I think I would make OD and ID laps from a softer material and lap those parts separately.

It was difficult enough to get all the bores and 45 degree seats concentric in the first place, I think the only way to lap them is how we used to grind car engine valves, ie one pare against the other. This is why I want to use Timesaver, as it’s non- embedding and it wears down to nothing. Separate laps for these components would be very difficult to make and get a fit. But thanks.

Ah, I'm with you. I thought it was just the diameters you were lapping. It makes sense to lap the valve seats together.

So has nobody used this stuff? Common fellers, give me some advice.....

I have used it but only on a steel shaft into a cast iron bore so far. 1 1/4" diameter, I used the green, no science, was what I had! I need to ease some bronze bushes in the second shaft bearings (bronze bushes, steel shaft) this year and will probably use yellow for that. Seems really good stuff, worked well on the part I did.

Paul.

Hello Zan,

I have used to to lap both the saddle and tailstock to the bed on an old Churchill Cub lathe I am renovating. I know that sounds like a foolish thing to do but the amount of material removed would be hard to measure.

The quality of the fit afterwards was quite remarkable, these components just glide over each other on oiled surfaces

In this case I used the green Timesaver

Regards Brian

Best to ask the folk who make the stuff. There is a contact form on the website **LINK**. Unfortunately the link to the information booklet download doesn't work (for me).

My understanding was that the yellow soft metal version breaks down more quickly to avoid over-lapping softer materials. Which makes sense considering that the basic process is to keep going until the material is "used up" and turns to slurry.

However its reported that the green ferrous metal version has been used to finish lap old style babbit big end, crankshaft et al bearings in situ by simply adding a prescribed quantity to the oil and running the motor off load. There are references suggesting this was a normal process for marine and other big engine rebuilders. Not a bodge shop or field expedient.

Which suggests it probably doesn't really matter so long as you keep an eye on what you are doing.

Clive

The valves on the steam pressure relief valve on my traction engine has 45 degree seats. Valve inserts made from brass and the seats from S/S. I used standard automotive valve grinding paste to lap the valves. It is normally supplied with a coarse paste and a fine paste.

Paul.

.

... That's rather sloppy of them

Fortunately, this seems to work: **LINK**

https://www.newmantools.com/lapping/timesaver_booklet.pdf

MichaelG.

Edited By Michael Gilligan on 06/01/2020 11:54:07

Bryan and Paul K . What grade did you use?

i will contact the sellers, but if people have actually used it on our situation the advice here is much better from the end user thanks for the link great help!  It’s packed with loads of info and it will take some digesting!

Paul L. , I have also used valve grinding compound on the cam operated stainless on bronze inlet valve seats ( there’s no exhaust in a uniflow) . I wasn’t happy with the possibility of embedding the abrasive which does not degrade in the same way as timesaver. In this position it’s actually directly in the cylinder., in any case I have no idea what the actual garage the “fine” and “coarse” is!

Edited By Zan on 06/01/2020 18:59:50

Zan,

Sorry I don't have the original packaging, I would say it was a fairly course grade though, was originally purchased by a mate for a job on a full size traction engine and he kindly passed on a small amount loose to me for my job. I can try to find out this coming weekend and if I do will let you know.

Paul.

Does this help?

Timesaver comound

.

Probably not much, John ... It’s another page on the site that Clive posted, and their link to the information booklet is dead.

MichaelG.

"Do not use Hard Metal Compound (Green Label) on Babbitt, brass, aluminum or bronze. For this work, use our soft metal compound (Yellow Label). Timesaver can be used on any hard metal friction surfaces where accurate fits are required, such as valve seats, machine tool wars, tool room applications, etc. "

..From..

https://ws2coating.com/timesaver-lapping-compounds/green-label-lapping-compounds/

see also..

https://ws2coating.com/timesaver-lapping-compounds/yellow-label-lapping-compounds/

..Hope this helps...

Very useful, DiogenesII

From the same page, I see this:

Timesaver Compounds absolutely do not embed or charge into any metal surfaces. Therefore, do not attempt to make a lead, copper or other soft metal laps to lap hard metals, as is done with emery, ground glass, silicon carbide or other similar charging abrasives. The lapping plate should be at least as hard as the surface to be lapped and harder if possible. The softer of the two metals will get the most wear.

... which is interesting in the context of an inconclusive recent discussion I had with Ian P

https://www.model-engineer.co.uk/forums/postings.asp?th=147064&p=2

Michael.

.

Edit: Link to our discussion added, for the benefit of  the curious.

Edited By Michael Gilligan on 09/01/2020 08:57:53

Zan,

I did say earlier, but I used the Green Timesaver.

Brian