Timesaver - which grades?

I need to lap a (new) steel shaft into a cast iron bearing, having re-bored the bearing and consigned the old (badly scored) shaft to my scrap box. I intend to use green 'Timesaver' lapping compound to get the final fit but suspect (e.g. hope) that I don't need all four grades to do the job. I was thinking 'medium' and 'fine' might be sufficient - assuming I start with reasonably well machined surfaces.

Any experience/advice please?

Regards,

IanT

Does one usually lap cast iron? I would have thought there may be some difficulty completely removing the lapping paste

Roy

ps  I'm quite happy to be shot down on this

Edited By roy entwistle on 10/07/2019 14:26:22

Time saver state any residue left will not be detrimental, I have used it for lapping steel liners but not with cast iron, I found it a very good product for the job, I have yellow and green grades.

Emgee

I've lapped in bronze half bearings and only used the fine (yellow) grade and it quickly smoothed out the machining marks on a 3/4" diameter bearing, that said I think you will be ok with medium and fine for your application, you may be surprised at the rate of metal removal.

I used Medium Green on steel gears on my 3" traction engine, it worked a treat with only one application, made them smooth and much quieter.

Time saver is not like conventional lapping compounds, it does not embed into metals so won't embed into either of the components, it disintegrates and can then be washed/cleaned off.

Nigel

Hi, perfect timing for this question. I was going to post the exact same thing!

I am currently building a Quorn and having bored out the LH and RH casting, the front bar calls for a "sliding fit" between these cast iron holes and the front steel bars. I did some research and it does seem that "Timesaver" seemed to be the right stuff.

I need to take off the last thou (ish) to get this desired fit.

It looks expensive though but I am told little goes a long way. It does seem that the compound does break down completely. Do not under any circumstances use emery or grinding paste as this will embed into the cast iron and the cast iron bore now becomes an external lap!

I also considered one of those 3 legged brake cylinder hone.

Going to try and use medium and fine as suggested. My local stockist has it in kits - comes in 4 grade, coarse medium, fine and extra fine.

Regards

Derek

OK thanks Nigel - I'll save a few bob and just order the two green grades. I did briefly think about buying the full kit of eight types/grades but the savings aren't that great..

I'll probably end up buying some yellow grades too eventually as I can think of some uses for them - but somehow smaller purchases over several years don't seem quite such a commitment as a single large one - especially when experience says I may not end up needing/using them all.

Regards,

IanT

There is/was a small 'sample or trial' kit of eight little tubs (2" dia. x 2" high) that I bought a few years ago.

Norm

That's how mine were bought, at that time (1990's) it was supplied from Scotland by post.

Emgee

My experience is much depends on the start point. If there are deep scratches then it's quicker to start coarse and step methodically down through all the grades. Conversely, when the lathe delivers a good surface from the get go, it's not smart to make extra work by spoiling it with a coarse grit!

The goal is to never use a fine grit to remove a significant amount of metal. As it takes forever, fine grades are best kept for finishing only.

Dave

Good point, when lapping I think it's beneficial aim for a smooth machined finish from which to start lapping.

Nigel

Edited By tractionengine42 on 11/07/2019 11:07:45

Are you slitting your Quorn bores or installing split cotters?

If I were doing it again I would definitely do the latter.

Hi, I am using the GHT cotter method. It worked fine on the dividing head, and UPT.

For the front bar of the Quorn, the fit between front bar and bore has to be a little more.....shall we say "slidey" without shake but not "tightey"