Bore honing

[Andy Bennett]

Back to basics
I would asppreciate some advice regarding honing a freshly machined bore.
I have access to a Flex hone of the right diameter to just squeeze in (the type that looks like a loo brush with carbon balls on the ends).
A look at YouTube seems to suggest 5 or 6 quick passes through the bore with a WD40 type lubricant.

Before I do anything irreversible I would appreciate some thoughts and opinions from the learned, in that:

5 or 6 swift passes on a medium electric screwdriver speed of a second or 2 per pass, or more?
should I reverse the 5-6 passes to create a diamond scoring?

Assume I am just looking for a result of light just visible scratches to hold a little oil rather than scoring of the bore.

thanks
Andy

[Colin Reed]

HI Andy,
How much was left for honing or was it bored to the finished size.
Those types of hones are only for Deglazing
you need a parallel hone which has adjustable stones

Colin
NZ

[Stuart Giles]

I use about 2 seconds down and 2 seconds up doing bores with a Flex Hone. This is usually with a 240 grit hone (blue blob on the tip). It would be a smidge quicker on each pass with a 180 grit hone (red blob on the hone's tip) I've never bothered to try and get a diamond pattern, just a uniform finish. Any light lubricant should work OK - I use ISO 32 hydraulic oil because I have gallons of it here.

[Andy Bennett]

Thanks both
Colin: I am working the principle that the bore must be machined to final size, with honing being a surface finish process rather than attempting material removal and yes I have also seen the flex hone used for deglazing but it does seem widely used for honing too as an easy to self centralise DIY tool.
Stuart: I am not sure what the grit size is but appreciate that just affects the rate/speed of the process. I have now found a few pics of 'after' so am happier now with what i need to aim for and why (appreciating it is more about bedding in the rings that oil retention).
This link seems to show sensible pictures:
https://mechanics.stackexchange.com/ques...thereafter
Thanks again
Andy

[Bob Culver]

It is odd that the machinist did not finish. Did you bore yourself? 

The parallel stone spring loaded deglazing hones can be acquired cheap 2nd hand as little use for nowdays. These not primarily intended for finishing after rebore because of rapid stone wear, but the amateur is unlikley to ever wear out. Books emphasise the cross hatch. I rebored a set of liners in lathe and finished with spring deglazing hone. All turning marks must go and very slight size adjustment can be made. Books reckon typically .001 to .0015 dia to clean up.


The rigid hones which precision correct and maintain dimensiosns are less easy to come by, and require more skill. (Although can do the whole rebore with)

The attraction of the ball hones is that do not ride on any wear steps, and less easily broken. Doubt if intended to finish after rebore.

Great emphasis is placed on cleaning of bore with detergent until a white paper unmarked.

For spring loaded parallel stones 280 was the standard grit, finer for modernes with modern OE rings..

[Andy Bennett]

Thanks Bob
I was assuming I would have a do the honing after machining but perhaps not. I will check thanks for giving me the thought.
Andy

[Colin Reed]

HI Andy,
Normally around .001  is left to the hone a lot depends on how fine the boring marks are because they must be removed,
the reason for the use of parallel adjusting hones is to keep the bore parallel  which is not possible with Deglazing hones.
I have done a lot of Rebores and there is no way around doing the job properly if you are going to the trouble of boring and you want the best fit for rings and pistons

Cheers Colin
NZ

[Steve Jones]

I've never had a re-bore that then required finishing with a hone. But there again, I don't know what your instruction to the machining man was. I simply tell them the size of the bore I want and that's it. These days with modern pistons that's normally an exact size +/- 0.000.

Steve

[Charles P]

I've never had a re-bore that then required finishing with a hone. But there again, I don't know what your instruction to the machining man was. I simply tell them the size of the bore I want and that's it. These days with modern pistons that's normally an exact size +/- 0.000.

Steve

I would expect that your rebore company actually bore and hone the block. It's normal practice. 
I too give them the dimension needed and instruct them to bore & hone it dead on. I would never expect to hone it myself. The control of finish that you can get with a Delapena or Sunnen type hone is very different from a "glaze buster" ball hone or one of those three legged expanding jobs.

Charles

[Stuart Giles]

The key issue with a lot of rebore work is just what the bore measures when you slide a Mercer guage down from top to bottom. Bores with pretty looking cross hatch honing might not actually look so great then.

A while ago, I bought a "newly rebored" block from a "well known auction site" it had 3 thou' taper top to bottom on the worst cylinder with a 4 thou' variance between the bore diameter from the smallest cylinder to the largest cylinder.

I wouldn't want any company to try to pull those bores back to an approximation of parallel using a rigid Delapena style hone, I'd want it bored properly in the first place. Then the hone is simply knocking the peaks off the bored surface.

BTW, I used my usual (not cheap) company to rebore this particular block to +80, when it came back there was absolutely no variance shown from the Mercer guage top to bottom - sometimes you do get what you pay for