Model Engine Maker

Help! => Tooling Review => Topic started by: Reggleston on July 10, 2018, 08:30:19 PM

Title: Cylinder Honing
Post by: Reggleston on July 10, 2018, 08:30:19 PM
Recently did a cast iron cylinder bore on the mill using a fine feed with a light cut to achieve what I thought was a smooth surface, based on my wife's touch and mfg. engineering experience she concluded it wasn't all that smooth. So I decided to try to improve the cylinder finish using a brake cylinder hone system using my electric drill with generous application of good old brown Sulphur  based cutting oil. Within a short period the bore was greatly improved. As this engine will run on compressed air only I will try a Delrin piston in the improved cylinder finish. First Delrin piston tried in the machined surface ID pretty well abraded the Delrin piston in short order.

Wondering if anyone else has experienced using the ID cylinder hone for any metal/ringed piston or Delrin piston application? Did it improve the ringed piston fit with the honed cylinder or better left without honing?
Title: Re: Cylinder Honing
Post by: Roger B on July 10, 2018, 08:58:45 PM
As I understand different material combinations require different surfaces. I have used diamond paste lapped cylinders with aluminium or cast iron pistons and cast iron rings. These require a fairly open surface for oil retention. O rings or polymer pistons may require a different, much smoother, surface to avoid abrasion. It is also important to ensure all traces of the abrasive are removed. I use an ultrasonic bath with a strong degreaser.
Title: Re: Cylinder Honing
Post by: Ye-Ole Steam Dude on July 10, 2018, 09:19:03 PM
I use a brake cylinder hone tool and believe that the oil retention in the cylinder is much better.

Have a great day,
Title: Re: Cylinder Honing
Post by: Brian Rupnow on July 10, 2018, 11:44:39 PM
I use a 3 stone brake hone at moderate speed, with light oil on a steel cylinder and dry if it is a cast iron cylinder. This is really only used to take out any machining marks, and to leave a light "cross-hatch" for oil retention. This is all that is needed if you are running cast iron rings. If you are running cast iron rings, the fit of the piston into the cylinder is not as critical as when you are running no rings at all or a Viton o-ring on the piston. I have a set of barrel laps that I use with #600 aluminum oxide paste to lap my cylinders that are running a viton o-ring. The lapping procedure removes 95% of machining marks that are left by the 3-stone hone. I run a bit of 2 cycle oil with my naptha fuel, and that seems to keep the viton rings happy. When running no rings at all, I hone and lap the cylinder, then machine the piston to about .0005 to 0.001" oversize and lap the piston into the cylinder---a very finicky and somewhat dangerous procedure.
Title: Re: Cylinder Honing
Post by: Art K on July 11, 2018, 02:58:24 AM
I will echo what Brian said. I have used a barrel lap. The paste is something I got from my dad. Clover brand silicon carbide grade A, whatever that means. It gave a really good finish. Ran it in the lathe a very slow speed worked best.
Title: Re: Cylinder Honing
Post by: Ramon on July 11, 2018, 05:50:41 AM
The two or three stone expanding cylinder hones work well to put a finish inside a well turned bore - providing the bore is not tapered or heavily scored, as the pivoting nature of the stones just follow the contours. If it is then the best way to rectify that is using a lap beforehand then use the hone to produce a cross hatched finish. I believe these 'hones' were actually originally designed as 'glaze busters' on polished brake cylinder bores and as such are not designed to straighten a bore or remove much material. Excessive use can lead to bell mouthing the bore. A well made lap is well worth making to ensure a good bore is achieved

This question has been raised before on several occasions - there's a lengthy post on my findings on such here,1908.0.html (,1908.0.html) which you may find relevant.

Hope that's of use - Tug
Title: Re: Cylinder Honing
Post by: john mills on July 11, 2018, 10:17:41 AM
The  3 stone brake cylinder hone that the stones are pushed out on springs will follow the bore it can produce a cross hatch finish but will not remove much metal in cast iron use kerosene a little oil can be used but much and it won't cut.I worked as an auto machinist we had the type of hone  JO showed in a post recently and would have used that for smaller sizes ,it uses two ruling strips and one stone pushed out by a strip with wedges so can help make the hole round and carrell .for larger bores a ridged hone is used stones pushed out by tapered cones,or other device that holds the stone solid.the cross hatch finish used for cast iron rings and also teflon filled material
rings.I had a job turning rings and seals mostly teflon type materials and that was the finish they liked.     
don't know about delrin.ON cylinder hones i have mainly used kerosene plenty of it to keep the stones clean and cutting. If using a hand drill would not do much if oil was used. only used honing oil on machine hones that would remove metal.  the brake cylinder hone should give a better finish for what you want.
Title: Re: Cylinder Honing
Post by: Jasonb on July 11, 2018, 11:01:39 AM
Another vote for kerosene as it tends to flush out the CI particles, oil just forms a paste and clogs the stones. I use the brake hones on all my ringed engines.
Title: Re: Cylinder Honing
Post by: Jo on July 11, 2018, 12:37:23 PM
Correct me if I am wrong but my understanding I that you want to run a plastic piston without rings in a cast Iron bore. If so then a cylinder hone will leave too rough a finish - while it seems smooth its rough enough to bed down a set of Iron rings. Smelly (my Delapena bench hone) could do it as he can be set to give a very controlled size/finish. The oil in honing is there to both lubricate and to take away the dirt so you need to be constantly putting new stuff on it ideally pumped on, cutting oil is not suitable, you need a thin light oil that does not dry on the job.   

Sounds to me like you are going to be using an aluminium lap and metal polish to get the finish you need. An Aluminium piston might be easier and would take up any remaining roughness on the bore better than plastic.

Make sure you boil the cylinder liner in washing up liquid water to remove the remains of the gritty stuff out of the liner - squirting it with brake cleaner is not good enough  :hellno:

I need to think about the problem of the compressed air cooling the cylinder and piston  :noidea: What is the diameter of the bore?

Title: Re: Cylinder Honing
Post by: Jasonb on July 11, 2018, 01:08:02 PM
Can't see plastic pistons being much different to O rings and they seem to be OK in my Honed bores on air.

Interesting your comment about the temp of the air, I tend to find the compressor makes it warmer and the bigger risk is moisture in the air condensing on the cold cylinder and causing rust. Assuming we are just talking single cylinder engines, compounds can get cold as the air looses pressure.
Title: Re: Cylinder Honing
Post by: nj111 on July 19, 2018, 10:02:30 AM
As stated above the three stone hones will follow existing inaccuracies but they will also bellmouth a bore quite quickly and quite significantly.
Delapena (or Sunnen direct equivalent) benchtop machines as referred to above by Jo are outstanding. Besides producing an excellent finish they will remove ovality and taper very quickly.
It's an interesting exercise to check taper & ovality of a bore from even the best lathes - using a cylinder bore gauge but this must be with 1/10 thou graduated indicator.  I've found my early 70's Dean Smith & Grace lathe is more accurate in this respect than more modern industrial machines. The little Delapena corrects any inaccuracies in a few strokes and is a great addition to the workshop. There are quite a few of these around but the hardest thing is finding one with plenty of tooling. Whatever your chosen method of honing or lapping (Thanks Ramon for your excellent guide on here)  I'd recommend a bore gauge that reads in 1/10ths as a useful addition to monitor what's going on as you hone. Nick
Title: Re: Cylinder Honing
Post by: Ian S C on July 19, 2018, 10:57:42 AM
For the cast iron, and steel cylinders I use on my Stirling Engines, I use wooden laps.... a cylinder to fit the bore, with a split along it's length held open, and adjusted with a wood screw in the end of the split. Used with fine grinding paiste it is time consuming but it works.
Ian S C
Title: Re: Cylinder Honing
Post by: Ramon on July 19, 2018, 01:25:39 PM
Rather topical subject as I've just re-lapped a worn bore in an old ED 2cc Competition special and made a new piston and contra piston for it. An old aluminium lap was re-cycled to do the bore and the piston and contra piston was done using slip stones. Engine fired up right away and proved a big improvement on before. Also have just lapped the cylinders on the 5cc ED Hunters and am about to make the pistons so I'll pop a bit up on that elsewhere when done.

As said before I do have a bench mounted Delapena hone the same as Jo's but have never felt the need to use it. I bought it from Polly Models just after building my first diesels (the 5cc Racers) but having had as much success as one could wish for using the laps as described I have never felt the need to use it. It was stripped down to clean it up and rebuild but has never had the motor fitted back on. I also bought two sets of Delapena external hones off ebay but again, due to the increase in control they give, much prefer to use the type of brass external lap also described previously.

Anyone who has made a two stroke diesel (model aircraft type) will know - the piston to liner seal has to be very good to get the compression required. I can honestly say that so far all my engines have very good compression using these simple and easily made tools which if used carefully provide fits of very high order in quite short time. I'm sure those who've seen them bite me will testify to that  ;D

Contra pistons need a very close tolerance fit to work correctly - the two fitted to these latest pair of diesels having proved the best fitted yet - honed with nothing more than two slip stones held between fingers. I say this purely to show (and this is not meant to be dismissive of others) but, nice as it is to have the right kit, it isn't always necessary in order to attain a good result.

Lubricant is always paraffin (kerosene) with a drop of light oil added (about 95:5)

Hope that helps a little more - back with some info on the new pistons later

Title: Re: Cylinder Honing
Post by: Florian Eberhard on September 29, 2018, 11:39:18 PM
Hi everyone.

What I heard is that if you use diamond lapping compound on cast iron, you will never fully get those particles out again
Instead, you should use carborundum compound as this breaks into smaller pieces during the lapping process and also rather gets dull than diamond.

If its true? I can't say, I didn't try it. But I always made one or two final passes with oil only after lapping with diamond compound. The Idea was that this should loosen up the grains that are stuck in the workpiece and either get them out or embed them in the lap instead of the workpiece. At least I never had any problems after doing so. So I guess it works.

One very important point: Your lap should be softer than your workpiece so the grains of the compound embed in the lap rather than the workpiece.

Cheers Florian
Title: Re: Cylinder Honing
Post by: Roger B on September 30, 2018, 07:54:52 AM
I had heard the same regarding diamond lapping paste with the additional comment that it can be cleaned in an ultrasonic bath, which is what I do.
Title: Re: Cylinder Honing
Post by: Mcgyver on October 17, 2018, 05:56:52 PM
I had heard the same regarding diamond lapping paste with the additional comment that it can be cleaned in an ultrasonic bath, which is what I do.

I think I'll disagree, on principles.  What embeds an abrasive in a material is it being pressed into it, by a harder material.  If I'm making a cast iron lap, and I press the material into the CI using the hardened race of a bearing, the abrasive will embed in the cast iron.  otoh, if I'm using a copper on a cast iron cylinder, it will not embed. 

I say on principle as I've done a fair bit of lapping, but not specifically cast iron with diamond.  I also doubt ultrasound will un-embed the abrasive, but I don't specifically know - it might be worth an experiment to see.  The amazing thing with a an embedded lap is that it actually becomes a cutting tool and parent material is never touched.

Usually laps are a cutting tool where abrasive is embedded, however for cylindrical work, loose abrasive that works the work and the lap is common.  It works because if you are careful, the lap and the work will end up a perfect cylinder.

Honing is done with stones.  the spring loaded style might remove grunge or polish, but do nothing to fix the geometry.  A Sunnen hone otoh will produce perfectly straight and round bores.  Hand held expanding laps can come close to the the same results but needs a bit more concentration on touch.   There a great low cost home shop solution to ge a finely finish bore that is straight and round.

a few photos for kicks of internal expanding laps I've made




Title: Re: Cylinder Honing
Post by: Mosey on October 18, 2018, 02:13:44 PM