Finishing piston o.d. with toolpost grinder

[L98fiero]

I'm glad you wrote this, as I have a hard time understanding the nomenclature of the inserts, even tho' I have studied them, examined them and used them, it is still very difficult for me to understand it.

If you do a search for 'carbide insert designation chart' there are quite a few examples, the problem arises though when you get to chipbreaker designations as each company seems to have their own descriptor. There are positive rake inserts for steel and just to add confusion to it all, you can download an ebook for Korloy at Catalogue | Download | KORLOY it will work for all the AliExpress 'Korloy' inserts. Starting at page 78 there is a list of different chipbreakers, with that in mind, that works for Korloy inserts but not for any other companies inserts.

 

[Brian Rupnow]

Kiwi2 thank you. That is a great video and an interesting method to hold the sanding paper.---Brian

 

[Bentwings]

I'm glad you wrote this, as I have a hard time understanding the nomenclature of the inserts, even tho' I have studied them, examined them and used them, it is still very difficult for me to understand it.

I can only barely remember some model airplane two strokes cold the piston would stick lightly at Tscheda. Then once running it loosened up these had ABC amuminum brass chrome liners very carefully honed. There was a local builder that had some really strong engines in the day these ran heavy loads of nitromethane using bakers castor oil for oil
Mix. Very messy clean up I had commercial ABC engines but I had ready access to “pure” nitro alcohol and castor oil so ran my models on “ kill” as we say in race car world. More than a few blew cylinders off or broke rods
Buron

 

[Bentwings]

If you do a search for 'carbide insert designation chart' there are quite a few examples, the problem arises though when you get to chipbreaker designations as each company seems to have their own descriptor. There are positive rake inserts for steel and just to add confusion to it all, you can download an ebook for Korloy at Catalogue | Download | KORLOY it will work for all the AliExpress 'Korloy' inserts. Starting at page 78 there is a list of different chipbreakers, with that in mind, that works for Korloy inserts but not for any other companies inserts.

I too have looked at tool post grinder but more as a drill so I could convert the late to a rotary indexer as needed, even though we have a rotary table and indexer . There are time when it would save a separate set up on the mill. Our little lathe simply does not have the machine accuracy to operate as a grinder. I’ve used so called small industrial grinder but so precision even the rooms temp was controlled as far as finishing we can produce about any finish needed for molding purpose required. Size….. well what ever the late and mill can produce. It’s hard enough just to get nice finishes let alone precise sizes . Early in top fuel cares pistons were of weldable aluminum so I often cut the burned area out ans TIG welded them up finishing them on pure old craftsman hobby lathe that was old 50 years ago. If I could get another couple runs out of repaired pistons they would more than pay for new ones. Pistons now days are of not recommended weld materials buy them, use them toss in recycle bin $200-300 each sometimes more. 8 per run add rods every couple runs call recycler every other week. Get enough cash back for lunch. Don’t get into fuel racing it’s easy to become a millionaire if you start As a billionaire. I started poor and remained poor.
byronLOL

 

[Brian Rupnow]

I asked this question because I want to bring a cast iron piston down to just a couple of tenths under the bore of a cylinder. I created a split external lap to use as well. So far, I haven't used either. I'm gathering information, thank you to those who gave an answer.---Brian

 

[DKGrimm]

I'm always grateful for the discussions on these forums. I've learned a bunch reading this string. Just a note about an alternative method for fitting the piston: when I built my Titan 60 many years ago, I turned the piston as close to finished size as I could, then lapped the steel sleeve to fit the piston. As I recall, that was the recommended method in the Home Shop Machinist construction article. With the tight fit as shown in the video I lapped the piston lightly in the cylinder using a slurry of thin oil with some jeweler's rouge. The engine started by hand and ran beautifully. It has something like 5 hours of running, and the piston seal has remained very good.

 

[Brian Rupnow]

I've done it like that, and have a marine engine running very well with no rings at all.

 

[chevell69]

I have a hard time holding +/- 0.001 accuracy when turning. I thought maybe if I used the grinder I could sneak up on my final dimension 0.001" at a time. That plus the fact that the surface finish on a piston is rather important.

If you got a bench grinder might still help you

 

[stewart drummond]

engine shops ( i mean car engine machining ) would laugh at this , they machine/hone bores to fit pistons , not pistons to fit bores . brake cylinder hone in a tiny cast iron cylinder like this would take hardly a minute . p.s.piston material to increase compression ? these things dont work like that

 

[Noel Gordon]

Mmmm i am finding it to be hard to understand that you believe that you are better to grind to size so why can't you turn to size.

 

[awake]

Mmmm i am finding it to be hard to understand that you believe that you are better to grind to size so why can't you turn to size.

Grinding tends to be done one or two ten-thousandths of an inch at a time. It is hard to take off that little of an amount of material when turning, no matter how sharp your tools are!