hone (brass barrel )

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Tim1974

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ok need help as i need to hone around 9 and some spare 1 inch bores about 2 inch long , ok problam is im in australia and cant find a lap for sale hear ?? any help and advice really wanted like pase and all the gritty stuff
lol
thanks in advance
 

WOB

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When I was faced with your problem, I bought a Sunnen portable hone (P-190) since I knew lapping was going to take a very long time. The honing process went smoothly and quickly once I learned how to use the hone. The hone was expensive, but I sold it on eBay afterwards and got about 40% of my money back.

The cheap alternative is making laps from brass or aluminum. It works but is very slow. This article http://adriansmodelaeroengines.com/catalog/main.php?cat_id=178 gives a good description and instructions for making the lap. This article is written around fitting a piston to a cylinder for a model diesel, but you can ignore all that material and just use the lap construction info. Abrasive paste in various grits is usually available on the internet. If your pistons are ringed, don't make the bore too smooth or the rings will take forever to seat. I would probably start with 220 grit and finish with 320 grit and try to leave a crosshatch pattern for ring seating. The trick with lapping is to get a nice uniform bore dia. from end to end. Another challenge is measuring the bores accurately. Telescoping gages are rather crude and technique sensitive. A far better way is to buy a used bore gage ( either plunger or split-ball style) with dial indicator on eBay or similar. I tend to buy used name brand equipment like Mitutoyo or Starrett rather than new cheap Chinese stuff, but it depends on what is around when I need it.

WOB
 

werowance

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so im guessing a brake cylinder hone is not what you need?
 

SmithDoor

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I have Use a brake hone . It works the only drawback is it slow.

I would use a reamer first then use the brake hone.

The other is very slow feed on the lathe.
FYI lock the cross slide and set compound at 6° (for older lathes use 3°) The compound dial each mark will be 0.0001"

Dave


so im guessing a brake cylinder hone is not what you need?
 

Hopper

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Confused between honing and lapping here. Which do you want to do? And brass, is that the material of the job or the proposed lap?
What is the application of the 9 bores to be lapped/honed? Radial engine? Material- steel or cast iron? If so, brake hone should do the job.
Or is it something else?
The devil is in the details.
 

Tim1974

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Hi there hopper..
Ok the cylinders are 1045 mild steel and yes you got it I’m doing a radial .
The cylinder bore is 1.000 inch finished so was thinking bore to .998 and then hone ???
Also thay will bee about 1.9 inch long any help really appreciated
 

WOB

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If the rough cylinder bore can be machined straight, constant dia. and reasonably smoothly finished( by whatever means) A brake cylinder hone, rigid hone( Sunnen), brass lap, or Flex-hone(http://www.brushresearch.com/product-line.php?line=1) all will do to finish the bore as needed.

The problem with flexible tools like a brake cylinder hone or a Flex-hone is that basic cylinder bore dia. is not readily controlled. This is where a rigid tool like a Sunnen hone or a lap is needed. For a one-off case like a single cylinder engine, it doesn't matter too much since the time and trouble are minimal to match the piston and rings to the cylinder dia. as it finishes up. If you are making nine of them, it is mandatory IMHO to have all the cylinders the same dia. so all pistons and rings can be made the same. Assuming 3 rings per piston, that means you need 27 rings. You really want them all the same dia. so the same tooling can be used to make all 27.

So, we need a method to make nine essentially identical cylinders. As outlined above there are a few different ways to do that. I chose a rigid hone because I wanted good results in a reasonable time frame plus I wanted to learn something about Sunnen hones. I also knew that a Sunnen hone would sell on ebay fairly easily and I had no plans to build more multi-cylinder engines.

My nine cylinders finished up with about 3 tenths variation between cylinder diameters and very consistent bore dia. over the full length. Looking back, I probably could have done it with ordinary boring (lathe) and Flex-honing for finish. However, I'm sure my scrap pile would have been much larger

WOB
 

SmithDoor

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If I can Chuck in lathe I use a dowel (broom stick) and sanding cloth/paper. I use 320 grit but can buy 600 grit. You can find 3,000 grit but this is use soft metals.
https://www.mcmaster.com/4687a234-4687A444


You can use a dermal with drum sander. Also a hand drill and flapper sander will works good too.

I have a hone on full size engine that look and work just brake hone.
The upside or down side to a brake hone it removes metal very slowly.
The only time I use a brake hone is when I can not Chuck in lathe.

Dave

O and sorry the pistons will have rings !
 
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Tim1974

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I think I will try a 3 leg brake hone and have a play first as thay are very cheep and can try on a bit of scrap before I bore the cylinders to work out if 1 or 2 thow under is needed or .0005 ? Will see , thank you all for your help this really is a very good site
 

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