Holding .0005 bore tolerance over 12"

[BWS JAZE]

Hey guys, long time listener....firstish time caller.

I have a part in the shop which is ST52.3 tubing which is "suitable to hone" and has an advertised -.006 to 0+ tolerance. This part needs to hold .0005 (five tenths) down the 1.75" bore which is 12". The customer states, 10.75" would work for them as well, if the 12" is not possible. The surface finish must also be single Ra but the customer and I will be trying out flex hones to up the finish in the bore. The flex hone people say this will not be an issue with dimensional tolerance as long as we leave .0001 on the walls to "hone"

I have good, accurate lathes. I imagine a worst case scenario would be dampened boring bar like Sandvik and tons of spring passes but have never done anything so long so it's all theory. You guys have any tricks up your sleeves for jobs like this? I'm a little worried that I might not be able to deliver. Thanks for helping us out here!

 

[SeymourDumore]

With the risk of sounding like a dick ....

1st problem: Boring 12" worth to a total of .0005 on a tube .... I wouldn't even try.
There is a very good reason companies like Sunnen exist. Your part is one of those reasons.

2nd problem: singe digit Ra finish .... Me thinks the flexhone people blowing smoke up your butt.

Seriously, find a shop specialized in honing and ask them what they need from you to get this done.

 

[Conrad Hoffman]

That's a job for a Sunnen if I ever saw one. That said, it will be expensive to tool up if the necessary arbor and stones aren't already on hand.

 

[Orange Vise]

What's the wall thickness of the tube?

 

[BWS JAZE]

What's the wall thickness of the tube?

The thickness while being bored is .25" so an OD of 2.25in. It will then be turned to 2.05" OD in what I planned to be the 2nd operation.

This one seems like a tough job, although I don't think it is impossible. The 1400 pc/per year they need might be lol.

 

[MaxPrairie]

With only 6 thou max on the ID, yes straight to hone. Boring will likely finish like hell with that material. But it did remind me of an older Keith Fenner video linked below. Would try this process before buying an expensive boring bar.

 

[BWS JAZE]

With the risk of sounding like a dick ....

1st problem: Boring 12" worth to a total of .0005 on a tube .... I wouldn't even try.
There is a very good reason companies like Sunnen exist. Your part is one of those reasons.

2nd problem: singe digit Ra finish .... Me thinks the flexhone people blowing smoke up your butt.

Seriously, find a shop specialized in honing and ask them what they need from you to get this done.

I like some tough love, gives more perspective to what you're up against.

I know of Sunnen for sure, I just figured SOMEONE out there is doing some type of this work.
Now, the flex-hone not upping the finish without going over .0001 I will admit seems tough but I don't see why it couldn't if my speeds and feeds are right. Will take a while to nail no doubt but an 800 grit abrasive with coolant at 900 rpm doesn't seem crazy although I'm just as skeptical as you are.

 

[BWS JAZE]

With only 6 thou max on the ID, yes straight to hone. Boring will likely finish like hell with that material. But it did remind me of an older Keith Fenner video linked below. Would try this process before buying an expensive boring bar.

This is pure genius. Always amazed at what a man on a mission can think of!

Going to look for someone with a honing shop before I lose my marbles over this job.

 

[BWS JAZE]

Does anyone have a suggestion when looking for a honing shop? I need some decent volume and the ones I've contacted seem to work in low volume.

 

[Garwood]

Scot Industries

 

[MaxPrairie]

This is pure genius. Always amazed at what a man on a mission can think of!

Going to look for someone with a honing shop before I lose my marbles over this job.

When a customer asks for a tight finish on a tight bore in mild steel. I first bang my head against the wall then I leave about 2 thou per side for finish honing/polishing. What exactly is the finish requirement? 8? 2? Have they considered a material that allows for better finish?

 

[Larry Dickman]

I would look for a hone shop that does hydraulic cylinders

 

[BWS JAZE]

When a customer asks for a tight finish on a tight bore in mild steel. I first bang my head against the wall then I leave about 2 thou per side for finish honing/polishing. What exactly is the finish requirement? 8? 2? Have they considered a material that allows for better finish?

Good thing is, the customer is flexible. This part is VERY similar to a hydraulic cylinder, where a seal must travel up and down the bore and not get chewed up.

I’m gonna give one a try but I’m fully expecting to have to outsource part of this job which kind of sucks. Really needed to get all my pennies from this job but such is life.

 

[Milland]

The thickness while being bored is .25" so an OD of 2.25in. It will then be turned to 2.05" OD in what I planned to be the 2nd operation.

This has me a bit worried about stress relief and going out of round. If you're honing to size I'd do this op first, then hone.

 

[triumph406]

If you did 1400/year, it would be worth investing in a Sunnen.

Sunnens can be had cheap , you could likely get a P28 mandrel off of ebay for $50-$200. Shoes ,stones and trueing sleeves aren't expensive off of ebay (well they weren't when I was tooling up a Sunnen a few years ago) so for an investment $1-2000 you could be honing your parts.

Learning to hone isn't hard, especially with large diameter parts, it gets tricky as the diameter gets smaller.

The other benefit is that you'll find all sorts of uses for a Sunnen hone.

I wouldn't quote that job without access to a Sunnen

 

[mmurray70]

Good thing is, the customer is flexible. This part is VERY similar to a hydraulic cylinder, where a seal must travel up and down the bore and not get chewed up.

I’m gonna give one a try but I’m fully expecting to have to outsource part of this job which kind of sucks. Really needed to get all my pennies from this job but such is life.

If customer is flexible, just tweak the part so you can use honed tubing that you can purchase already done. Shouldn't be hard to get 1.75" honed tubing. They sell this stuff all over for hydraulics shops.

I bet you actually have way more then that to work with. Engineers dealing with sealing stuff go crazy with tolerances and surface finish. If they actually spent a day or 2 in a hydraulic shop and see what actually works in the real world their mind would be blown.

 

[guythatbrews]

This has me a bit worried about stress relief and going out of round. If you're honing to size I'd do this op first, then hone.

For sure. At least rough the od if it can't be finished first for some reason.

If customer is flexible, just tweak the part so you can use honed tubing that you can purchase already done. Shouldn't be hard to get 1.75" honed tubing. They sell this stuff all over for hydraulics shops.

I bet you actually have way more then that to work with. Engineers dealing with sealing stuff go crazy with tolerances and surface finish. If they actually spent a day or 2 in a hydraulic shop and see what actually works in the real world their mind would be blown.

Good advice here too. Buy it already honed if you can. My gut feeling is 0.0005 tolerance might be skyhooked. It happens. What does the seal manufacturer recommend?

The flexhone seems pretty iffy at best, especially going from turned finish to single digit. Also no improvement in roundness which will be hard to achieve by boring on that thinnish long tube. If you decide to get a honing machine consider one with auto stroking capability. Or hire a big dude. That big a part is a real workout.

 

[SeymourDumore]

This part is VERY similar to a hydraulic cylinder, where a seal must travel up and down the bore and not get chewed up.

Shouldn't be hard to get 1.75" honed tubing. They sell this stuff all over for hydraulics shops.

I bet you actually have way more then that to work with. Engineers dealing with sealing stuff go crazy with tolerances and surface finish. If they actually spent a day or 2 in a hydraulic shop and see what actually works in the real world their mind would be blown.

Yupp!!!
Finish? Yes, that is what makes the seal last.

Size? Not so much as that is what the seal supposed to take care of!