Holding +-.0001” on 7/8 bore with cnc lathe

[Conrad Hoffman]

Well, actually you will. You'll look back to not having a stinky oily mess and a process that's more of an art form than something you can stick a button pusher on. You'll look at a machine that sits unused way too much of the time. You'll wonder why you never ever have the right (expensive) mandrels or stones for the job. I've been honing to stupidly tight tolerances for about 40 years and enjoy the process greatly, but I've never found management or "normal" machinists to be very fond of it. Honing and grinding should be the easiest jobs in the shop, but they're both becoming relics of the past, given what you can do with a CNC machine.

 

[Ianagos]

The issue with ball sizing is the ball can drift a bit side-to-side depending on local hardness. So even if you measure to spec, you could have unseen "wander" in the cylinder, which is likely a no-no here.

I'm with the honing crowd, ditto those that say check with the customer as to how they plan on measuring the parts. You'll need to copy their method.

Yes I’d be concerned with ball sizing. There is a circlip groove in the bore that has to go in when the bore is rough turned. To me te possible the ball would make a different bore axis when it hits the groove.

This part is disc shaped with zero flat surfaces to grab for second op except for the bore itself and a small flat surface to reference on. Basically imagine a triangle revolves around the bore. Second side machining is tricky as is.


The single pass diamond hone is what I’m going to be looking into deeper. Nobody with a sunnen for sale at the moment.

I’m fairly confident I could do it on the lathe but I think it would take much longer and high rate of scrapped part. Material is pretty expensive to have any scrapped parts.

Off topic: Do you guys have a bs13 manual by chance?


The more you guys talk about it the more a sunnen sounds like the right machine. But like someone else said I don’t want a oil leaking mess all over and a machine I’ll be using for one job 4 times a year.

 

[gappmast]

You might try these guys for a single pass diamond hone. Di-Coat Corporation
800-637-9194

I have 2 of their units and they work quite well for me.

The single pass tools will hold a very consistent size but they have a couple issues in this application
1. You have a very tight size that you need to hold. These tools can be a challenge to adjust to a tight size.
2. They don't like 300 series stainless, gummy gummy gummy, It sticks to the diamond and tends locks up, have you ever reamed bronze and had it pull the reamer in. I won't say you can't make them work but you need a special oil, controlled feed rate, and only a few tenths stock removal.

 

[FredC]

The single pass tools will hold a very consistent size but they have a couple issues in this application
1. You have a very tight size that you need to hold. These tools can be a challenge to adjust to a tight size.
2. They don't like 300 series stainless, gummy gummy gummy, It sticks to the diamond and tends locks up, have you ever reamed bronze and had it pull the reamer in. I won't say you can't make them work but you need a special oil, controlled feed rate, and only a few tenths stock removal.

They work great with hard brass, never used them on 300 series stainless. Good to know. With the OPs size and tolerance temperature before and after honing or lapping will be critical. We mostly finish 1/8 or there abouts and temperature is not really an issue. Might talk to them and ask if there is a variation that will work in 300 series stainless. Knowledgeable people that will not steer you wrong.

 

[EmanuelGoldstein]

The more you guys talk about it the more a sunnen sounds like the right machine. But like someone else said I don’t want a oil leaking mess all over and a machine I’ll be using for one job 4 times a year.

No reason for it to be leaky, that's silly, and the oil doesnt stink, it's not TrimSol, and if you had one, you'd find uses for it. They aren't very big. Honing is useful.

But it's true that the mandrels are expensive.

 

[gbent]

... and the oil doesnt stink,...

Maybe Sunnen has new oils now, but the old stuff was certainly high sulfur stinky.

I agree the easiest way to finish the bore and hold size if its a through hole is a hone. Your total tolerance expressed as delta T is 19 degrees F. That doesn't give you much room unless you have not only temperature control for the air, but coolant chillers/heaters.

 

[Conrad Hoffman]

Sunnen MB-30 is the standard oil and has a significant odor. Not awful, sort of sweet, but my shop is attached to the house, so it's a non-starter. They have non-sulfur oils that are probably better. Tennessee Abrasive also has some alternative honing oils that should be less stinky. Note that honing oils are purpose-blended and the process may not work well without them. The hones don't leak but you're flooding the operation with oil. If the part gets away, or even if it doesn't, oil tends to sling. Think of riding through a mudpuddle on a bike without fenders. We all remember that stripe up the back! In the case of the hone, it's to the left and right. Not a biggie if you keep the RPM reasonable, but sooner or later...

 

[gappmast]

Use Sunnen's SHO965 oil, no mineral oil or sulfur. It will make your hands nice and soft.

 

[gappmast]

you said you have 2 tenths total on size does the print have any bow or cylindricity call out?

 

[Ianagos]

you said you have 2 tenths total on size does the print have any bow or cylindricity call out?

There are perpendicularly to a face and concentricity tolerances to the axis of the part but no there are no bow or cylindrical tolerances given on the print.

The tolerance on this part is tighter than it needs for the application in my opinion but 100% inspection on these so I have to hold whether it really need it or not.

 

[gappmast]

With the length and diameter you don't have to worry about honing moving the hole. With that tight of a tolerance I'm surprised they don't have a cylindricity call out.

 

[EmanuelGoldstein]

Maybe Sunnen has new oils now, but the old stuff was certainly high sulfur stinky.

Now that you mention it, as a gear guy, sulfur oil is our natural environment. Maybe my judgement on smell is not to be trusted

I still think bad TrimSol stinks tho ....

 

[pavt]

Now that you mention it, as a gear guy, sulfur oil is our natural environment. Maybe my judgement on smell is not to be trusted

I still think bad TrimSol stinks tho ....

Oh goodie, a gear guy!
Was gonna ask, do you think something like SULFLO, INC.
has any use for threading on a manual machine.... turns out they are local to me and I'm interested in supporting local industry.

 

[EmanuelGoldstein]

Was gonna ask, do you think something like SULFLO, INC. has any use for threading on a manual machine.... turns out they are local to me and I'm interested in supporting local industry.

We used something that sounds similar on the broach - used to brush it on the broach before a pull, on the more difficult parts. Worked, I guess. Never stuck the broach, anyhow. (Some less careful guys did. Pick up your check on the way out ...)

For threading and especially on stainless, used this stuff

Anchor Lubricants LLC

it's pretty good. Not messy.

I was always a fan of Chevron Metcut 505 for oil .... kind of a caramel color, not black and I guess less stinky (my nose has been discredited now). It was kind of a compromise between the heavy sulfur and straight oil, worked well. Used that on just about everything.

If you've got someone local, that's cool. Berkeley had a place called (I think, D from O would remember better) Withrow. They made all kinds of low-volume special cutting oils. No chlorine, yes chlorine, clear, golden, but not the junky black crap plumbers use. They were always real helpful, if you've still got that locally, go buy from them. It's a great resource.

Try a little thing of anchorlube, it's good. Use to be called westlube, I think.

 

[Forestgnome]

This thread brings a question to mind. What kind of tolerance to expect with reaming?

 

[Conrad Hoffman]

IMO, reaming depends on the material, the reamer, the age of the reamer, the lube and probably the phase of the moon. It might be consistent but I wouldn't expect absolutes better than a few tenths and sometimes worse. Reamed holes might not be round. Or, they might be. Still, I like reaming if it can get the job done.

 

[gappmast]

Oil requirements for honing are different than for machining especially when you get into 300 series stainless. You will also need brass shoes if using a conventional honing tool.

Has anybody mentioned the surface requirements for this part?