How much material can be removed by honing?

[Evan LaCava]

I have a part that I'd like to make, for an oil pump (piston type positive displacement metering pump)
I currently make all other parts for this pump except this one. But if I start making this one I can guarantee my pumps will be 110%.

It's a hardened steel "ring" that is purposely pressed in to a housing so the pump is serviceable when the parts wear.

It's actually a very simple cylinder, with two milled slots in it, I'd say 280-300 deg or so around the part in one plane. I'm almost positive it's 52100, my heat treated agrees.

So to make this part I was thinking of having a CNC shop make the ring O.D. Oversized, and the ring I.D. Undersized. But due to the slot geometry and heat treating, the heat treater feels that it may twist slightly.
I can center less grind the O.D. To final size, but then a rotor fits into the I.D. Of the ring with only .0005" on each wall. So I would want to leave the I.D. Undersized and hone it to the final size. I'm just wondering how much to leave in the here? Is - 0.003" too much to leave?

The OEM does exactly this process, I'm almost positive of it. Cross hatches are visual on the I.D. Of the ring, and the rotor has to just barelyyyyyy drop in, if it's the slightest bit crooked it won't even start. But once it starts and is home, it rotates freely with no binding. So I'm pretty sure they're machining undersized then honing it to final size.

I have no honing capability at my shop hence the lack of honing knowledge and hence my question. This would be contracted out to a shop that is very familiar with cylinder honing.

Ohh I.D. Would be 1.126, 1.251, 1.878. I'll be making 3 rings total for 3 different pumps. Idk if that even matters but can't hurt to say what size they are.

 

[Davis In SC]

Concentricity is my worry.. Hone is going to follow path of least resistance. if there are cut-outs. Might get some special wide mandrel shoes to prevent this. OR, may not be that critical..

 

[Evan LaCava]

Think the factory is pressing in the ring (collapsing it a few tenths) then machining round (boring) then honing to final size?

I'll post pics tomorrow but I'm pretty sure they're honing cross hatches in there...

 

[mixdenny]

You can hone as much as you want :-) Many decades ago, I decided to rebuild a 6 cylinder BMW engine that needed over sized pistons. I bought the pistons (can't remember if they were .010" or .020" over). I bought a hand Sunnen hone from a mechanic friend who assured me it was what they used to build their engines. I borrowed a dial bore gauge from him, hung the hone's support spring over the block, put the Sunnen in my biggest drill motor and began stroking. And stroking. And stroking.

After days of work I had everything honed right where I wanted it. I mentioned to my friend how hard it was to hone an engine to a larger diameter. His jaw dropped and he explained to me they bored it out on the mill then just did the final thousandth by hand!

Anyway, frequent checking with the bore gauge had kept everything on track. I put 50,000 more miles on that engine until I sold the car, ran perfectly and never smoked.

As an aside, I also tig welded a crack in the head between a valve pocket and a cooling passage, which every engine builder told me couldn't be done, and it never failed either.

Dennis

 

[gappmast]

Dennis if you would have been using a Sunnen SV10 honing machine when you did your BMW you would have been done in an hour.

Minimum stock removal is twice what the problem is your correcting. If the hole is .001 out of round leave.002 stock to hone. If the hole has .002 taper leave .004 stock to hone. When talking about honing all numbers are on diameter not per side.

 

[IronReb]

I used a Sunnen (spelling?) hone at oe shop I worked for years ago and have used portable hones more than I care too.
The hones we use were I work now are also made by Sunnen I "think", they are the kind that have certain ranges for each kit and are the kind that will flip your ass on your head or
twist an arm off if you adjust it to tight in the bore.

In my experience hones are great for the first couple of thou then after that the material rate is SLOOOOOW to remove even with coarse grit stones.

I realize that I am only aware of a small sample of whats out there in the honing world but everything I have used will not like the slots in the bore and would be destroyed after a short while
running across the slots.

Im sure it can be honed but it will take the proper length of stones so they cant drop off into the slot and even then you would not wanna be in the hole to long or the stones will start to get screwed up.

Any way you could make and heat treat the sleeve, hone to size then cut the slots with carbide end mill and with some trial and error figure out exactly what the diameters should be before pressing into hole?

 

[Onepass]

I really can't get a mental picture of what the slots look like, but if it's not too hard,,could you not finish machine the ring ( grind, hone etc.) then machine the grooves? Although I don't have any personal experience with it, I've been ts that D2 doesn't move when heat treated- would that be an option? Would buying a grinder, say a Brown & Sharpe # 13, and grind the ID ? For that matter, I'm sure I could make a setup on my Monoset for that as well.
As far as how much stock removal on a hone, I've got an d Sunnen hone with the attachments for redoing engine bores. The booklet with it explains about removing .020 to .030 with the hone and roughing stones! (1930's ) However, a Sunnen hone machine like you see in a machine shop, I'd think a couple of thousandth is a more typical envelope.

 

[ebenbildmicroscopes]

I frequently hand hone dovetail slides using Clover compound. Just like sandpaper, it comes in different grits and it is very easy to "over hone" in soft material with too course lapping compound. Stop often and measure....is the watch-word!

 

[tdmidget]

I frequently hand hone dovetail slides using Clover compound. Just like sandpaper, it comes in different grits and it is very easy to "over hone" in soft material with too course lapping compound. Stop often and measure....is the watch-word!

Clover compound is not honing. Lapping maybe but in no way is it honing.

 

[Vancbiker]

Dennis if you would have been using a Sunnen SV10 honing machine when you did your BMW you would have been done in an hour.

It is pretty common for automotive shops with one of these Sunnen vertical power stroking machines to hone to the oversize without boring. Faster to just set up just one machine. As long as the bores are true to the crank centerline, they set up the hone and go. If the bores need to be moved that's when the boring machine gets used.

 

[tdmidget]

Automotive boring machines as a rule center on the bore and thus have no ability to change location.

 

[Peter from Holland]

Diamond has speeded up honing significantly

Peter from holland

 

[ebenbildmicroscopes]

I have to somewhat agree with tdmidget and my use of "honing" to connote "lapping" inasmuch as my dovetail slides have been "honed" as a result of the initial machining process. Most engines only need a honed finish and are not subject to the tolerances of lapping - it was in THAT context that I probably mis-sanctioned semantics. Point taken

 

[ebenbildmicroscopes]

Honing, unfortunately, is a red-headed step child sotuv term. When lay people use knife steels in their kitchens, they're "honing" (truing a surface) when they use a whet stone, they're sharpening (removing material).

 

[Evan LaCava]

From the color differences you can see where these were machined pre / post heat treating.

Slots cut before heat treating.

 

[Davis In SC]

Those should be OK to Hone.

 

[Evan LaCava]

I'm
Going to leave .010-.015" on the I.D. To hone. That should hopefully allow them to clean up round

 

[scojen]

I'm
Going to leave .010-.015" on the I.D. To hone. That should hopefully allow them to clean up round

Whoa there, too much material try .005 and if your bores are good try .002 a lot of time can be saved here, time is money.

 

[Davis In SC]

Whoa there, too much material try .005 and if your bores are good try .002 a lot of time can be saved here, time is money.

+1 Time is money, and stones and mandrels are, too.....

 

[gappmast]

Once again what ever problem you are trying to correct leave twice that in stock.

What tolerance do you need to hold?