ID grinding hard chrome.

[Milland]

No special tools are required to make small size grinding wheels. Any high speed steel drill will make many holes in any type of aluminum oxide wheel. Regrind the cutting flutes when they become to dull. Of course the drill will eventually become garbage. The wheels are rough cut using a course tooth band saw blade. Again, many pieces can be cut & the band saw blade will become garbage. You can make or purchase heavy paper pieces to glue, with rubber cement, on to both sides of the wheels. Clamp the stones to the mandrels shaft with machined steel washers, but never directly on the stone's surface!

I've never tried this, but it sure sounds counter-intuitive...

 

[eKretz]

It may sound counterintuitive, but it's true. I've done it myself plenty of times. It's sort of similar to the way a coarse diamond grinding wheel cuts tungsten carbide so easily when roughing by mostly cleaving it apart at the sintered bonds between tungsten carbide grains rather than actually grinding through the tungsten carbide grains. Something similar happens with the grinding wheels. Even mild steel can "cut" them (should probably more properly say "shape" them - it's more or less just grabbing the abrasive grains and pulling them out of the bond) if it's used properly. I have read anecdotes of old time shops resizing grinding wheel IDs in a lathe using a piece of unsharpened mild steel like a boring bar.

A tip from Capt. Obvious - if you use a drill to open up or make a new hole, don't use a good one... It will pretty rapidly destroy the lands of the drill and make it worthless for drilling anything else.

 

[Terry Keeley]

For one thing I'd slow that traverse/stroke rate WAY down. That looks like it's going way too fast. Try to set that so your wheel is moving something like an absolute max of 1/4 of its width per revolution of the part. For another, how fast are you spinning the part? I'd probably start that at about 40-50 FPM and see how it goes from there.

I tried it much slower and faster, didn't seem to make a difference. The lathe is at 120 rpm so for the 0.970" bore that's about 30 sfm. The grinder is 30K.

I'm kinda with Ed here on both those items except maybe not quite that slow on traverse. But your workhead speed is making the chrome harder, and it's already hard enough. Also, not real enamoured with the way I see sparks on the reverse ? How are you infeeding ? In a heald, you normally infeed at the beginning of the in stroke, no feed on the return. That way the front edge of the wheel takes all the wear, and it kind of gives a spring pass on the way back out.

It does seem like you are grinding tho, from your description it was just rubbing the poor thing to death. You my still need a different wheel but slow everything (except wheel speed) down and give it another try. And cut your infeed, I think. Normally in just carburized steel I'd be taking a tenth per side per pass in a much beefier setup.

A coarser, more open grit might help too.

You'll get there, eventually. Looks better than your description sounded, to be honest.

I've just been infeeding randomly (a tenth or less), I thought with the wheel in contact all the time (it out feeds 1/2 the wheel width at each end) it wouldn't matter. I'll try at the beginning of the stroke. Wheels are dressed aggressively as mentioned, they feel quite sharp. I'm only infeeding a few tenths total at times before the light show begins. The wheel in the video is fairly big for the bore I think but I also tried much small diameter wheels (1/2 the bore) and it made no difference.

I was being a little conservative since the sparks seem to be showing that his setup is lacking rigidity - very inconsistent. Sometimes with the sparking and sometimes not. Kinda' weird. Unless you're onto something and he is infeeding on the return?

Yup, "kinda weird". It'll seem to be doing fine then all of a sudden (without further infeed) it'll grab and spark like hell. Like it's lacking rigidity as you mention. I'm sure the lathe's bearings are good and tight but I might replace the bearings in the grinder to eliminate that possibility, they do feel good though.

What engine is that for?

I presume your grinding taper into the bore.

There's a few websites where people discuss making model engines, The ones who make ABC and AAC liners would likly know the answer to your wheel dilemma.

Yup, 0.004" taper on the diameter, that's why a straight hone won't work as mentioned although some guys have used a Sunnen hone and tricked it somehow to cut a taper.

See post #124 of this thread

.90 cu in, 30,000 RPM, 7.2 HP custom built nitro engine

from the post

I make the stones, which are mounted on tapered mandrels of different lengths, from scrape surface grinding wheels. For example, the ID of the engine's cylinder is 1.125". I drill a 1/4" hole & cut with a band saw, 1/2" or 3/4" wide, 100 grit aluminum oxide wheels which are dressed round after mounting. The size of the dressed wheels are approximately 1.000" to 1.100

I use a sulfur based grinding oil, Sunnen #MB 30-5, which has been used to previously grind chrome.Never use new grinding oil to finish grind hard industrial chrome.

No dressing of the stone will be necessary to finish many pieces

from post #132

No special tools are required to make small size grinding wheels. Any high speed steel drill will make many holes in any type of aluminum oxide wheel. Regrind the cutting flutes when they become to dull. Of course the drill will eventually become garbage. The wheels are rough cut using a course tooth band saw blade. Again, many pieces can be cut & the band saw blade will become garbage. You can make or purchase heavy paper pieces to glue, with rubber cement, on to both sides of the wheels. Clamp the stones to the mandrels shaft with machined steel washers, but never directly on the stone's surface!

I never met Jim but talked to him on the phone several times and replied to his posts, sadly he died about a year ago.

He does mention using MB-30 sulphurized honing oil so I tried the Rustlick full strength, it didn't like it at all.

 

[eKretz]

How much play is in that grinding slide stroke mechanism? Is that a linear slide or...? Have you checked it for any free play with an indicator? I might try locking that out if possible and using the carriage just for the process of elimination. That has me a little nervous.

As far as the speed of the stroke... How slow can it go? Is it electric motor powered, or...? I would really recommend getting that down a lot lower with your symptoms and the fact that you are on a small lathe and not on a dedicated grinding machine.

 

[Big B]

I didn't see it mentioned yet but are you sure that your diamond dresser point is sharp? If not it will glaze your wheel and it won't cut very well. Look at it under magnification to make sure that it comes to a sharp point.

I ran into this one time and a much more experienced grinder hand told me to check the diamond and it was rounded out and glazing the wheel over. I put a sharp diamond in the dresser and was back in business.

Also as mentioned before, make sure to dress some relief into the trailing side of the wheel so you aren't using the whole length of it.

 

[Milland]

If you have time, throw a tenths test indicator onto various parts of the lathe and grinding spindle and apply light loads (in multiple axis), and see what deflections you're getting. You might have a situation where some aspect is more flexy than you'd guess.

I'd also ensure the grinding wheel is above center, maybe by ~.020" or more, to make sure it can't deflect down and increase load.

 

[Terry Keeley]

How much play is in that grinding slide stroke mechanism? Is that a linear slide or...? Have you checked it for any free play with an indicator? I might try locking that out if possible and using the carriage just for the process of elimination. That has me a little nervous.

As far as the speed of the stroke... How slow can it go? Is it electric motor powered, or...? I would really recommend getting that down a lot lower with your symptoms and the fact that you are on a small lathe and not on a dedicated grinding machine.

Virtually no play in the stroke mechanism, it's air driven and can go quite a bit slower, the carriage itself would be quite a bit looser I'd think.

I didn't see it mentioned yet but are you sure that your diamond dresser point is sharp? If not it will glaze your wheel and it won't cut very well. Look at it under magnification to make sure that it comes to a sharp point.

I ran into this one time and a much more experienced grinder hand told me to check the diamond and it was rounded out and glazing the wheel over. I put a sharp diamond in the dresser and was back in business.

Also as mentioned before, make sure to dress some relief into the trailing side of the wheel so you aren't using the whole length of it.

Using a new diamond as mentioned, it's sharp and gives a sharp dress.

If you have time, throw a tenths test indicator onto various parts of the lathe and grinding spindle and apply light loads (in multiple axis), and see what deflections you're getting. You might have a situation where some aspect is more flexy than you'd guess.

I'd also ensure the grinding wheel is above center, maybe by ~.020" or more, to make sure it can't deflect down and increase load.

I'll have a look at the spindle itself and probably install new bearings as mentioned but everything else is tight.

I just talked to Mike at Diagrind:

Quality, Precision, Experience… - Diagrind Inc | Superabrasive Internal Grinding Wheels

He was very quite knowledgeable and didn't mind helping a noob, said their business is fixing problems.

He said one of their resin bond wheels would be best at the SFM I'm running (30 krpm), also they can be trued with a single point diamond and opened up with the white dressing stick and they're also "freer" cutting than the vitrified wheels. He said typically you want the wheel to be about 60% of the bore diameter so I ordered a 5/8" x 1/4" 100 grit wheel to try.

 

[Milland]

What is your wheel height relative to the lathe spindle? I'd have it a little above, as mentioned.

 

[Terry Keeley]

What is your wheel height relative to the lathe spindle? I'd have it a little above, as mentioned.

On center.

Just talked to my toolmaker buddy, he thinks it's lack of rigidity, got some things to try and stiffen things up...

 

[triumph406]

Yup, 0.004" taper on the diameter, that's why a straight hone won't work as mentioned although some guys have used a Sunnen hone and tricked it somehow to cut a taper.

I think people who hone with an unmodified mandrel/stone, hone thru and then progressively back out and hone more of the bore away from TDC, that way creating the taper. There's an engine builder in OZ (Rothwell) who mentioned it takes a lot of practice to get the technique down

Barton Model Flying Club :: View topic - Cylinder Chroming

from the thread:

Then, with the right machine, in my experience it's much easier to hone to size
than either turn or grind.

With experience, on a suitable production machine, correct stone choice and
technique, honing chromed cylinders to shape and size doesn't take much time,
Henry does them in 4 to 5 minutes from start to finish, I'm slower than that but
still, it doesn't take long when you get the hang of it.

I've seen posts saying that chrome can't be honed, yet every cylinder Henry
sold was chromed and then honed to finished size and shape, obviously he has
done many 1000's of them and he always did the honing himself.

(Henry being Henry Nelson, but you already knew that)

I remember a visit to K&B in 1984 watching a lady honing chrome cylinders in only a few minutes each and Bill W saying she was the only person who had the magic touch in the factory.

My understanding is that K&B didn't deposit a thick layer of chrome, so there was very little honing to be done to get the right finish.

I was talking to somebody who used to work at COX, and he told me the best honers at COX were women, especially on the TeeDee engines.

-----------------------------------------

I have some 3.5cc diesel cylinders (not chromed) to hone, I'm going to try the honing technique of honing thru the progressively work out towards the bottom.

Also might try free floating the stone with a spring under the center and a pin to stop the stone from moving axially. Probably a very high chance of bell mouthing the bore.

Another thing I'm going to try is making a tapered sleeve to size the mandrel and stone. That would likely work if the cylinder is already tapered and the hone will remove the minimum of material

 

[triumph406]

On center.

Just talked to my toolmaker buddy, he thinks it's lack of rigidity, got some things to try and stiffen things up...

have you tried to grind a steel cylinder to see if the setup is rigid enough to do a different (but easy) material?

 

[EmGo]

I've just been infeeding randomly (a tenth or less), I thought with the wheel in contact all the time (it out feeds 1/2 the wheel width at each end) it wouldn't matter. I'll try at the beginning of the stroke.

Grinding typically wears one edge of the wheel, the leading edge, more, into kind of a taper. Then when you get close to finish, you dress once to get the taper out, take a pass, measure, then finish.

Never ran a Bryant but Healds always infeed when the wheel is at the very beginning of the stroke, that way most of the wear will be on the leading edge and the rest of the wheel is straighter. I always traverse farther out than it looks like you are doing to get past this area, but you're in some kind of fixture so can't comment. Usually at least 1/4 of the wheel past the part on both sides tho. That way you're taking most of the meat off with the leading edge.

You are correct, wheel goes on-center. Mill, you are just inventing stuff. This is standard i.d. grinding, there's proven methods. I don't think there's anything loose, it's just a really hard material, your wheel is loading up and floating instead of grinding, then the pressure gets high and it digs in. Find a wheel that cuts and it will work.

But I bet Ed is still correct, your work speed seems way fast. And traverse a little fast. And the motor bogging down, that's from trying to push too hard. ID grinders have like a 5 hp motor on the wheelhead so that doesn't happen but you don't have that luxury so have to pussyfoot around.

 

[Milland]

On center.

Just talked to my toolmaker buddy, he thinks it's lack of rigidity, got some things to try and stiffen things up...

Yeah - raise the wheel up a bit. With a flexy setup, you don't want the wheel on center.

 

[EmGo]

Yeah - raise the wheel up a bit. With a flexy setup, you don't want the wheel on center.

No, you are wrong. It's not any flexier than any normal id grinding. Any time you have 1/2" wheels on a quill you're talking "flexy" and there's no magic gimmicks that will fix that.

The wheel just isn't cutting. That's the underlying problem. Fix that and the rest will follow.

 

[Turbowerks]

On honing a taper, we use shorter stones with normal length guides to keep from tapering blind bores with sunnen hones beings you cant overstroke on the bottom or end, i have honed perfectly wrong tapered bores with out them so with a little practice you could taper a bore but .004 would be a chore on that short of bore with a hone


When I find it I don’t need it
When I need it I can’t find it!

 

[Terry Keeley]

I think people who hone with an unmodified mandrel/stone, hone thru and then progressively back out and hone more of the bore away from TDC, that way creating the taper. There's an engine builder in OZ (Rothwell) who mentioned it takes a lot of practice to get the technique down

Barton Model Flying Club :: View topic - Cylinder Chroming

from the thread:

Then, with the right machine, in my experience it's much easier to hone to size
than either turn or grind.

With experience, on a suitable production machine, correct stone choice and
technique, honing chromed cylinders to shape and size doesn't take much time,
Henry does them in 4 to 5 minutes from start to finish, I'm slower than that but
still, it doesn't take long when you get the hang of it.

I've seen posts saying that chrome can't be honed, yet every cylinder Henry
sold was chromed and then honed to finished size and shape, obviously he has
done many 1000's of them and he always did the honing himself.

(Henry being Henry Nelson, but you already knew that)

I remember a visit to K&B in 1984 watching a lady honing chrome cylinders in only a few minutes each and Bill W saying she was the only person who had the magic touch in the factory.

My understanding is that K&B didn't deposit a thick layer of chrome, so there was very little honing to be done to get the right finish.

I was talking to somebody who used to work at COX, and he told me the best honers at COX were women, especially on the TeeDee engines.

-----------------------------------------

I have some 3.5cc diesel cylinders (not chromed) to hone, I'm going to try the honing technique of honing thru the progressively work out towards the bottom.

Also might try free floating the stone with a spring under the center and a pin to stop the stone from moving axially. Probably a very high chance of bell mouthing the bore.

Another thing I'm going to try is making a tapered sleeve to size the mandrel and stone. That would likely work if the cylinder is already tapered and the hone will remove the minimum of material

have you tried to grind a steel cylinder to see if the setup is rigid enough to do a different (but easy) material?

I got some Dispal S226 piston material from Steve Rothwell maybe 25 years ago, good stuff but RSP 431 seems to be the "go to" now so I'm going to try that.

Yup, apparently honing a taper on machine that's designed to do straight bores is a real art, that's why I got this unit when I saw them years ago, I've used it for other grinding projects and it's worked very well.

 

[eKretz]

No, you are wrong. It's not any flexier than any normal id grinding. Any time you have 1/2" wheels on a quill you're talking "flexy" and there's no magic gimmicks that will fix that.

The wheel just isn't cutting. That's the underlying problem. Fix that and the rest will follow.

I don't know about any of the rest of y'all fellers, but I've never once moved an ID or OD grinding wheel from centerline. I don't think that's a good solution for this problem either.

 

[Milland]

I don't know about any of the rest of y'all fellers, but I've never once moved an ID or OD grinding wheel from centerline. I don't think that's a good solution for this problem either.

If the setup is "flexy", the same logic of having a boring bar a little above center applies - you don't want load from the cut to deflect the edge further into the work.

My view of the sparkfest posits as the wheel goes through the interruptions it deflects. If it deflects down it suddenly has a greater bite, where if it's a touch above center that's not as likely.

It's an easy thing to try, isn't it?

 

[eKretz]

If the setup is "flexy", the same logic of having a boring bar a little above center applies - you don't want load from the cut to deflect the edge further into the work.

My view of the sparkfest posits as the wheel goes through the interruptions it deflects. If it deflects down it suddenly has a greater bite, where if it's a touch above center that's not as likely.

It's an easy thing to try, isn't it?

I don't think it's going to work quite how you think it will. The forces are a little different with grinding. There's generally not much vertical component involved. Since the depth of cut is so shallow, most if not all of the force will be pushing straight out against the wheel.

 

[michiganbuck]

I have used a drill to size an iD grinding wheel hole. it doesn't matter drilling the same direction or the other because you are crushing the hole not drilling it. A carbide drill works Ok also.
I use my spin dresser at an angle with my thumb on my dresser wheel to let it run at about 300 RPM to make the ID wheel OD run true., likely you don't have an abrasive wheel dresser. You might fab a diamond and dress the od of your wheel, I like an OD wheel to feel like it is running true on the OD.
I usually go inside a part ID but not all the way through and get a little rub and grind on the way out nd lt the wheel overtravel the part about 1/4 - 1/3 of the wheel.
*I don't know if that wheel will grind Chrome, might try a CBN wheel.

*You should mention how much stock you need to take and what kind of fit you need.

Your setup looks Ok from here. If it is goint=g to be a regular job I would definitely get a grinder.
I might travel a little shower.