Another Rupnow 1 by 1

[CFLBob]

Bob--Glad to see you are still at it. I was beginning to worry. The way I made that cylinder is to first cut a piece of cast iron about 1 1/2" longer than the finished size, stand it on end in my milling machine vice and center drill one end with a center drill until I had a divot on center big enough for a lathe live center to fit. Then I chucked the entire length up in my lathe 3 jaw and supported the outboard end with a tailstock live center. Then I turned everything to finished size, even the portion that is rectangular. Then I put a 15/16" drill in the tailstock chuck and drilled out the center and reamed it to finished size all in the same set-up. I then used my parting off tool to part off the cylinder at the correct overall length. This leaves you with a "stub" of cast iron about 1 1/2" long that you will eventually use on some other build. After it comes off the lathe, the 4 sides of the square part can be band-sawed or milled off, leaving it square.---Brian

No need to worry. It was the usual mix of other things that need fixing and my tendency to overthink things mixed with Thanksgiving.

I was converging on just going ahead and putting it on the lathe. Put a dimple in the end with the biggest center drill I've got and use my live center. I used the live center on the crankshaft, too, turning between centers, but since this is square and not even an inch longer than needed, I was going to put it in my four-jaw get it all centered, then start from the end in the live center and cut the features down to the square side. Looking at the assembly, it looks like .025 over sized on the square flange won't be a huge deal, just a small lip where it meets the crankcase - as long as the holes are in the right place.

 

[CFLBob]

The start over has been in progress since last Tuesday. This time I squared the blank to 1.80" on a side (don't recall how different they were, but it was under .005"), and then took it to the lathe to turn it into a cylinder.

With the sides of the block 1.80" and the desired diameter of the cylinder being 1.750", how much do I remove? I drew the two shapes up in CAD and it told me that from the tips of the square to the rim of the circle is 0.397". That's roughly 19 passes cutting .020 (radius) at a time, plus a final cut or two to sneak up on the final size. Each pass takes about four minutes, which argues that with some clean up time, it should have taken about two hours. My lathe has power feed, so I can put everything in position for the next cut and engage the gears. Do "something else" for the majority of the cut and then go stop it at the critical point. Four minutes is just enough time to not get much "something else" done.

It's starting to look like a cylinder.

That was yesterday. By this time I had drilled through my entire blank with a 1/2" bit and then used an end mill in my drill chuck to enlarge that to 9/16".

While trimming the square bar into the roughly 2.00" long cylinder taking up most of the blank, I noticed the vibration was enough to cause both axes on my lathe to move. I was able to stop that with a simple fix.

Blue painter's tape on both dials. It seemed to work repeatably. I don't know of any other way to lock those in position. The entire carriage can be locked in position with a screw I keep an allen wrench in - you can see it just to the right of the crosslide, almost under the compound. The compound rattles more when at the left end of its travel, so I do this with it at the right end. The power feed (engaged here - notice the vise jaws are blurred) moves that big handwheel on the bottom left, not the small one on the right that's taped.

Just finished up several passes of my boring bar in the cylinder and it's now at 0.826" ID, on the way to 1.000".

 

[Steamchick]

Hi Brian, noting you probably have a very accurate set-up, gib strips set on the main saddle, and cross slides, but have you mic'd a 3 in long OD cut to check if the bed is truly in alignment with the axis of the headstock? Maybe with a DTI on 0.0001" accuracy, you can confirm if a test bar is good, but under load (with wear and tear?) Maybe it is not quite so parallel? And if you can accurately check the bore, you may find it is tapered? Loads from simple boring bars are the opposite direction on the main traverse to OD cutting. I always find a fraction of a thou taper on my bores from the lathe. Even using an end- milling cutter from the tailstock, so always finish bore down the hole on the miller-driller.That way it bores a true cylinder. (Less corrective honing!).
But my lathes were worn, and a thou out of true when cutting, due to bed-way wear....
K2

 

[CFLBob]

K2 - I honestly don't know how to do that. When I first got the lathe (2014), I put a live center in the tail stock and a dead center in the head stock, then verified they were actually point to point. That's the only test I've done. I regularly use a dial indicator to minimize runout in pieces I'm turning, but haven't done

What I get now is wobble in the compound. I just re-adjusted the gib in it, not even an hour of machine operating time ago, and yesterday, I could grab the compound and feel it move.

 

[Eccentric]

Bob,

Have you seen this for aligning the lathe? worked for me:

 

[Steamchick]

Hi Bob ( Sorry, Dyslexia called you Brain, or something?) To control the saddle against cutting torque there is a sort of hook of a running surface beneath the back of the bed slides. The saddle needs to be adjusted to prevent lift at the back - there should be a gib hidden under the back? Frontal down-thrust is taken on the alignment long wedge slide. I suggest using a molybdenum loaded or lithium grease wiped on the bed tracks as the light (7W) lathe oil I find dissapears quickly... especially if you use coolant?
There may be a gib strip on the front of the saddle? (Non-thrust face when the tool is tightened against a workpiece). But my lathe only has the one at the back. Actually, the stability of the saddle on the bed is the pair of "wedges" that the saddle sits on. If the gib beneath the back rail of the bed is correctly set, then there is sliding motion but no lift at the back, which ensures the saddle does not chatter on the wedge on top of the bed.
You say the movement is in the top slide, which is much simpler to set. My technique, is to set the slide mid-travel, adjust the middle screws, then go to either end of travel to adjust the end screws for the gib strip. When set and locked it lasts me years, but I'm not doing more than a few dozen hours lathe work in a year. But lubrication is more frequent, cleaning is after every operation, or when there is a table spoon of swarf. Sometimes after each cut or 2. Swarf is really a killer for precision sliding surfaces.
Enjoy! K2

 

[CFLBob]

Bob,

Have you seen this for aligning the lathe? worked for me:

Thanks for the link. Got busy and haven't watched it yet, but will watch it in the morning.

Hi Bob ( Sorry, Dyslexia called you Brain, or something?) To control the saddle against cutting torque there is a sort of hook of a running surface beneath the back of the bed slides. The saddle needs to be adjusted to prevent lift at the back - there should be a gib hidden under the back? Frontal down-thrust is taken on the alignment long wedge slide. I suggest using a molybdenum loaded or lithium grease wiped on the bed tracks as the light (7W) lathe oil I find dissapears quickly... especially if you use coolant?
There may be a gib strip on the front of the saddle? (Non-thrust face when the tool is tightened against a workpiece). But my lathe only has the one at the back. Actually, the stability of the saddle on the bed is the pair of "wedges" that the saddle sits on. If the gib beneath the back rail of the bed is correctly set, then there is sliding motion but no lift at the back, which ensures the saddle does not chatter on the wedge on top of the bed.
You say the movement is in the top slide, which is much simpler to set. My technique, is to set the slide mid-travel, adjust the middle screws, then go to either end of travel to adjust the end screws for the gib strip. When set and locked it lasts me years, but I'm not doing more than a few dozen hours lathe work in a year. But lubrication is more frequent, cleaning is after every operation, or when there is a table spoon of swarf. Sometimes after each cut or 2. Swarf is really a killer for precision sliding surfaces.

I enlarged my cylinder bore to 0.950 this afternoon, and will use a few more passes for the last of it. I only measured the ID by using a telescoping ID gauge and it didn't look like it had any taper; at least nothing that showed up on my calipers. I'll redo that with my micrometer tomorrow, and get a better feel for it.

I went through the manual trying to find the gibs you mentioned but nothing in the manual seemed obvious. I'll spend some time looking for that tomorrow. It's a SIEG lathe like so many others so I'm guessing it's probably built like the 7-by or 8-by lathes that are everywhere.

 

[Ghosty]

Bob,
The Sieg lathe that I had needed the head machined to get it straight, not machined straight from the factory, as it bolts direct on the lathe bed there is no adjustment to get it parallel
Cheers
Andrew

 

[Nerd1000]

Hi Bob ( Sorry, Dyslexia called you Brain, or something?) To control the saddle against cutting torque there is a sort of hook of a running surface beneath the back of the bed slides. The saddle needs to be adjusted to prevent lift at the back - there should be a gib hidden under the back? Frontal down-thrust is taken on the alignment long wedge slide. I suggest using a molybdenum loaded or lithium grease wiped on the bed tracks as the light (7W) lathe oil I find dissapears quickly... especially if you use coolant?
There may be a gib strip on the front of the saddle? (Non-thrust face when the tool is tightened against a workpiece). But my lathe only has the one at the back. Actually, the stability of the saddle on the bed is the pair of "wedges" that the saddle sits on. If the gib beneath the back rail of the bed is correctly set, then there is sliding motion but no lift at the back, which ensures the saddle does not chatter on the wedge on top of the bed.
You say the movement is in the top slide, which is much simpler to set. My technique, is to set the slide mid-travel, adjust the middle screws, then go to either end of travel to adjust the end screws for the gib strip. When set and locked it lasts me years, but I'm not doing more than a few dozen hours lathe work in a year. But lubrication is more frequent, cleaning is after every operation, or when there is a table spoon of swarf. Sometimes after each cut or 2. Swarf is really a killer for precision sliding surfaces.
Enjoy! K2

I disagree on the topic of using grease on the lathe bed. The problem is that even a thin film of grease will attract dirt and swarf that grind down the ways. Ideally you should use way oil, it contains 'tackifiers' that help it stick to the slides and not get washed off. Failing that, for my Atlas milling machine the manufacturer specified SAE 30 motor oil... Which will no doubt have the purists up in arms, but you can't satisfy everyone.

A big help for bed lubrication is a set of felt way wipers, they'll prevent the swarf from getting under the saddle and also act as oil wicks to keep re-oiling the ways as the saddle moves.

 

[Steamchick]

Thanks Nerd1000, I'll take note.. - My lathe has felt wipers as standard, but doesn't specify oil or grease. I agree it is the finest dust does most damage! (I never grind on my lathe for that reason.). I have added a catch-all tray beneath the tool (on the cross-slide - passes beneath the chuck) that keeps most swarf away from the bed anyway.
Ta,
K2

 

[Steamchick]

Just found this...
K2
https://www.acculube.com/way-oil-wa...oil, is,parts move over the top of each other.

 

[Steamchick]

Or this - in the UK.
https://www.ebay.co.uk/itm/373484164095?hash=item56f56413ff:g:2MwAAOSwZqthXFV1Or this...
https://www.ebay.co.uk/itm/392271333053?hash=item5b553186bd:g:te4AAOSwAEJfnzeyK2

 

[Steamchick]

Bob, You could make a GO-NOGO gauge that can check the bore as you get close to size...
K2

 

[CFLBob]

Bob, You could make a GO-NOGO gauge that can check the bore as you get close to size...
K2

Isn't that what my piston is for?

Kind of joking, but as I understand it, the usual work flow is to make the cylinder first so that I can fit the piston to the engine. It doesn't matter if my cylinder is a a few thou oversized or undersized as long as the piston fits it. It needs to be fairly cylindrical and not tapered.

 

[L98fiero]

I disagree on the topic of using grease on the lathe bed. The problem is that even a thin film of grease will attract dirt and swarf that grind down the ways. Ideally you should use way oil, it contains 'tackifiers' that help it stick to the slides and not get washed off. Failing that, for my Atlas milling machine the manufacturer specified SAE 30 motor oil... Which will no doubt have the purists up in arms, but you can't satisfy everyone.

A big help for bed lubrication is a set of felt way wipers, they'll prevent the swarf from getting under the saddle and also act as oil wicks to keep re-oiling the ways as the saddle moves.

Most machines that recommend other than waylube suggest an ISO VG 32 hydraulic oil, retail it's sold in small quantities as 'jack oil'.

 

[minh-thanh]

Hi CFLBob !

and not tapered.

When i do the cylinder : a little taper at TDC is no problem.

 

[Steamchick]

The intent for a GO-NO GO GAUGE is to check for taper. IC engines manage taper as they expand more at Hot-Top-of-stroke than at the cooler Bottom of stroke. Steam engines -especially those without rings- benefit from no taper as the temperature is more uniform (steam fed from both ends), hence parallel expansion.
Your IC engine is likely to have a wider top.... but a narrower top is desirable as when hot it becomes nearer to parallel. As this is only identified by lots of tests on a design, for optimum durability, (and using lots of expensive gauging), and as your model is a one off, I guess you won't bother, however it turns out.
I can only advise what I know to be best practice. For what 50 years experience is worth....
So you can use a piston as a gauge, not joking!
I can explain more about boring, and tapers, but you'll probably get too bored with the subject and your interest will taper-off.... ( That pun even made me groan!).
I think?
K2

 

[CFLBob]

Your IC engine is likely to have a wider top.... but a narrower top is desirable as when hot it becomes nearer to parallel. As this is only identified by lots of tests on a design, for optimum durability, (and using lots of expensive gauging), and as your model is a one off, I guess you won't bother, however it turns out.

Because of the way the cylinder is mounted in the lathe, if anything, it's wider at the bottom - which is the farthest from the point where I set the diameter. That's ideal, because if it expands a little at the top, then it becomes less tapered (or not tapered), and yet it's easier to get the piston started into the cylinder with the slightly wider bottom.

I find that when it has been a long time since I've measured cylinder inside diameter, and it has been two years since I setup the cylinder in my Webster, I need to practice lots before I get consistent, so I'm not sure exactly what the taper is, but I think it's around .0015 wider at the bottom (far end). That's one reason I stopped at .050 short of final size - get practiced before I shoot for the real size.

 

[awake]

Bob, you may have already addressed this above, but just in case - as you get close to size, are you taking a spring pass each time?

 

[CFLBob]

Bob, you may have already addressed this above, but just in case - as you get close to size, are you taking a spring pass each time?

I'm still doing rough shaping, .050 short of final size, so I haven't been doing that yet, but I'm with you on that.