K321 Block boring/honing on a small lathe.

[BurtB 88]

Will be doing an engine rebuild of my K321 in the near-ish future. Trying to figure out if my 6" Atlas/Craftsman will be big enough that I can strap the block to the carriage to do the bore. Not ready to tear the engine down yet.

 

Anyone know, roughly, the distance from the center of the bore to the face/plane of the bearing plate mounting face?

 

 

 

[Gasaholic 224]

You don't even wanna try that.  You need an end mill with boring bar , unless your lathe and skills are such that you can get your bore precisely centered and perfectly square in every direction to the milling cutter, and I have never seen a hobby lathe capable of that...  If your rig or cross slide flexes even .0005 (half a thou) in any direction, your milling job is gonna be screwed up, and I just don't see how you'd achieve that rigidity mounting the block on the bearing plate surface, considering even that may not be perfectly perpendicular to the bore.. (even the cast iron will have a tiny bit of flex to it which is why you'd want it mounted on the base.) I would not even dream of trying to do such a precision job on a lathe.. I'd take it to a machine shop that knows and understands how to do small engine blocks (or at least a speed shop with the precision equipment to do the job)  If you have ever seen the machines and set-ups a shop needs to bore out Kohler blocks (Which I have) you'd understand the problems you're facing.. so if you do go ahead and bore that thing on a lathe, and it actually works the way you think, then you should go buy a lottery ticket because that'd be one hell of a stroke of luck! 

[ri702bill 8,319]

Interesting concept.... try it on a scrap block!!

 

The only "backyard" block machining I have done is resurfacing the valve seats using a Shopsmith MK5 as a large throat drill press with the tilt table. Fixtured the block to be true centered and square to the valve guide running a 5/16" reamer up & down thru the guide. Lowest speed on the 3 step pulley, coarse mounted stone to clean, fine stone to remove marks from the coarse one.  Spun the valves in the lathe to verify straightness, blackened the angle with a Sharpie, & used a stone on a toolpost mounted Dremel to dress the valves.... Lap the daylights out of them, check and cut the valve clearances to the high side of the spec....  Done 3 this way, no issues.

 

I agree with @Gasaholic that boring is best done by a QUALIFIED shop that posesses the correct equipment and skilled staff.

[oliver2-44 9,745]

From your introduction I take it that you have significant machining experience.  

I've had machine work done on large and small precision equipment all my career,

But I'm a very amateur hands on machinist. 

I've used an Atlas a little and it does seem light weight.

But I've watched videos where people have really hot rodded their Atlas lathe

 I've heard of it being done on a larger lathe.  

But then again you are only boring it .010 or .020 so its not like you would be taking heavy cuts. 

I'm curious why you would want to make a jig to mount it from the bearing plate side verses from the bottom oil pan face. 

Is it because it would be easier to shim to center and square it from the side plate?

Just wanting to learn some things

 

Edited August 23 by oliver2-44

[oliver2-44 9,745]

Before you jump into rebuilding you K321 you might consider: 

Do a leak down test to determine where its leaking bore, valves, etc.

Maybe it just needs a good valve job, carbon cleaned of the valve stems and a head de-carbon.

On a new to me old tractor I like to pull the head, de-carbon and measure the bore so I know what I have.

The pull and clean the carb, open and clean breather, pull an clean valves, relap and adjust valve clearance.

Kind of a major maintenance before getting into a full bore overhaul.

if you engine has been sitting for a few years, pour same acetone or Marvel Mystery oil  down the cylinder and let it soak the rings awhile.

Then just run it, getting it up to full temperature for a while, can help loosen up rings that are sticking a little.

If  you don't have a leak down test and can fine one to borrow from an auto supply at least try to do a compression test.

With the compression release mechanism you can't do a compression test in the normal manner.

But you can rig up to spin the engine backwards from another engine or electric motor and get good readings.

I use an electric motor crudely screwed to a piece of plywood that the tractor front wheel is parked on to hold it in place.

I only have to bump the electric motor to spin the engine enough times to get a compression reading.

 

Also before you jump into rebuilding you Sundstrand Hydro. 

Use it a while now that you've changed the oil and filter.  

if it was like the used tractor's I find, the oil was probable filthy and neglected.

Use it a while, working it to get it fully warmed up so that clean oil can wash some of the crud out to the filter.

If it seems to be improving change the oil again after you've put some hours on it. 

 

Clean and do a maintenance on the F/R cam speed control area and linkage.

sometimes the cam area and linkage are so dirty it can't travel full stroke each direction.

 

Consider pulling and inspecting the 2 little acceleration valves.

The small springs in these get messed up and its an easy fix to replace. 

All this cost you is a few O-rings and maybe 2 correct springs.

 

If your transmission tow Valve is stuck, start soaking  it with a good penetrant (Kroil is expensive but worth it for this task) 

 

While I like to fix things right, you can see theirs's a bit of old farm boy that comes out of me at times.  

 

Check out Aldons great Restoration thread for other GT14 idea! 

 

 

 

Edited August 23 by oliver2-44

[lynnmor 7,305]

I have a tool & die shop and wouldn't even consider doing a bore and hone job on an engine.  There is a local shop that does an excellent job with professional equipment for $85 per hole.  Trying to bore on lightweight machine tools with skinny boring bars will result in real disappointment.

[Mickwhitt 4,622]

As a home shop machinist with decent quality lathes I would 100% steer clear of this kind of job.

We have very few professional machine shops on the UK but it's the only way to get a rebore done on any engine.

The level of precision required is just not available with home machining. The measuring equipment itself would be beyond most home setups. 

And once you've taken it off, you can't put it back on. 

 

[BurtB 88]

2 hours ago, Gasaholic said:

You don't even wanna try that.  ..... If you have ever seen the machines and set-ups a shop needs to bore out Kohler blocks (Which I have) you'd understand the problems you're facing.. so if you do go ahead and bore that thing on a lathe, and it actually works the way you think, then you should go buy a lottery ticket because that'd be one hell of a stroke of luck! 

 

1 hour ago, lynnmor said:

I have a tool & die shop and wouldn't even consider doing a bore and hone job on an engine.  There is a local shop that does an excellent job with professional equipment for $85 per hole.  Trying to bore on lightweight machine tools with skinny boring bars will result in real disappointment.

 

29 minutes ago, Mickwhitt said:

As a home shop machinist with decent quality lathes I would 100% steer clear of this kind of job.

We have very few professional machine shops on the UK but it's the only way to get a rebore done on any engine.

The level of precision required is just not available with home machining. The measuring equipment itself would be beyond most home setups. 

And once you've taken it off, you can't put it back on. 

 

 

Oil change was full of glitter and it smokes. It's burning oil. It's leaking oil. It will be coming apart for gasketing at a minimum.

 

Not trying to be cocky, I'm an aerospace machinist with 25 years or so. I've made everything from chicken house floor scrapers to parts on the space station.

 

My lathe is 1944 or earlier and has the bronze oilite bushing bearings in the headstock instead of the later less rigid timkin roller bearings. (the roller bearings can run longer at fast speeds without getting hot, but I prefer the accuracy of the bronze bearings.) I've rebuilt the lathe as well.

 

The block wouldn't be on the spindle, it would be strapped to the carriage with the cross removed. It's called line boring. You use the tail stock to hold the other end of your bar. I would indicate it 6 ways from Sunday. I'd be using dead centers in headstock and tailstock with a dog driving my bar. I'd have to knock a bar together, use a fine thread screw at an angle to drive the bit, real light cuts. Finish hone. Wouldn't be going for speed, here, just doing it right and slow. Not like I'm being paid for this job.

 

I have trouble believing you can't line bore a cast iron block from the '60s accurately enough for a one cylinder small engine. Machinists been doing it that way a long time...

 

It's a question of clearance, not ability. Don't know if my lathe is big enough.

 

Line boring on a lathe example from a quick search:

 

[oliver2-44 9,745]

Thank you for the description.  

I've certainly seen enough horizontal boring machines to grasp what your proposing to do.

Again questions to learn.

Since most lathes have more wear in the bed ways in the roughly 12" area in front of the chuck.

Could you use a long boring bar so the machining would happen on the tail end of the bed ways.

That way you could tighten the carriage gibbs up just a touch more, since you usually have to adjust them to both the head end and tail end of the lathe. 

Of course a long bar could have some flex in it, so could you add a steady rest on the bar between the headstock close to the part?

 

One of the reasons I'm interested in this, is like many here I've looked for years for a machine shop that would touch a small engine for years

I finally found one 4-1/2 hours away. There's one old machinist there that does the small engines. he's up in age and could retire any day. 

When you set up your new shop I suspect you cold find a fair amount of business boring blocks and making parts for WH and other brand old tractors.

Of course the question is would it be profitable? 

 

25 minutes ago, BurtB said:

It's a question of clearance, not ability. Don't know if my lathe is big enough.

 

I have a block I can get measurements on later today or this weekend

Edited August 23 by oliver2-44

[Mickwhitt 4,622]

Burt.

Please don't think I was questioning your experience or abilities. 

You obviously know your machine far better than anyone else and are confident in how it will cope with such a job.

If you can set up a line boring rig then it is possible to do what you are proposing. 

It's a question of will the block fit and give you enough travel to machine the bore. 

If it will then I can't wait to see you crack on with this project. 

Having stripped my engine to replace bearings and gaskets I decided to have it bored and ground.

Runs like a new one now so it was well worth the effort.  

Mick 

[BurtB 88]

3 hours ago, oliver2-44 said:

Since most lathes have more wear in the bed ways in the roughly 12" area in front of the chuck.

Could you use a long boring bar so the machining would happen on the tail end of the bed ways.

That way you could tighten the carriage gibbs up just a touch more, since you usually have to adjust them to both the head end and tail end of the lathe. 

Of course a long bar could have some flex in it, so could you add a steady rest on the bar between the headstock close to the part?

 

Yes, you can use a longer bar to get into a more consistent area of the ways. Often, not that it's a great practice, you end up making cuts on one area of the bore and then adjusting the gibs and moving down and taking some more passes. Not great to do it that way, but if you hold your mouth right, you can often get away with it. For this job, I would be trying to get into an area of the ways that are consistent enough that I can do the full length.

 

If you take light cuts, you won't need a steady. Steadies often cause problems, hit a chip and bounce the bar. Go with a bigger bar and you have less flex. IDK, a good running steady is definitely a possibility. I have a shop made steady but likely won't use it for this. This job, I would be taking real light cuts, slow speed (have back gearing that gets me down around 60 RPM, IIRC), slow feed, and sneaking up on my finish diameter. With dead centers and a drive dog, it's possible to pull the bar and take measurements in between passes. Like I said, I'm not being paid for this job, time isn't an issue. Doing it just right is more important.

 

3 hours ago, oliver2-44 said:

Of course the question is would it be profitable? 

 

That's the perennial question. I'll be shooting for a shop rate of $150/hr minimum. If people are willing to pay what it costs, I'll do small engine work or whatever. This isn't vanity, but I doubt I'll have trouble getting work.

 

The machinists that taught me had journeymen's papers, by the time I came along, the apprenticeships were gone as the unions were busted. Great recession happened, and there were many layoffs. Pay was terrible. Few people stayed in the trade in my generation. I'm 43 and have been the youngest guy in the shop for most of my career. There are more young guys around now, but they suffer for lack of good mentorship. Most machinists are very old and retiring or dying. I know my value and the value of my work. I also know my rarity. I'm going to charge what the market will bear. 

 

I plan on a firm 40hr week max rule. If the backlog is 6mo, it is what it is.

 

3 hours ago, oliver2-44 said:

I have a block I can get measurements on later today or this weekend

 

That would be really awesome! No rush. If it will fit, I'll post a step-by-step pictorial on how I do it. It will likely be a few months.

 

2 hours ago, Mickwhitt said:

It's a question of will the block fit and give you enough travel to machine the bore. 

If it will then I can't wait to see you crack on with this project. 

 

Yup, that's why I want to know that one dim. I'm looking for the shortest distance from center of bore to a roughly perpendicular plane. That determines if I can do it with the machine I have. I have around 30" on length. 3" or so, at best, over the carriage with cross and compound removed. Bore is 3.5" diameter. So, 1.75" to center of bore. It might be possible.

Edited August 23 by BurtB

[ebinmaine 67,474]

 

 

I don't speak this language but it's a very interesting thread.  

 

 

Incidentally, my own local small engine repair place still uses a single cylinder hand raised/lowered machine.  

[Bill D 1,920]

Welcome to Red Square.  Glad you're here.  Following.

Edited August 24 by Bill D

[oliver2-44 9,745]

@BurtB Sorry I haven’t gotten you those block measurements. I had to come down to my moms house to take care of some things for the week. 

[oliver2-44 9,745]

@BurtB

Here's some measurements of a bare k341 block. The CL's would be the same on a K321 block. 

Just a slight difference in bore diameter which doesn't matter since these are CL measurements.

 

12-3/8"  Block Height Overall

 3-3/4" from bottom of block to Centerline of crankshaft

 2-15/16 - 3" roughly from bearing plate side of block to centerline of bore (I didn't have a great way to establish C.L.

I measured a36" Atlas lathe I have access to and from the top of the Cross Slide Ways to the CL of chuck was 3-3/8" 

But from the top of the Cross Slide to CL of chuck was 3-0"  

So if you completely removed the cross slide and mounted your mounting plate to the cross slide ways you would have 3/8" to work with.

[oliver2-44 9,745]

One more measurement, the bore is 6" long from the top of the block.

[BurtB 88]

6 hours ago, oliver2-44 said:

@BurtB

Here's some measurements of a bare k341 block. The CL's would be the same on a K321 block. 

Just a slight difference i

 2-15/16 - 3" roughly from bearing plate side of block to centerline of bore (I didn't have a great way to establish C.L.

I measured a36" Atlas lathe I have access to and from the top of the Cross Slide Ways to the CL of chuck was 3-3/8" 

But from the top of the Cross Slide to CL of chuck was 3-0"  

So if you completely removed the cross slide and mounted your mounting plate to the cross slide ways you would have 3/8" to work with.

 

Oh man. I was already figuring on having to mount to the cross ways.

 

We got something to cook with here.

 

Thank you so much for the thorough measurements. Sorry for the late response. Been real busy. Been clearing overgrowth down one side of the garage and clearing out the drainage system in front. Running Ethernet cable inside the house and about a billion other things.

 

Bought the kid a temporary riding lawnmower while we work on the GT-14.

 

Current tasks in order for the Wheel Horse:

 

Make center mount tach-o-matic lever clamp that fits 48" deck. Rewind Clutch. Rewire/rebuild engine/rebuild tranny.

 

I'm waiting on a bigger piece of metal for the clamp. I'll post a full write up when it's done.

 

I've got to get the garage more organized and wired before I attempt engine rebuild.