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snowman
12-23-2010, 07:02 AM
Discuss:

http://www.youtube.com/watch?v=oLEbwiWURT4&feature=related

Interesting concept.

GKman
12-23-2010, 07:20 AM
1:06 Waste Of Time.

Magicniner
12-23-2010, 09:37 AM
That's a minute of my life I won't get back!
Was there a point to this?

mike os
12-23-2010, 09:48 AM
.......zzz zzzzzzz zzzz

Carld
12-23-2010, 11:14 AM
I don't consider that fancy lathe work at all but it is a very safe way to do it. Just a common sense method of boring the cylinder that is done at many shops. It's one of a few ways to do the job.

tdmidget
12-23-2010, 12:19 PM
I feel the same. OP , want to come back and explain what was so fancy here? Did you understand what was being done?

mochinist
12-23-2010, 12:37 PM
I dont know whats so confusing about what is being done, or calling it a waste of time either. I see stuff like that and even though I may not have a use for it at the moment, I catalog it in my head and someday I may have something similar to setup and hopefully I'll remember it.

I think "fancy" probably wasnt the best choice of words, but maybe the op had never seen anything like this and was curious if it was a safe way to do it, etc. :confused:

Arcane
12-23-2010, 12:55 PM
Well said, mochinist.

Some people's responses were rude to say the least.

snowman
12-23-2010, 01:02 PM
Fancy maybe not, but quite interesting.

Like Macona said, it's something that you file away.

I had personally not seen anything done in that manor before.

As for the rude comments, there are a lot of people here who are obviously better suited for practical machinist, where the crabby burnt out professionals hang out.

tdmidget
12-23-2010, 02:34 PM
So for us rude, crude types who should go back to PM, What was notable about it?
I'm not even sure of what I' seeing and there is no explanation. The boring bar appears to pass through the work piece and chuck to what? The left end of the spindle has something in running about 3/4" off center so I would assume that has nothing to do with the boring bar.

So speaking of rude, how about popping some totally unexplained, unremarked , scrap of video and saying "discuss".

Seastar
12-23-2010, 02:48 PM
Now, now, children.
Mind your maners!
Bill

gwilson
12-23-2010, 03:57 PM
I must agree,not fancy. Simply not remarkable in any way,and I'm not a burned out pro for saying it. It's just true.

mike os
12-23-2010, 04:43 PM
I would consider myself very much an amateur ...... possible not even that qualified,:D but would still consider that to be a "normal" operation.....

macona
12-23-2010, 05:37 PM
Like Macona said, it's something that you file away.




Wha.. Who.. Me?

aboard_epsilon
12-23-2010, 06:04 PM
Anyone got the plans for this one

please post them

http://www.youtube.com/watch?v=Iz3pDMP7IsE&feature=related

all the best.markj

davidh
12-23-2010, 06:29 PM
Discuss:

http://www.youtube.com/watch?v=oLEbwiWURT4&feature=related

Interesting concept.

so lets discuss. . . . how did the cylinder stay in the chuck ? a few tie bolts it appears, secured to a shiney adapter that was held in the chuck securely by a tie bolt running thru the spindle ? maybe ? cool.

i have filed the long tie bolt info away in my memory. a fixture to make a rig, to make another rig to do a job is a cool thing.

thats what separates the men from the boys.

remember even us old dudes have not seen it all nor do we know it all. . . .

snowman
12-23-2010, 08:30 PM
so lets discuss. . . . how did the cylinder stay in the chuck ? a few tie bolts it appears, secured to a shiney adapter that was held in the chuck securely by a tie bolt running thru the spindle ? maybe ? cool. .

That's what I got out of it. Workpiece was bolted to a faceplate held in chuck, faceplate was bolted, though the spindle, to hold it and work securely in chuck.

Void
12-23-2010, 08:41 PM
That was pretty cool.

I think a more accurate way to set that up especially if one is doing lots of them is to make a fixture for the cross slide and mount the boring bar between chuck and a live center in the tailstock. I think the technique is called "boring between centers."

ETA: I have done several jobs that were very similar in setup as in the OP. They were all bearing pockets in electric motor rear housings. Much less overhang than in the video. Blind holes so they had to be bored that way. They could also have been done on a mill... as could the operation in the video.

-DU-

GadgetBuilder
12-23-2010, 08:43 PM
Mark,

A slightly different square hole drilling jig is shown here:
http://www.youtube.com/watch?v=9qEhyQfbImY&feature=related

The magazine with the article/plans:
http://www.myhobbystore.com/product/23972/model-engineer-magazine-no-4285

See the bottom of the front cover, looks like it is the right magazine. You might be able to get it on-line by subscribing to their archives.

John

tdmidget
12-23-2010, 09:53 PM
David the spindle being bored is not held in the chuck. It is held to a fixture with the tie rods and flange. This prevents distortion by the chuck jaws. Not real sure why it needs anything through the lathe spindle unless the workpiece is out of balance enough to worry about it wobbling its self loose.
Still , unless I missed something, this is elementary bread and butter lathe work.

snowman
12-23-2010, 10:30 PM
Still , unless I missed something, this is elementary bread and butter lathe work.

Nope, your not missing anything, I'm just an ignorant ass I guess.

I've been doing basic machine work for 15 years +, I've never seen such a setup.

Sorry for wasting your time.

Black_Moons
12-23-2010, 11:57 PM
If you don't have anything nice to say, You should go back to PM :)

I thought it was kinda intresting.

Oldbrock
12-24-2010, 12:19 AM
I've been at the game for 60 years and I found it a great, non-distorting, non fly out of the lathe setup. It is also good for repeatable operations, saving set up time if multiple cylinders were to be machined. I have a job coming in in the new year that could use this idea to advantage. Thanks for the link. Peter;)

Void
12-24-2010, 03:45 AM
David the spindle being bored is not held in the chuck. It is held to a fixture with the tie rods and flange. This prevents distortion by the chuck jaws. Not real sure why it needs anything through the lathe spindle unless the workpiece is out of balance enough to worry about it wobbling its self loose.


Thanks for the clarification tdmidget.

Still seems a rather deep bore for the boring bar. If he is going all the way through I could see chatter being a problem. But as long as it's cutting smooth ... just get on with it.

I can also see how it is quick and easy to fab up the fixture out of some long bolts or allthread and a couple of chunks of aluminum or mild steel. As long as the ends are true and normal to the axis it should center up well. Holding the fixture base in the chuck would also make it easy to center. The rod through the spindle is some nice extra insurance against it working loose in the chuck. Not that it would fly far because the boring bar will prevent that... but things can get sideways in a hurry sometimes and it could ruin the cylinder and break the boring bar if it got loose.

Make a couple of those fixtures and one could be swapping parts out of one while the other is mounted.

I have seen chucks that have T-slots between the jaws which would make it easy for a one off. When I have done similar jobs I used a faceplate.



Still , unless I missed something, this is elementary bread and butter lathe work.

I agree.

-DU-

airsmith282
12-24-2010, 07:17 AM
Anyone got the plans for this one

please post them

http://www.youtube.com/watch?v=Iz3pDMP7IsE&feature=related

all the best.markj

now thats a toy i can get alot of use out of that and a hex model to , i could make my own sockets lol
better not mention that part to the wife she just might buy me the tools to do just that and ill never get to buy real tools again hahahahahhahaha

snowman
12-24-2010, 07:22 AM
I agree.

-DU-

Congratulations on insulting someone....on your second post.

You'll fit in well here.

aboard_epsilon
12-24-2010, 08:12 AM
Mark,

A slightly different square hole drilling jig is shown here:
http://www.youtube.com/watch?v=9qEhyQfbImY&feature=related

The magazine with the article/plans:
http://www.myhobbystore.com/product/23972/model-engineer-magazine-no-4285

See the bottom of the front cover, looks like it is the right magazine. You might be able to get it on-line by subscribing to their archives.

John

ho ho ho ..do you think I'm going to pay a bunch of money for blurry pdfs ....that you cant see the dimensions on ..

there was discussion here a few weeks ago about the MEW archives..not a lot of people are happy .

all the best.markj

aboard_epsilon
12-24-2010, 08:16 AM
Congratulations on insulting someone....on your second post.

You'll fit in well here.

I've never seen that set up either ..

think a lot of people answewred here ..and didnt actually make the observation of what it really was or what was going on .

All the best.markj

bob ward
12-24-2010, 08:18 AM
A tie rod through the headstock to secure a job in the chuck on which you may only have a tenuous hold?

Good idea! I'll file it for future use.

To the critical, firstly recall the words of Bambi's mother, then look at the title of the forum and contemplate that there are many on here who don't know anywhere near as much about machining as they want to know.

aboard_epsilon
12-24-2010, 08:24 AM
A tie rod through the headstock to secure a job in the chuck on which you may only have a tenuous hold?

Good idea! I'll file it for future use.

To the critical, firstly recall the words of Bambi's mother, then look at the title of the forum and contemplate that there are many on here who don't know anywhere near as much about machining as they want to know.

no, it not the rod ..the rod is bread and butter ..used it a few times ..
it's the fact that the cylinder is in a jig.

all the best.markj

JCHannum
12-24-2010, 09:33 AM
It is a good idea that is poorly presented. It took a couple of passes for me to understand what it was about. Granted machinists are not film producers, but better lighting with the lathe stopped, pointing out the setup would have done a much better job of getting the point across.

Void
12-24-2010, 10:32 AM
Congratulations on insulting someone....on your second post.


I had no idea it was so easy to insult someone by simply thanking them for clarifying a technique and agreeing with them. ;)


You'll fit in well here.

Thanks. ;)

-DU-

oil mac
12-24-2010, 12:55 PM
Hold your hair on guys, There is a germ of an idea here, &i thought i had seen something similar before, My one solitary braincell remembered it from back in my formative years in the Jurassic period.:eek:
The machine shop across the road from where i worked at that period, used to bore out castings, components, not unlike in appearance to the one in the video, These were carried out in batches of about maybe twenty a time (a guess as to numbers)

however what the guys did in that plant was as follows, As it was an on-going job, a fixture had been made, This was fixed on the lathe faceplate, &trued up, It consisted of a flange similar to the one the operator was using in his chuck, the component was slipped on to the face of this flange and supported by a fairly heavy sort of sleeve, Bolted on to the faceplate flange which gripped the outer & inner flanges of the casting being operated on, the whole setting up of the component took a very short space of time &gave repeatability, I think light cuts might have been the order of the day

gnm109
12-24-2010, 02:33 PM
Congratulations on insulting someone....on your second post.

You'll fit in well here.


I noticed that as well. Come to think of it, isn't that the main use for the internet - anonymous contradictions, offensive statements and general flaming?

Frankly, if I really wanted an accurate boring job, I would have to get something like a Van Norman boring bar and some nice torque plates. Good luck doing that on your lathe.

With that cylinder rolling around and the boring bar swaying in the wind, he will be lucky to get any sort of accuracy.

It may be elementary but it still looks dumb. But I mean that in a nice way....:)

Oldbrock
12-24-2010, 05:31 PM
Sorry gnm, looks like a skookum setup to me, however I would have used a more stout boring bar. If you look at the setup again you will see a. plate in chuck and plate over end face constitute torque plates, b. Torque plate in chuck is secured with a drawbar through the lathe spindle. c. The speed isn't high enough to throw anything off center. If the lathe turns parallel then I would predict a perfect bore and repeatable as the torque plate in the chuck stays put ready to receive the next casting. Don't put down someone who sees something you don't. Anyway I still wish you and all others on this site a Very Merry Christmas and a Happy New Year. Peter

RussZHC
12-24-2010, 06:13 PM
It did get me looking...

http://www.youtube.com/watch?v=FfcukAV_Zhk&NR=1

after the head is removed you can see what I suspect is a similar jig to the one in the OP posted video, but also that this is a head casting it sounds like they often do, so the jig is a bit more "permanent"

http://www.youtube.com/watch?v=H0_6VmY6mns


http://www.youtube.com/watch?v=uFKQrKMNYig&feature=related


http://www.youtube.com/watch?v=J4EtmJhDYHQ&feature=related

of the bunch, this last one is what a noob like me is after and can very much use...the years it takes to accumulate this knowledge...and love the wobbling pin to find center ;)

aboard_epsilon
12-24-2010, 07:28 PM
It did get me looking...

http://www.youtube.com/watch?v=FfcukAV_Zhk&NR=1

after the head is removed you can see what I suspect is a similar jig to the one in the OP posted video, but also that this is a head casting it sounds like they often do, so the jig is a bit more "permanent"

http://www.youtube.com/watch?v=H0_6VmY6mns


http://www.youtube.com/watch?v=uFKQrKMNYig&feature=related


http://www.youtube.com/watch?v=J4EtmJhDYHQ&feature=related

of the bunch, this last one is what a noob like me is after and can very much use...the years it takes to accumulate this knowledge...and love the wobbling pin to find center ;)

last video has a very good tip ive never seen before..plastersene and a bit of wire as a centre finder .

worth looking at that ..

all the best.markj

lazlo
12-24-2010, 08:49 PM
It did get me looking...

http://www.youtube.com/watch?v=FfcukAV_Zhk&NR=1

after the head is removed you can see what I suspect is a similar jig to the one in the OP posted video

Ditto. It sure looks like the OP is just bolting the casting to a faceplate with tie-rods through the flange bolt-holes, same as this guy is doing boring the Harley cylinder.

Seems pretty mundane, or am I missing something?

gnm109
12-24-2010, 10:49 PM
Ditto. It sure looks like the OP is just bolting the casting to a faceplate with tie-rods through the flange bolt-holes, same as this guy is doing boring the Harley cylinder.

Seems pretty mundane, or am I missing something?


Nothing special about it...

The Harley-Davidson service manual shows cylinders being measured with torque plates bolted across the tops and bottoms of the cylinders. That is done to approximate the shape of the cylinder when it is bolted down to the crankcases.

One of those videos shows the cylinder being spun on the lathe with only two bolts and some nuts holding it down. That's not the way it's done by the Harley dealers. They use torque plates with the cylinder bolted down under the table on a boring bar. The boring head is very strong and stiff and moves slowly down into the cylinder. In that way, a perfect job can be done.

Without torque plates and with that boring bar extended some 8" as shown, it's not going to make for a round hole. With clearances on a touring engine down to slightly more than .001, there is little margin for error.

I guess it may work, but I wouldn't care for it.

RussZHC
12-25-2010, 01:09 AM
What I found interesting was that when possible due to size (work v. swing of lathe) it looks best to fix the work somehow and do it between centers or similar; sort of between centers, then bar in chuck work fastened down, then work in chuck bar fastened.

Lack of experience but I just assumed between centers was how it was always done and if the work was too large you either found a different machine, got a lathe with more swing or didn't do the work...going back to the original video there appeared to be a bung/spigot of some sort on one side, would it have helped the smoothness enough to make it worth while by adding a "counter weight" of similar size to the opposite side? And for the size of the opening a bigger diameter boring bar more rigid?

tdmidget
12-25-2010, 01:34 PM
Ditto. It sure looks like the OP is just bolting the casting to a faceplate with tie-rods through the flange bolt-holes, same as this guy is doing boring the Harley cylinder.

Seems pretty mundane, or am I missing something?

Yes. It is not a jig nor a face plate. A jig guides the tool. A fixture may be part of a jig but not necessarily so. A face plate does not locate the workpiece. If you look closer at the Harley cylinder set up the bottom diameter of the cylinder slips into the fixture and is located as though it were on the engine. However his clamping stinks. He should have had a ring or plate to replicate the force applied by the cylinder head. The 2 studs will produce an oval hole. Subsequent honing should also be done in the same restrained condition.
The OP's video showed what was called a spindle mounted on what was called a "mandrel". It appears to be a fixture that would locate on the end and the OD near the headstock. I don't see how it can be called a mandrel since you could not bore hole with a mandrel in it. It is possible that he is boring only at the tailstock end of the workpiece and thus it could be on a mandrel but then what would the tie rods be for? There is not enough information to do more than guess.

gnm109
12-25-2010, 03:53 PM
Yes. It is not a jig nor a face plate. A jig guides the tool. A fixture may be part of a jig but not necessarily so. A face plate does not locate the workpiece. If you look closer at the Harley cylinder set up the bottom diameter of the cylinder slips into the fixture and is located as though it were on the engine. However his clamping stinks. He should have had a ring or plate to replicate the force applied by the cylinder head. The 2 studs will produce a oval hole. Subsequent honing should also be done in the same restrained condition.
The OP's video showed what was called a spindle mounted on what was called a "mandrel". It appears to be a fixture that would locate on the end and the OD near the headstock. I don't see how it can be called a mandrel since you could not bore hole with a mandrel in it. It is possible that he boring only at the tailstock end of the workpiece and thus it could be on a mandrel but then what would the tie rods be for? There is not enough information to do more than guess.


Quite right. That's not a proper way to clamp a Harley cylinder for boring or even honing.

Oldbrock
12-25-2010, 04:30 PM
Quite right, you need a top torque plate with four studs and the nuts torqued to engine torque specifications. I wonder if he used two torque plates when honing. When he loosened the TWO nuts holding the cylinder in the fixture they sure were not torqued to specs, too easy to undo. Don't know why he posted a video of how to do it when he doesn't know how in the first place. I still like the original setup that started this thread. Peter

The Artful Bodger
12-25-2010, 06:52 PM
This is the correct way to bore a motor cycle cylinder, from the folks at Drummond via lathes.co.uk.

http://www.lathes.co.uk/drummond/img25.gif

Clamp it between two blocks of wood!

gnm109
12-25-2010, 06:57 PM
Quite right, you need a top torque plate with four studs and the nuts torqued to engine torque specifications. I wonder if he used two torque plates when honing. When he loosened the TWO nuts holding the cylinder in the fixture they sure were not torqued to specs, too easy to undo. Don't know why he posted a video of how to do it when he doesn't know how in the first place. I still like the original setup that started this thread. Peter


I went back and asked him where the torque plates were. Here's his response.....

"When the cylinders are honed I put them in my torque plates. I leave about 0,25mm (.010") for finish honing. This is easier then with my KwikWay boring bar, it's too large and cumbersom to bore these cylinders, at the end of the day we both get the same results."

That means that he used a long, flexible boring bar which can flex and had no torque plates during its use. Thus, when he was finished taking out the majority of the metal, he only then used torque plates on the possibly egg-shaped cylinders.

It would have been better had he used the torque plates in the KwikWay bar that he has. Then he would have had round cylinders.

I sure wouldn't have put that video up.

gnm109
12-25-2010, 07:03 PM
This is the correct way to bore a motor cycle cylinder, from the folks at Drummond via lathes.co.uk.

http://www.lathes.co.uk/drummond/img25.gif

Clamp it between two blocks of wood!


That's actually quite good. Notice the stout boring bar and the solidity of the blocks and bolts holding the cylinder in place. Notice also that the cylinder is stationary while the bar rotates and is advanced by the operator. While not set up with torque plates as such, it's probably the next best thing.

lazlo
12-25-2010, 08:35 PM
While not set up with torque plates as such, it's probably the next best thing.

Boring it between centers like that is probably the most rigid way you could do it.

tdmidget
12-25-2010, 08:41 PM
I can see that stout oak blocks might damp vibration well but Drummond, et, al need to explain how to center that bore.

gnm109; If that guy knew what he was doing , he would know that the first rule of honing is do as little of it as possible. If one starts with round cylinders then that's a lot of the problem solved. If he has to hone .010 then he's doing something bad wrong. If he did a good job of boring he could leave .004 and have plenty to work with. He is advertising his incompetence. Many of his potential customers are probably savvy enough to see that even if they couldn't do it themselves. The average guy knows better than to screw something up so you can fix it.

gnm109
12-25-2010, 10:37 PM
I can see that stout oak blocks might damp vibration well but Drummond, et, al need to explain how to center that bore.

gnm109; If that guy knew what he was doing , he would know that the first rule of honing is do as little of it as possible. If one starts with round cylinders then that's a lot of the problem solved. If he has to hone .010 then he's doing something bad wrong. If he did a good job of boring he could leave .004 and have plenty to work with. He is advertising his incompetence. Many of his potential customers are probably savvy enough to see that even if they couldn't do it themselves. The average guy knows better than to screw something up so you can fix it.

Absolutely. And as I mentioned before, that boring bar of his has to reach all of the way into the cylinder, something like 7 inches. If it even deflects a thousahdth of an inch due to a pre-existing oval condition, the job will be ruined at the end.

Like many here, I suppose, I've been around and ridden, worked on owned motorcycles all of my adolescent and adult life. I still own a Harley-Davidson, one of about 40 motorcycles in many years. I've always had my cylinders bored by experts when needed since I never had the proper equipment such as a dedicated automotive boring bar. I've been in many a shop, even worked in shops where cylinders were bored and I've never seen one done on a lathe until that video.

gnm109
12-25-2010, 10:38 PM
Boring it between centers like that is probably the most rigid way you could do it.


That's really a good setup. As you say, it's quite rigid.

The Artful Bodger
12-25-2010, 10:43 PM
I can see that stout oak blocks might damp vibration well but Drummond, et, al need to explain how to center that bore..

Maybe he was starting with a raw casting.:)

oldtiffie
12-25-2010, 10:50 PM
This is the correct way to bore a motor cycle cylinder, from the folks at Drummond via lathes.co.uk.

http://www.lathes.co.uk/drummond/img25.gif

Clamp it between two blocks of wood!

Thanks for that AB.

Unless I'm way off the mark, that lathe is very similar to one that Steve aka S_J_H (??) did up beautifully not so long ago.

He also line-bored his S-B tail-stock on his S-B lathe using a similar method except that as I recall the tail-stock was fed along the lathe-bed way/s.

If Steve sees this perhaps he will post the links as they are really worth seeing bot the first time - and again.

RussZHC
12-25-2010, 11:11 PM
Now I know its just a painting and not a photo of the Drummond but is there something odd there or is it perspective or me wrong?

IF one is boring between centers (as the drawing appears to be) is it not the cylinder head fixed to the carriage that is then moved/advanced?

IF that is the case to me the drawing is odd in that you can see the cutter and if the carriage is the part moved there appears to be no way that the head can move close enough to the headstock end if the carriage is moved to the left and conversely if the carriage is moving to the right there can be no way (since it would have started at the opposite end of the bore) it could have started at the very end of the cylinder...right?
Now perspective plays a role here too, still...

lazlo
12-25-2010, 11:32 PM
IF that is the case to me the drawing is odd in that you can see the cutter and if the carriage is the part moved there appears to be no way that the head can move close enough to the headstock end

IIRC, the carriage feed on those turn of the Century Drummonds was the handwheel at the tailstock end of the bed.

Ordinarily, you'd take the topslide off and mount the casting to the carriage, like this picture from Chris Heapy's old site (RIP):

http://www.astronomiainumbria.org/advanced_internet_files/meccanica/easyweb.easynet.co.uk/_chrish/bore1.jpg

RussZHC
12-26-2010, 12:12 AM
Sorry, poor choice of wording...the point for me was it looks like if the carriage in the Drummond drawing is moving towards the headstock, and given the gap, won't the carriage either crash into the faceplate or partially fall into the gap before the boring tool has reached the far end of the bore?

This assumes of course that the boring goes from end to end and it certainly does not need to...

lazlo
12-26-2010, 12:19 AM
the point for me was it looks like if the carriage in the Drummond drawing is moving towards the headstock, and given the gap, won't the carriage either crash into the faceplate or partially fall into the gap before the boring tool has reached the far end of the bore?

Ah, see you what you mean Russ. Agreed -- they should be moving the carriage towards the tailstock, so the between-centers boring bar should start at the tailstock end of the cylinder.

oldtiffie
12-26-2010, 12:43 AM
http://www.lathes.co.uk/drummond/img25.gif

Perhaps there are several tools - with one that is cutting about to clear the tail-stock end of the cylinder and the other/s - including the visible tool near the head that is retracted and not cutting. Some of those line-boring bars/tools had several tool positions.

RussZHC
12-26-2010, 02:10 AM
OK...had not thought of that...so it could be (and this is worth filing away to me:D ) possible to mount several cutting bits at various points on the bar and in effect make several passes at once if a lot of material needed to be removed...thanks!

tdmidget
12-26-2010, 02:58 AM
But in both these deals with the workpiece fixed to the cross slide did ya ever notice that height above the cross slide is always perfect and needs no shims or other means of elevation? Maybe that's why they make a fixture for the chuck/faceplate- it's automatically centered. I don't see why it should be a problem with a stout enough boring bar plus the part can restrained as in service to get a round hole under service conditions. I have bored a 10 1/2 " long hole and was within .001 end to end. It WAS a big ridgid machine, mot like those pictured. But it can be done and with a fixture in the chuck, achieve reasonable production.

snowman
12-26-2010, 09:53 AM
I've always wanted to add a fixture to my lathe for the vertical centering difficulty you are describing. It would go on top of the cross slide, with the compound removed. So, imagine a plate on the top of the cross slide, at the outer edges of the Z axis there is a wedge hanging over the cross slide. That wedge rests upon another wedge that is permanently affixed to the cross slide itself. Movement of this plate for and aft would change the vertical position of the part (Y axis centering). Movement of the compound still allows for X axis centering. Movement of the saddle allows for the actual boring operation.

Now, the wedge would not be supportive of weight, but would allow you to easily find centerline, then place jack screws of some sort to actually take the clamping force and make the whole setup ridgid.

Does the scenario make sense? I don't have any CAD applications on this computer.

John Stevenson
12-26-2010, 10:03 AM
All it takes is to give an idea for your imagination to take over.

Does everyone want the instructions down to the last i and t ???

tdmidget
12-26-2010, 12:42 PM
I've always wanted to add a fixture to my lathe for the vertical centering difficulty you are describing. It would go on top of the cross slide, with the compound removed. So, imagine a plate on the top of the cross slide, at the outer edges of the Z axis there is a wedge hanging over the cross slide. That wedge rests upon another wedge that is permanently affixed to the cross slide itself. Movement of this plate for and aft would change the vertical position of the part (Y axis centering). Movement of the compound still allows for X axis centering. Movement of the saddle allows for the actual boring operation.

Now, the wedge would not be supportive of weight, but would allow you to easily find centerline, then place jack screws of some sort to actually take the clamping force and make the whole setup ridgid.

Does the scenario make sense? I don't have any CAD applications on this computer.

No. A lathe does not have a Y axis. The X axis 0 is always the axis of rotation. Unlike a mill , where the X and Y 0s can be moved to suit the part on a lathe the part must be moved to the X0. This means that you must be able to move the ends of the part separately in the vertical and horizontal directions to have this axis of rotation in the very center of the bore in this case and straight with the bore.
This is a waste of time when the workpiece already has datums established for both X and Z. Turn a fixture with a recess that is a close fit on the machined end of the piece and flat and perpendicular to the axis of rotation where it touches the fixture. Viola!!! The part is aligned with axis of rotation
If the part bearing on the fixture is indeed the datum and not a surface coplanar to it then Z 0 is the face of the fixture and X. 0 is the centerline.
It is critical to establish these with repeatabilty if making multiple parts or reworking/repairing old ones where the new work must match the old (assuming that it was done right the first time and this provides a set up for verifying that it was).