Harrison lathe accuracy ?

[Harold Hall 1Participant @haroldhall1]

Your said David

"Again, perhaps it is my industrial background that makes me aware of the ongoing requirement for "extra" kit to make a machine useable"

Are you suggesting that my lathe is not useable? Looking around my workshop and home it does not seem that way to me.

Sorry, will be away from early tomorrow till mid July so will be unable to reply to any further comments in this thread

Harold

 

Edited By Harold Hall 1 on 11/06/2012 21:33:22

[David LittlewoodParticipant @davidlittlewood51847]

Martin/Nigel,

I think we will just have to agree to differ on this matter. I do have a precision level, and I do use it to set up my lathes initially to be level (horizontal) but I find it is still necessary to check with a turning test (over 10 or 12 ", not 4) and make some fine adjustments. It is the latter which matters to me, not absolute horizontality. If I had to choose, the latter would always win, and I suggest most users would find the same.

Also, the definition of "level" in authoritative dictionaries (and I don't consider Google to be such) does include "flat", but only after numerous primary definitions meaning "horizontal", which is the one the average person would be likely to assume is meant. To avoid confusing the reader, it is a best to avoid using a word with a main meaning and a subsidiary meaning, intending the reader to know the latter is meant.

David

[blowlampParticipant @blowlamp]

Posted by David Littlewood on 11/06/2012 21:47:55:

Martin/Nigel,

I think we will just have to agree to differ on this matter. I do have a precision level, and I do use it to set up my lathes initially to be level (horizontal) but I find it is still necessary to check with a turning test (over 10 or 12 ", not 4) and make some fine adjustments. It is the latter which matters to me, not absolute horizontality. If I had to choose, the latter would always win, and I suggest most users would find the same.

Also, the definition of "level" in authoritative dictionaries (and I don't consider Google to be such) does include "flat", but only after numerous primary definitions meaning "horizontal", which is the one the average person would be likely to assume is meant. To avoid confusing the reader, it is a best to avoid using a word with a main meaning and a subsidiary meaning, intending the reader to know the latter is meant.

David

David.

You are starting to sound desperate.

Desperate: Google Definition.

Martin.

[jason udallParticipant @jasonudall57142]

I feel kind of spoilt at work.HARDCREAT…Seen five Hardinge lathes installed…not one needed "leveling"..installation even notes this..DO NOT ATTEMPT TO TRUE MACHINE BY JACKING.

now Mazak…thats a different horse..much as discribed here. still if you want it true to 0.15 micron on 200 mm….and that was at limit of "clock". .. we work to +/-3 microns in production but then most things ground later….

But none of this answers OP

Looking forward to the answer when he has checked HS out

Rgds

[RICHARD GREEN 2Participant @richardgreen2]

You will all be pleased to know that the problem I had with accuracy on the Harrison M500 lathe has been solved,

I was sitting in my workshop a couple of weeks ago, trying to work out what was wrong with the accuracy of this lathe, it's never been really accurate since I bought it.

I realised that when I originally did the first accuracy test, the "gap piece" was in place on the lathe, and it occured to me that if this had been incorrectly refitted by a previous owner it could be altering the travel of the saddle at the headstock end,

An old friend of mine 80 + years old , an ex machine tool fitter of years ago, came to see me today and we removed all the shims that I had fitted under the headstock, also removed the "gap piece" completely from the lathe.

Then we did a test piece to see what it was now turning like……………….

Without any shims or the gap piece, we had an accuracy of less than a thou over 5",

Then we did a boring test, same thing, better than a thou over 4",

The moral of this story is, check the simple things first, before you start looking for problems that are not there.

I know some one will say I should be getting better accuracy than I've got, but it is a large lathe of probably 30+ years old, I can probably put some of it down to a small amount of bed wear near the headstock, but all in all I'm now very happy with the lathe,

The gap piece is quite large at 14" square by about 5" thick, and quite heavy, it fitted well where it met the main bed, and the saddle ran over the joint without any binding or jamming, it could have been crud under the gap piece at the headstock end causing the saddle to rise up as it travelled towards the chuck, either way it seems like the problem has been solved,

When I eventually re-fit the gap piece I will make sure that everything is spotlessly clean and all evenly tightened down.

I was so happy this morning that the severe inaccuracy had been solved, that we also fitted a new set of 5 V-belts on the main motor,………………thats another job done.

Thanks for all your help and advice,

Richard.

[Sub MandrelParticipant @submandrel]

Congratulations for fessing up Richard.

Not that I've ever done anything remotely like that myself, you know

Neil

[RICHARD GREEN 2Participant @richardgreen2]

Hello Neil,

You might call it "fessing up", but I've never been ashamed to admit when I've made a boo boo, or missed the obvious, nobody's perfect, and we can all be clever after the event.

I just thought my little story might help someone in the future, although I have over 40 years workshop experience, it jolts you back into reality very quickly, and let's you know that you are only human, and can still be caught out.

Richard.

[blowlampParticipant @blowlamp]

Richard.

Great news that you got your lathe sorted. I reckon you could get it closer still, but if you're happy enough then that's all that matters – it'll still turn out good work, I'm sure.

I think the merit of checking with an engineer's level at several points along the bed, is surely beyond question in this kind of situation, where nothing seems to quite add up.

Martin.

[RICHARD GREEN 2Participant @richardgreen2]

Martin,

I think that now the lathe seems to be getting sorted out, It might be worth just checking the bed with a level, I might be able to lose that thou with some minor adjustment.

I'm going to run it for a bit to let things settle down, and then check it.

Richard.

[Anonymous]

Hmmmm, now I'm embarrassed. I had a very similar problem on my Harrison M300 a couple of years ago, and it turned out to be the same issue. It didn't seem worth mentioning in amongst the forthright dicussions above.

The thing that really threw me was that my lathe turned taper at the headstock (about 5 thou in 3 inches), but seemed to bore parallel. I spent many hours trying to work out a geometry that would fit those facts. I also spent hours mucking about with a precision level and jacking bolts on the stand to no real avail.

It was only after I'd turned the journals on my traction front axle, out near the tailstock, and found them parallel to within a couple of tenths that the light began to dawn. Further tests showed that the taper only occurred when the saddle reached the removable gap piece.

With that in mind, and a good think about the order in which the gap piece should be tightened up, the problem was solved. Of course, as Richard says, the gap piece and bed must be scrupulously clean as well.

Regards,

Andrew

[RICHARD GREEN 2Participant @richardgreen2]

Hello Andrew,

What procedure did you use for tightening down the gap piece ?

I'm going to have to re-fit this one of mine at some point, so I would like to get it right.

Richard.

[Anonymous]

Hi Richard,

On my gap piece there is the following: two diagonally placed M10 bolts in the central portion, and one M10 bolt at the back of the gap piece. At the outboard end there is a taper pin with a countersunk screw and washer for extraction. At the headstock end there is a horizontal M6 grub screw pushing against the headstock. After cleaning and fitting the gap piece I fit all the M10 bolts and do them up until they're just gripping. Then I fit the taper pin and knock it home with a brass drift. Then I tighten up the M6 grub screw that forces the gap piece against the outer section of the bed. Finally I tighten up the M10 bolts.

The way I see it the taper pin locates the gap piece. The M6 grub screw forces the gap piece against the main bed and ensures it is square, and the M10 bolts merely hold the whole lot down.

I don't recall seeing anything in the manual about fitting the gap piece, and the above may not be correct, but it seems to work for me.

Regards,

Andrew

[John McNamaraParticipant @johnmcnamara74883]

Hi Richard

Mind the Gap!

Running a lathe without a gap piece for long periods is not a good idea.

A while back I had an old Colechester its previous owner used it without the gap piece in place; with this particular lathe the saddle actually went over the gap meaning it was less supported. Using the lathe this way there was uneven wear under the saddle and the ways of the bed itself were also worn at the gap end.

When I refitted the gap there was a tiny step of a couple of thou or so.

My current lathe does not have a gap but if it did I would leave it in position as much as possible only removing it when necessary for turning large diameter work.

My Vertical Mill has removable taper pins to lock the overarm to the column at 90 deg. They do a good job but not a perfect one. After fitting the gap ,setting the taper pins and locking it down I would check with a dial indicator mounted on the saddle set at 90 degrees to the V flat face (Checking both sides one at a time) by running the saddle up and down the bed over the gap, You may find a small error. If found loosen the lock down screws and tap (a very light tap) the gap piece with a fibre hammer (Be careful not to mar the finish). then retighten and recheck until the error found is the same both sides.

My guess is there will be an error to be averaged out unless the lathe is new.

Cheers

John

[RICHARD GREEN 2Participant @richardgreen2]

John,

I have removed the gap piece to prove the point that it was that which was causing my trouble, Now having proved that, and while the gap piece is out of the lathe, I am going to fit the large faceplate, and machine the 25" flywheel from the 6" Burrell that I am building.

After that I'll refit the gap piece , I totally agree that It's bad practice to use a lathe for long periods without the gap piece in place.

Andrew, You are right, the works manual does not say anything about re-fitting the gap piece, I think we're on our own with this one !

My gap piece has got 4 x 12mm holding down screws, one in each corner, also a 12mm dowel, also a screw to push the gap casting back towards the main part of the bed.

Perhaps I could e-mail Harrisons for the correct re-fitting procedure.

Richard.

[Ian S CParticipant @iansc]

Might be best to torque the bolts down so that you get them even. Ian S C

[Anonymous]

Richard: It seems an oversight on the part of Harrison not to mention re-fitting of the gap piece. I guess that way back when it was assumed that the foreman would have the knowledge anyway. If you get a reply from Harrison then I'd be interested!

I have in mind that for some far eastern lathes removing the gap piece invalidates the accuracy limits. I assume that this is because once the gap piece has been removed it cannot be easily replaced in the correct position. Anybody know if this is true?

Regards,

Andrew

[jason udallParticipant @jasonudall57142]

Got a WARD at work.

gap bed mc "dovetails" are square section about 30 mm AC front and back <>—–<> like

OK so 12 " between edges 6" center height (with out gap!) 50 " between centers.

never seen missing gap bit

saddle is about 12" in Z and 28 " wide 10" throw in X…can still turn to 2 though over that length ( only use it for roughing out ) and making liners..

built 1924…

the thing is built like a brick privvy I guess if its gonna warp it has now.

[RICHARD GREEN 2Participant @richardgreen2]

Andrew,

I've e-mailed Harrisons yesterday, We'll see what they have to say.

Richard.

[RICHARD GREEN 2Participant @richardgreen2]

A lathe manufacturer who wishes to remain unknown, has sent me the following information regarding removal and re-fitting of lathe gap pieces, and has given me permission to show it on this website,

It is general information, and not aimed at any specific make or model of lathe, but we should all find it useful information.

Richard.

[Anonymous]

Richard: Thanks for posting the instructions. It looks like I've been on the right track. It is slightly odd that the taper dowels are not mentioned in the re-fitting process. I'd had thought that they should be tapped home between operations 5 & 6?

Regards,

Andrew

[John McNamaraParticipant @johnmcnamara74883]

Hi Richard

Step Six "Align by hand" An interesting proposition. I am not sure you can "feel" the last tenth or so particularly if there is a radius on each side where the edges meet.

This is where an indicator mounted on the saddle and run along the both sides of the v-ways across the join, will give a better indication of the centring of the axis of the gap piece with the ways. It will also reveal if there is any wear.

Cheers

John

[Roger HampsonParticipant @rogerhampson72116]

I have read with interest the discussion of lathe levieling, i own a Harrison M300 which stands on a concrete floorand i have leveled the maching to be as close as a 12" moor and wright ;evel will show.

and the machine turns almost parallel on its original stand but i get a puddle of coolent that sits at the front of the lathe driptray, the only way i can drain this is to jack up the front of the entire stand and lathe by some 1/4".

question to the group. is this normal??

[Anonymous]

A lathe bed doesn't need to be level to turn parallel. The important point is that the bed isn't twisted. It doesn't matter what angle the bed is to the local gravitational field. My M300, on the manufacturers stand, turns parallel to better than a thou over 6", but leans backwards so coolant doesn't collect at the front.

Andrew

Edited By Andrew Johnston on 30/10/2021 16:19:52

[Howard LewisParticipant @howardlewis46836]

Again, it seems that the word level means different things to different people.

Although we often talk of "Levelling" a lathe what is usually meant is removing twist (stress ) from the bed, so that the machine will turn parallel

This can be done using a sensitive level across the ways, at each of the bed, or the "Dumbell" method as advocated by Myford, Ian Bradley, etc. Sometimes known as "Rollie's dad's method".

A lathe without twist in the bed does not have to be level, in the sense of horizontal in either, or both, planes.

Indeed when flood coolant is used it may be necessary to incline the bed in one or both planes so that the coolant runs towards the drain back to tank.

With regard to lathes on ships, some years ago, I helped a friend to install a lathe that had started life on a ship as part of Lease-Lend.

The bench weighed a lot more than the quite substantial lathe. It was made entirely of 4" x 3" channel iron, with reinforcing members halfway along the front and rear., with thick steel top .

I think that rigid would be a fair description.

Presumably, the bench was intended to minimise the effects of the ship rolling or pitching.

It was claimed that the bench was made in this way so that it could withstand a full broadside!

Whether fired or received was not made plain.

It has always puzzled me that I have seen lathes, but never seen a milling machine in an engine room workshop

Howard  fat fingers, yet again

Edited By Howard Lewis on 30/10/2021 17:22:36

[SillyOldDufferModerator @sillyoldduffer]

Posted by Howard Lewis on 30/10/2021 17:20:54:

…

With regard to lathes on ships, some years ago, I helped a friend to install a lathe that had started life on a ship as part of Lease-Lend.

The bench weighed a lot more than the quite substantial lathe. It was made entirely of 4" x 3" channel iron, with reinforcing members halfway along the front and rear., with thick steel top .

I think that rigid would be a fair description.

Presumably, the bench was intended to minimise the effects of the ship rolling or pitching.

…

What's unacceptable in a ship is for a lathe to come loose in a storm. Hundreds of kilograms of cast iron sliding around as the ship moves violently will do a lot of damage and the crew will have trouble stopping it. The bench has to be strong enough to cope with the worst of maritime bad weather.

My ex-RN brother-in-law was caught in a storm in the Bay of Biscay. He said the crew thought it was rough until the stabilisers failed. After that anything not fixed down professionally took off causing many minor injuries – his mates arm was broken by a flying typewriter. Debris everywhere mixed with splashes of vomit because everyone was sea-sick!

Not amused – he joined the Navy for foreign travel, a girl in every port, and water-polo!

Dave

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