Author Topic: Union Lathe .... Help !!! (Read 21033 times)

Darren · « **on:** October 10, 2009, 02:53:41 PM »

I hope someone can help me here as I'm banging my head a bit too much for my liking this last couple of days.....

I've set up my Union Lathe to cut a 6 tpi thread. It's got more than enough power even though it's only got a 1/4hp motor on it. That's not an issue, in fact I stopped using the slow speeds as it cut nicer if it was run a little faster.

The problem I'm getting is creep, very time I take another deeper cut the tool tip has moved forwards. This of course is a disaster when cutting threads. But I just can't figure out what's causing it? I mean gears are gears and they sould keep a constant relationship with the leadscrew, but something is amis.

The leadscrew is engaged with a dog clutch so can only go in the same spot every time so it can't be that.

This is the lathe, In fact this is "THE" lathe .... the very same one .... http://www.lathes.co.uk/harrisonwood/page7.html

tinkerer · « **Reply #1 on:** October 10, 2009, 05:51:29 PM »

The tool is moving in relationship to the work, or the work is moving in relationship to the tool. Does the spindle have end play? Is the tool moving on the tool post? Is the compound changing the angle? Every moving part involved will have to be verified as stable, from the lead screw to the spindle and everything inbetween. It will take patience and perseverence. A process of elimination.

sbwhart · « **Reply #2 on:** October 11, 2009, 01:30:19 AM »

Darren

Give the tool a good run up to the work to take all the back lash out of the system.

Good luck

Stew

Darren · « **Reply #3 on:** October 11, 2009, 05:46:54 AM »

I'll have another go this week.

It'd be a shame if I can't sort this out as it's cutting this 6tpi thread in it's stride with either normal low gear or any of the three back gear ratio's.
The dog clutch is nice to use as well, no need to have a reverse on the motor.

I've set the gearing up to give me 25, 50, 101, 157, 314, 628 and found the 25rpm to be too slow, even for threading, well this thread at least. Maybe more use on a larger diameter.

One problem I am getting is the pulley wheel "welds" itself solid to the spindle when I use back gears, but I think I have that sorted now .... too much pressure from the drive belt causing metal "pick-up" jamming it solid.

Still, like I said, not given up yet just looking for ideas .... I'll try a longer run in to the work Stew ....

Darren · « **Reply #4 on:** October 11, 2009, 07:54:32 AM »

I think I've sussed the problem, rather silly of me really but we live and learn ....

The leadscrew handwheel, like much of the other parts, is fixed to the screw with a drift pin. When disassembling the lathe to clean it up I managed to get all the pins out easily enough but I could not get any of them back in. The diameters were just too large. I even ground a taper on the ends to help but still they would not go back.

Anyway, when I put the leadscrew handwheel back on I hammered, soft headed leaded mallet, and it was really tight. But I left the pin out and forgot all about it. The wheel has moved to the left which now allows the leadscrew to creep too the right.

I feel so silly now ...

I'll sort this out and have another go, prob tomorrow as I'm busy today.

Thanks for letting me blather, helps the thought process .....

bogstandard · « **Reply #5 on:** October 11, 2009, 08:06:21 AM »

Sure they aren't tapered pins Darren, and you are trying to fit them in from the wrong end?

John

Darren · « **Reply #6 on:** October 11, 2009, 08:12:22 AM »

Good point John, I'll measure them later and get back on that one ...

Darren · « **Reply #7 on:** October 11, 2009, 02:12:29 PM »

Got a chance to have a look, yep taper pin ....

Thanks John

However, didn't cure the problem .... so wasn't that.

I'm now thinking that it has something to do with engaging the dog clutch at the wrong place?

When I first tested cutting a thread I tried 8tpi, which is the same pitch as the leadscrew. So after taking a cut I could dis-engage the leadscrew with the dog clutch, wind the carriage back and re-engage the lead screw. Of course as I was cutting an 8tpi thread and the leadscrew is also 8tp then one turn of the leadscrew matched one pitch of the thread being cut. Simple and easy.

But when I cut a 6tpi thread one turn of the leadscrew does not match the pitch of the thread being cut. At least that's where I'm beginning to think the problem is?

I'm not sure how to get around this, leave the lathe leadscrew engaged and reverse the lathe? That would be a monumental PIA with no reverse power. But would it work?

And what about all the other threads on the threading chart, do they also need the leadscrew left engaged?

Me thinks me needs a reverse ..... poo

sbwhart · « **Reply #8 on:** October 11, 2009, 02:25:06 PM »

Has it got a threading dial ?, if it has drop in the same number each time, If not you may have to use the old trick of marking the position with chalk wait for the chalk marks to line up and then drop it in.

Hope this helps

Stew

Darren · « **Reply #9 on:** October 11, 2009, 02:27:55 PM »

Hi Stew, No threading dial, the leadscrew will only drop in at one point no other option.

What's this chalk thingibob....

Darren · « **Reply #10 on:** October 11, 2009, 02:32:03 PM »

A little clarification,

The carriage cannot be disconnected from the leadscrew, it's a permanent engagement. What you do is operate the lever at the left hand side of the leadscrew under the headstock to engage and dis-engage the leadscrew. (what I call a dog clutch?) It only has one point of engagement.

andyf · « **Reply #11 on:** October 11, 2009, 02:35:40 PM »

Darren, have you been using the dog clutch to disconnect the drive from the leadscrew so you can manually return the saddle ready for the next cut? That would work for cutting an 8 TPI thead (the same as the leadscrew), but not for 6TPI. You can use single-point dog clutches to pick up threads, but they need to be at the start of the gear train, not at the end of it (he said authoritatively, having just looked it up in Martin Cleeve's book on screwcutting, without entirely comprehending it).

Andy

sbwhart · « **Reply #12 on:** October 11, 2009, 02:36:25 PM »

Two mark in line, one on the chuck the other on the spindle bearing housing where you drop it in, mark or set the start position of the saddle, take your cut, take it out of gear, put the saddle back to the same start position, wait for the chalk marks to line up drop it in, and you should be in pitch.

Stew

Darren · « **Reply #13 on:** October 11, 2009, 02:41:59 PM »

Thanks guys, that makes sense ... I'm only guessing but something like every third turn or sumut would be in line? I'll give it a go in a mo

tinkerer · « **Reply #14 on:** October 11, 2009, 04:03:58 PM »

I didn't even consider that you had said you were disengaging the lead screw and moving the carriage. The picture shows a handle on the lead screw on the right hand end. Can you not use it to return the carriage to the start point? Do you have to disengage the clutch dog before returning the carriage?

Darren · « **Reply #15 on:** October 11, 2009, 04:18:36 PM »

Hi, Tink, I don't have the strength to wind it back with the leadscrew handle when in gear.

Here is the lathe,

The belt is not in line, it all moved about as it settled so i will re-do that

I managed to cut a 6tpi thread of sorts, it's dog rough but it is 6tpi !!
In the end I wound everything back with the large countershaft pulley, not much fun but it proved leaving everything engaged works. I'm still not sure I'm going to manage with this lathe, the finish is nowhere near good enough. Too much backlash for a start and the top slide has a really crude mounting which doesn't help.

But it is a 6tpi thread. I'll have a bit more of a try and see if I can improve the finish. What keeps me going is the fact that this lathes cuts this thread easily, the swarf just curls off nicely. But the whole lathe needs refining and fettling to make it sweet regarding slop.

Still, it's a good feeling to get this far, esp with a lathe so old ...... anyone got a Colchester Student they want to sell ... that's the lathe I think I would really like next.

spuddevans · « **Reply #16 on:** October 11, 2009, 04:39:13 PM »

Quote from: Darren on October 11, 2009, 04:18:36 PM

Hi, Tink, I don't have the strength to wind it back with the leadscrew handle when in gear.

Is there a way to perhaps attach a drill temporarily somewhere to power the reverse pass?

Tim

bogstandard · « **Reply #17 on:** October 11, 2009, 04:41:51 PM »

Darren,

Have you had a good look around the change gears area, a lathe with that sort of setup usually has some sort of tumbler reverse, to reverse the leadscrew.

It does seem very strange for something like that not to be on the lathe.

John

Darren · « **Reply #18 on:** October 11, 2009, 05:01:08 PM »

John, I'd not even considered the tumbler. Though it's not the best design it's worth considering.

They could have put a handle on it !!!

Darren · « **Reply #19 on:** October 11, 2009, 05:07:06 PM »

A handle on the countershaft would do it, it would then be geared to help ...... mill a square on the end of the shaft and use a milling vice handle.

Or drill and fix a handle to the large pulley. Not sure about drilling it though in case of weakening it. It's cast iron though so I guess would be OK?

andyf · « **Reply #20 on:** October 11, 2009, 06:41:50 PM »

Darren, when you are winding it back by hand using the big countershaft pulley, the relative sizes of that and the motor pulley means that you are fighting the ratio and trying to turn the motor much faster. Is there a quick and easy way to slacken off the belts between cuts? Loosening the one from the c'shaft to the spindle would be best, because you could then just turn the leadscrew handle (if there is one) with a bit of gearing down (8:6) between it and the chuck. If no handwheel, turn the chuck by hand, taking care that it doesn't come unscrewed from the spindle - OK, the ratio from spindle to leadscrew is uphill at 6:8, but that shouldn't be hard if you eat your breakfast Weetabix.

Looks to me as if this lathe is crying out for half-nuts, rather than a leadscrew which is permanently engaged to the saddle. 8 TPI is a very common leadscrew size, so maybe an old set of half-nuts from another machine would trigger more

Andy

bogstandard · « **Reply #21 on:** October 12, 2009, 01:58:55 AM »

Darren,

That doesn't look much like a tumbler reverse, maybe a reverse set for cutting left hand threads, tumblers wouldn't have a clamp.

It really does look like you are flogging a dead horse, with too many problems to overcome just to get basic threading sorted.

The simplest way you are going to achieve anything is do what I have to do when screwcutting imperial, some way to reverse the motor. I did that on my Atlas, but it did mean I had to fit a new motor and switch gear to do it. Cost just under 100 squid to buy the bits.

It would most probably be a lot cheaper to source the part you need to make.

You are never going to get this lathe to do everything you really want it to do without throwing your time and cash at it, and even then you still might not get anywhere near to what you really want.

That lathe could have an enthusiastic following, and as it is still in good original condition, you might lose all intrinsic value if you start hacking it about.

It is a bit of a letdown to walk away from a job in defeat, but there is no shame in it.

Maybe this is one of those times.

John

Darren · « **Reply #22 on:** October 12, 2009, 03:47:27 AM »

You are possibly quite right John, one of these lathes in worse condition just sold for £160 on the bay without the motor and countershaft. This one is at least compleate, in good condition and running.

The cash could at least be put towards what I would really like and that is a Colchester Student or a Smart and Brown. There is a Smart and Brown up the road from me. Totally unused as he prefers his Viceroy for some reason and the S&B is in the corner with about 8ft of stuff piled on top of it. I have asked about a year ago if he would sell but no was the answer. Maybe I should call again.

The Union has potential with some work but will never be what I really want from a lathe.

I can eliminate the leadscrew backlash quite easily with a little work, but the top slaide will be a little more involved to sort out. Though not impossible.
The motor is reversible and only needs a switch if I could find one.

For the moment though it's all I have and I'm learning something if only what to look for in my next lathe ....

Darren · « **Reply #23 on:** October 12, 2009, 04:30:14 AM »

This would do the reversing

http://cgi.ebay.co.uk/250VAC-DPDT-Centre-OFF-Screw-Terminal-Toggle-Switch_W0QQitemZ170392946135QQcmdZViewItemQQptZLH_DefaultDomain_3?hash=item27ac3605d7&_trksid=p3286.c0.m14

bogstandard · « **Reply #24 on:** October 12, 2009, 04:32:20 AM »

There is your answer then Darren.

Find your changeover switch and reverse the motor.

The one at the bottom was the one I used and was from Chester UK.

John

Darren · « **Reply #25 on:** October 12, 2009, 04:41:19 AM »

Thanks for that John, just what I need for my Milling machine in 415V.

Remember I said the table transverse motor runs continuously whenever the power is on, select engagement and direction with a lever. That's prob why this part I'm painfully trying to make is worn out. It's continuously working when most of the time it doesn't need to be.

Darren · « **Reply #26 on:** October 12, 2009, 04:46:15 AM »

Where did you find that switch? All I can find is "coming soon" with no details, can't find a search box either

bogstandard · « **Reply #27 on:** October 12, 2009, 04:50:51 AM »

This is a snatched pic out of their downloadable catalogue. As yet, these switches aren't on their site.

If you phone them up with the number before midday it will usually be with you next day.

I had it switching a half horse single phase.

John

Darren · « **Reply #28 on:** October 12, 2009, 04:59:41 AM »

Thanks John, that's a big help as I have been searching for such an item, best I could find was about £60 ...... ta !!!

Darren · « **Reply #29 on:** October 12, 2009, 06:59:18 AM »

I'm almost tempted to get the credit card out ...... oh my that is having some wiered effect on me for some reason .....

http://cgi.ebay.co.uk/SMART-BROWN-MODEL-A-CENTRE-LATHE-TURNING_W0QQitemZ320434952130QQcmdZViewItemQQptZLH_DefaultDomain_3?hash=item4a9b6957c2&_trksid=p3286.c0.m14

Darren · « **Reply #30 on:** October 12, 2009, 07:08:20 AM »

Quote from: andyf on October 11, 2009, 06:41:50 PM

Darren, when you are winding it back by hand using the big countershaft pulley, the relative sizes of that and the motor pulley means that you are fighting the ratio and trying to turn the motor much faster. Is there a quick and easy way to slacken off the belts between cuts? Loosening the one from the c'shaft to the spindle would be best, because you could then just turn the leadscrew handle (if there is one) with a bit of gearing down (8:6) between it and the chuck. If no handwheel, turn the chuck by hand, taking care that it doesn't come unscrewed from the spindle - OK, the ratio from spindle to leadscrew is uphill at 6:8, but that shouldn't be hard if you eat your breakfast Weetabix.

Andy

You know what Andy?

You are right, thanks for making me feel so stupid

Flip the belt tension lever to disengage the motor and counter shaft and spin the lathe in reverse using the leadscrew hand wheel is oh so easy .....

I'm going off to hide now till my blushing has gone .......

What a great place this forum is......

andyf · « **Reply #31 on:** October 12, 2009, 08:09:06 AM »

Don't beat yourself up, Darren. I'm the man who spent hours making a component for my lathe, and was delighted with getting it (almost) perfect in every detail. And it would have fitted perfectly too, if the lathe had been a mirror image

You must be threading at low speed; might really sharp HSS give a better finish than the carbide tool shown in your pics?

Andy

bogstandard · « **Reply #32 on:** October 12, 2009, 08:47:28 AM »

Darren,

I didn't realise it had a handwheel until just mentioned, so I went to have a look.

On my screen your pictures actually spill over the RHS and you have to move the bar at the bottom to see that part.

Maybe reducing your piccies a little bit so we can get the full picture

John

NickG · « **Reply #33 on:** October 12, 2009, 08:53:28 AM »

I never thought you'd be able to turn the whole spindle over with the leadscrew handwheel .. is that just possible because the back gear is engaged then?

That smart and brown looks stunning ... imagine how rigid that must be, seems a good price.

Nick

Darren · « **Reply #34 on:** October 12, 2009, 09:26:01 AM »

John, Sorry about the pic's, they are the smallest my camera will take and even then PB reduces them further automagicaly. I don't really want to edit every picture?

Nick, I dunno, just bumbling along me is......

Yep I'm itching to buy that S&B .... I really shouldn't, but if I sold my other mill and this Union lathe.........

So back to the story, I chucked another bit of stock in and had a go with Andy's suggestions ....

This is what I ended up with, I cut the main out with the carbide tip but that is 60 deg and I want 55. So I finished with HSS ground to 55. And it chattered

To be fair it's the top slide that's at fault here, I need to remove it and make a toolpost to fit the crosslide dovetails.

Anyway, the flash makes it look worse than it is by loads, it's almost OK and fits the the other wheel just fine. It even spins it nicely...... A bit more to go and I'll almost be there...

Darren · « **Reply #35 on:** October 12, 2009, 09:39:53 AM »

Sorry Nick, just re-read your question,

No you can't spin it by the leadscrew handle when in backgear, just too much effort needed.

I'm doing all this in normal low speed gear about 160 rpm. Sounds quick for threading 6pi but it's ok I'm comfortable with it.
I could change the motor pulley to aa smaller one I have to get 135 rpm but it hardly seems worth it.

NickG · « **Reply #36 on:** October 12, 2009, 09:47:34 AM »

Oh right! I thought with the back gear engaged it'd be easier to spin over from that end! Perhaps I'm getting confused

You should buy it!!!! If you don't, someone else will. I remember when I was looking at lathes, some I went to see people had just bought them to do a specific job, e.g. a colchester student just to drill 200 bits of steel bar etc! sacrilege!

That looks like a very good thread to me, what are you making again?

Nick

Darren · « **Reply #37 on:** October 12, 2009, 09:55:23 AM »

Backgear is easier from the front end of the gear train (motor) but harder at the other end (handwheel)

I'm making a replacement part for my milling machine .

Or trying to ....

Darren · « **Reply #38 on:** October 12, 2009, 11:02:59 AM »

Oh poo, he's offered me that lathe delivered free for the price ....

I'm in trouble now !!!

Darren · « **Reply #39 on:** October 12, 2009, 11:20:30 AM »

Anybody near Dudley that can offer me some of their spare time that knows their way around a lathe that could give this the once over for me?

Just on the off chance I thought I'd ask .... fingers on the button but it's the "not seen" that's holding me back.

NickG · « **Reply #40 on:** October 12, 2009, 11:23:48 AM »

If it's rubbish, couldn't you just use the paypal thing to your advantage for once

Seriously though you're right, you need to see these things before buying. I couldn't try mine as it was 3 phase but at least I could turn it over, wind slides around etc.

Nick

Darren · « **Reply #41 on:** October 12, 2009, 11:26:28 AM »

Now Now Nick....

We're honest folk here ...... it would work though, but he might be bigger than me ....

andyf · « **Reply #42 on:** October 12, 2009, 12:34:24 PM »

Quote

Before he started daydreaming about his next lathe, Darren wrote: This is what I ended up with, I cut the main out with the carbide tip but that is 60 deg and I want 55. So I finished with HSS ground to 55. And it chattered
To be fair it's the top slide that's at fault here, I need to remove it and make a toolpost to fit the crosslide dovetails.

Though it's a bit laborious, could you lock the topslide gib up for the finishing passes?

BTW, how did you work out that 55 degrees was the correct angle to match the worm wheel?

Andy
(off to France in the wee small hours to spend a week making sure the vintage is OK

Mon Dieu - wrong glass!)

Darren · « **Reply #43 on:** October 12, 2009, 12:53:18 PM »

Hi Andy, it's not the gibs but the way the topslide mounts to the carriage..... I'll post a pic later. I'm on the case though

andyf · « **Reply #44 on:** October 12, 2009, 01:06:14 PM »

If space permits, try a G-cramp to hold the topslide firmly down to the cross-slide.

Andy

CrewCab · « **Reply #45 on:** October 12, 2009, 01:57:51 PM »

Quote from: Darren on October 12, 2009, 11:02:59 AM

Oh poo, he's offered me that lathe delivered free for the price ....

I'm in trouble now !!!

Yup, your right

............. they had a Smart and Brown at RDG when I was looking round, just before I bought my Boxford, very nice piece of kit

but, at the best part of a ton, much too heavy for me to get into my little den unfortunately.

Would make a nice addition to your new workshop mind

CC

Darren · « **Reply #46 on:** October 13, 2009, 10:30:38 AM »

I mentioned the topslide had a really naff mounting, here it is. The slide is upside down and you can see the roundy bit that fits in the hole on the carriage. Secured with a single grubscrew from the side. It's prob OK'ish with normal turning but not for what I'm doing at the mo.

So having decided to remove the topslide altogether I now needed a way to secure the toolpost directly to the carriage. Having T-slots made doing this quite simple.
This is what I came up with. It's a raiser block made from steel bar with one central 10mm thread for the toolpost and two 8mm through holes for 8mm bolts to clamp with the T-nut.

A couple of pic's, I won't go into making the block as that should be fairly obvious to anyone here.
I had to clamp all the bits together to make sure it all fitted properly. So in this state it was clear that some other tasks would be easier to manage.

Sawing the T-bar to length

Centred the block in the four jaw and trimmed the ends of the bar equally, not necessary but why not as it was now in place. Then I trimmed both 8mm bolts to a suitable length. Note the use oh a HSS tool, I have learnt not to try this with carbide tips ....

A little de-burring and now fitted to the lathe carriage

QCTP fitted...lovely ... that should help the chatter I was getting from the compound slide ....

Darren · « **Reply #47 on:** October 13, 2009, 10:32:07 AM »

Bogs, changed the settings in Photobucket, is that better for you

I can't tell cos I have widescreen..... posh eh ...

NickG · « **Reply #48 on:** October 13, 2009, 11:07:22 AM »

Darren,

I was going to say last night that you could change the defaults in photobucket! Fat lot of use I am!

Yes, they don't go off the screen now.

Do you have 3 different lathes at the moment then? Presumably the smart and brown you were looking at could do all the jobs the other 3 could, although not at the same time

Nick

Darren · « **Reply #49 on:** October 13, 2009, 11:46:53 AM »

Hi Nick,

Yes I'm blessed with three lathes and not one to get me where I want to be

Ain't that always the way....

I would prob keep the S&B lathe as that is a turret and a 5C collet lathe that spins up to 3,000 rpm, so quite useful in it's own right. I have had the need in the past to churn parts out and once set up it can manage 100 parts an hr all identical. I intend to go there again at some point.

The Union can go once I get another screwcutting lathe. TBH once I've finished fettling with it it's not a bad little machine which could easily be improved further.

The 7x12, I'll prob keep simply because of all the work John has done on it and it's now a sweet little thing. Besides it takes no room. If I do decide to let it go I'll offer it here first. But that may or may not happen.

I did a bit of research last night and got in touch with some guys on the S&B Yahoo group. That lathe according to them is quite overpriced which surprised me so I'm hanging fire at the mo while I think some more.

NickG · « **Reply #50 on:** October 14, 2009, 05:48:08 AM »

Oh right, it is surprising where these things can be found though. Like I say, I saw a few that weren't in the sort of places you'd expect! I think the pure weight and size put a lot of people off but bargains can be had for people that have the room. There was a colchester student I saw the guy wanted £300 for but he couldn't show me it running and it was a hell of a size / weight! He had a really nice chipmaster at the back of his shop too but he wouldn't sell me that!

Keep looking, you'll find something!

Nick

Darren · « **Reply #51 on:** October 27, 2009, 04:37:20 PM »

Finally I got around to having another go at this part. Now with the compound slide removed and replaced with a raising block things should be a lot more rigid.

The crosslide gibs nipped up and I added a temporary DRO. This really made a difference as I could retract the tool before winding back the carriage and re-position the tool exactly where I wanted it. The DRO was only temporarily held in place with some clamps but worked perfectly.

And this is the finished article. After all the effort to get this far and considering the lathe I'm using I'm chuffed to bits. about 1" 6tpi thread. The tool was plunged in, if you can call 0.10mm per pass a plunge, reducing to 0.05mm towards the final cuts. The lathe coped fine, a touch of flexing but not enough to worry about.

That should do the job

andyf · « **Reply #52 on:** October 27, 2009, 05:51:05 PM »

That's great! Having just compared it with the original worn out worm shown on your Beaver gearbox repair thread,

I bet you're feeling

And it just goes to show what can be done with an old machine.

Andy

Darren · « **Reply #53 on:** October 27, 2009, 08:25:55 PM »

Thanks Andy, this lathe is quite sweet to use, it will be interesting to see how it copes with other tasks?

I've added the original part here to show why I made this part

NickG · « **Reply #54 on:** October 28, 2009, 05:16:26 AM »

Darren this / that is an excellent thread

How long did it take to do with those small cuts? Looks like it paid off. The spindle on my harrison is 1.5 x 6 TPI, fancy making me a back plate?!

Darren · « **Reply #55 on:** October 28, 2009, 05:53:25 AM »

Nick, about 3 weeks .... but I did a couple of other things in between

About half hour or so ... I took light cuts mainly because the tool flexed and was trying to go under the work. This was about as rigid as i could make things with what I had to hand.

I'm beginning to think these small QCTP are a bit small, I see a project coming

sbwhart · « **Reply #56 on:** October 28, 2009, 01:38:24 PM »

Nice going Darren

Stew

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Author Topic: Union Lathe .... Help !!! (Read 21033 times)

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