Author Topic: C3 mini lathe bed and gibs  (Read 18076 times)

Offline 28ten

  • Full Member
  • ***
  • Posts: 107
C3 mini lathe bed and gibs
« on: July 30, 2009, 02:38:04 PM »
Like quite a few people i own a mini lathe, size wise it is more than adequate for my current needs, but as others have found the finish is a little rough.
the first thing I think I need to sort is the bed, I have read and re read bogstandard's post   :bow: and I have a similar problem, however I don't have a mill  :( I have read other accounts that suggest filing and/or lapping the high spots.
so the question is has anybody else tried lapping? I am wondering if I should just bite the bullet and get it sorted by a local machine shop?
Any views most welcome!
If it ain't broke, i'll fix it until it is.

Offline Bernd

  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 3688
  • Country: us
  • 1915 C Cab
    • Kingstone Model Works
Re: C3 mini lathe bed and gibs
« Reply #1 on: July 30, 2009, 04:13:18 PM »
28ten,

Lapping takes a while since it only removes very little metal. Filing by hand I would think will leave an uneven surface. So that leaves choice #3. Take it to somebody that has a mill.

I don't think I'd want to mess it up by filing or lapping.

This is strictly my opinion as to what I would do.

BTW I have one of those small lathes and it's in need fo that kind of work and I'm hoping as the cooler season od autum and winter get here that will be on the top of the list to do.

Regards,
Bernd
Route of the Black Diamonds

bogstandard

  • Guest
Re: C3 mini lathe bed and gibs
« Reply #2 on: July 30, 2009, 04:35:51 PM »
As Bernd has said, filing and lapping over that length would take a rather long time, plus the fact it is really a very skilled job to get right.

I don't know what the local workshops charge in your area, but I wouldn't expect to get any change out of 100 squid, and maybe a lot more. A cheap rate workshop usually charges 60 squid an hour, and that includes set up times and parts of an hour as well.

You live a fair way from me, I live in Crewe, Cheshire.

If you got the inkling to bring just the bare casting across, I could have the machine ready to drop it onto. The setup and machining should take less than a couple of hours, which means if you got here fairly early (before 11am), you could take it away with you as soon as it is finished.

My charges are rather expensive, a doggy chew for Bandit would just about cover it.


Bogs


Offline 28ten

  • Full Member
  • ***
  • Posts: 107
Re: C3 mini lathe bed and gibs
« Reply #3 on: July 30, 2009, 05:23:06 PM »
Bogs
thank you for your most kind offer, I shall ring round a few local places and see what they say.  I could go via Merryhell and drop the wife and kids off which might get me some brownie points :D
What flavour doggie chew is best?
If it ain't broke, i'll fix it until it is.

bogstandard

  • Guest
Re: C3 mini lathe bed and gibs
« Reply #4 on: July 30, 2009, 06:52:43 PM »
Postman is OK, but he really prefers double glazing salesman flavour (kneecap and below), he is only a small dog after all, and has never tasted anything higher. Except for when we had a visit from some boy sprouts, he really licked into them.

PM me if and when.

Bogs

Offline 28ten

  • Full Member
  • ***
  • Posts: 107
Re: C3 mini lathe bed and gibs
« Reply #5 on: July 31, 2009, 03:38:57 PM »
Postman is OK, but he really prefers double glazing salesman flavour (kneecap and below), he is only a small dog after all, and has never tasted anything higher. Except for when we had a visit from some boy sprouts, he really licked into them.

PM me if and when.

Bogs
Does he like home made fruit cake??
I tried 2 local places today and was quoted over £200  :jaw: essentially it's not a quick CNC job so they are not interested.
Anyway I shall be stripping the machine this weekend as I can't do much until I have sorted this.
My current work order is
Fix the bed
drill for a  saddle lock
re use the old gibs whilst milling the new tapered gibs

with that done I shall turn my attention to the cross slide
hopefully then it will be rigid enough to use the form tool for forming wheel treads
well that's the plan anyway........

If it ain't broke, i'll fix it until it is.

Offline Darren

  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 3795
  • N/Wales
Re: C3 mini lathe bed and gibs
« Reply #6 on: August 01, 2009, 06:02:07 AM »
28ten,

My exp with a banana 7x12 was very poor, it was relegated to being used as a polishing machine as I eventually bought another lathe.

Now after John has fettled with it it is most certainly capable of precision work. People say it only affects the early lathes, mine is not that old. About 3-4yrs.


But if you really had to spend £200 and I assume plus vat and traveling and the extras that will no doubt crop up, I would be looking at replacing it.
If John sorts it out for you, then it most certainly would be a keeper, even if you ended up buying another lathe to go with it....

A few options available to you, but if you can get it fixed without spending too much then I would go that route myself.

You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline 28ten

  • Full Member
  • ***
  • Posts: 107
Re: C3 mini lathe bed and gibs
« Reply #7 on: August 01, 2009, 10:01:01 AM »
Darren
this lathe is about 12 months old, I bought is S/H unused. as it was raining I stripped this morning and I can confirm that is banana shaped.
what was the cross slide like on yours? this one is quite rough  :bang:
If it ain't broke, i'll fix it until it is.

Offline rleete

  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 534
  • Country: us
Re: C3 mini lathe bed and gibs
« Reply #8 on: August 01, 2009, 12:47:00 PM »
Can you get a replacement bed?  LMS sells them for the minilathe, so maybe you could contact them to see if they are available for the C3.

Also, Grizzly sells the C3, maybe they can get replacement parts?  Might be cheaper than getting someone to machine the old one.
Creating scrap, one part at a time

Offline Darren

  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 3795
  • N/Wales
Re: C3 mini lathe bed and gibs
« Reply #9 on: August 01, 2009, 02:06:21 PM »
The only problem, well two really

The new bed may be as bad as the old...or worse

Shipping costs....

I don't think it's really an option.... :scratch:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline Darren

  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 3795
  • N/Wales
Re: C3 mini lathe bed and gibs
« Reply #10 on: August 01, 2009, 02:07:51 PM »
Darren
this lathe is about 12 months old, I bought is S/H unused. as it was raining I stripped this morning and I can confirm that is banana shaped.
what was the cross slide like on yours? this one is quite rough  :bang:

TBH going by the work that john did to it mine was rough too. Quite some squaring up to do to get it workable.....

It's all in the write up, and much more.... :thumbup:


I know a lot of people say theirs is fine and well made etc....but give it to someone like John and they may be able to tell you a different story.....
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

bogstandard

  • Guest
Re: C3 mini lathe bed and gibs
« Reply #11 on: August 01, 2009, 02:35:14 PM »
John will be putting another banana right very soon.

Offline CrewCab

  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 851
Re: C3 mini lathe bed and gibs
« Reply #12 on: August 01, 2009, 03:35:07 PM »
John will be putting another banana right very soon.

In which case, you deserve ...................  :ddb: ............... a  banana ............. 


CC

Offline 28ten

  • Full Member
  • ***
  • Posts: 107
Re: C3 mini lathe bed and gibs
« Reply #13 on: August 01, 2009, 03:53:44 PM »
A red banana at that  :D  :ddb: :ddb:
I thought you might to see a couple of pics of the some castings I have turned,  and the form tools i use. generally I turn the wheel tread to within about 5 thou and then finish with the form tool, even when I had access to an ML7 I still would follow the same procedure.
Any chatter produces a poor finish as the contact area is so large, I would  generally use about 100rpm and the lightest of touches on the cross slide.
If it ain't broke, i'll fix it until it is.

Offline CrewCab

  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 851
Re: C3 mini lathe bed and gibs
« Reply #14 on: August 01, 2009, 04:22:37 PM »
Very nice work, how about talking us through the procedure  :beer:

CC

Offline sbwhart

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 3530
  • Country: gb
  • Smile, Be Happy, Have Fun and Rock Until you Drop
Re: C3 mini lathe bed and gibs
« Reply #15 on: August 01, 2009, 04:39:09 PM »
Hi 28ten

What loco are the wheels off? :- they look nice casting as well.

Cheers

Stew
A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

Offline 28ten

  • Full Member
  • ***
  • Posts: 107
Re: C3 mini lathe bed and gibs
« Reply #16 on: August 02, 2009, 09:58:54 AM »
The turned wheels are off a GWR 2-6-2 45xx and the unturned castings are for a Dean goods. A chap called Alan Harris makes them and they are superb, the only drawback being the cost... about £18 each  :bugeye: .

I could do a step by step photo account when the banana has been straightened. it is a fairly straightforward process (it must be if I can manage it!) but it does require a light touch. the trickiest part is finishing the back when you have to hold the casting by the tapered wheel tread, this is where the soft jaws come into their own.
If it ain't broke, i'll fix it until it is.

Offline CrewCab

  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 851
Re: C3 mini lathe bed and gibs
« Reply #17 on: August 02, 2009, 10:19:36 AM »
the trickiest part is finishing the back when you have to hold the casting by the tapered wheel tread, this is where the soft jaws come into their own.

That's what was intriguing me, do you take a light skim off the back to remove the infill between the spokes  :scratch:

Cracking job btw  :thumbup:

CC

Offline 28ten

  • Full Member
  • ***
  • Posts: 107
Re: C3 mini lathe bed and gibs
« Reply #18 on: August 02, 2009, 03:12:43 PM »
the trickiest part is finishing the back when you have to hold the casting by the tapered wheel tread, this is where the soft jaws come into their own.

That's what was intriguing me, do you take a light skim off the back to remove the infill between the spokes  :scratch:

Cracking job btw  :thumbup:

CC
after turning the tread and drilling and reaming for the axle, the casting is transfered to the vice and the spigot is sawn off, then mount in the soft jaws and skim the back until the correct depth is achieved, which should expose the spokes. I then take another 20 thou off the spokes, but not the tread, to allow some clearance for frame detail hornblocks etc. obviously the spokes are very fragile so gently does it  :D i have never broken a spoke but I have ruined a tread when it wasn't quite tight in the chuck  :bang:
I think It's a very different method to turning large scale castings
If it ain't broke, i'll fix it until it is.

Offline CrewCab

  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 851
Re: C3 mini lathe bed and gibs
« Reply #19 on: August 02, 2009, 05:45:37 PM »
Thanks 28T, seems like it's a steady job  :bow:

CC

Offline 28ten

  • Full Member
  • ***
  • Posts: 107
Re: C3 mini lathe bed and gibs
« Reply #20 on: August 09, 2009, 03:09:43 PM »
A big thank you to Bogs  :clap: :clap: and the banana has been straightened. The casting was nowhere near as bad as Darrens, but it is now within a thou along the bed. Next stop is the gibs!
If it ain't broke, i'll fix it until it is.

bogstandard

  • Guest
Re: C3 mini lathe bed and gibs
« Reply #21 on: August 09, 2009, 03:19:01 PM »
Glad to have been of help, but as I told you, don't forget the oil, that is a major factor in getting it run smooth and accurate.


John

Offline Mike K

  • Full Member
  • ***
  • Posts: 114
  • Country: us
Re: C3 mini lathe bed and gibs
« Reply #22 on: August 09, 2009, 07:39:39 PM »
2810,

One thing you might consider for the gibs is using shims.  Tapered gibs are nice, but a lot of effort.  And from what I've heard from the shim crowd it'll last quite a while before having to re-shim.  I think this is the route I'm headed.

One thing is for sure: the factory push-pull screw setup needs improvement.  Let us know what you wind up doing.

Mike

Offline klank

  • Full Member
  • ***
  • Posts: 128
  • Sunny East Devon
Re: C3 mini lathe bed and gibs
« Reply #23 on: August 10, 2009, 11:19:33 AM »
Hi 28Ten,
I noticed you mentioned "drilling for a saddle lock"?

Just in case you did not know - there are two tapped blind holes and socket head screws lurking inside (M6 I think) on the left hand side of the carriage saddle - next to the oiling points, which act as friction locks for the carriage.
If the screws in them are screwed down, their ends mark the bed surface.
To save fabricating/drilling for a carriage lock and avoid marking the bed - I made a 5mm dia. brass slug/pad insert to a tight fit in the end of an M6 socket head screw, so as to cover its steel tip, and screwed it into the front hole where it bears on the flat side of the bed.
The rear hole bolt will bear down on the "V" part of the bed, so I filed up a wedge ended 5mm dia. slug of brass and drilled/tapped the flat end M3 so it could be extracted later if necessary by a bit of threaded rod. This was dropped into the hole so the filed/angled end mated up with the V and followed it up with another M6 bolt to push on the flat (threaded) end of the slug.
Its a simple job to lock the carriage now by just doing up these two M6 bolts and push the brass pads against the bed a bit.

I do wish the lathe bedways had been induction hardened though - they seem to show marks all too easily.

I just dismantled all of the jibs/screws (the ones at the rear of the carriage were all gummed up with powder coat), replaced the chocolate jib adjusters with proper socket head screws, and csarefully lapped all of the dovetails and jib strips with grinding paste. Worth it but a lengthy job and tedious.

I hope this may help?

Peter

Offline 28ten

  • Full Member
  • ***
  • Posts: 107
Re: C3 mini lathe bed and gibs
« Reply #24 on: August 10, 2009, 04:00:58 PM »
I have re assembled it electrically and done a quick test with the old gibs and john's magic oil and it is already much better, so the effort to mill it has been worthwhile. I can't make tapered gibs until I have replaced the current flexi gibs, so I will indeed shim it in the first instance, if this proves satisfactory I won't be in any hurry to make tapered gibs.
Klank, Bogs gave me some very handy brass grubscrews for the carriage lock, so I can do something with them. I agree with you about the gib adjustment, the current ones will go, once all that is done I will turn my attention to the dovetails.
Bogs also milled out the carriage so I can get extra travel on the crossslide so I have that to sort as well, but at the moment I need to get it up and running so I can make the parts  :D life is tough when you only have the one machine available  :)
If it ain't broke, i'll fix it until it is.