Mini Lathe Rear Tool Post

[Ron LadenParticipant @ronladen17547]

[Ron LadenParticipant @ronladen17547]

Whilst I have been working on the mini lathe I have also been thinking of fitting a rear tool post for the purpose of parting off. Unless anyone can tell me otherwise I cant find a rear tool post that is available for my Amadeal CJ18 lathe, that is probably because there are no fittings or features on the cross slide to fit one.

I can buy a Warco rear tool post for £20 which on their machines fits to a cross slide mounting plate. The Warco cross slide must be slotted as the plate is fixed with T nuts, the plate also takes a milling attachment.

My thinking is to make a mounting plate machined to accept the tool post lower tenon and fasten the plate to my cross slide. My cross slide is 9mm thick and I was thinking four counter bored holes in the plate for cap heads M8 or maybe M6 would be enough..?

A couple of pics below of the tool post and also my cross slide as it is now, I have no experience of rear tool posts so any comments or advice on what I am thinking would be welcome.

Ron

Edited By Ron Laden on 15/12/2018 16:57:41

[John RuddParticipant @johnrudd16576]

I'll throw something out there for you…

Our illustrious editor Neil, made and published the details of a crosslide for the mini lathe featuring alternative tee slots…I made such an item for mine and works great with a proprietry qctp… The beauty being that it is thicker and more stiffer than the original….

Might be a bit more work for you but worth a consideration?

[Michael Cox 1Participant @michaelcox1]

Ron,

I made a rear toolpost for my minilathe, see:

http://mikesworkshop.weebly.com/rear-toolpost.html

Before making the toolpost I had already made a tee slot cross slide which was considerably longer than the standard cross slide.

The tee slot provide a ready means of attachment for the rear toolpost but I think the rear toolpost could be attached directly to the cross slite it a hole were drilled and tapped .

The big problem that you will have using the standard cross slide is there will be little distance between the front toolpost and the rear toolpost and this will limit the size of work that can be turned. If you are only making small parts than maybe this will not be a problem.

Perhaps the cross slide could be extended back by bolting a piece of steel plate to the top of the cross slide that overhangs the back. The rear tool post could be mounted on the overhang.

I hope this is useful

Mike

[Patrick GalvinParticipant @patrickgalvin70195]

Hi Ron,I have the same lathe and I made the front parting off toolholder for use upside down with the lathe ran in reverse as recommended by David Fenner in his book The Mini-Lathe.It has the very same effect as a rere parting off in forward motion.It works really well with clean parting and no breaks.

[Ron LadenParticipant @ronladen17547]

Thanks John, can you point me to Neils cross slide which you made, I,ve been searching for it but havnt found it yet.

Mike, I have been reading about the lathe mods in your "mikesworkshop" you certainly have done a few and made a nice job of them. Interesting stuff I will read through it again in detail in the morning, thanks Mike.

Ron

 

Edited By Ron Laden on 15/12/2018 21:59:31

[ZanParticipant @zan]

On my s7. I had a real roolpost but it really got in the way and sold it

The saddle had to be wound a long way back when measuring, a problem when the tailstock support was being used, not enough room to use a tailstock die holder without the danger if impairing my hands. A lot of winding of the cross slide to get it into position. Too many problems. Yes it did work well, but not as well as the 2 mm inserted tip version I now use without any problems in the normal toolpost. I wouldn’t have one.

Access on a mini lathe will m be worse it will get in the way. But enjoy the task of drilling and tapping your nice cross slide……

[Ady1Participant @ady1]

I use a rear for general machining and roughing because once you make one the toolbit is upside down so it's always at the correct height when you slip a general square toolbit in so no shimming is required

The swarf also falls and piles up at the back of the lathe, particularly useful for cast iron work

A decent rear post is another string to your bow and has it's time and place

edit

It's easier on a proper cross slide with t-slots because you can use one toolpost for the front or the back, just slip it into position, nip it down and slide in a toolbit

Edited By Ady1 on 16/12/2018 00:14:45

[Danny M2ZParticipant @dannym2z]

I realise that this has already been mentioned in the past but as a reminder, an upside down front mounted parting tool mounted in a QCTP (to get the centre height correct) with the mini-lathe run in reverse is very effective.

I have tried this as an experiment and it worked although it's a bit of mucking about setting up the tool height on centre.

I found it easier to tighten the gibs and just plunge in with a sharp tool and plenty of lube. A 'V' groove in the tip of the parting tool seems to help.

P.S. Do Not try this with a screwed on chuck!

* Danny M *

[JasonBModerator @jasonb]

Neil's slotted slide is here

[Ron LadenParticipant @ronladen17547]

Posted by JasonB on 16/12/2018 07:15:50:

Neil's slotted slide is here

Thanks Jason

[Neil WyattModerator @neilwyatt]

If I made it again, I would use smaller T-slots, and possibly as two along its length rather than three across.

Neil

[Ady1Participant @ady1]

and possibly as two along its length rather than three across

I think there's a good reason they always went fore to aft

[JasonBModerator @jasonb]

Posted by Ady1 on 16/12/2018 09:50:11:

and possibly as two along its length rather than three across

I think there's a good reason they always went fore to aft

Maybe you could tell Myford what it is

[Ron LadenParticipant @ronladen17547]

I guess in the grand scheme of things the question is, is parting off using a rear tool post the way to go..? I know many say it is but as Patrick and Danny mentioned plus I have seen it elsewhere recently that a good tool inverted in the front post with the lathe in reverse is just as effective..?

Putting parting off to one side I do like the idea of making a heavier duty cross slide making it a little wider and longer. I am tempted to have a go at this and with T slots I can see it been a worthwhile mod. I can get some 3" x 3/4" bright EN3B flat bar locally, though having never used it I dont know if it would be hard work machining the T slots and dovetails.

Ron

[egaParticipant @ega]

Anyone who can readily fit a rear toolpost should not be deterred from trying one; with any particular way of working its advantages may or may not outweigh the problems experienced by Zan.

The GHT version can be swivelled 90 deg to get the blade out of the way and instantly reset to either of its two blades when needed. Having a separate turret means that other tools – boring, knurling, etc – can be deployed. Those who use form tools will get better results with the tool in the rear toolpost.

Myford were far from the only maker who favoured "across" tee slots and although their own early RTP was fastened by only one bolt the "across" style allows a firmer fixing via two slots.

[I.M. OUTAHEREParticipant @i-m-outahere]

I had a rear toolpost on one of my lathes , mainly because it had a screw on chuck and it did fix my parting off woes which were caused by the flimsy compound slide / toolpost on the unit . My bigger lathe and mini lathe have bolt on chucks so i just use an inverted parting off tool and run the lathe in reverse . One thing with rear toolpost though is if you leave them in place they can get in the way of other operations . You will find that if you don't use the compound slide often maybe removing this and fitting a more solid arrangement similar to the gibraltar style toolpost or an adaptation of it will serve you better . One thing i noticed when using my minilathe last time was the gib strip on the cross slide isn't thick enough , this means it rides on the tips of the grub screws and not the inside of the dovetail , this provides a pivot point and allows the cross slide to rock when under load . A simple spacer strip fixes the problem and I remember doing the same thing to my old lathe – it made a difference on many fronts !

[mechman48Participant @mechman48]

I made a rear parting off tool post for my WM250V-F from castings out of a Hemmingway's kit, works a treat,although a larger machine it has two longitudinal slots that allow a tenon fit & sufficient sliding/ clearance for large diameters. Have a look in my albums 'rear tool post' for my set up.

George.

[Howard LewisParticipant @howardlewis46836]

One of the first jobs on the successor to my original ML7 was a four way indexing back toolpost. (Only made a one way for the 7)

Front chamfer, part off, back chamfer all in one place. And can be swung out of the way to obtain more room.

Definitiely worth the trouble of making it.

Very rarely comes off, except to display at Shows.

Howard

[Neil WyattModerator @neilwyatt]

Here we are, I've found the article:

http://www.model-engineer.co.uk/news/article/don't-do-this-at-home–a-t-slotted-slide-for-a-mini-lathe/

Neil

[Neil WyattModerator @neilwyatt]

Posted by XD 351 on 16/12/2018 11:57:26:

One thing i noticed when using my minilathe last time was the gib strip on the cross slide isn't thick enough , this means it rides on the tips of the grub screws and not the inside of the dovetail , this provides a pivot point and allows the cross slide to rock when under load .

I had this problem when I made a gib strip for my slide (see above).

the solution I found was simply to make sure the holes for the grub screws went at least half way through the strip, this changes the geometry and the strip behaves.

Neil

[JasonBModerator @jasonb]

Posted by Neil Wyatt on 19/12/2018 15:12:02:

Here we are, I've found the article:

http://www.model-engineer.co.uk/news/article/don't-do-this-at-home–a-t-slotted-slide-for-a-mini-lathe/

Neil

Could have saved yourself the trouble if you followed my link posted 3 days ago

[Ron LadenParticipant @ronladen17547]

When parting off the two alu pulleys I have just made I had the tool dig in a couple of times, nothing too bad and I just carried on with the feed and they parted off ok. However it did highlight the lack of rigidity in a small mini lathe as I was quite surprised at how much the tool post flexed/kicked when it happened.

So I am going to go with making a heavier duty cross slide to hopefully improve the rigidity, I think that and a solid rear tool post must offer more rigidity for parting off. Having said that I suspect that most of the lack of rigidity is above the cross slide through the top slide and tool post. To be fair I havnt tried a front mounted parting tool inverted which a few recommend. I like the idea of a heavier cross slide though which can have T slots something I dont currently have. I can see it useful for job or tool mounting and give the lathe a bit more capability.

I was considering making the cross slide from EN3B but with dovetails/T slots to cut it would be easier machining in cast iron. A question I have, is cast iron available as flat bar..? I have been searching but can only seem to find round or square and I need a size that I can get 7 inch x 3 inch x 1 inch out of.

[Frances IoMParticipant @francesiom58905]

yes I bought about a year ago a slab 500mm by 100mm x 25mm for a similar purpose – not that cheap however I recall about ?60-70 for this and abt the same length of abt 40mm dia bar – but maybe because my supplier had to order it specially from his supplier in Birmingham (luckily his lorry was going there for another order)

[JasonBModerator @jasonb]

Ron, M-machine list 100 x 180 which they sell by the inch, I'm sure they would cut you off say 30mm to allow for clean up. Also bear in mind the rectangular stuff has a radius corner so allow for that..

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