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Mini Lathe Rear Tool Post

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Ron Laden15/12/2018 16:53:21
972 forum posts
145 photos

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

rear-tool-post-lathe-wm-240b-240-250-250v.jpg

dsc06320.jpg

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

John Rudd15/12/2018 19:30:29
1364 forum posts
58 photos

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 115/12/2018 19:34:53
503 forum posts
27 photos

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 Galvin15/12/2018 21:07:40
1 forum posts

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 Laden15/12/2018 21:56:42
972 forum posts
145 photos

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

Zan15/12/2018 23:43:29
82 forum posts
2 photos

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......

Ady116/12/2018 00:11:11
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3462 forum posts
513 photos

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 M2Z16/12/2018 04:06:09
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719 forum posts
276 photos

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.

grooving parting tool - 1.jpg

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

* Danny M *

JasonB16/12/2018 07:15:50
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Neil's slotted slide is here

Ron Laden16/12/2018 09:05:47
972 forum posts
145 photos
Posted by JasonB on 16/12/2018 07:15:50:

Neil's slotted slide is here

Thanks Jason

Neil Wyatt16/12/2018 09:41:37
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If I made it again, I would use smaller T-slots, and possibly as two along its length rather than three across.

Neil

Ady116/12/2018 09:50:11
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3462 forum posts
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and possibly as two along its length rather than three across

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

JasonB16/12/2018 10:11:34
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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 isdevil

Ron Laden16/12/2018 10:41:56
972 forum posts
145 photos

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

ega16/12/2018 10:45:30
1115 forum posts
90 photos

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.

XD 35116/12/2018 11:57:26
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1210 forum posts
83 photos

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 !

mechman4816/12/2018 12:17:59
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2296 forum posts
387 photos

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 Lewis19/12/2018 15:03:06
1812 forum posts
2 photos

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 Wyatt19/12/2018 15:12:02
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Here we are, I've found the article:

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

Neil

Neil Wyatt19/12/2018 15:43:46
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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

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