Home Made Rear Toolpost Issue

[HopperParticipant @hopper]

I was thinking of a T nut with a larger thread, more like 8mm or the full width of the T slot which might be about 3/8 from memory. Pretty much the biggest thread that will fit through the T slot. Using the more square type T nuts. You could mill up a longer one to fit your T slots and drill and tap it to fit a thread just slightly smaller than the T slot narrow part. Make the T nut as long as the width of the toolpost base for maximum strenght. .Or a bit less so you can keep the end sections of that locating tennon you machined on the bottom for location purpose.

Edited By Hopper on 03/03/2021 09:20:17

[Dr_GMJNParticipant @dr_gmjn]

Posted by Hopper on 03/03/2021 09:18:11:

I was thinking of a T nut with a larger thread, more like 8mm or the full width of the T slot which might be about 3/8 from memory. Pretty much the biggest thread that will fit through the T slot. Using the more square type T nuts. You could mill up a longer one to fit your T slots and drill and tap it to fit a thread just slightly smaller than the T slot narrow part. Make the T nut as long as the width of the toolpost base for maximum strenght. .Or a bit less so you can keep the end sections of that locating tennon you machined on the bottom for location purpose.

Edited By Hopper on 03/03/2021 09:20:17

I think what I'd do is just mill a horizontal slot along the front of the block and use one of the clamps I made for the milling vice. That would stop the front lifting, and would be a very simple addition, if it's necessary.

[Howard LewisParticipant @howardlewis46836]

! Your toolpost looks to be sturdy and rigid, and well located.

GOOD! Rigidity is like cleanliness, next to Godliness.

Don't worry too much about a M6 thread exerting enough force. It is a fine thread and so capable of delivering aPossibly it will crack the Myford Cross Slide before the thread strips, if you apply enough torque!.

Screw threads are intended to provide a big mechanical advantage. Think how you can lift a car with a comparatively small diameter thread in the jack! A thread is only a long lever wrapped around a bar.

(Compare how far your hand travels in comparison with the distance that the load is lifted. )

Howard

[Dr_GMJNParticipant @dr_gmjn]

Posted by Howard Lewis on 03/03/2021 11:32:42:

! Your toolpost looks to be sturdy and rigid, and well located.

GOOD! Rigidity is like cleanliness, next to Godliness.

Don't worry too much about a M6 thread exerting enough force. It is a fine thread and so capable of delivering aPossibly it will crack the Myford Cross Slide before the thread strips, if you apply enough torque!.

Screw threads are intended to provide a big mechanical advantage. Think how you can lift a car with a comparatively small diameter thread in the jack! A thread is only a long lever wrapped around a bar.

(Compare how far your hand travels in comparison with the distance that the load is lifted. )

Howard

Thanks Howard. I think the potential issues here are the quality of the thread I put on the end of the stud, and the small surface area over which the load is applied to the underside of the T-Slot.

But the clamp I have in mind should address those issues. I'll post an image in a while.

[Dr_GMJNParticipant @dr_gmjn]

This is a milling vice clamp – It should just fit once a slot has been milled:

[Ron LadenParticipant @ronladen17547]

Well the clamp will help obviously help but since you have fitted the T nut and milled the key have you not tried parting to see how it performs..?

Edited By Ron Laden on 03/03/2021 13:50:18

[Howard LewisParticipant @howardlewis46836]

You can always make an elongated T nut so that although the load is applied in the centre, it will be applied along the length ofn the T nut and the T slot in the Cross Slide. The Base of your toolpost will take the load, so that it is unlikely that a small T nut would pull through the Cros Slide, unless some MAJOR disaster happened.

I've loaded a picture of the one that I made to secure my Four Way Indexing Back Toolpost into my Album.

AS I've said the parting tool is mounted at horizontally at centre height, and has no Top Rake..

For deep parting cuts, a gravity drip feed of soluble oil is used. The fluid drops onto the tip of the tool, or on deep cuts into newly produced groove. The shop made jet and needle valve mounts on a short vertical stud in a small magnetic base.

This helps the swarf to fall away rather than build up in the groove.

Howard

[duncan webster 1Participant @duncanwebster1]

Advantage of the hold down bolts in front as per GHT design is that the bolts are right under the load. This reduces the bolt load and hence the load applied to the tee slot

[JasonBModerator @jasonb]

The other option would be to ditch the M6 nut and your stud an use a 3/8" tee bolt instead.

[Dr_GMJNParticipant @dr_gmjn]

I think whoever made the original stud tried to use the full width of the slot, but for some reason decided to peen it in place. I’ll try to find a suitable T bolt.

[Howard LewisParticipant @howardlewis46836]

If anyone is interested, have just posted another couple of pics of the 4 way back toolpost into my album, showing the locating dowels.

The central clamp stud was 10mm only because I happened to have one lying about

Howard

[Neil WyattModerator @neilwyatt]

Posted by Dr_GMJN on 02/03/2021 23:30:59:

Still needs setting to centre height, so I guess I'll see how it goes. At least it's very easy to remove if it's junk!

Thanks all.

I realise that may just be illustrative, but that seems a lot of overhang for easy parting off.

Neil

[Dr_GMJNParticipant @dr_gmjn]

Posted by Howard Lewis on 03/03/2021 17:27:46:

If anyone is interested, have just posted another couple of pics of the 4 way back toolpost into my album, showing the locating dowels.

The central clamp stud was 10mm only because I happened to have one lying about

Howard

Thanks Howard.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Neil Wyatt on 03/03/2021 17:34:37:

Posted by Dr_GMJN on 02/03/2021 23:30:59:

Still needs setting to centre height, so I guess I'll see how it goes. At least it's very easy to remove if it's junk!

Thanks all.

I realise that may just be illustrative, but that seems a lot of overhang for easy parting off.

Neil

Thanks Neil, it was purely to show something along the axis of the chuck to show the clearances with a typical workpiece. I wouldn't try to part anything off as it's shown.

[John BaronParticipant @johnbaron31275]

Hi Guys,

I perceive one problem with all the rectangular rear toolposts !

That is ensuring that the tool is dead nuts parallel to the chuck ! Any slight miss alignment in the positioning will cause parting issues. Here I'm talking about angular and or rotational alignment.

[Dr_GMJNParticipant @dr_gmjn]

Posted by John Baron on 03/03/2021 17:57:00:

Hi Guys,

I perceive one problem with all the rectangular rear toolposts !

That is ensuring that the tool is dead nuts parallel to the chuck ! Any slight miss alignment in the positioning will cause parting issues. Here I'm talking about angular and or rotational alignment.

I checked it with a dti – its fine. The key in the base has the advantage that it's repeatable too without having to re-set everything when fitting.

[old martParticipant @oldmart]

The one I made just requires lining up with the cross slide when the bolts are tightened and it is dead square.

[Ron LadenParticipant @ronladen17547]

The base plate on my tool post has 4 dowel pins which locate in the two T slots for alignment on the cross slide. I always sandwhich a piece of 10mm square tool steel between the parting blade and the face of the chuck as a quick check that the blade and holder is sitting square.

Edited By Ron Laden on 05/03/2021 07:08:40

Edited By Ron Laden on 05/03/2021 07:09:52

[Dr_GMJNParticipant @dr_gmjn]

Posted by Ron Laden on 05/03/2021 07:04:35:

The base plate on my tool post has 4 dowel pins which locate in the two T slots for alignment on the cross slide. I always sandwhich a piece of 10mm square tool steel between the parting blade and the face of the chuck as a quick check that the blade and holder is sitting square.

Edited By Ron Laden on 05/03/2021 07:08:40

Edited By Ron Laden on 05/03/2021 07:09:52

Thanks Ron, that’s a good idea. I’m hoping my 3/8” T bolt arrives today, so I can give it a try.

[Dr_GMJNParticipant @dr_gmjn]

So I milled the key to clear the new bolt:

and set it up using the "against the chuck" method suggested earlier in the thread:

I tried it on some steel, and then some brass. It was "OK", but in no way was the step change I thought I'd notice having read about the improvements to parting this should give. I thought I noticed some movement, so I went ahead and milled an extra slot in the block, for a clamp, which fitted perfectly:

I then tightened the bolts after setting against the chuck again, and…something felt wrong. Surely not a stripped thread?

No:

This really sums up for me the utter misery of making tooling – I spend hours fettling something, for it to fail. I suppose I should have investigated further why it was in a box in the first place – and the out of square on the faces should have prompted me to treat it with more suspicion. I think it may have been cracked already, and using it for the first time yesterday propagated it a bit, then re-tightening it was the final straw.

I'm having no luck at the moment at all with trying to fettle my equipment. Even the leadscrew nuts I was sent for the slides didn't fit, and I'm having to modify them. I'm not sure if this happens to anyone else, but sometimes I can't make any progress, and it would be easy to give up and just sit and watch telly. That's two weekends' worth of free time wasted on various dead end projects in the garage.

So, undeterred – for now – can anyone recommend a rear toolpost for an ML7, and also a good parting tool? Please don't suggest making one – I have less than zero interest in making tooling, I just want to buy something that works.

[Chris CrewParticipant @chriscrew66644]

I am sorry that you have suffered this failure, but please don't give up because (only speaking for myself) we all have disasters and learn from them. Also, you are not alone in having to make things fit, it's part of my workshop activities and consider myself lucky that I have the necessary equipment and a little bit of skill to be able to do this. If you are not prepared to splash out on a OEM Myford rear tool post I would suggest that, unless someone has another type to sell you or Ebay is not forthcoming, then your only alternative is to make one. I would copy the Myford myself because, although I am a great admirer of GHT as a mentor and guide, I am not so enamoured of his designs which always seem to me to be lightweight and lacking substance. And before anyone takes a shot, I am not setting myself up as knowing more than the great man himself. It is just that as he was such a superb craftsman I always imagine that his tools were always super sharp and so perfectly honed that they needed very little force to effect a cut. A state of perfection I have never been able, and never will be able, to achieve!

You can copy the the ML7 rear tool-post easily enough, I copied a Colchester rear tool-post out of noggins of mild steel and it works perfectly well for me. In fact if you are anywhere near the middle of Lincolnshire I have more than a lifetime's supply of suitable noggins and you are very welcome to collect one. One thing I would say, again only as a personal opinion through experience and not withstanding the crack in your tool-post, is that if something is going to hold and grip securely, it will do so with not much more than a 'nipping-up' and will not require any excessive heaving on a spanner or allen key. How many tee-slots will have been broken out by excessive tightening by people thinking that this will stop a work-piece or tool shifting? A soft card gasket usually cures a tendency to shift under most cutting forces but if it doesn't you should be looking at other ways to secure a tool or work-piece.

Edited By Chris Crew on 07/03/2021 18:45:17

[Dr_GMJNParticipant @dr_gmjn]

Thanks Chris – giving up because of a setback isn’t really an option, but sometimes…bloody hell I feel like it! Not sure whether the Gods of ME on here have these days…

[Dr_GMJNParticipant @dr_gmjn]

By the way I think this thing was made from cast iron. If I’m forced to make another (and let’s be clear it’s a last resort), what material should I go for?

The Arc Euro insert type parting tools look substantial – anyone got one?

Thanks all.

[David George 1Participant @davidgeorge1]

Hi Dr_GMGN how about just making a top plate to clamp the blade similar to my one. It looks like it would make similar and you can then slide the blade in or out to suit the job to part off.

David

[Chris CrewParticipant @chriscrew66644]

For my two-pennyworth, mild steel does for most jobs probably simply because I acquired a mountain of the stuff when my erstwhile employer closed its tool room and workshop a few years ago and it is very easy to work with. I have made most things out of it even where other materials have been specified. Of course, it would not do in industry or a professional environment, but in the home workshop where sliding or rotating parts are not in use eight hours a day, five days a week, it is very unlikely that it will ever wear beyond use. The only things that I use higher quality hardening steel on are, obviously, home-made cutting tools. The Colchester rear tool-post I copied is made out of mild steel and works fine for me.

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