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Member postings for John Baron

Here is a list of all the postings John Baron has made in our forums. Click on a thread name to jump to the thread.

Thread: Tool post height
12/07/2021 15:46:25

Hi Guys,

I agree with the comments that Tangential lathe tools are quite easy to male and use. I made one quite a while ago.

Easy to set up and easy to sharpen. You get a good finish too.

This is a drawing of one that I made. Just scale to suit whatever HSS or carbide you want to use.

tangentel tool.jpg




As you can see the finish is not too bad.


Certainly better than my photography smile

Thread: Power feeds for Chinese mills
12/07/2021 15:25:49
Posted by duncan webster on 12/07/2021 11:42:34:

Many moons ago I made a drive for the Naerok miller using a DC motor and a train of gears. This had two disadvantages:

  1. When the cut started and more load went on the motor it all slowed down, by quite a lot, in fact if set for a very slow feed it would just stop.. I can wax lyrical about why, but not here
  2. you had to disconnect the drive to do manual feed.

I overcame the first by incorporating a feedback loop. I suspect people using windscreen wiper motors just have a lot of oomph to spare so it doesn't slow down as much.

The setup on my Centec uses a stepper with tooth belt drive. It is so much easier. If you use one of the pulse generator things referred to above it is just buy some bits, make up a mounting bracket, join the bits together and go. No need for a clutch, just wind the motor round. No need to know anything technical about steppers or controllers. Mine is a bit cleverer as it incorporates acceleration ramps

Hi Duncan,

I made mine using a car window screen wiper motor. They just don't stop, at all ! They are amazingly powerful.

I actually twisted the centre out of the primary gear on mine by forgetting that I had locked the table. Fortunately I had a spare gear.

I drive mine from a 3 amp 30 volt variable voltage power supply. Usually at about 7 volts. But I have put the full 30 volts on the motor several times for rapid feed without any issue.

Thread: Tool post height
08/07/2021 20:35:29

Hi Guys,

Just in case there are those that don't know what the "Norman" patent tool post looks like. This is the one that I made and use. The tool slot will hold a 1/2" inch tool and the height is adjusted by altering the silver M6 cap screw that bears on the surface below. The tool holder is secured by a spilt cotter using an M6 thread. It takes about a quarter of a turn on the cotter screw to go from locked to loose.


Drawings for the Myford size one are in my album !

08/07/2021 15:17:34
Posted by Tony Pratt 1 on 08/07/2021 13:54:10:
Posted by Roderick Jenkins on 08/07/2021 13:50:14:

Lots of "theory" on here about the lack of rigidity of QCTPs. I have never had a problem with mine on my S7. I have a Gibraltar post and have only ever used that with a boring bar that is too big for the tool holder (and for my J&S knurling tool which has a shank which is too big).


I agree, if you tighten a QCTP correctly there should be no problem with lack of rigidity.


Its nothing to do with how much you tighten a QCTP ! The problem is with the amount of overhang some have. The tool needs to be within the footprint of the cross slide for maximum rigidity.

07/07/2021 20:02:44

Hi Guys,

I'm not an advocate for QCTP at all having used one and got rid of it in favour of the "Norman" patent tool post and holder. I can use 1/2" inch tools without a problem ! I don't need shims and can set tool height in a fraction of the time it takes to set a new tool using a QCTP. Particularly since I predominantly use HSS tools.

Myford also used the "Norman" patent tool post in the earlier days as did RR in their workshops. I've still got the original Myford four way but its in a box and not used any more.

I do agree about the loss of rigidity with a QCTP particularly the extra overhang that it has.

Thread: Split cotters
04/07/2021 09:47:47
Posted by Howard Lewis on 04/07/2021 08:43:34:

John Baron,

That was exactly the point that i was making, that when clamped to the bar angular and linear movement is prevented. The whole purpose for using split cotters, surely?


Yes I agree ! I misread your post then couldn't edit mine. I do apologise.

03/07/2021 18:09:17
Posted by Howard Lewis on 03/07/2021 17:32:27:

From a practical standpoint, split cotters would seem to prevent movement of the main bar, in two ways.

1 ) The two halves of the split cotter grip the bar like brake shoes, and being a close fit in their bore prevent rotary or linear movement of the bar.

2 ) By clamping against the bar, and having a gap between the ends, there would be a wedging action which exerts a force between the one side of the collets and their bore, forcing the bar outwards against the bore in which it is located. The frictional forces resulting will tend to prevent the bar from angular or linear movement.

If either of these hypotheses is correct, the split cotter does what is required of it, in preventing movement in any plane, once clearances have been taken up.

If anyone is so inclined, reference to the dimensions of a particular arrangement can allow the forces to be calculated, having made assumptions about the coefficients of friction of the materials and threads involved.


No it doesn't prevent rotary motion, nor linear motion until the two halves are pulled together. As long as there is a few thou of gap between the halves when tightened they will firmly clamp whatever they are pressed against.

As far as a diameter for the cotter is concerned a larger area for the clamping surface simply means that the force required to lock a shaft is less than a small area.


This is 14 mm diameter cotter intended to secure the block to a 35 mm diameter post using an M6 screw. That gap is just under 2 mm.

26/06/2021 08:14:36

Good Morning Guys,

I understand both points of view !

Only if one side of the cotter is longer than the other could there be any possibility of wedging, this could happen if the cotter were cut off centre or the cotter was a very loose fit.

Since a cut in the centre of the cotter would remove material and make both halves shorter by equal amounts the very fine taper on each would be removed.

Any burr on the cut edges will dig into the shaft being clamped and cause sticking and shaft damage so it must be removed.

I agree that the cotter provides a linear clamping action rather than a wedging one ! However as shown in the diagram that Michael posted the red arrows showing the force direction that will be directed at the back of the bore that the cotter slides in.

25/06/2021 16:53:54
Posted by John Baron on 25/06/2021 15:19:08:

Hi Guys,

Michael is right, facing off the inside ends would only tend to reduce or remove the burrs that the saw or parting blade left. FWIW I just use the bandsaw to cut the cotter across its centre. This usually leaves a 30 thou gap in the middle. Occasionally I face the inner ends if the cut is a bit rough.

? How about considering a split cotter clamping a square cross section !

Quite right, my error !

Since it wont let me edit my original post, error corrected.

I do understand where you are going Martin, but the cotter wont work if there is no gap between the halves. So the risk of any locking is non existent. As far a CAD package is concerned, I use Qcad. The community edition is free but a perpetual licence is only £30.

Thread: dirty clutch trick
25/06/2021 15:27:37

Hi Brian, Guys,

I've not heard any horror stories about Myford clutches, but slipping a belt is a useful trick ! I deliberately run mine a little loose.

Thread: Split cotters
25/06/2021 15:19:08

Hi Guys,

Michael is right, facing off the inside ends would only tend to reduce or remove the burrs that the saw or parting blade left. FWIW I just use the bandsaw to cut the collet across its centre. This usually leaves a 30 thou gap in the middle. Occasionally I face the inner ends if the cut is a bit rough.

? How about considering a split collet clamping a square cross section !

25/06/2021 11:04:36

Hi Guys,

The clamping angle varies very little for a given collet diameter and ultimately depends upon the diameter of the clamped part.

split cotter.jpg

This drawing of a 12 mm cotter with an M6 clamping screw shows the angles for a 20 mm diameter and a 50 mm diameter shaft. The blue lines representing the collet, whilst the red lines the diameter of the clamped item. There is barely 7 degrees between them. A larger collet diameter will only make a small difference. Hardly a locking taper.

As I mentioned earlier the sharp edge on the scallop edge will cause binding and should be removed. I few swipes with a stone is enough.

24/06/2021 16:31:23
Posted by derek hall 1 on 24/06/2021 14:55:19:

Hi everyone, thanks for your input !

In the Hemingways instruction in building the Quorn the offset is given by:-

D = bore being clamped, d = the diameter of the clamping bolt that squeezes the two collets together (NOT the diameter of the collets as I presumed it to be)

D/2 + d/2 + 0.02" = the centre to centre dimension for the split collet and bore.

Now I checked this with the GHT articles on his kit and his offset is 0.01" larger than suggested by Hemingway, that is:

GHT method is:- D/2 + d/2 + 0.03 = the centre to centre dimension of the clamping bolt and bore.

So both methods seems to suggest that an offset anywhere between 0.02" and 0.03" is the optimum

Without boring you too much more, GHT does say that "while the clamping effect is very powerful, the 2 halves of the collet may not separate when the clamping pressure is removed. This is down to one or both of these reasons (a) the offset between the bore and the clamping bolt is too large and (b) the shortening of the back of one of the collets was insufficient".

In addition GHT mentions that this offset is important and is recommended that it is held to within 15 thou (0.015"

Well I have lots of these to do on my Quorn so I feel confident that this offset works without stuffing up any castings!

Kind regards


Hi Derek, Guys,

Whilst the formula are basically correct I just add a couple of MM to the clamp screw diameter. However one thing that you do need to be aware of in cast iron. Split collets exert a great deal of pressure and whilst very effective at clamping that pressure has to be contained. So take very great care that the wall thickness directly opposite to the split collet is adequate to contain the pressure.

In Steel it isn't a problem, but I've seen castings broken by excessive tightening of a spilt collet ! One way round this is to use a small/smaller diameter material for the collet. Virtually all mine are in steel, I've only one in cast iron and one in aluminium.


24/06/2021 07:13:27
Posted by Michael Gilligan on 23/06/2021 21:39:01:
Posted by DC31k on 23/06/2021 17:47:06:
Posted by Michael Gilligan on 23/06/2021 08:48:25:

Perhaps I am missing something, Derek … but I can’t see why the ‘offset’ should be particularly significant.

A different offset will produce a different angle on the cotter.


dont know

I made no reference to angled faces on the cotter …

‘bored in-situ’ was my phrase.



23/06/2021 20:01:48

Hi Guys,

I think that every one is under the impression that split cotters are hard to make ! In my opinion they are not difficult at all. I use an M6 thread for my split cotters, so this immediately determines how far away from the shaft you are going to clamp, the cotter needs to be. Obviously you need to make a couple of MM allowance so the thread in the cotter does not touch the shaft.

After that I use any convenient size round bar for the cotter that I have a drill for. I drill the cotter all the way through the cotter, tapping size and then thread the drilled hole. It helps if you have some long series taps, depending upon how long you want to make the cotter.

At this point we now have a piece of bar for the cotter drilled and threaded. Making sure we have correctly calculated and marked the hole position for the cotter, we drill the hole for it making sure that its is a good fit in the hole.

If the cotter is fitted in a through hole where you have access to both ends, just use suitable bolts and washers to clamp the cotter in place. If the hole is blind then you need to drill and place a grub screw near the end at the bottom of the hole, again using a bolt and washer to secure it.

Once the cotter blank is fastened in place bore the hole for the bar that you want to clamp. This will automatically create a scallop of exactly the right dimensions in the cotter. After simply split the cotter in the middle and drill the threads out of the loose half.

I mentioned earlier that the sharp edges need to be removed from the middle of the scallop to prevent any marking of the bar being clamped and to ensure that it will release properly.

I've used split cotters on my "Norman" Patent tool holders and also my "Brooks" TCG as well as a number of other items. Photographs in my album.


This is a picture of my "Norman" Patent tool holder block being measured showing the collet held in it. I've used a short length of threaded rod on this one with nuts at the ends.

23/06/2021 09:36:50

Hi Guys,

I've always made my split cotters in one piece and then split them after machining the bore. Usually the thickness of the hacksaw or bandsaw blade is adequate gap ! Usually the sharp edges on the cut scallop have to be removed to prevent them cutting into the clamped shaft and causing problems both marking the shaft and sticking.


More pictures in my album.

Thread: Myford Super 7 Toolpost issue
05/05/2021 07:54:19

Hi Guys,

I can use 1/2" inch tools in mine but much prefer 6 or 10 mm HSS ! Far less work profiling and sharpening !

Thread: Quick release collet chuck clevis
05/05/2021 07:49:54
Posted by David George 1 on 05/05/2021 07:22:51:

Hi Tim I havn't seen the collet chuck for your lathe before but I would have thought you would be able to turn something that fitts. It won't need to be a very close fit and should be made from mild steel or silver steel. Have a go you will learn by your mistakes and a if it dosn't fit change design and make again.



Thread: Harrison L5A tool post mod
05/05/2021 07:46:05

Hi Francis, Guys,

I think that the cone is used to clamp the "T" slot, so removing it will mean you need something to replace it ! A flat steel plate would work, and give you a surface to mount another type of tool block. Personally I made my own new toolpost and tool holder to replace the QCTP and four way tool block. A relatively simple job, but you would need a mill to cut the tool holder slot. Even that could be done on the lathe but I wouldn't recommend milling using the lathe.

This is a picture of mine !


It is called a "Norman Patent" tool post. I also made one for the rear of the cross slide, mainly for a parting blade but the tool holders are interchangeable so I can use either at the front or rear. No shims needed to set tool height either. The silver cap head screw sets the height of tool.


I made this height gauge to use to set the tool on centre. The underside of the cap is used for the front and the top of the bar used to set the parting blade height.

Moe pictures in my albums.


Thread: "TINKER" tool & cutter grinder
10/04/2021 08:43:29

Hi Guys,

The "Tinker" TCG is best considered an idea that needs your own input rather than a set of poorly drawn details ! GL is a writer of books containing lots of ideas culled from around the world very few if any of which are unique. I don't remember the details of which magazine the "Tinker" was published in other than the ones I mentioned earlier !

If GL was as awkward as you say, I would give it no further consideration !

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