Harold Hall QTCP, MEW 50, any one using it?

[Goran HosinskyParticipant @goranhosinsky61367]

Has anyone used the QTCP that Harold Hall published in MEW 50 (also at http://www.homews.co.uk/page38.html). If so, I would like to hear their opinion of it.

Goran
Canary Islands

[Goran HosinskyParticipant @goranhosinsky61367]

[Bill PudneyParticipant @billpudney37759]

When I was researching my recently completed QCTP upgrade I came across this one.  I obviously admire and respect Harold Halls work generally, but in the case of this QCTP it seems over complicated and unfinished as presented. 

 

I can see what he is trying to do, but the pad seems to me to be unnecessary, if the whole thing was dimensioned differently, and better; and the location bar, the one with a flat on it, could be replaced with a square or rectangular bar.

 

Its very interesting though, shows there’s more than one way to skin a cat!!

Or am I missing something??  I often do.

 

cheers

Bill Pudney

Adelaide, Australia

[Goran HosinskyParticipant @goranhosinsky61367]

Bill, what was the outcome of your research?

Goran

[Peter RiedieParticipant @peterriedie26302]

I have built a QCTP to John Stevenson’s design which is on the web at

 

http://www.metalwebnews.com/howto/toolpost/toolpost.html

 

Works well for me and the tool holders are very easy to make.

 

PR

[Bill PudneyParticipant @billpudney37759]

I started off deciding what was required.  My lathe is a Sieg C3.  The major  requirements turned out to be:-

1/ 12 toolholders, plus 2 for parting off blades (I use 0.040″ x 1/2″ and 1/16″ x 1/2″ blades from LMS)

2/  Keep everything as small and stiff as possible, to reduce vibration and chatter.  This mean’t using steel rather than al. alloy as is sometimes seen.

3/  Reduce overhang from the compound slide.  The original toolholders overhung by up to 25/30mm for the parting toolholders.

4/  With the quantity of toolholders required, reduce machining as far as possible.

 

After quiet a lot of thought I decided to use a pillar and clamp on toolholder type.  The pillar was made as large as possible, this turned out to be 35mm diameter.  The toolholders were 25mm slices of 50mm x 50mm square S1214 steel, freeish machining steel(35mm slices for the 2 parting toolholders).  The 35mm diameter bore was a challenge, quotes for watercutting and laser cutting were obtained and dismissed as being too expensive.  A bi-metal holesaw was tried but didn’t work for me.  So they ended up being drilled and red in the 4 jaw.

 It was all a fair amount of work, but so far I’m really pleased with the result.  there are some photo’s at……..

 

http://madmodder.net/index.php?topic=3823.0

 

I hope I haven’t broken any protocols by adding a link to another web page….

cheers

Bill Pudney

Adelade, Australia

 

 

 

[Goran HosinskyParticipant @goranhosinsky61367]

Bill, is your toolpost indexable, that is, can you change tools and then get the old one back again in the same position?

 

I am using a set of 4-way toolholders, I have got 5 of them. which makes for a quick an easy tool change and no overhang, but I cannot get the tool back to exactly the same position (in rotation of the toolholder) except if I use the top slide parallel with the lathe axis, where it fouls the TS. That is why I am looking for an alternative.

Goran

 

[Bill PudneyParticipant @billpudney37759]

The toolholder rotates on the post, 360 degrees!!  This is from choice, as I have removed the small spring loaded detent pin in the compound slide, which enabled indexing to some degree.  It wouldn’t be a problem to reinstate it should that be required.  I do take great care to make sure that the parting blade is perpendicular to the spindle axis though.

cheers

Bill

[Bill PudneyParticipant @billpudney37759]

To clarify the parting toolholder construction I’ve just added some photos here…………

http://madmodder.net/index.php?topic=3823.0

cheers

Bill Pudney

[TerrydParticipant @terryd72465]

Hi Bill,

 

Do you have to reset the height every time you change tools with your design?

 

Terry

[Bill PudneyParticipant @billpudney37759]

Hi Terry,

Not once a cutter/toolholder assembly is set up.  If the cutter is removed from the toolholder and changed for another cutter then the height would have to be reset.  Thats why I made 12 toolholders and 2 parting off toolholders.

 Since I’ve been pratting about with the 0.040″ parting toolholder (taking photos, taking it all apart etc) then I will have to set the height on that one.

So far it all works really well.

[TerrydParticipant @terryd72465]

Hi Bill,

 

When you change a cutter carry out an operation and then put the original back how do you ensure that the original is at the correct height?

 

Terry

[Bill PudneyParticipant @billpudney37759]

Hi Terry

Just behind the cutter slot and at 90 degrees to it (parallel axis to the 35mm central bore) is a tapped hole.  In the tapped hole is a set screw (metric grub screw) with a brass end pad Loctited to the screw.  When the toolholder is loosely located on the pillar, by screwing the brass tipped set screw up and/or down the height of the cutter can be changed.  Once the correct cutter height is established then the clamping screws (2 x M6 SHCS) can be tightened.

The point in having 12 available toolholders is so that it is not required to do a lot of cutter changing whilst making any particular part, or series of parts.  Twelve toolholders permits me to have most, if not all of my commonly used tools set up and ready to go.

It seems to me to be a bit futile to have a QCTP with (say) two toolholders!!

Even though currently I don’t really know what I’d use them for, apart from maybe a tangential toolholder, and a specific boring bar holder, I’m thinking about getting some more 50mm x 50mm x 25mm bits of S1214 with my next material order.

My next little project is a tool setting gauge.

cheers

Bill Pudney

[John Stevenson 1Participant @johnstevenson1]

I think I could do with a few more.

 

 

 

 

I’m running out………………

 

John S.

[Sub MandrelParticipant @submandrel]

“Just another 12 toolholders and I can make a start on my first project…”

 

 

Neil

[Peter EParticipant @petere]

I would like some more info on the best way to use the dovetails. On my version – see separate thread “My C3 QCTP” – I have chosen to have the “male” part as part of the tool post, and the “female” part as part of the tool holder.

 

From what I can see on Mr Stevenson´s picture above, the use is the opposite.

 

My thinking is that with the male part being part of the tool post, it will be easier to design the dimensions so that the total overhang of the tool compared with the cross-slide is as small as possible. I will even try to mill the top surface of the C3 top-slide circular so that the tool holder can pass below the top-slide top surface. All to give the largest possible range of movement. Is my thinking correct, or am I out in the blue (as usual) ?

 

/Peter E

Edited By Peter E on 08/12/2010 23:00:23

[John OlsenParticipant @johnolsen79199]

I certianly agree that it is dificult to have too many tool holders. I have one of the Dickson clones, it was useful even with just the four holders it came with. (Boring, parting, and two general purpose.) It gets more and more useful as you add holders, so that you very rarely actually have to set a tool up any more. When you only have a few , you have to think about which ones you are going to want for a repetition job and set them up ready.

One thing about it with the Myford, it eliminates the problem with the standard toolholder where the clamping force distorts the topslide. There is still of course the problem with the topslide wanting to foul the tailstock. Sometime I will make a better topslide….

 

regards

John

[TerrydParticipant @terryd72465]

Hi Bill,

 

Thanks for the explanation.  I’m investigating toolpost design for when I get my new lathe (if ever the builders get their act together).  I was looking at the HH design but yours is intriguing, do you think it possible that your design could be made with the HH design of height adjustment.  I.e. a cap head screw with a fixed washer under the head, in the top of the toolholder which rests on the central column and then locked with a grub screw (with a copper pad to protect the cap head screw threads)?

 

I’d be grateful for your thoughts.

 

Terry

[John Stevenson 1Participant @johnstevenson1]

I built my original one, which was smaller than the one above for an ML7 that I owned.

it was built before any of the cheap imports came into the country and the only ones available to me were the Dickson ones which where too expensive for me at the time.

 

I though long and hard over the design and based it on the above because internal dovetails are harder to do than external and you only make one post [ normally ]

My thinking was any detail work would only need to be done once.

 

The design was probably done around 1980 and I think it was published in ME in about ’85 or ’87.

 

The tool holders, of which you need more, can be done as mirror images of the toolpost using conventional dovetail cutters but I chose to make them in 24″ long strips on a horizontal miller using a 60 degree angled cutter which lasts far longer and can remove far more metal than a dovetail cutter. One side of the cutter is vertical, the other side is at 60 degrees and can put the profile for one side along the 24″ in one pass and the work is turned round and a second pass taken – job done.

All that needs doing is to saw off to length as required and finish as a tool holder, boring tool holder etc.

 

The posts and holders in the picture are larger to fit 6 -7″ centre hight machines but the design has just been scaled up.

I actually have three of these posts, all the same on three lathes and about 46 holders between the three lathes, only the hight stop on each post differs so all the holders can interchange.

 

I was going to make a far larger one for the big TOS lathe 11″ x 84″ but found a Dickson one with about 10 holders at a reasonable price. I’m pleased I went this way as I don’t like the Dickson one on the TOS.

Too may sticky up pieces for turning to get ravelled around and on heavy interrupted cuts they shake loose because of the cam arrangement not being positive.

However for what it gets used for it can stay until it gets retired next year

 

[edit]  Also if you notice I do not have a top slide fitted, instead it’s been replaced by a large steel block, for me rigidity is worth more than the odd taper I need to do, the top slide is in the cupboard with it’s original 4 turret toolpost set up with three common tools for the three times a year I have to use it.

 

 

John S.

Edited By John Stevenson on 09/12/2010 00:09:06

[Bill PudneyParticipant @billpudney37759]

Hi Terry

I almost made the height adjustment as you suggested, what stopped me was the “sticky up bits” as John described them getting wrapped up with swarf, exactly the same rationale as John in fact.

There were several compromises in what I did, like…

1  Not using a dovetail design, because of the anticipated difficulty in generating the dovetails.  I would have used a similar, but smaller set up to that described by John.

2  Using socket fasteners throughout, as appropriate square headed fasteners and screws would  be hardish to make, whereas decent quality socket fasteners are available off the shelf.  Yes I know that its tedious getting swarf out of the sockets.

3  Originally the clamping mechanism was intended to be a single M8 screw.  When the 50mm x 50mm toolholder size was selected, an M8 fastener was simply too big, so 2 x M6 fasteners were used.  This obviously mean’t double the drilling and tapping, which was made worse because I chose to use as long a thread as possible, to minimise any problems…wear etc.  Drilling and tapping all those holes was a major part of the whole.  The advantage is that with two screws, the clamping effect is very good.  Being a pedantic barsteward I’m going to measure the torque required to achieve a secure set up. 

4  The use of a 35mm diameter pillar, rather than the more usual 25mm.  This was to achieve the greatest possible clamping area, and therefore the greatest resistance to inadvertent movement, despite the extra work involved in boring a 35mm accurate hole.

What I’m trying to say is even with a basic concept (i.e. “pillar and clamp on toolholders”) even the most minor details should be thought through, and it should be understood that all detail design will require some compromise.  It seems important to me to make those compromises to suit the user (in our case the designer and manufacturer).  Hopefully whatever is made will be in use for a long time, so any minor irrits during manufacture will be acceptable…..classic “Design for Manufacture” scenario!!  I suppose that this is the major area of compromise.    As an ex draftsman, I enjoy lots of conceptual doodling as well!!

 cheers

Bill Pudney

 

[Peter EParticipant @petere]

Thank you for answering John S, very useful.

 

I never though there was/is any difference in cutting outside dovetails compared with inside ones – they are equally tricky to me The one on my pic in the other thread is the first one ever. Secondly, I have a vertical mill only so I have to stick to dovetail cutters.

 

I agree that exchanging the top slide for a riser block will do much for stability. That is one thing I am going to look at after producing a dozen or two of various tool holders. Someone mentioned possibilities to have firm stops for the tool post. This, I think, can be fairly easily solved by a spring-loaded plunger coming up from the riser block into a suitable recess in the tool post under-side – something like the tool post lock on G H T´s rear parting tool post. Hmmm will look into that as well.

 

Peter E

 

Edited By Peter E on 09/12/2010 22:00:06

[Peter EParticipant @petere]

Reading through the thread I noticed that also another type of QCTP was mentioned, namely the type having a cylindrical tool post with tool holders nipping the post.

 

I made that type for my first lathe, a Unimat clone called MJ-189. A really good little lathe once it was adjusted. After using it for a while I got fed up with keeping track of all the packing pieces to get the cutting tools at proper height. I then made a cylindrical toolpost from a 35 mm dia piece of BMS turning the main part down to 20 mm. The result was a 20 mm dia post with a 35 mm dia foot.

 

The tool holders were made from 15×30 mm BMS in 40 mm lengths. A 20 mm hole drilled/bored in its center and slitted for nipping to the post using a 6 mm cap screw.  I found two pics showing two types of tool holders, one for ordinary turning and one for boring.

 

and 

 

As can be seen, I tried out ordinary screws for clamping as well as a screw with a lever handle. The slit-and-nip works very good, but if I were to make more of these now I would go for a brass clamping dog pulled by the screw and not use a slitted holder. The internal clamping dog does a much better job of clamping with less force when locking.

 

My experience of this type was generally very good. The circular tool post gave perfect support at any angle of the tool, something that the original rectangular holder did not do.

 

But for the C3, it will be the dovetail style stuff.

 

 Regards

/Peter E

[Clive FosterParticipant @clivefoster55965]

Given the inevitable budget constraints, both fiscal and temporal, concerning Home Shop and Hobby activities I think there is much to be said for a system based on interchanging tool bits in nominally fixed Armstrong type holders.  Provided of course that your lathe is large enough to accept Armstrong holders which may rule out anything below about 3″ centre height unless the top slide is removed.  Because the Armstrong holder mounts the tool bit with an upwards slope setting the bit to centre height also sets its projection to close limits.  The optical centre height gauge described by Ted Wale in the November 2004 issue of Model Engineers Workshop is by far the best type, especially in this sort of application.  I was familiar with the principle for many years previous to Teds description but never felt it would be enough better than what I was using to make one. Needing a new gauge to suit my Smart & Brown 1024 I finally got round to it and seriously regretted a quarter of a century doing things the usual way. Square tool steel is inexpensive compared to inserts and butt welded, forged shank tooling so its economically feasible to have a good range of bits ground to appropriate angles making it pretty much unnecessary to adjust the tool holder position in normal work.  Grinding square tool bits to accurately repeatable shape needs only simple angle setting jigging.  Some of the but welded tools can be a right pain with limited facilities.

 

Clearly a simple two slot block will suffice to carry the normal turning, bent to the right, holder and the face turning, bent to the left, holder.  Simple stops to set the 180° rotation needed for interchange should be no great problem.  Such blocks can be bolted up from stock sections.  Similar holders will clearly suffice for parting tools and any insert tooling you may choose to use.  If you use the common “mutant golf club” boring and internal threading tool forms hated by Geo.H.Thomas shimming must be resorted to.  His eccentric holder and boring bar system would work well given a suitable block.  Given a Tee slotted top slide switching blocks becomes trivial if complete assemblies with locking handles and Tee nut are made.  In my South-Bend driving days I had multiple four ways made up in this manner carrying but welded tools which worked well  save for the usual shimming tedium.  The normal nut on a stud system shouldn’t be impossibly tedious but, if so, there are various ways of arranging quick release.  For example the centre stud could be arranged to be freely rotating with a cross hole drilled close to the top for a locking handle in the form of along pin.  If an externally threaded sleeve with a castellated top is screwed into the tool block the locking handle can be passed between the castellations and though the hole in the stud.  It should be no great problem to arrange matters so that  third of a turn or so goes from locked to loose enough for the handle to be withdrawn and the block lifted away. 

 

Obviously considerable refinements of the basic idea covering, for example, indexing et al are possible to suit individual needs.  Clearly it works just as well with insert holders if pre-loaded blocks are interchanged.

 

Clive 

[Bill PudneyParticipant @billpudney37759]

Whats an “Armstrong type holder”

A picture  speaks a thousand words

Bill Pudney

[Harold Hall 1Participant @haroldhall1]

The brief answer to Goran’s original
question is Yes, I have, but looking at my name that should be
obvious. Those who read my articles in MEW will have seen very many
illustrations of it being used.

I do not though think mine is the be
all and end all in QCTH design but as Bill Pudney comments it shows
that there’s more than one way to skin a cat!!

A few comments about the design may be
of interest to those coming to this thread.

The original was developed to limit the
amount of milling required firstly to minimise the time taken to make
them and secondly making it practical for those who only have a lathe
and drilling machine.

The time element should be obvious as
drilling a hole through two holders clamped back to back will take no
more than a few minutes, milling dovetails on two holders would take
considerably more, perhaps a half an hour. If one intends to make a
large number of holders that is a considerable saving. I would though
recommend the hole to be reamed as drilled holes can be a little
barrel shaped, though mine work adequately.

A technical aspect of the design is
that the length to width ratio of the half round location is around 4
to 1 whilst most dovetail holders this will be around 1to1 maybe
less. This should make it pull into place more precisely but there
are other considerations. If you are unsure, consider a longish
piece of 10mm diameter held in the three jaw to a depth of 10mm, then
place it in 40mm, I know which will be running more accurately at its
end.

Of course, with commercially made
dovetail holders having a good finish, may be ground and hardened
then they will move more freely over the two mating surfaces than
ones made in the average home workshop. Of course if power feed to
the milling machine table is available then it will be less of a
problem but hand feed will cause furrows if the feed is slowed or
even stopped.

It was also suggest that a square key
to be used but the two curved surfaces coming together act as a mini
inverted dovetail whereas the corners of a square would tend to dig
in.

If I where making a set again with the
experience gained I would just ream my drilled holes that make the
locations and increase the throw of the clamping cam by just a
little, though I think I have included this in the drawings on my web
site.

I do not normally visit the forum, I do
not have the time, but will keep my eye on this thread should any
comments need answering.

[Author]

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