By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by allandale

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

All Topics | Latest Posts

Search for:  in Thread Title in  
Goran Hosinsky04/12/2010 15:18:56
41 forum posts
Has anyone used the QTCP that Harold Hall published in MEW 50 (also at If so, I would like to hear their opinion of it.

Canary Islands
Bill Pudney04/12/2010 21:00:20
339 forum posts
11 photos
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.
Bill Pudney
Adelaide, Australia
Goran Hosinsky04/12/2010 21:13:32
41 forum posts
Bill, what was the outcome of your research?
Peter Riedie04/12/2010 21:19:14
3 forum posts
I have built a QCTP to John Stevenson's design which is on the web at
Works well for me and the tool holders are very easy to make.
Bill Pudney05/12/2010 03:17:57
339 forum posts
11 photos
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........
I hope I haven't broken any protocols by adding a link to another web page....
Bill Pudney
Adelade, Australia
Goran Hosinsky05/12/2010 08:08:33
41 forum posts
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.
Bill Pudney05/12/2010 22:53:01
339 forum posts
11 photos
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.
Bill Pudney08/12/2010 01:24:28
339 forum posts
11 photos
To clarify the parting toolholder construction I've just added some photos here............
Bill Pudney
Terryd08/12/2010 06:13:41
1926 forum posts
179 photos
Hi Bill,
Do you have to reset the height every time you change tools with your design?
Bill Pudney08/12/2010 09:20:59
339 forum posts
11 photos
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.
Terryd08/12/2010 10:46:59
1926 forum posts
179 photos
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?
Bill Pudney08/12/2010 21:45:36
339 forum posts
11 photos
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.
Bill Pudney

John Stevenson08/12/2010 21:51:38
5068 forum posts
3 photos
I think I could do with a few more.

I'm running out..................
John S.
Stub Mandrel08/12/2010 21:59:25
4302 forum posts
292 photos
"Just another 12 toolholders and I can make a start on my first project..."

Peter E08/12/2010 22:59:13
48 forum posts
22 photos
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 Olsen08/12/2010 23:13:57
817 forum posts
85 photos
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....
Terryd09/12/2010 00:00:35
1926 forum posts
179 photos
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.
John Stevenson09/12/2010 00:05:30
5068 forum posts
3 photos
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 Pudney09/12/2010 01:31:28
339 forum posts
11 photos
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!!
Bill Pudney
Peter E09/12/2010 21:59:05
48 forum posts
22 photos
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

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer!

Find Model Engineers' Workshop!

Email News - Join our newsletter

Love Model Engineering? Sign up to our emails for the latest news and special offers!

Latest Forum Posts
Support Our Partners
Meridienne Mid Mod Eng Show. Aug 21
Expo Tools July 14
Allendale Electronics
TRANSWAVE Converters
Reeves 2000
Advertise With Us
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest

Visit the Model Engineer
Exhibition website

Model Engineer Exhibition