Yet another Quick Change Tool Post

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romartin

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What a marvelous mine of information and stimulus HMEM is!
Before becoming an HMEM member I hadn't encountered the idea of Quick Change Tool Posts and so calmly accepted the time needed to change tools in the one place post that came with my lathe when I bought it in 1985. I had encountered four and three place holders and indeed had designed a three placer (based on a design published by Chris Healy) and even purchased a suitable slice of metal from a 100mm diameter bar. But I hadn't started any real work. Now, stimulated by the enthusiasm of many HMEM posts, I've decided to build a QCTP. My design is based on the design by Nifty, with minor modifications to adapt to the dimensions of my lathe and to the material I have. I have uploaded the drawings as two pdf files into HMEM's Download section : title is "My QCTP". Any comments and suggestions will be very welcome. In particular I am wondering what material to use for the Pistons? My stomach says bronze? The other parts will be machined from what is called in Italy AVP - a (very) mild steel with small amount of lead.

I have no milling machine and so all machining will be done on my lathe. The attached photo shows my lathe setup for milling. I have to live with limited Y and Z excursions of 100mm and 60mm. The vertical slide is simply the compound slide of the lathe mounted on an angle plate. The machine vice can be mounted either vertically or horizontally.
MillingSetupH.jpg
 
Hi Ian,
You know what they say "necessity is the mother of invention". I used a dedicated milling attachment on my lathe for years and got by quite well. Ah but it's nice to have a mill.
Keep us informed.
gbritnell
 
Nice Job Ian! That looks pretty stout!

Dave
 
Ian,

For a tool post, I would use a could quality steel for the various components.

I built a near duplicate of that design for my old Atlas, and I used 12L14 for the body and 1018 for the tool holders. For the clamp however I used a Alloy steel ( AISI 4150 HT) I also used a Grade 8 bolt for the clamp bolt These two parts are wear items.

It ran great for years. Sold it with the Atlas....and now wish I hadn't! :big:

I'll be watching!

Dave
 
Hi Ian,
First off welcome, you have thought out the process with a true home engineers mind, well done.
And drawing out your design is a must in all projects, that stops items being remade or being deposed of at high velocity in the direction of the scrap bin.
Good Luck post plenty of pictures as this is what motivates others.
Kindest Regards
Beagles.
 
Hi Ian
If it is the first attempt I agree with you on using mild steel so You can learn how it works! Maybe when the tool posts will show some wear sign You can do another one with the appropriate steel quality!!!!!
Best regards
 
Thank you all for your comments. I had some doubts about the wisdom of using mild steel and I thank you for putting me right on that score. Unfortunately I have experienced great difficulty both in identifying the names and properties of the various steels and, above all, in buying small (i.e. non industrial) quantities. However, while waiting for the 60deg milling cutter to arrive, I will try again using a suggestion which Paolo gave me offline.
 
Building activity on my QCTP has not started as I am still waiting for the dovetail mill cutter to arrive. In the meantime, following a suggestion from Paolo, I have finally found a steel supplier with some sympathy for DIYers who dont want 3 tons of steel; this morning I managed to buy better quality steel sufficient for the Tool Post and a few Tool Holders. This steel is termed C40 and has a nominal carbon content of 0.4% and a small amount of Mn.
Browsing in HMEM I was struck and amused by a reply to someone else who had posted his new self-built QCTP. This reply said roughly - "Great job mate! Now you'll spend the rest of your life making Tool Holders!" I guess there is a risk of this sort - I remember a Bogstandard post saying that he has more than 40 and still needs a few more when he finds the time to do them! Wow! Got to find somewhere to keep them as well! Thinking about this I came up with two reflections:
- Having a dedicated Holder for every Tool is an option but not an obbligation. I could have a two or three general purpose holders with slots of different sizes, in which I change tools as need be. With respect to the situation with non QCTPs, I'd still have the advantage of adjusting the tool height without messing with shims. To me this seems acceptable for tools which are unlikely to be used more than once or twice a year.
- For smaller Tools, for example ground from 6mm (or 8mm) square HSS which BTW I prefer anyhow, one might be able to build Double-Barrelled Tool Holders (DBTHs) i.e. holders which hold two tools thus reducing the Holder building time per tool. On my lathe the line of centers is 19mm above the upper surface of the compound slide. Of this 19mm, the tool shank uses 6m (or 8mm), while the Holder metal below the tool slot needs at least 7mm. This leaves 6mm (or 4mm) of space between the bottom face of the Tool Holder and the upper face of the lathe's compound slide.
This second reflection led to the 3d model shown in the following images. This DBTH has the following differences respect to the standard single barrelled QCTP Tool Holder:
- It can hold two tools A and B. The holder can be mounted in two positions - "upright" and "up-side-down". In the upright position tool A is in business and tool B is upside down at the back as shown in the first two images. In the Up-side-down position, tool B is in business and tool A is at the back up side down as shown in the third image.
- Each tool has its own height adjustment mechanism. These mechanisms take the height reference from the top surface of the compound slide which is below the bottom surface of the holder. The height of the tool in business is adjusted from the top by turning it's Height Bolt with a screwdriver and then blocking the position with the brass Lock Nut. Naturally the top of the Height Bolts, the top of the Height Lock Nuts and the tops of the tool Fixing Grubs protrude above the top surfcae of the holder by less than 4mm.
DBTH01.jpg

DBTH02.jpg

DBTH03.jpg

Note that the particular 6x6mm tools shown in this model are just examples of tools which I happen to have and use frequently. They are not pertinant to the proposal to build double barrelled Tool Posts.
Note also that, when not in use, the tools protruding from Tool Holders should be protected, for example by plastic caps or tubes. In the case of the tool at the back end of a DBTH, this protection should be left in place to protect the user's hands from the tool!
 
Making toolholders is part of the fun, for me, while replacing tools into the holder is not. To say nothing about setting to height. ;D
Got 33, IIRC, and will make a few more next time I will put my hands on a 66x30x350 alu. bar. ::)
Marcello
 
Ian,

I fully understand your predicament, but there is an easy solution if you make your own toolholders, as I do.

I have a largish T200 piston QCTP, normal size is a T100, but the solution is the same.

My holders are geared towards 16mm (5/8") tooling, but I also use a lot of smaller sizes that I grind up myself for more intricate jobs, namely in 3/16" and 1/4" sizes, and they do become rather difficult to hold in a 16mm holder.

Where you are contemplating a double sided holder, it does get rather complicated.

I am about to make up a dozen or so half height holders, that is only using 1/2 the material of a normal holder, and cutting smaller slots in them, all the way across, so they can easily be used in different orientations to take the smaller tooling. Of course, at the same time, I will be using much smaller dog nosed grub screws as well.

I have done a trial a fair while ago, and if used on a normal sized piston toolpost, they clamp down just as well as a normal sized holder.

I will have to make the adjusting screw on the top slightly longer, to get the tool to correct centre height, but seeing that it is only a bit of threaded rod, costing that little bit extra shouldn't come into the overall cost of the new holders.

BTW keeping all these toolholders organised can be a bit of a problem, but I came up with a very cheap and easy to do solution.

http://www.homemodelenginemachinist.com/index.php?topic=18966.msg196951#msg196951

Just enjoy what you are doing, and work on the consequences later.


John
 
Half sized holders work perfectly on my lathe, too, though they're made in alu.
The tiniest two, for 4mm tools, can be seen on the bottom left of the tool shelf I made from a CD holder.

1_LatheToolsRack_IMG_0452.jpg


Marcello

 
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Thank you very much John and Marcello for these replies to my Double Barrelled TP proposal. For small tool sizes, the alternative of half height holders is certainly both simpler and has the enormous advantage of having a sound track record! I will probably take this route and intend to report progress in this thread. What do you think is the minimum height needed for holders (C40 steel) for 8mm square HSS tools? The rusty rectangular chunk of C40 from which I'll cut the blanks for my first holders is 75 x 30 x 170mm.

I'm surprised to learn that Marcello's tool holders are made in Al! What metal do you use John? How do you think automatic steel (11SMnPb37) would fare in that role? What are the components of your Tool Posts made from? What do you think of my plan to use C40 for all Tool Post components?
 
Ian,

If you set up in production mode to make tool holders, consider making four or so solid ones in aluminum to use as holders for stuff other than cutting tools. I use one for a DI to center stock in the fourjaw and another to hold a Dremel as a poor man's toolpost grinder. The more you use your QCTP, the more ideas you'll garner for uses that don't require steel holders.
 
Thank you Marv for this suggestion. I'll be on the lookout for a suitable chunk of Al.
 
Ian,

I never quote metal numbers unless absolutely essential, plus the US tend to have a different range of numbers to us lowly UK folks.

If I just want some steel to do a job, I stand it outside in the rain for a week, and if it goes rusty, that'll do me. If it doesn't go rust ridden in that time, I class it as stainless. ;D

There are no astronomical forces usually involved with holders, so just use the cheapest steel you can get hold of that is the right size.

For an 8mm (make it about 8.5 mm wide) slotted holder, if I was making them, they would be somewhere between 16 to 20mm high, with the slot at least 4mm from the bottom face, they would be plenty strong enough.

Also, take good notice of what Marv has said above.
Having other tooling mounted onto your toolpost can make your setting up and doing some jobs a lot easier. They can come from your own imagination, or tips picked up from here. Almost anything goes if it helps you to do something.


John

 
Another use for the Al holders is to hold a wiggler to aid in centering in the fourjaw. I prefer to use a pump center but some folks like wigglers.

Like Bogs, I can't imagine that the grade of steel for toolholders is a major concern. The loading at which toolholder strength becomes an issue is more than likely so far beyond the strength of your lathe that the whole matter is moot.
 
Thank you very much John and Marv. I confess to not knowing what a wiggler is - it sounds interesting. Do you have a pic?
I'm dying to get started on my QCTP but have to wait a) for the dovetailing cutter to arrive and b) the Rome heatwave to pass; it makes my little workshop on the roof unbearable! During the past month the atmosphere around here is three parts of steam to every part of air.
Ian
 
romartin said:
I'm surprised to learn that Marcello's tool holders are made in Al!

I'm surprised they lasted so long! (and still show no signs of wear)
Made them in alu because at the time it was the only material I had in suitable sizes: with the intent of leaving a little more beef into the less robust item, I inverted
the dovetails positions from the drawings I had made, cutting the males on the holders and the female on the qctp, which is steel. Never got around updating the drawings.
The only drawback I experienced was when overtightening the holding screws on the holders with the largest slots (first floor on the rack, left): that prevented them from
being inserted into the qctp (dovetails are close fitting) due to some flex into the holder. But there's no need to apply such torque.
Marcello


 
I can finally report an initial step towards building my QCTP.
BodyChunkRusty.jpg

BodyChunkSized.jpg

As shown in the two pics, I reduced the 44mm X 90mm dia rusty chunk to the required sixe of 38mm X 75mm dia. The process required the removal on over 40% of the raw material for a total of over 130ccs of C40 steel. For me this was a new experience. I soon realised that continuous cooling at the cutting point was essential and, with help from Paolo, a quick solution was found, ie copiously squirting cutting fluid from a hand held one litre squeeze bottle, having first placed a rectangular plastic vase tray under the lathe bed to collect the droppings.
This experience confirmed the importance of cooling and gave me some idea of the quantity of cutting fluid needed. However the cramp in my arm together with an uneasiness at not having both hands free to react quickly when necessary told me that I needed a cooling system which didn't need my arm as its motor.
And so I am now in the middle of building a simple cooling system... This reminds me of an mature machinist who taught me much as a young lad and once said to me that making a tool to help you make your product was fine in principle provided you didn't exagerate. But, he said, if you catch yourself making a tool to help you make a tool, then you're probably off the track... This conversation took place in his workshop in Eshowe, Zululand, while he watched his enormous lathe making the final cut on the new gunmetal lining for bore of the enormous big end of a sugar cane farmer's mill engine.
Be that as it may, I will report on my cooling system in a separate thread afer I have used it and found it to be satisfactory. Then I will return to my QCTP. And then I want to make a chuck back stop. And then I want to finish the steam engine I started last winter...
I think I need a holiday! In fact from tomorrow I will be in a small village in the north of Italy and, as plans stand, will be off-line until the end of August.
 
After my long holiday I am finally back in Rome and able to practice my favourite hobby! I have completed a first stab at a system for cooling/lubrificating ("Coolube") and have resumes work on converting that chunk of C40 steel into the Body of my Quick Change Toolpost.
The image below shows a 3d model of this Body just to remind us what the target is.
Base023DModel.jpg

The work plan is:
1. Machine the two outer flats making sure that they are mutually square. These flats will be the reference for positioning the other features.
2. Machine the dovetails.
3. Machine the bore.
4. Machine the two holes for the pistons.

The image below shows the advanced setup for preliminary "machining" of the two outer flats. The bucket on the floor is to collect the sweat. I have found that sawing goes better if I hum "I love to go awandering; Along the mountain track" etc.

Body03sawing.jpg


The next image shows the result of these wanderings along many such tracks.

Body04Finishedroughflats.jpg


The cuts leave roughly 1mm of steel to be removed by fly cutting to final size. I used the milling setup of my lathe, holding the chunk in the machine vice. This will be the first real test of Coolube. The image below shows the fly cutting under way with the Coolube fluid soothing the antagonists.

Body05Flycuttingflats.jpg


As illustrated in the next image, the positioning of the body so that the second flat will come square with respect to the first flat was done with the help of a 12mm ground steel rod held in the chuck. The first flat was held aligned against this rod while tightening the jaws of the machine vice.

Body06Settingflat2square.jpg


The final image of this post shows the Body with the finished outer faces.

Body07Finishedflats.jpg


That's it for now. Before proceeding to machine the dovetails, I will correct a couple of minor problems which showed up in Coolube.
 

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