New Proxxon lathe question #3

This seems a little more complicated. Everything that I read and the people that I talk to say that a quick-change toolpost is more of a
necessity than a luxury.
Choices seem to be:
Buy the Proxxon one
Buy the A2ZCNC 60% of AXA one
Build one, probably of the circular post plus split-bushing type
The Proxxon version costs about $115 with two holders, plus $21 from another holder. It replaces the existing toolpost, which is a rectangular chunk of aluminum with a dovetail slide on the bottom and a threaded hole in the side; it doubles as the top slide! It thus retains all of the flexibility and deficiencies of the current slow-change toolpost, but tools get changed quickly.
The primary deficiency seems to be that the tools are fixed at the same angle as the top slide. One cannot (for example) set the top slide to 29 degrees and then set the tool perpendicular to the work.
The A2ZCNC version costs about $100 with four holders. It completely replaces the top slide, mounting to the slot in the cross slide. Reports are that it is a quality product. It apparently allows you to set the tool at any angle to the work by loosening the mounting screw, rotating, and re-tightening. However, there is no top slide with this unit in place. That means no 29-degree threading (which apparently cannot be done with any other option either). It also means using the current slow-change toolpost for tapers. I don't know of any other function of the top slide, but I am a beginner so I am probably missing something.
Then there is the DIY option. The advantages are probably educational value and low monetary cost (but high time cost). It would probably consist of a circular post mounting to the slot in the cross slide, plus holders consisting of rectangular blocks with a hold up the middle with a slot and a clamping screw. The tools could be set at any angle, but again there is no top slide.
Any other good options?
Any advice?
Bob
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QC toolposts save you from fussing with shims under the bits. They are convenient but certainly not a necessity. I put up with a home-made lantern post like this for quite a while.
http://www.vannattabros.com/20063rd/post3.jpg
On a small lathe they can hold the bits directly and don't need thin shims to adjust the height.
http://www.autoartisans.com/Lathe/LANTP.JPG
jsw
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I would not buy a fancy tool holder right now. Obviously the Proxxon people think what comes with the lathe is adequate. And if you use that for a while you may see that it is good for the machining you do.
Lathes used the lantern type of tool holder for about a hundred years before the use of better tools, higher speeds and feeds required a more rigid way to hold tools.
Dan
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Thank you, maybe I should try the older ways for a while...
On Sun, 4 Mar 2012 05:05:16 -0800 (PST), snipped-for-privacy@krl.org wrote:

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The unusual design of the Proxxon PD 230 lathe leaves few options for any of the more commonly available QCTP quick change toolposts.
There is very little space available in the dsign for adapting a common QCTP, since having a dovetail to match the base of the top/compound slide is required, so it's not likely that it will be easy to design a QCTP which will utilize the rotational position feature common to most types of QCTPs. Also, the feed screw of the top slide is fitted in a way that maintaining a feed screw feature almost demands the supplied toolpost or the Proxxon QCTP.. however the Prox model still doesn't rotate except by unlocking and rotating the top slide.
I think you'll find that the supplied toolpost is adequate for most operations you'll end up wanting to do. The supplied TP appears to be capable of 2-way cutting tool mounting, at least, so that's a definite advantage. As with most lathe work (and many other tasks), planning out the sequence of required events/steps is what makes the most practical use of one's time. Generally, the ability to plan these "time saving" steps effectively, comes with experience.
On other lathes which can utilize commonly available and easy to install QCTPs, they are merely luxury conveniences. They have several good features which make tool changes convenient, but as someone mentioned, lathes with more primitive tool holders have been used successfully for generations without QCTPs. In addition to making many of the machines and weapons for 2 world wars, manual lathes and rigid or lantern toolposts were used to advance every type of technological progress which took place since the first lathe was produced.
As a beginning lathe user, it may be very useful to start with plastic stock to help you get accustomed to the various general aspects of cutting rotating material. Scraps of PVC pipe, empty pen bodies and various parts of items which will be discarded, should all be seen as potential parts now.. definitely good materials for practicing anyway.
A shallow chip tray/pan can be fabricated from any number of materials or unused products which you may have in a cupboard or closet, such as a baking pan for example. Many small lathes have features on the bottom to enable the owner to mount the base to a table or bench. Those features can be utilized to place block spacers between the base and a chip pan, where rubber feet/pads can be mounted to the bottom of the pan under the blocks to prevent sliding around during use.
When metal parts become a regular part of lathe use, you'll discover how easily chips attach themselves to clothing and shoes, which then transfer them to various other locations.. so try to set up a work table away from the busy traffic patterns within a household, and be aware of the parasitic characteristics and behaviors? of chips.
I'm not familiar with the design of the Prox lathe, but you may find it useful to have a hand crank for the spindle, if one can be attached on the left end of the spindle. Hand cranks are useful for certain operations, and I find them very handy for short threaded sections such as you may be contemplating for lens adapters. It's always the best practice to unplug a machine before installing something like a hand crank which is likely to cause machine damage or personal injury if the machine power is accidently turned on with an unbalanced spindle hand crank in place.
In addition to DoN's excellent recommendations made earlier, one lens type that I know of has inch-pitch threads, and those are C-mount video lenses, which are 1" 32 TPI.
A couple of other items needed for machine use would be some small brushes for cleaning away chips (compressed air can actually force chips into places on machines where thay may do harm), and an oiler with an oil suitable for your new machine. The manufacturer may recommend certain lubricating products for your machine, and indicate which parts need to be kept very clean, and lubricated.
Finally, I hope you get a great deal of enjoyment from your new machine.. I find metalworking projects to be very gratifying.
--
WB
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Thank you for the extensive post.
Comments interspersed:
On Sun, 4 Mar 2012 12:38:21 -0500, Wild_Bill wrote:

Yes, I am beginning to see the issues and I will try practicing patience.

Good idea; there is certainly lots of that sort of stuff around here.

Yes, the Proxxon has two notches for mounting bolts. I am now thinking about just screwing it to a thick wooden cutting board with rubber-shod feet. That ought to keep it from tipping or moving around.

Good point; I am looking at an out-of-the-way side of the basement...

Good idea!
There seem to be two possible ways to attach a hand crank to the spindle.
One would be to start with a taper that fits the spindle, extend a shaft from the narrow end of the taper out through the back of the spindle, and add a crank. The taper and shaft would need to be inserted before mounting the work and left in place; the crank could be added and removed.
The other possibility is to remove the spindle "gear" (actually a timing belt pulley) and mount a crank to the exposed outside of the spindle shaft.
Any advice?

The notorious example is Leica Thread Mount, which is 39mm x 26TPI! The Royal Microscopical Society thread standard for microscope objectives (known as the Royal Screw) is .8 inches by 36TPI Whitworth.
The Proxxon thread chart does not include either 26TPI or 36TPI pitch settings, which is unfortunate from my point of view. Those two threads could be useful to me.

I got some brushes.
The manual recommends where to oil, but not what oil to use. I assume that the duty is light enough that almost any lubricating oil (not penetrating oil or anything else silly) will work fine.

Thank you again!
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On Tue, 6 Mar 2012 13:11:26 -0500, Wild_Bill wrote:

That's a good idea. Sort of an inside collet, with a sleeve forced open by a wedge?
Bob
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I'm not sure that I could find a picture of the type of hand crank attachment I made, but I'll try to describe the methods used.
Turn a length of stock to within a couple of thousadths of the ID of the spindle (ID minus ~.002") and long enough to reach into the spindle maybe about half the depth. The stock should be long enough to have a shoulder just outside of the end of the spindle, and a suitable amount of remaining stock for the attachment of a handle/crank (flat bar stock or handwheel with a speed knob).
Drill a center axial hole into the stock that includes the full length.. which may require drilling from both ends (depending upon available length of twist drills).
The stock then needs to be cut at an angle (a little less than 45 degrees worked well), so that when a bolt/stud passing thru the hole draws the two pieces together, the angled cut causes the parts to shift off-axis, expanding in the spindle to securely lock it in place. The sharp edges around the angled cut of both pieces should be rounded over with a file so as to not cause digging or gouging inside the spindle bore.
The ends of the holes nearest the angled cut can be filed out-of-round or oval shaped to allow the shift to take place without too much tightening of the bolt/stud.
A stud can be threaded into the shorter end (deepest in the spindle) in tapped threads and staked to lock it in place, or pinned etc. and the stud extends outward to the left passing thru the longer section enough to allow a nut to be installed on it.
So, with the shoulder of the longer section against the left end of the spindle, there should be ample stock sticking out for attaching the preferred handle/crank. As the nut is tightened firmly but not extremely tight, the angled cut causes the two sections to wedge securely in the spindle bore.
I tried using a split expanding collet type of locking bar (quartered sections), but it didn't grip as well as the second model utilizing the wedge type bar.. which doesn't mean that it wouldn't be a good choice for others. I think the wedge type is actually easier to fabricate, though.
One caution about using an expanding bar in the spindle, would be to only tighten the nut enough for a secure grip in the spindle bore. Some lathe spindles can be somewhat wimpy as far as wall thickness, so over-tightening an expanding accessory with a grunt could potentially distort the spindle.
The scale of the Prox lathe being somewhat small, may present more of a challenge than the spindle bores of my machines, where I could use a 1/4" diameter (or larger) stud to draw the wedged sections together.
The 230 model specs show a 10.5mm spindle bore which is considerably smaller than the bores in my machines, so a different method of attachment may be a better choice.. it's difficult to try to determine what other methods may be suitable without knowing what features the spindle may have at the left end (smooth OD, threaded, locking collar etc).
The length of the crank is a matter of preference and comfort.. one wouldn't want to use an excessively long crank since that would require a wide range of arm movement just to advance the small point of a cutting tool with a light chip load for a short distance.
I prefer accessories to fit the scale of my machines, where operating performance is tempered by a light duty machine's capabilities. I don't try to run at excessive rates of metal removal, producing buckets of hot blue chips, but prefer instead.. just enjoying the experience at more moderate/less severe rates.
--
WB
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On Wed, 7 Mar 2012 00:06:21 -0500, Wild_Bill wrote:

I understand. Nice clear description.

It is interesting that the expanding collet didn't work as well. Torque-holding ability ought to be proportional to the outward force, which ought to be greater with the expanding collet because it probably has a much shallower angle than 45 degrees. Probably there is some secondary effect that I am not thinking of.

The left end has the "spindle gear" (actually a timing belt pulley) at the end, with essentially no free space beyond it. In normal turning the belt is on the outer end of the pulley. For screw cutting it sits a little further in, some one could think about clamping a handle to the pulley, but that is a little worrying, and besides there are two different pulleys for inch and metric threads.
It think that the inside bore is the only attractive scheme.
Bob
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I was faced with a similar situation when I wanted to adapt my benchtop drill press to operate by a hand crank for using the drill press for tapping holes.
I added a hub/puck of aluminum round stock to the top pulley edge (extending a flat, thick surface above the spindle pulley) and drilled it to accept 2 pins, which the arm for the crank would have, to facilitate easy installation and removal of the crank. On the DP I have, releasing the quill return spring is just a matter of removing a nut on the spring cover, so it's a fairly simple transition.. and man, I like simple (just my speed).
After cutting a hole in the belt cover over the hub, I'm able to (First) unplug the power cord, then release the drive belt, close the cover and drop the pins of the hand crank into the holes in the hub, for tapping use. The DP table vise can hold the workpiece in any position, so tapping any part is very easy to accomplish.. no leaning sideways to try to get a tap started at a weird angle or various other stunts which sometimes seem reasonable, heh.
Anyhoo.. a simple modification for utilizing a hand crank for your lathe will very likely occur to you.. and maybe when you're not even thinking of it. (and I hope it will happen at an appropriate moment, wink-wink, nudge-nudge).
The expanding collet type of spindle adapter may have worked if I'd have pursued improving it, but I had a shift in ideas when I recalled the type of joint used on my bike decades earlier, so I went that route.
Another great aspect of metalworking is that scrap from one project has many possibilities for another part of a new project.. there are no bad parts in as much as they are excellent learning opportunities.. win-win, as they say.
Are you feeling enthusiastic yet?
--
WB
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Sov n'a gun.. I found 2 pics of the 9x20 lathe spindle hand crank. http://www.flickr.com/photos/52345158@N03/sets/72157629540058769 /
The 9x20 spindle bore is about 3/4" for a judgement of scale of the size of the parts.
Talk about never throwing anything away.. well, the pics were transferred to this PC when it was the new replacement, back when I was still building a personal metalworking website (concept scrapped since then).
This handwheel model was a second version.. the first one used a length of flat aluminum bar stock for the crank arm instead of the cast aluminum handwheel (free upgrade, given to me by a friend, the ball bearing "speed knob" was added from junk box parts).
--
WB
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On Thu, 8 Mar 2012 10:26:52 -0500, Wild_Bill wrote:

It looks much as I pictured it from your description, other than the snazzy handwheel.
I suppose that it would work the same if both parts of the tube were drilled for clearance and a pair of locked nuts were jammed on the end of the threaded rod. It wouldn't look as nice when it was out of the machine though.
Or it would probably work much the same if the thread on the end piece was not locked, and you used a screw/bolt instead of a stud and a nut. The thread turning in the end piece would draw the stuff together.
I guess there are lots of way to do this. The only tricky part seems to be drilling a fairly small hole down two inches of rod, and I suppose that is straightforward on a lathe.
Bob
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Could you mount a handwheel behind the chuck? You can't spin it fast but a larger wheel will have more torque to drive a threading cut.
I just pull on the chuck (or the leather drive belt) to finish a threading cut at a definite stopping point.
Before you start, can you easily disconnect the spindle from the motor? There may not be much point in this if you can't and have to fight the drivetrain drag..
Some of us have old industrial lathes with somewhat different controls from yours:
http://www.practicalmachinist.com/vb/attachments/f25/29725d1293930509-south-bend-picture-gallery-dsc04198.jpg
The lever on the base declutches the motor drive from the spindle, making the chuck very easy to turn by hand.
The similar, smaller lever on the right side of the carriage apron releases the leadscrew so the handwheel to its left can move the carriage quickly, or hand-feed a cut.
The tailstock base slides sideways for turning tapers between centers.
The compound has a tee slot in the top to hold a separate tool post, which looks like it's aligned like yours on that lathe.
AFAIK yours doesn't have these and suggestions that mention them don't apply. I've used a Prazi which is like yours, but didn't cut threads on it because it had a broken plastic gear. .
jsw
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On Thu, 8 Mar 2012 18:14:10 -0500, Jim Wilkins wrote:

Well, I suppose that I could turn a disk with spindle and chuck mounting features fore and aft, and holes for the chuck screws, and get some longer screws and attach the chuck through the plate. The handwheel could only be about four inches in diameter to clear the bed, and only about half of the circumference would be reachable, and grabbing it would be awkward so close to the chuck, and it couldn't be installed and removed without re-mounting the chuck. Maybe I am not visualizing what you are thinking of; it sounds awkward.

I could slip off one of the drive belts.
But turning the motor by hand is not difficult on a machine this small.

On the Proxxon lathe the T-slot is on the cross-slide not the compound slide.

Bob
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On Tue, 6 Mar 2012 13:11:26 -0500, Wild_Bill wrote:

Good idea!
I went through the available combinations and found one that will give 36 TPI. There were also several other interesting combinations; 2/3 mm pitch and 4/3 mm pitch sound like they ought to be good for something...
No 26 TPI though.
So I started trying "what if" combinations. If I had a 26-tooth leadscrew gear I would have 26 TPI to the same accuracy as all the usual inch threads on this machine (.0463%). That would require gear cutting, and I have several things to learn before I try that.
I can also get close (well under 1%) to 26 TPI with a spindle "gear" of 17 or 19 or 22 "teeth". This "gear" is actually a timing belt pulley, which is probably more difficult to make than a gear would be.
I didn't explore a new intermediate gear, since that is a double-layer thing with a belt on one side and a gear on the other.
Bob
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It appears that you're well ahead of the curve, Bob, as far as new machine owners goes.. many just assume that what the chart shows reflects their only options.
Another possibliity exists to expand the available number of threading possibilities by adding just one more change gear to the set, as a number of machine users have done on machines which rely on a set of gears to change thread pitches. Proxxon probably has replacement parts available.
And, don't know if it's too early to mention this, but, you may be seeing other machine purchases in your (near) future.. so your ability to add new features to existing machines becomes almost endless.
Metalworking on any scale, is full of inspirational ideas and nearly infinite possibilities.. a very rewarding use of time, IMO.
--
WB
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On Thu, 8 Mar 2012 02:16:30 -0500, Wild_Bill wrote:

I went looking for a 26-tooth metric module 1 gear with a bore 5.5mm or smaller, and I found Google surprisingly unhelpful. I suppose that I need a better search term.
The only one that I found was http://www.rc-monster.com/proddetail.php?prod=5mmmod1pinion&cat @ I have no idea where they are or what they are like.
It has a 5mm bore but that could be bored out.
Proxxon has lots of optional extras, but apparently not more gears.
Bob
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On Thu, 08 Mar 2012 17:17:01 -0500, Bob S wrote:

A slightly alternative approach is to get two gears which DO give you the ratio you want and mount them outboard of existing change gears of smaller diameter (turn a two-size mandrel, mount, drill & tap three holes, then bore the new gears large enough to take the axle-fixing screws). You may have to do some playing about to find a combination that fits your existing gears and carrier travel.
It beats looking for that ratio in your particular pitch. For Minilathes in particular, Sherline makes an affordable 127/100 combination.
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It's not a good sign when a manufacturer doesn't provide replacement parts. I wouldn't take one person's opinion as the final word, though.
Then again, it may take some creativity to get someone to go against that scary, threatening, carved-in-stone company policy, and make an exception.
Something like a letter to the company CEO, spelling out in graphic detail how your neighbor's dog ate the grear and you've been looking thru steaming hot piles of stool trying to reclaim the gear, to no avail.. but then again, s/he might be a cat lover and feel no sympathy at all.
The RC/model industry is fairly vast in terms of accessories and "upgrade" parts, making a wide variety of small mechanical parts much more commonly available.
Trouble is, generally, RC and various parts suppliers do such a poor job at listing actual parts specs, finding something can result in a fairly complicated research project.
--
WB
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On Sat, 03 Mar 2012 21:26:32 -0500, Bob S

Shop around for the best price on the AXA toolpost. The quick change toolpost is a big time saver, meaning more time spent making chips. It's also easier to use which means less aggravation, which saves time, time you can spend making chips. When you do get the AXA size toolpost, make sure to get the wedge type instead of the piston type. The wedge type repeats better. At least in my experience they do. I make my living as a machinist. Have been doing so for the last 35 years or so. My opinion is that if you can afford it buy the tools which will enable you to cut metal the fastest. After you have some experience you can decide if making your own toolpost for special work is something you want to do. In the meantime you can learn about turning, facing, boring, threading, and parting off while you make your lens parts. You will be using, most likely, a turning/facing tool, a boring bar, internal threading tool, external threading tool, and a part off blade. That's 5 tools used to make one part. Get those tools set and then it is much easier and faster to make your lens parts. And since the tools are each in a separate, quickly changed tool holder, you only need to set each tool once. Eric
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