Member postings for Paul Fallert

Andrew

I owe you so much for your knowledge, insight and opinions.

You will be missed.

Please come back after a sabbatical.

Thank you,

Paul

Here is an old technique for operating a mill, following the above suggestions and taming backlash for the X axis.

Starting with the RH (right handwheel), turn it CW (clockwise) and move the table sufficient distance to take up the backlash. Lock the table when you reach where you want your X-axis zero.. Set your handwheel index to zero. Now coming from the left side, move to the LH (left side) handwheel (x-axis table lock still tightened). Turn the LH handwheel CW until it takes up the backlash. Set the LH handwheel index to zero.

Unlock the table lock.

You can now get back to zero when moving from the right, so long as you move from the right with the right side handwheel. Same concept when approaching from the left using the LH handwheel. Just don't reset the index settings. This takes some unlearning or a locking screw on the index wheel (which explains one reason why some machines use a thumbscrew instead of just friction for the index)

You can check your settings with a DTI/or dial indicator or a fixed pointer, by measuring against a block on the table or vise. To verify, fix the precision block (1-2-3?) at your zero point. Move the table (with its clamped block) toward the DTI and zero the DTI at your index dial zero line. Repeat the move and see how close you get.

Since you have a precision block, you can check the other handwheel index coming from the opposite direction (plus/minus the width/thickness of the block). Some ops tape or quick clamp a vertical piece of precise thickness to the edge of the block to measure against from the opposite direction.

If you forget and change an index dial, you can go to the opposite wheel and go back to your original zero point.

A solution for keeping track of "turns" is to use a magnet-equipped ruler. Position the ruler under a fixed pointer when you are at your zero set point (established as above). To move 100mm, you can make your move and watch the pointer vs the ruler. When you get close to your goal, you use the readings on the index dial. Moves from the right, use the right wheel. Moves from the left use the left wheel.

GHT and others suggest all moves should measure from the same starting (zero point), to reduce accumulated errors. Takes some practice to change bad habits.

Old school tech used a movable ruler locked on the front/side of the table, with a fixed pointer pointing at the ruler. Using a magnet equipped ruler is an update of this concept AND the magnetic ruler can be used anywhere, X, Y or Z axis.

Improvements or clarifications welcomed.

Paul

Edited By Paul Fallert on 18/09/2020 15:54:08

I have the Picador clone, Sears Craftsman 9-6677, 6* tilt toward wheel.

The link to Graham Meek's fix for tilted pivot is #404, aka quarantined.

I have the 180* stop and adjustable base micrometer-style mod implemented.

Should the drill bit cutting faces be vertical (align with parting line of tray casting) or 11 to 5 ? I noticed that the tray parting vertical line is not 90* to the Horizon (or my own instinct of vertical), but the parting line of course is constant, no matter how you look at or move the face of the bit.

Should a V insert be used to raise the bit above the tray on larger bits, or just a shim to shift the bit toward or away from the pivot axis? Or washers added between the base and compass to shift the axis?

Locating the tip of the bit at 12 on the clock (wheel) seems to deal with getting the grind to 90* to face.

Thanks for any help in locating Graham Meeks fix or for answering my questions. This is one of the best forums.

I am encouraged by how close I'm getting with all of the Forum suggestions and links, except this #404. I have no access to EIM.

Paul

As someone who has actually cut foam slabs on several occasions, I recommend a purchase. In my case, if the result was not acceptable, then a purchase would be made. Nothing to lose and everyone agreed in advance.

If you have no carpenter hand working skills, this will be challenging. This process employs a full size hand saw. And you should make a practice cut to see how patient, accurate and persistent you can be.

Warning, Don't expect to measure the final surface against your surface plate. However it was better than i expected. I did use a coarse old (but sharp) saw. The old rule of thumb applies here, the softer the workpiece, the coarser the blade. Also, make long and slow strokes to keep on the lines. Best that the saw starts on a corner, so you can aim the saw against two of your perimeter lines. Another piece of advice, whether drawing a straight line or using a band or power saw, keep shifting your eye focus to the distant point where you want to end the cut.

Procedure: Draw a visible cut line around the perimeter with a good marker that will dry and not bleed later. Stand the slab against a solid surface, which could be a sheet of building board or wall. Double-face removable carpet tape will help to stabilize. You need to stand with the edge of the slab central to your body, so you can maneuver the saw to make full length strokes without impediment.

Let the saw do the cutting of its own weight, don't apply pressure down.

Paul

Edited By Paul Fallert on 31/07/2020 19:23:00

George H. Thomas uses some ink in his book discussing the benefits of higher, rather than lower RPM and he used HSS tools. When I tried it, I became a believer and I part-off from the tool-post (front). Mostly at 300 RPM and occasionally at 600 RPM. I do have a carbide insert blade, but I usually use HSS, unless the work is hardened. I also thought GHT's experiments with a tool with a V-groove top made sense, and once I found one, it became the one to use. A slight touchup on the front edge relief and it cuts with confidence. I think they call it a "P-type" blade.

However, I do use a QCTP and dedicate one holder to this one tool. It is important to pay attentionn to the height of the tip of the blade, especially as the diameter reduces. You can see it dip on gnarly/difficult steels. The tool either stops cutting or skipping or worse; begins to dig-in. Infrequent at higher RPM for the reasons already oulined previously.

Of course, I align the tool against the face of the chuck with a rectangular piece of steel trapped between the chuck face and the side of the tool to bring the axis of the tool (not necessarily the holder) perpendicular to the lathe axis). Otherwise, the tool will bind and break as the cut goes deeper. Keep the tool stickout as short as possible, even starting-out with a short stickout and stopping to extend it as the cut goes deeper.

Andy

I only had a (worn-out) lathe and some hand tools and bits. Stuff that any self-respecting model-engineer would have binned. So, I made a L-shaped mini-boring-threading-"bar" to internally thread that 3/8" dia thread. I did not know that you cannot easily do such a small internal thread, so I naively proceeded. Because there was only one Acme shaped tooth, my shaping was by a tiny triangle file and pocket stone. This boring/threading tool was silver steel. When the shape of the thread was wrong, I just ground a little more here and there and made another attempt . My point (no pun), is that filing and grinding this single point was very little time. The difficulty was patience. The advantages were the diameter of the bore was under top slide depth control, not re-grinding a tap. Starting over is quick, just re-heat and re-bend and quench-harden. You fit the tool to a visible section of the screw, not disassembled. To make a tap, you have to make a single-point tool AND then a tap. The angle of the thread is adjustable via the tool-post. Not so easy to adjust a tap. The depth of the bore is within the capability of a small-dia round-boring-threading-tool close to the edge of the top-slide. Very little tool extension/flex. [If I were to do this today, I would know to make a holder for the internal-threading-tool, just a 1/2" x 1/2" x 3" rectangular bar, with a hole in the end to closely fit the thread tool and a set screw to tighten and easily adjust the tool angle. Also, I now have a crank-handle on the back end of the spindle to hand-turn the spindle with absolute total control and no crashes. This is supposed to be relaxing, not a factory]. Harold Hall featured this tool-holder in several articles and his books.

Paul

Andy Carlson

You might try making an aluminium nut and hacksawing it in half longitudinally. Apply one half to the screw and you will see where the cutter needs any "minor" correction.

Being able to SEE how your thread fits the screw is a big help. I was surprised to see the mismatch on the first one. Yet, a quick test would have me believe that it was "good", but the contact area when cut open was very slight and would have become sloppy very quickly.

I made three before I did brass and the brass nut was a really good fit. Another dodge, assuming the screw is worth keeping, is to make a nut that best fits the worn area of the screw and use it to lap the less worn area of the screw. This avoids the loose/tight problem, but only if we are talking about slight wear of the screw. One "safer" lapping compound brand is Timesaver, which comes in grades and stops lapping after a certain point. Of course, use a very fine grade, frequent testing and meticulous removal of the lapping compound. When you have the threading process working, make a few extra brass nuts. It takes very little time passing before you forget how to set-up and cut a proper left hand Acme thread.

Paul

Diogenes II

Really nice improvements to the tool.

For simple lapping, could you skip doing the jig by using your new holder? The angles are already done. The top of the tool bit aligns with the top of the holder (nice touch) and it has a neutral rake. A suitable lapping surface and a little lapping compound (only under the tool bit face).

If you wanted to remove a measured amount by lapping, just use a shim under the upside-down holder body, loosen and extend the tool bit. Tighten. Remove shim. Lap until the lap stops cutting.

Note: Kitchen foil is around 1 thou thick as is fag paper. I have found various sheets about the house that are half that thickness.

ps: Saw an advertisement for "machinist wanted". Work with 200 foot planers and lathes. It said, "your CNC skills are useless here". Ouch!I

Steviegtr,

Have you tried removing the insert that is not in line and trying other inserts from your stock? Is it the insert or the pocket?

A brass or steel shim can be stoned down to whatever works. Alt, the pocket might need an irreversible stoning. Note: DaveM of YouTub MiniMachineShop.com had success with a shim, but he is willing to pursue any problem to a resolution, no matter time invested, patience required or difficulty.

Even name-brand inserts have been known to have "slumped/shifted" after baking!

Paul

Sam wrote "Well I met the engineer". RPM @ 188 aka = 1/3 plus fast feed. Cutter sharpened by hand!!! Same lump of steel.

Job done". Several posters here suggested steel might be hard-tough.

1) Does anyone else think Sam's lump of steel was hard-tough steel? I ran the FS-Wizard and consulted the Presto chart.

Both assume coolant and suggest reducing rpm by 1/2 if no coolant. That gets me to around 200 rpm. Sam's tool likely blunted-chipped by too much rpm on hard-tough steel, right-away.

2) Any suggestions on how to identify hard steel before blunting tools? How did Sam's new friend identify the steel?

3) Sam: Will you share your hard-won secret on how to sharpen endmills by hand?

Paul

JasonB:

This also makes it clear why it is important to reduce feed when entering and exiting a cut. Thank you for sharing.

Tim Stevens mentioned how the "Tangent Method" tends to maintain a positive force on the [gibs/table dovetails], thus reducing clearances/backlash. Someone called this a "chasing cut" and it works well when rough facing. This can be followed by parallel climb cuts for the finish if that is a cosmetic preference.

An open question (for me) is whether one can safely combine the "Tangent Method" with climb cutting. Is it risky to use a solid EndMill (EM), an insert EM or a FaceMill or does it depend on the material and/or axial depth of cut (ADOC)?

Andrew Johnston says he uses climb milling, mostly, but I have not been able to discern from his postings just when it is safe to do so. I've had my share of dodging HSS while experimenting.

Paul

"Tangent Method", "Tangential Milling Technique"

I have since discovered that Harold Hall in his WPS Complete Milling Book talked about this method, but did not call it by this name.

He describes in a project reducing the height of a workpiece by profile milling along the X axis, then turning the corner and moving along the Y axis, turning again and continuing the cut along the X axis, then Y back to the origin. Some have called this a "chasing pattern". It saves time. It keeps the clearance forces of the gibs and v-ways going in the same direction and under certain conditions can accommodate climb milling. Andrew Johnston has (in another posting about milling) talked about keeping the cut "tangential" to the work.

Michael-W

Thank you for that additional comment re: cast iron hard spots, hardel steel and other alloys. In my original request, the 40mm insert face mill was knawing/hammering on a pre-hard alloy AXA toolholder. It was the only carbide cutter available at school. Our instructor was old-school and preferred HSS (as did I), but HSS.cutter could not cut the alloy.

Does anyone know more about this Tangent method? It was not covered elsewhere. And seems to.be essential aspect of milling in certain instances.

Paul

Muzzer: Thank you for your response and questions.

I, too had trouble with Harvey's meaning of "tangent", until I made a simple 2D pencil drawing and played with an imaginary (transparent circle) endmill hovering over the drawingl. Harvey's main suggestion is to make the cut-length as long as possible to avoid hammering. This took a few trials on paper to understand when that would and would not occur and why Harvey described this arrangement of the cutter's path as "tangent" to the workpiece. I had to lookup the Wikipedia definition of tangent and relate that to the imaginary "tool-path". If it helps, ignore the "tangent" concept and focus on "maximum cut-length". I think tangent is tangential to the solution.

As is so often the case, the cut width and depth were limited by the drawing/project conditions. So using the full length of the flute to "load and dampen" the tool was not possible. Also not possible to use the full cutter width. The task was also not a slotting cut, I think it is called a profiling cut (along the edge).

Yes, as you suggested, a second tooth in the cut would balance the load and reduce cutter deflection (which makes the hammering sensations worse). In the imaginary case, it can be seen that two of the four teeth were in the cut when the cut length was at its maximum.

The available tool was a 40mm carbide insert 4-flute facemill and the workpiece 20mm width. Why? Because this event occurred in a Vocational-Tech classroom with tooling limitations. Many of us must carry on with less than optimal kit.

You asked: "Do you mean the cutter should be placed centrally." No. If you place a 40mm cutter centrally on a 20mm wide workpiece, I found that the cut-length will be quite short (and per Harvey, you will truly get a hammering effect as the insert is then positioned nearer to 90° for much of the shortened cut-length. Harold Hall also explains this in his WPS: Milling, a Complete Course via Sk.4.

James Harvey's suggestion was to try to use a cutter not much wider than the workpiece (not practical in this case).

Paul

My original posting titled "Facemill & MT2" raised several questions. Andrew Johnston suggested that my width of cut was rather narrow. The hammering persisted, but it was lessened by following suggestions in that thread.

Now solved. Recently reading John Harvey's book "M/C Shop Trade Secrets", Harvey pointed out that using too large of a cutter (40mm in my case) relative to a narrow workpiece can cause hammering. And, his solution works a treat. You must position the cutter over the work so it is tangent to the work. The goal is to make the longest possible chip. My way to visualize this was to make a full size sketch of the work and position a clear circle over the work, aiming for cutting the longest possible chip. The solution is that the cutter will be tangent to length of the workpiece.

Of course, everyone knows that, but I thought I should post it just in case someone else might find it helpful. I appreciate the many helpful posts on this site.

Thank you.

Paul

I prefer dry ways when cutting cast iron. Paper covered with tinfoil (Aluminium) works in some areas, but only if the saddle pushes it along the bed both to and from the headstock. Actually the dust will still go everywhere, such as between the saddle and the tailstock, leadscrew, top and crosslide. And op's nose and lungs, etc.

No oil. Oil plus iron powder equals a grinding paste.

If it is going to be a longish session of iron, then rub dry powdered graphite on the ways with a fresh cotton waste.

A vacuum nozzle located under the end of the lathe tool cutting edge will capture some of the iron chips. The next line of defense is a atrong magnet in a plastic bag, but sadly, I have found that strong magnets produce strongly magnetized iron chips, which then attach themselves to every metal surface and are even more difficult to remove.

Needless to say it, but I avoid iron when possible. Old-timers tell me they just wiped dry and replaced their equipment as needed. Not an option for most of us.

Paul

MT2 tightening the drawbar (short of heat shrinking the cutter into a dedicated holder)

How much to tighten a MT2 drawbar?

I found: "finger tight plus 1/4 turn"

Paul

Additional thank you's for more postings.

Jon:

My mill has a brake-band style spindle locking lever. I have older MT2 collets and a set of new imports. I don't recall which one slipped (other than it was 1/2" which I use frequently). The problem has only happened when side-milling with a high helix endmill when taking a deep cut in softer steel alloy (e.g. leaded) or aluminium. I have a bad reputation for overtightening everything, so maybe the problem is compensating too much, but more likely it is the Far Eastern manufacture, although others seem not to have that problem. I do have a torque wrench and this discussion is prompting me to use it. I wonder what the torque should be? I did have to make an extractor because the collets would not release (again duo to overtightening). At school all of the drawbars were ruined from overtightening the R8 collets and the day-school teacher gave one of them the task of making new drawbars, which did not last very long, either.

Paul

Edited By Paul Fallert on 06/05/2018 23:02:41

To JasonB:

At school we had six variable-speed Bridgeport mills with the larger tables. I use a Clausing 6"x24" Model 8520, pulley driven at 180-3,500 rpm with a 1/2hp motor. Ironically, this mill came from a school shop and had seen very little use and the only abuse was one shallow drilling mark on the table.

At Vo-Tech we were told to not use climb milling. Our training was in speeds and feeds, but not about where to position the milling cutter with respect to the workpiece. I am now seeing that speeds and feeds is but 20% of what you need to know and the other 80% was neither in the classes nor in most of the textbooks I have found, so far. On the web, I finding videos from major tool suppliers (CNC oriented, of course) and that's where I began to realize that there is so much more to "balancing" the cut, step over, overhang, when to use climb and when to use conventional milling. Most of the people I have talked to tell me, "just do it". But, I now see that there are some fundamental "do's and don't do's" that could be shared. A recent MEW "Milling for Beginners" article mentioned a 66% width of cut. Harold Hall mentioned something similar in his book on milling.

Thank you for pointing out Murray's videos.

Paul