gtwr Technical Bulletin

(German Version)

Category: Uncategorized

  • Machine shop re-organization

    It was time to re-arrange my machine shop a bit – I have two separate rooms, the smaller one contains my manual milling machine and the lathe, the bigger one has the surface grinder, CNC mill and all the support equipment like bandsaw, hardness tester, measuring microscope and drill press.

    Storage room in the shop is always a problem and very sacred – I had a drawer cabinet that I got from my old day job in very rough condition in the basement.

    It is an original Deckel accessories cabinet, they were supplied with different drawer layouts and inserts depending on the machine they were matched to and what accessories the customer wanted to use.

    I decided to refurbish the cabinet and move it into the shop, giving me a lot of additional drawer space. It has a larger footprint than the cabinet currently in that spot, but by moving the lathe I was sure to be able to make it work.

    Since I didn’t want to make it into a science fair project, I voted against striping/sandblasting them completely. Instead, I sanded the entire cabinet and the drawers with a random orbit sander and removed the rather heavy rust in the drawers also by sanding/scraping/wire brushing.

    The lightly sanded original paint was a sound underground for the following paint job.

    Everything was prepared by wiping down with acetone, followed by a heavy coat of self-etch primer.

    All paint layers were applied with a brush for the internal edges and a foam roller for the flat surfaces.

    For the final paint the decision was easy – RAL6011 Reseda green, matching the color of my milling machine – And overall being a very pleasant color.

    There was more to the cabinet than a bit of paint – All the ball bearings where worn out, rusty and moved very rough, I could not leave them like that.

    The original bearings are an odd solution – They took the outer race of a 608 bearing, but with a custom inner ring that has a 6mm bore (compared to 8mm on a regular 608 bearing), a large countersink for the screw head and the backside of the inner race is proud 0,5mm to prevent the outer race from rubbing against the drawer/cabinet.

    I would have been able to source very similar bearings on Aliexpress but opted to use off the shelf bearings with a little modification.

    A bit of investigation showed me that the countersunk screw is not necessary, the head of a standard M6 DIN912 socket head cap screw has enough room between the drawers and cabinet to not create any problems.

    All that was left was to machine bushings with a 6mm bore and a step on the back to space a regular bearing off.

    The bushings where machined from 1.4305, a free machining stainless – Not necessary for this application, but that was the stock that I had at hand in that diameter. They are a mild press fit in a stock 608 bearing.

    The new bearings screwed against the drawer and cabinet.

    One gripe I have with drawer cabinets: They are hard to move around. You have no way of grabbing them with a pallet jack, usually you are stuck with sliding them across the floor or raising them with a prybar to get it up on blocks before getting a pallet jack under them.

    Certain cabinet makers like Lista sell frames to raise the cabinets and get a pallet jack under them – But not for this very old Deckel branded cabinet, so I had to fabricate something myself.

    Since I am not really set up for fabrication work with things like a large weld/fixture table and a cold saw to cut square tubing to final size without additional prep, I must improvise a bit.

    I cut square tubing with the bandsaw and mill the ends on the FP1 using the horizontal spindle. For me it helps if the joints are already very tight and square before welding. A real fabricator will probably turn up his nose, but I am a machinist, not a fabricator 🙂

    Welding the frame and adding the holes for adjustable feet.

    Prime and paint:

    Meanwhile I cut an old bamboo tabletop to size to go on top of the cabinet. And cut into a stainless-steel threaded insert that I had forgotten to remove. That’s a sawblade that will require sharpening.

    The cabinet with the frame under it and the bamboo tabletop on top of it. I am very happy how it came out.

    Time to rearrange the lathe to gain some useable space. The Weiler Primus is super easy to move with a pallet jack – All that’s required are two pieces of lumber with 100x100mm cross section, since the jack does not go up far enough.

    You can also see a tool cart to the right of the lathe, with my surface plate and the heigh gage on top of it. This was another point of unhappiness that I wanted to solve.

    The cart is branded Metra and overall, very nice for the money, but with the wheels a bit to wobbly to create a reliable platform for measuring.

    My solution was to fabricate a frame with adjustable feet that bolts to the underside of the cart instead of the wheels. I tried to match the color of the cart to the frame (I used RAL5001, which is very close to the color of the cart.)

    With an additional wooden tabletop, the surface plate now rests very nicely on the cart gone cabinet.

    The surface plate has three ball supports glued to its underside. I drilled 35mm holes into the wooden top in the correct spots, added a thick washer and a smaller ball socket washer (from a mill clamping stud kit) on top of it.

    The feet of the surface plate rest on the smaller washer and can move a small amount on top of the larger washer, to allow for any misalignment and thermal expansion/contraction, without influencing the flatness of the surface plate.

    The rearranged shop – The “new” drawer cabinet next to the milling machine will contain all the smaller accessories like vises, toolholders, collets and setup tooling.

    With the lathe in front of the window I gained a bit of space to the left for a small drawer cabinet – Its on wheels so I can access the left side of the lathe, where the coolant tank/pump is located.

    The modified cart for the surface plate nests very nice on the right side of the lathe – Its not ideal from a cleanliness perspective, but a small shop has always problems in that regard.

    The “dead” corner is a good spot for my oxy-fuel rig.

    A re-arranging project like this is very destructive to a shop, but I feel it was worth it, it looks cleaner and more streamlined, yet I gained some storage space.

  • Spin fixtures, Punch grinders, Toolroom spindles

    One thing that I noticed when learning about toolroom practices around the world – Europe tends to run separate ID/OD grinders for even very small and simple operations, while in the USA the surface grinder gets utilized as a universal platform for all sorts of grinding operations, including a fair share of round work.

    For grinding round parts, you need a spindle to spin the work – The most well-known one is probably the Harig Grind-All. Also known as “Punch grinder”, “Punch former”, “Whirly Jig” or “Spin fixture”

    Assfalg400 Punch former with a sliding v-block

    Newbould indexer with a sliding v-block and a 5C collet taper, when the v-block is removed.
    (Picture by Adam Demuth)

    These are fairly accurate devices that can be used for grinding round work, perform direct indexing, indexing via a vernier scale or indexing/segment indexing via adjustable stops.

    Be aware, they are expensive tools, and they should be handled with care.

    The earliest version of what we know today as a spin fixture can be found in a patent from 1946 – Still very crude:

    https://patents.google.com/patent/US2449459A

    A later patent, granted in 1960 shows already something that’s looking like the spin fixtures we can buy today – It also shows the bearing arrangement with the single row of balls running between beveled races, forming a four-point contact bearing.

    https://www.datamp.org/patents/displayPatent.php?id=63980

    https://patents.google.com/patent/US3094821

    The basic Layout is always the same:

    • A housing with a foot, usually meant to go onto a magnetic chuck.
    • A short spindle, running in some means of ball bearings. Most designs use a single row of balls running on integral ball races.
    • Work holding: Semi-Standard is a sliding V-Block to hold workpieces and adjust them to run true.
      Options are 3 Jaw Chucks, ER Collets Chucks, integral Collet Tapers, Magnetic Chucks or integral zero-point systems like 3R or Erowa.
      Systems with an integrated ER Collet chucks or 3 jaw chuck are in my opinion a very bad choice for general use,
    • Most have rotational stops that can be adjusted and integral 24 Position direct indexing with a shot pin.
      Additional systems like the Newbould indexer exist, that allow for very accurate angle setting via differential face gears.
      Adam demonstrates the face gear indexing in this Video:

      Differential gear tooth indexing
      https://youtu.be/3oE2axs0I5o?si=Pyjh15RAdjISfdT1

    There is a modification to the sliding V-Block version, that allows a sliding motion in two axis – the second axis sliding motion is done via a rack/pinion drive from the backside of the spindle. This arrangement blocks the trough bore of the spindle, which makes it in my opinion less desirable for general work.

    Some manufacturers/sellers call them one-way / two way punch formers.

    This second axis of motion allows to dress wheels at an angle with a diamond held in the V-Block or to create polygon shapes with corner radii offset in two axes.

    Applications

    • Grinding round/prismatic Workpieces
    • Toolgrinding
    • General indexing/rotary work
    • Other

    Examples of operation:

    Tool grinding, ID threading tool:

    Grinding a 55° threading tool out of a 8mm solid carbide blank.

    All operations are performed using the spin fixture on the surface grinder. The neck of the tool is ground by putting the blank out of center, which is very easy to be done with the sliding v-block.

    In general, the surface grinder with a magnetic chuck is a very powerful tool to grind tools, very often faster to setup than a real T&C grinder.

    Grinding the excentric neck and splitting the cutting portion in half. The punch grinder is spaced off the fence with a parallel.

    This is a recurring theme in using them – They are very universal, but with that universality comes some pain in getting them into a spot that allows you to access the part, not run out of machine travel and not to collide with anything.

    Since the spin fixture can be taken off the magnet and go back on very repeatable against the fence, it is easy to take it off, use whatever measuring instrument – like a toolmakers microscope – for inspection and go back to the grinder for adjustments.

    Angles can be set very easily with angle blocks against the fence.


    Tool grinding, boring bar

    This is an example where a boring bar has been ground from a 8mm solid carbide rod to fit a certain application.

    The angle adjustable transfer block is a great addition to the punch grinder, it allows very quick angular settings with having to set a sine plate.

    Grinding a custom plug gage / gage pin

    Sometimes a custom gage pin is required – Cylindrical grinding out of hardened stock is a very viable option.

    Here an old 16mm HSS Endmill is cut down and ground to a diameter of 12.6mm. Note that the V-Block has been removed and a ER25 chuck has been installed instead for clearance reasons (The clamp of the V-Block was interfering with the wheel nut.)


    Indexing on the milling machine angular cross holes

    For light duty applications, the punch grinder can be used on milling machines as a workholding and indexing tool.

    In this case, the punch grinder is held in a vise at an angle, to drill angled holes into a small component.

    A tooling ball, superglued to the end of the workpiece is used to locate the work.

    The workpiece was too short to be held directly in the V-block of the punch grinder, instead a ER11 collet chuck with straight shank is held in the V-block and used to clamp the part.

    Adam Demuth provided me with a wealth of pictures for uncommon setups using different spin fixtures – Thank you Adam!

    Adam on Youtube: https://www.youtube.com/@adamthemachinist

    ID Grinding

    ID grinding a large, hardened ring using a CBN Cup wheel. The work is mounted to a Newbould indexer.
    Adam mentioned that the Newbould indexers have a stiffer bearing arrangement than others, which is very helpful in situations with heavy/larger workpieces or large overhangs.

    Grinding edge radii on small workpieces

    Speaking of large overhangs, this is an interesting fixture to put radii on the edges of workpieces.

    Adam mentioned some problems with this setup: The spindle axis of the spin fixtures is not that perfectly aligned with the base of the fixture as we would like, and the large overhang is on the edge of practicability for this Harig Grind All Nr. 1.

    This fixture is mounted on the spin fixture instead of the stock V-Block – Two axis of movement are required to get the corner of the workpiece into the right position.

    The first one is sliding the entire fixture in the ground slot of the spin fixture (Red)

    The second axis is built into the fixture, by sliding the small block, that’s inset to the fixture, side to side. (Green)

    This block has also threaded holes for work holding and work stops.

    Using a spin fixture as a bender

    Here the spin fixture is utilized in a very uncommon scenario – As a bending fixture for prototype work.

    A bending blade is held in the V-block and a workpiece rest/clamp is mounted on a base plate.

    This goes to show the spin fixture has uses outside of grinders/mills/jig grinders too.

    ID work on a Jig Grinder

    This is an interesting setup – Not with a punch grinder, but a 5C spin fixture, also made by Harig. The principles stay the same, would also work with a punch grinder.

    The spin fixture is mounted against a large rotary table to swing it at an angle. This arrangement can be used for tapered ID grinding, grind radii or to, grind radius pockets.

    There is a hand full of manufacturers making and selling Spin fixtures:

    Harig

    https://harigmfg.net

     Herman Schmidt

    https://www.hschmidt.com/areas/spin-indexing

    Imperial Newbould

    https://www.imperialnewbould.com

    Gin Tech

    https://www.gin-chan.com/en-US/pfilter1_1_2-punch-formers

    Pfeil Magnettechnik

    https://pfeil-magnetspanntechnik.de/Stempel-Schleifgeraet-Delphi1

    More exist, but thats the common and to me known ones.

    Conclusion

    All in all, a punch grinder of any form is a great addition to a machine shop – A surface grinder along with one of these devices can solve a lot of problems, replace in a lot of cases a tool and cutter grinder, its useful for metrology purposes or for delicate work on milling machines.

  • Machinetools in movies – The Man with the Golden Gun

    Something different this time – A scene from a movie classic: The Man with the Golden Gun from 1974

    This scene does not look like a movie set, but as if it was filmed in a real shop rented for filming.

    Right on entry, we can see a Boley lathe:

    When Roger Moores character is aiming down range, we can see a what appears to be a Deckel FP1 on the left and an Oxy-Fuel setup along with a forge in the middle of the frame.

    The second picture gives a better view on the FP1 – It could also be an Alexander “Master Toolmaker” (https://www.lathes.co.uk/alexander/) since large parts of the movie where filmed in the UK and Alexander being a British Company making a copy of the Deckel FP1.

    While getting some information from Lazar, the gunsmith played by Marne Maitland, we can also see an Excel No.2 die filer.

    The entire scene can be reviewed on Youtube:

    THE MAN WITH THE GOLDEN GUN – “I’m now aiming precisely at your groin…”

    https://youtu.be/rzlDjnUWq1Q?si=rtdwpsIxdHgzZ6yK

  • Pyramid spotting drill

    Spotting and centering small drills is not a trivial task. Normal NC spotting drills have a wide web and tend to create a spot with a flat bottom that’s unsuitable to guide small drills.

    There are specialized one or two flute carbide spotting drills for small diameter work, but they tend to be rather expensive and extremely delicate.

    One alternative that I was made aware of is the pyramid spotting drill – This shape is referenced in literature a few times, not only as a spotting drill, but also as a micro engraving tool for hard materials.

    Trying to visualize the problem with the chisel tip/web of standard spotting drills – They leave quite a large flat spot, that might already be too big to guide small drills.

    How big is that flat spot left by the web? I am glad you asked.

    On a good quality 6mm 90° spotting drill I measured a web width of 0,75mm:

    A similar 3mm 90° spotting drill still had a 0,52mm wide web:

    The two spotting drills measured:

    You can clearly see the wide web of the drill in the second picture.

    As mentioned, there are spotting drills with thinned webs or single flute versions that have almost no web but are extremely vulnerable to damage and wear, so I try to avoid them.

    The pyramid spotting drill is available as a commercial tool by Mitsubishi, in a nice, coated version.

    https://www.mitsubishicarbide.net/mhg/de/drilling/10000516/20077520

    It also comes with a technical datasheet that points out the advantages of this shape and recommendations for speeds and feeds.

    For commercial use, I would absolutely recommend purchasing these drills and not bother grinding them in-house.

    But, as hobbyists or operating a small shop, it can be an option to grind them out of carbide stock – The shape is very simple and forgiving. All that’s needed for grinding is a way of indexing the blank in 120° increments and some sort of grinder.

    A D-Bit grinder, surface grinder with spin fixture, a milling machine with a dividing head or a real tool and cutter grinder will all do a similar nice job.

    The angle the facets need to be ground can be determined in CAD – This example shows a setup for a 90° spotting angle – The Angle off the facets must be 63.4°

    The following example has been ground on a Deckel S1 T&C grinder out of 3mm carbide stock aka the shanks of good quality endmills.

    This very simple tool creates amazing, clean and round spot drills. The three cutting edges have a very negative cutting angle and are very robust, no matter what common material is machined.

    Interestingly it works very badly when used dry, without any cutting fluid.

    What I found works best is a small amount of cutting oil for steel/stainless steel/hardened steels and red metals like copper.

    Used with oil it has a very nice and soft cutting action, creating fine, needle like chips:

    When cutting aluminum, alcohol can be used as a cutting fluid, with the advantage of flashing off and leaving clean, dry workpieces.

    Examples of Cutting:

    Spotting in aluminium AW5083 – The engraved numbers next to the spot drills represent the diameter of the spot:

    Magnified view:

    0,4 / 0,2 / 0,1mm spotting diameter, left to right.

    Since the drill is ground to a very small tip (As small as the grinding wheel and the grain size of the carbide allows)

    Spotting in hardened steel, an Old Carl Zeiss gage block:

    Even in hardened steel, the pyramid drill leaves a very good center with minimal burr – Its amazing how well the unconventional geometry of the tool cuts almost all common materials.

    Spott drilled stainless steel workpiece:

    Conclusion?

    This type of tool does not seem to be very well known, but it is sure worth giving it a try, if you have the capability of grinding them yourself.

    Danny Rudolph mentioned these a few times in posts on Instagram, if you go back far enough in his posts.

    https://www.instagram.com/dannyrudolph

    Thank you, Danny, for making me aware of this tool.

    One thing you, the reader, might ask: A 90° spot drill is problematic for carbide drills, since the tip angles don’t match up, right?

    That’s at least the common conception, but with micro drilling it seems to be less of a problem. Getting a center/spot that’s small enough for a micro drill is already hard enough and on such a small scale there’s more effects at play – The drill might vibrate for a very short period when touching the spot before calming down and actual cutting. This can be observed with a video microscope very well.

    The issue is, with a larger tip angle, this style of tool starts to cut less well, since the included angle between the clearance and the top rake surface get bigger and bigger therefore more and more negative, requiring bigger force to make the tool cut well.

    90° Spotting angle:  78.5° included angle

    118° Spotting angle: 96.5°included angle

    If you want to give a 118° version a try, here is the angle to be ground onto the pyramid:

    Despite that, give them a try, I think you will not be disappointed – It has become one of my absolute favorite tools – Simple and very reliable.

  • Toolpost grinders – What are they good for?

    There will be a moment in time in almost every lathe owners’ career when the desire for a tool post grinder starts to grow.

    I have a strong opinion on tool post grinders, and it’s not a good one.

    The idea:

    •  Creating higher precision parts, possibly out of hardened materials

    The reality:

    • Grinding is not an inherent more precise process
    • Grinding adds another layer of complexity
    • Lathes are not designed to be a very good ID/OD grinder
    • Tool post grinders are often quite crude devices. Very heavy and cumbersome to setup, often with belt drives that tend to add vibrations, motors sitting on top of a large stack up that add vibrations to the entire system

    There are exceptions of course – Some materials just can not be cut with carbide/diamond or CBN inserts in a cost-effective manner. Ceramics and Carbide can be such a exception, also they have some utility when working with hard chrome plated items like  hydraulic rods.

    ID work in hardened steels or ceramic/carbides can be a case where grinding on the lathe is a viable solution, if no other machine is available.

    But even then, it’s a good idea to keep the actual grinding done on the lathe to a minimum – I had to make some carbide bushings, to keep grinding to a minimum, I had the ID bore wire EDM cut to almost finished size, the OD of the stock was chosen to be the final dimension, and the length was ground on the surface grinder.

    The actual grinding on the lathe was performed with a high-speed air driven spindle, held in a boring bar holder. This setup has some advantages over a classic tool post grinder, since it’s easy to setup.

    Most standard belt driven tool post grinders are too big to mount into a quick change tool post, they require to be bolted to the compound directly.

  • Tools for locating features on milling machines

    Centering and locating features on either a CNC or manual milling machine is a very important step. The industry provides us with a wonderful selection of tools for this purpose, edge finders, mechanical 3d probes all the way up to electronic probes that talk to the CNC controller.

    There are tools and techniques beyond of the here shown, like centering microscopes that let you pick features visually, the very oldschool wiggler or even a simple dowel pin in a collet.

    But the ones here shown are the more common that I have to say something about.

    Edge Finder

    The simple edge finder is a tool that I like very much – It is very affordable and reliable yet delivering a high degree of precision when picking up workpiece edges.

    The design of the tool does not necessitate perfect runout, the work just as well, when you put them into a drill chuck.

    Mechanical 3d Probe

    The least favorite Solution for me is the mechanical 3d probe – They have a surprising high actuation force that is not equal in all directions, they are highly depending on their runout being set correct, they need a dedicated toolholder (That’s more a nuisance on a manual mill than on a cnc) and are overall not very confidence instilling to me.

    These types of probes also require a fair amount of clearance between the spindle and the work.

    Dial test indicator

    My favorite solution is a dial test indicator that is in some way mounted to the spindle of the machine and has some adjustability built into it.

    This can either be a flexible arm – like what is used on a magnetic indicator stand – Held in the spindle or clamped to the spindle/toolholder.

    This is an example of a flex arm mount that is clamped to the ER25 collet nut of a high-speed spindle.

    Holding them in a drill/collet chuck is also an option:

    These holders give a great range of freedom, but that’s also a drawback, since its quite time consuming to align the probe tip in a meaningful way.

    Personally, I prefer a holder that has less freedom of motion, like the very popular halfmoon shaped holders that can also be held in a toolholder or clamped to the spindle/toolholder with an additional clamp.

    These can either be purchased commercially or make for a neat little shop project. The one shown here was built in-house, a set of drawings for the half-moon holder is available in the files section.

    Held on a milling machine spindle vs. held directly in a collet:

    For certain types of machines, like CNC routers height clearance is a real concern – None of the commercial options are very satisfying in that regard. That’s why I came up with the following design that’s extremely low profile and has the necessary adjustability to line the stylus up with the center of rotation built into it.

    The set of drawings for this holder can be found in the Files section of this blog.

  • Back to blogging?

    Hi! Stefan here – You might know me as a that long haired dude on Youtube creating videos related to machining.
    With this blog I will try to create a spot on the internet that is not created by AI, Language models or other artificial means.