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As the photos show I used a lathe and a milling machine. Some may have noticed the lathe is a heavy tool room lathe a (VDF) Heidenrich and Harbeck RO model about 30 years young with a 2 metre bed; totally unnecessary for this project. There would be no difficulty doing all the turning on a Myford size lathe or many smaller than that.
Some of the parts were milled and bored on a Shizuoka VHR milling machine. Also about 30 years old, apart from the table there is nothing that could not be done on a Mill drill or a milling attachment on a lathe as mentioned above.
The table itself nominally 12mm thick is easy enough It can be ordered cut to size from a metal merchant. The semi circular milled arc would not be easy on a lathe, not impossible but difficult. A mill drill and a rotary table would make the job quite simple.
When I set up the workshop the VDF begged me to rescue it from a dealers back store. It was unloved and so gummed up it hardly moved. Having spent its life as a hydraulic copy lathe, it had a very worn bed however the leadscrew (4tpi Imperial), cross slide, and top slide were almost as new. No doubt because they are not used with the Souter copy attachment in place The Headstock is all geared, so pretty inside…. just looking at the gears will cheer you up. The bed, 2 metres long, has now been reground (In situ) by me and stoned. I have not completed that but currently it is quite useable, the first metre is already near perfect within 2 tenths I still need to do a little more at the tailstock end. After the initial motorized grind done with an attachment I made; it was a matter of an hours measuring and an hours stoning The measuring being the most important part. (Using a ten second level a straight edge and piano wire) after the bed was prepared the saddle was set on epoxy bearing material To its original height as posted in another thread in this place. You can see a picture of the lathe as well.
As far as carbide is concerned I only used it for turning, and the boring bars I used are carbide. For fine dimension turning I still prefer HSS. My lathe has a max speed of 1250 rpm, a bit slow for carbide if you are turning small diameter work
You can grind epoxy aggregate after it has cured, however as shown I only did that to tidy up the edges. When working with this method you have to plan carefully. It will result in you achieving much, saving a lot of time.
All holes, threaded steel insert attachment points, cast in bearings, steel slide ways if needed, Oil passages, coolant drain pipes, Electrical conduits, Etc are pre positioned in the mould.
With a high quality mould you can position to .001” and get flatness to .001 over 300mm. There is little need for post cure machining for many projects.
Think for a little about the possibilities.
Edited By John McNamara on 13/07/2011 17:06:31
Edited By John McNamara on 13/07/2011 17:19:21
John,
Thanks for sharing your experience.
The MOGLICE site that you linked is also very useful.
MichaelG.
It’s been a while since I have been able to work on the Epoxy Worden grinder.
After a lot of experimentation with the motor I have decided to make this first version in the same way as the original, with the motor mounted in the center of the base in a fixed position.
As mentioned previously I would like to experiment with a motor and separate spindle that is adjustable. When I find the right motor (It needs to be small and powerful) I will make another grinding head.
The new metric motor I purchased turned out to have a tapped hole, (M4) about 16mm deep in the end of the 14mm shaft, the motor shaft also has a small step after the 30mm long by 14mm diameter shaft mounting section….Perfect, this was a lucky find. Surprising to me the motor had little axial play it appears there must be some preloading. Time will tell if this remains or some looseness develops. I guess that can be addressed if need be in the future.
I also had to hand a small grinding wheel adaptor for 1.25 inch bore grinding wheels; it has a tapered bore to enable it to be accurately centered on a tapered spindle. I believe it was originally designed to fit a Cincinnati number 2 tool and cutter grinder, Another find at a market. When I have the time I will make several more in a batch
I already have another spindle I made up that was used to grind the lathe bed that used this adaptor. By having each wheel in its own adaptor should mean that you do not have to re-dress the wheel when it is fitted.
After some effort I found this site where you can purchase ready made similar but not exactly the same wheel adaptors however they are not inexpensive, and will not be that hard to make up a batch of your own.
http://www.wmsopko.com/catalog.php3?pagelist=31-32-33-34-35-36-37-38-39-40-41-42-43-44-45-46-47-48-49-50-51
Then the shaft was drilled 12mm and bored out to 14mm. I used a snap gauge to measure the bore and a micrometer set to the motor shaft diameter (which was slightly undersize) to test the bore against the motor shaft, snap gauges are very useful allowing you to test the size of the inside of the bore along its length, Far more accurate than a caliper, a good result there…. a medium push fit on the motor. Once the bore was done the previously turned taper was skimmed lightly again to correct any possible errors introduced by the drilling and boring. Then the cone was parted off and placed in the wheel adaptor and tapped home with a soft hammer this allowed the adapter with the cone in position to be placed in the lathe chuck and gently faced off. The cone did not come loose while doing this.
An M4 high tensile bolt while quite adequate to retain the wheel adaptor has a fine thread, I am concerned that the thread will wear in the motor shaft with use I therefore chose to use the threaded portion cut from an m4 high tensile bolt as a stud and having screwed that into the motor shaft, locked it in place with a nut. If the stud wears with use it can be replaced the motor shaft thread has been protected. The wheel adaptor itself will be retained with another nut on the stud (Not shown in the photo).
This method has allowed the grinding wheel to be fitted very close to the motor with little overhang, tightening the mounting bolt will compress the adaptor harder onto the shaft. There was no need to split the adaptor with a light press fit.
When I tested it there was no visible wobble or movement of the grinding adaptor, the advantage of machining the inside and outside of the piece in one chuck setting, and little vibration, a very satisfactory result. In Hindsight a three phase motor would have been a little smoother. Single phase motors are never quite a good in that regard.
The next step will be the motor mounting pad then the table and graduated dials.
Hopefully I will have a little more time over the next week or two, It will be great to finish this project. And test the results.
Cheers
John
Edited By John McNamara on 28/07/2011 14:41:32
Edited By John McNamara on 28/07/2011 15:22:37
Mike If you can drop your ‘hooks’ on an old spin dryer motor. The ones with brushes all you need is the bearing head set (2 Tangential ball races or 2 cone rollers). Make the pulleys to suite the elastic belting used in some washing machines. A cheapo fan controller kit –the pulsed DC type-(to give you variable speed) and away you go. The spin drier motors run up to about 12,000 RPM higher with no load so watch it when you are testing them (I had one Russian motor burst its ‘commutator’ before it ran up to ‘windage’ the fan on it was slipping)
I will post some Pics later
Regards
Dick
I neglected to state the angle of the grinding wheel adaptor. As used by Cincinnati it is 4.5 inches per foot. As shown in the site link posted in my previous post.
The adaptor I have has an overall diameter of 50mm. If anyone wants a drawing. I will be pleased to email one. When the project is finished I will post a full set for the entire machine.
Cheers
John
I have observed that posting a Microsoft word document into the “Post a reply” edit box, the “paste from word” button, causes the right hand advertisement boxes on the forum to overlay the forum user text window.
This is clearly a bug in the webpage design. However until it is fixed if you use the clipboard to select text in word then paste it using the “Paste plain text” Button (NOT) the “paste from word” button the problem will not arise.
I use internet explorer and windows 7 there may be different results from other web tools.
Cheers
John
Edited By John McNamara on 30/07/2011 06:12:36
At last some time to do some interesting work on the Epoxy Worden Grinder.
The motor mounting base has been poured; tomorrow it will be ready to strike from the mould and after a tidy up if the sharp edges and any blemishes will be ready to use.
This is the most complex casting so far, as the illustrations show it has 4 steel bushes turned, and grooved (I used a parting tool) from 18mm black mild steel drilled and counterbored for M8 hex cap screws to attach it to the base. The motor mounting block is cast on top of the base in situ; the bushes were tightened securely to the base using the existing holes prior to casting. A perfect bearing has resulted.
Note the location of the mounting bushes is not ideal; I changed the design making the mounting block larger to allow the different to originally chosen motor mounting point.
However with 4 M8 high tensile bolts holding the motor mounting block it will be an extremely strong connection. I will relocate the bolts in the final plan for aesthetics. For others building this machine it is easy to relocate the inserts for motor mounting
I also provided for the motor to be shifted off centre left and right. In practice the left or right edge of the wheel is used. I suspect the best position is actually off centre not as in the original Worden design. The Epoxy worden also has a micro adjustable XY table for further adjustment.
The motor mounting cast in inserts made from 12mm mild steel rod turned, grooved and tapped M6 to match the motor base, can be seen mounted on a piece of scrap metal. Accurately located and drilled, this plate will be plunged into the mould after the Epoxy casting material is placed, I had not done this before and was concerned there may be a less than perfect cast around the inserts, I planed to strip the steel as soon as the epoxy was set “Green” so that a patch could be done while the epoxy was still green if need be. It did not prove necessary to patch but I will continue to do this in future casting as you cannot see under the plate. You could use Perspex but that is expensive unless you are making a number of parts.
In the centre of the motor base can be seen a steel part, this houses the pre loaded nuts for the y axis feed. Made from a piece of 1 inch by 1/8 inch seamless mild steel tube, from the scrap bin, inserted at the front end is an 80mm long steel insert threaded M12x1.5 (I had to extend the tap it was too short) this was made to a light press fit (I also pinned it just in case)
At the rear another 80mm insert threaded M12x1.5 this time a sliding fit and at one end. A small shoulder was turned to locate a press fitted a disk about 50mm diameter by 8mm thick up against it. The disk has 3x5mm holes for the M5 Cap screws that screw into the threaded inserts made from scrap to be cast in. This part can be seen in the photos it is wrapped in 4 layers of masking tape to provide clearance around the edge and to stop it from being stuck to the epoxy (This part has to move to allow adjustment of the preload), only the inserts are visible. I also had to relieve the 25mm tube slightly to clear the inserts.
Interestingly I had planned to simply cast in the inserts and the disk part would have sat proud of the motor base. I am still trying to clear my head of thinking as a metal designer. The recess would be a time waster machining it. Casting removes the constraint 5 minutes masking it and the job was done. The part will look better and it will keep dust out.
The front end of this part sits directly under the grinding wheel; it would not be good for the nicely greased preloaded clearance thread to be bathed in dust. The 20mm projection will allow the attachment of a sliding shroud to keep dust out.
By using 2 rather long 80mm nuts any cyclical errors in the roll formed threaded rod tend to be evened out. A smooth and extremely rigid action resulted. I am very pleased with the fit and will use this method again.
Moulding Hints:
As can be seen the mould itself is just 4 small pieces of melamine MDF scrap screwed together with bugle head drywall screws, I do not use glue, It is important to drill the screw mounting holes to clear the screw and the end grain attachment point slightly smaller than the screw, about 1.5mm less, if this is not done the end grain will split. The mould inside was coated with a little grease to stop the epoxy sticking. I used a sheet of “kitchen baking sheet” a kind of waxed Paper also greased to protect the base. I also wrapped the steel plate that holds the motor mount casting inserts in the same paper to stop it sticking.
For this batch I used the following Epoxy / Mineral casting mix.
Fine washed sand 70 percent, Megapoxy HICB 30 percent to make a total of 2.66 litres of mix. HICB is normally used in rock crushers to mount the hard facings; it is made from about 65% silica powder and the balance epoxy. Therefore the actual amount of epoxy used in this part is around 14% by volume the rest being sand and silica powder. The quantities worked out fairly well with less than a cup left over I used it to make a small sample. The cup I think it contained yogurt was made from polypropylene; epoxy does not stick to it. Note the high surface finish when it was turned out.
If I was using straight epoxy I would have used a similar amount around 14% of epoxy the balance 86% being sand and silica powder if available.
The material was mixed for about 15 minutes by hand; hard work as it is quite stiff and very necessary.
Continued next post……..
Edited By John McNamara on 07/08/2011 15:17:54
If was doing this again I would have a hole in the centre of the steel plate, to enable the last bit material to be rammed in and completely cover the top of the formwork (but leaving a 2mm gap between them), then only the centre hole area and the 2mm sprue around the edge would need to be cleaned up after the mould is stripped. As done in the example there will be a bit of wet grinding with a rough oilstone to level the top, it is times like this I wish I had a surface grinder. It looks like I have to remove about 1.5mm on average to remove the high spots. It is also planned to arris all edges with a disk grinder.
The epoxy material is fairly clean to work with; rubber gloves are a good idea as it is hard to get off your hands and some people may be allergic. If you do get it on your hands and to clean your tools turpentine and mentholated spirit (Mixed on a rag will clean it off quickly.) The mix works better than one solvent alone. (No safe to use or available chemical solvent will remove epoxy that has set)
Altogether a pleasant day’s work, I will not strip the rest of the formwork for the next 24 hours.
The next step is to make the bracket to join the Y axis feed to the carriage, and then finally the table slot and mounting points and the knobs and handle. I will post a photo of the motor in position in a day or two.
Cheers
John
Edited By John McNamara on 07/08/2011 15:46:00
A small sample made from left overs… Note the high surface finish the cup was polypropylene epoxy does not stick to it.
Edited By John McNamara on 07/08/2011 15:53:43
I learnt something today….You can machine sand/silica based epoxy castings with metal inserts!
As noted in the previous post there was a need to clean up the casting top, about 1.5mm needed to be trimmed of the top to level it (See the notes in the previous posts to avoid this happening).
My first plan was to stone the top using a rough silicon carbide stone I know this works, but it was going to be slow. I kept thinking there must be a better way; about that time I remembered an old cutter I got with a mill drill I purchased many years ago. A photo is attached. I was never very happy with this cutter as it tended to produce a rough finish on steel. Luckily I had a 3 Morse taper to 40 int taper adaptor so I could use it in my new 30 year old mill. As the picture shows it uses removable carbide tipped tool bars. Although a couple of the tips were chipped I though it would be no loss to give it a try.
I assumed a slow cutting speed would be best and set the spindle speed to 75rpm and the feed to 2.9 inches per minute (The mill is imperial not metric) I did try to increase the cutting speed but the result was a rougher finish. Also when the cutter hit the inserts you have to imagine what is actually happening, the cutting edge of the carbide is covered with grit and you are asking it to cut steel. The result was not very pretty. The motor mounting inserts as luck would have it were made from a scrap of rather “Gummy” Steel. And were smeared as well as cut, I had to drill and re-tap them. Surprisingly the larger inserts for the base mounting bolts cut far more cleanly.
I also wondered if the cutter would hold up or would need resharpening during the job, it held up OK. Yes it does need a resharpen but it did before I started…… And I know of a fantastic grinder to do it coming up. The picture attached is after the job was done.
After milling the top the formwork around the sides was removed. That was not as easy as the other castings because this time I rammed the epoxy very hard and in doing so must have partly removed the grease I had used as a release agent. Not the end of the world but 20 minutes wasted chiseling the formwork off. And I managed to chip an edge note the patch. After that a lick with a small angle grinder with a flat flap wheel did a good job of rounding the edges and tidying up the patch. I gave it a quick spray with etch primer. When the machine is finished I will disassemble and paint the machine properly.
As you can see the motor is now mounted in position, also the y axis feed screw is installed. The next step is the Y axis bracket and the table movements will be complete.
Cheers
John
Edited By John McNamara on 08/08/2011 15:38:51
Edited By John McNamara on 12/11/2011 07:25:51
Hi All
Its been a while since I started this thread……Gee time is on the wing.
Bit by bit I am gathering the tools and ideas to build a small CNC Mill.
I know I could use a Chinese high speed ER collet spindle; EBay is full of them, the trouble is they do not lend themselves to quick changing and setting the cutting tool.
As an alternative just maybe making a DIY spindle is doable. A fair amount of lathe and lapping. I do not have a cylindrical grinder. OK a workshop made spindle may be less accurate and durable than a commercial product but it will be affordable, and there is the pleasure of making it.
Anyway I am drawing one up. Before I do That a bit of research.
I am tending to think BT30 will be the best choice for the nose taper. I don't want a huge spindle and 30 taper tooling can be found at markets etc. It also reduces the bearing sizes (and prices)
Also smaller bearings generate less heat. I am hoping for 15000 RPM Water cooled if need be with grease lubrication preferably. A fixed R8 collet as used by TorMach (It stays in the machine) might be a contender however their system relies on a (Patented) stop ring on the tool holders. It also limits the size of cutter shank (with its holder). that can be inserted into the spindle. Hence my preference for BT30. I guess the modernists will want HSK, It also suffers from very little projection inside the holder into the spindle nose, it is also difficult to machine the required taper and face (it requires a perfect fit on both faces) and really requires a hardened and ground spindle nose… Too hard for me.
Has anyone found other high speed spindle documents that may be of interest in this area?
Regards
John
Some are slow to load all tested OK.
I found this paper on spindle design:
**LINK**
Also this brochure from NSK:
**LINK**
I used this Google search:
**LINK**
Edited By John McNamara on 21/10/2014 13:46:08
Edited By John McNamara on 21/10/2014 13:52:14
Hi John,
What about this: http://www.model-engineer.co.uk/news/article/lathe-bearings/19136 ?
Some very practical arrangements there that would also work with angular contact bearings.
Neil.
Hi Neil
Hi All
Thank you for the links, for slower speed designs easy to do.
Higher speeds 15000 RPM being my target is not so easily achieved using tapered roller bearings.in the larger sizes 80 to 100mm OD, a speed mostly beyond their specified capabilities. Interestingly thin parallel roller bearings with tapered bores that allow them to be set up with preload (that have no axial stiffness only radial stiffness) are being used in some of the high end NSK spindles as shown in the NSK documents to be found at my last link. not as the end support bearing but in pairs at the business end of the spindle in combination with angular contact bearings.
Interestingly my lathe has the same parallel roller bearing with a tapered bore for the front headstock bearing, In this case backed up by roller and thrust bearings. However the lathe has a top speed of 2500RPM although mine is slower being a long bed version for safety.
I really like the NSK designs. I was surprised to find them on the net having had an old paper version in my files;.very nicely detailed and dimensioned too, together with the speed rating for the particular design, This takes a lot of the guess work out of achieving a soundly based design. .
I know I will get serially stressed when I ask a bearing supplier the cost of the bearings themselves from NSK but maybe there are lower cost alternatives.
Making the spindle housing, The end caps spindle itself and bearing retaining nuts will be an interesting exercise in lathe work. Obviously that will be the easy part getting the bearing mounting surfaces up to the required accuracy will be another matter, I will have to hone my lapping skills (Pun intended). A larger lathe will be preferable although I have seen some amazing setups on bench lathes in my time. Anyone that can turn and bore and hone a set of cylinders for a steam engine should have little difficulty making one.
Finish grinding the tapered socket for the tool holder on first thought might appear difficult. It is not! I have done that procedure before by mounting the finished spindle set up with its bearings in place on a steel table and using a small precision slide set up at the correct angle with a small die grinder attached set up at the spindle centreline. I ground the taper in situ.
I used a small gear motor to rotate the spindle while passing the grinder in and out. I got the run out to around a tenth .0001". Very satisfying. Many commercial spindles are finished in the same way
Note the simple ball bearing type pull stud clamps used in the NSK designs a lot easier to make than the claw type often used. Hardened and tempered pull studs are available at modest cost… within the spindle housing there will need to be a hardened surface for the balls to bear against, this could be made easily, then hardened and Loctited in place. The ball carrier at the end of the draw bar will also have to be hardened and tempered
Yes it would be easy to order an Asian spindle on the net, but they are not quick change and have limited torque.
For a drive I plan to use a 2800 rpm AC motor driven via a VFD. in direct drive that gives a speed range of (depending on the motor and drive) maybe 500 to 4500 rpm in direct drive. However it will not be directly driven instead a two step (preferably) or three step pulley system. say 3.4 to one geared up and 3.4 to one geared downGiving a speed range of about 147 to 15300 RPM with reasonable torque throughout the speed range. the final ratios would need to be checked against the Motor drive selected. and the speed range of the machine required.
FADAL in the US used this drive setup on many of their machining centres with a rather ingenious and easily built air operated selection system.
The above are my investigations so far. I jhave never built a high speed spindle I have built one that worked at 4500 RPM Using NT40 taper tooling with a threaded drawbar…. That worked fine. High speed I know will be a lot harder. Anyway it will be a fun project. Time to hit the drawing board..
I would really appreciate hearing from anyone in here who has built one? Please post or PM.
Regards
John
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