Machining Setup's with Few Comments

Topics include, Machine Tools & Tooling, Precision Measuring, Materials and their Properties, Electrical discussions related to machine tools, setups, fixtures and jigs and other general discussion related to amateur machining.

Moderators: Harold_V, websterz, GlennW

User avatar
Carrdo
Posts: 1234
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo » Wed Dec 09, 2020 12:17 am

One additional photo.

Getting there but not quite done yet.
Attachments
139 An Attempt to get a Better Photo.jpg

User avatar
Carrdo
Posts: 1234
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo » Wed Dec 09, 2020 5:14 pm

Towards completion.

The grinding as close as it was to centre of the end mill still left a small "pip" of raised material right at the centre point on the end mill.This raised material had to be removed in order for the end mill to cut.

Some thinking out of the box was required to remove this last bit of raised material. After trying several things which didn't work so well, the setup shown in the first photo did the trick.

The two small watchmakers collets shown in the photo, one holding a small tapered diamond dental burr with the other holding a tiny dental carbide ball form burr were tried first. This didn't work out very well although a little bit of material was removed probably because I got them both used, for free, from you know who.

By chance, a few weeks ago, an old broken 1/8" dia. two flute carbide end mill was "sharpened" on the fancy Christen drill grinder here simply because I was curious as to what would happen if I tried it. It turns out that it sort of turned the end mill into something resembling a sharpened drill on its end.

I had no intended use for this cutter until I thought, I have nothing to lose, maybe I can "drill" the remaining pip material and turn it into a small recessed dimple using this "funny" drill. And guess what, it was tough drilling but it worked! I just peck drilled several times with the lathe turning at its top speed and it removed the remaining pip material and formed the dimple.

Even if the carbide cutter was chipped or dulled in the process (and it doesn't seem to be), I can resharpen it again dozens of times like a normal jobbers twist drill as the Christen drill grinder came with a diamond wheel as purchased. This now seems to be the solution to making the necessary centre relief for all of the small end mills which I use.

I know that most home shops don't have such fancy equipment so this method is not open to most of you but I think there are other ways of achieving the above using something like a Dremel and a small abrasive cutoff wheel. I will report on this in the future.

Finally, the proof of the pudding is always in the eating, so I will conclude with some photos of how the end mill actually performs now cutting mild steel (either hot or cold rolled).
Attachments
141 The Setup to Remove the Centre Pip.jpg
142 Now no Centre Pip but a Centre Dimple.jpg
143 The Centre Dimple.jpg

User avatar
Carrdo
Posts: 1234
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo » Thu Dec 10, 2020 8:42 pm

From scrap to a working cutter.

A block of cold rolled steel surface milled with the sharpened cutter. The resulting milled surface looks excellent.

But in the end I had to employ my hand held high speed die grinder and an abrasive tapered grinding wheel to remove the raised burrs left around the dimple by the "funny" carbide drill. Hand grinding leaves quite a messy, unprofessional looking centre and always the ever present danger grinding the cutting edges but was needed, in the end, to give the fine milled surface as shown in the photo.

Looks like I will be investigating Plan B...F... to improve the above in the future but thats it for now.
Attachments
144 A Block of Cold Rolled Steel Surface Milled with the Sharpened End Mill.jpg

User avatar
Carrdo
Posts: 1234
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo » Thu Apr 08, 2021 1:10 pm

As usual, I am often the author of my own misfortune.

The latest adventure started when, some time ago, I bought myself a former Soviet Union made Russian centre locating microscope package. It came with what is seen in the first photo. It also included a target piece for locating/picking up edges or workpiece corners.

If you have digital on your mill none of this is now relevant but since I still do things the old fashioned way before anything digital existed, I often find myself needing to pick up fine scribed centre points which have been located using the fine Starrett height gauges which I have.

These centre locating scopes are still being sold on ebay and if you type in "centering microscope" there, they will come up. It is stated they come with Morse # 2, 3 and 4 taper shanks but it appears that only the # 4 Morse taper is now being sold. Not too useful for anything in the shop here.

You can get other western built centre locating scopes as well but not at the prices the Russian ones are selling for so I took a chance. All I can say is the scope is built like a battleship, the Russian's never caring much about aesthetics. But the optics are very good being based, historically, on the German Zeiss optics.

Detailed instructions come with the unit but they are in Russian. So I had to cast about to get an English translation which, fortunately, I was able to obtain. An excellent translation of technical Russian through a friend of a new TSME member here (see the second photo).

Since my milling machine has an R8 spindle nose taper, one can buy, commercially, an R8/MT4 adaptor which I did initially (see the third photo) but I soon saw this was far from ideal due to the resultant length of the two piece combination and the inherent runout errors involved. But what killed it was the fact that even though the MT4 shank has a drawbar thread and the R8/MT4 adaptor has a drawbar thread, there is no through hole in the adaptor to be able to lock the scope to the spindle of the mill. This leaves the situation where the scope is held by taper friction only. While this may be OK for some situations, it is not foolproof. And since there are no replacement parts or is there anything to repair a damaged scope...

So, time for a re-think and what would be the most simple solution?

I could make new straight shank flanged adaptor which fits directly in the body of the scope as this was possible and one which would also fit the largest standard collet (3/4") a R8 spindle accepts. Simple and straightforward - in theory yes...

To be continued.
Attachments
1.jpg
2.jpg
3.jpg

pete
Posts: 2135
Joined: Tue Feb 10, 2009 6:04 am

Re: Machining Setup's with Few Comments

Post by pete » Thu Apr 08, 2021 3:03 pm

You may have figured out the same or have already done something different making this redundant anyway. My mill is also R8 and the Haimer 3D I have uses basically a dedicated tool holder it's more or less permanently mounted in. These Haimers use just a straight shank and it looks like the shank on yours might be removable? I chose to use a 3/4" end mill holder with mine. And yes the same run out issues are present and affect there accuracy with them. What they did is build in 4 set screw adjustments at the upper end of the tool. During it's initial set up you use a dti on it's probe tip and zero it much like an independent 4 jaw chuck to the tool holder, spindle and probe tip with those set screws. With that centering scope it might require two rows of 4 set screws to get it both vertically in line with the spindle and on the spindles C/L. It's about the only use I've found so far for the index pin used inside the R8's spindle taper. The good thing about the type of scope you have is there quite easy to self check the cross hairs accuracy in both X,Y just by checking the cross hairs C/L to a part with prescribed center lines on it.

User avatar
Carrdo
Posts: 1234
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo » Thu Apr 08, 2021 3:48 pm

The basic machining requirements on the new straight arbor were, it had to be straight, dead on size and dead concentric throughout. Easy enough to do if everything is machined all over at the same setting. This assumes you have a bar long enough to hold in a chuck and still do the all over machining supported by the tailstock centre.

However, I started with a 2-3/8" dia. mild steel bar only 4-1/2" long (I don't know the alloy) as that was what was available and handy. It machined quite easily with a good finish. But the short length of the bar turned out to be a problem later on.

Because of the amount of material which needed to be removed to produce the 3/4" shank and to speed up the job I decided to rough turn the blank first in the Herbert 2D turret lathe ("the heavy") and then finish it in the 9" SB. See photos 5 & 6. But this required the bar to be turned end for end to rough turn both ends on the bar. I knew this procedure would leave the bar centres out of line but I had a "fix". Everything was left 0.030" oversize.

Other than the blue hot chips coming from this operation, everything went fine at this stage.

To be continued.
Attachments
5.jpg
6.jpg

User avatar
Carrdo
Posts: 1234
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo » Thu Apr 08, 2021 4:21 pm

The start of the "fix".

The setup shown in the photo in the 9" SB lathe.

Even though the not completely aligned centres caused the blank to wobble a bit, I didn't care at this point as I could still turn everything in place all over because of the oversize blank. To get what I wanted, I took several test cuts on and along the blank shank, measured the resultant diameter with my best 0.0001" micrometer and then adjusted the tailstock over and repeated the procedure several times so that by the time I was at the final 0.750", the final shank diameter, the shank was true running, it was on size to within 0.0001" and it was straight as an arrow as measured by my best 0.0001" test indicator. I also machined the front face of the flange and the periphery of the flange at the same time ensuring that these surfaces were square and on size as well.

I was surprised with the above as I don't think that a SB lathe bed is even scraped to this degree of accuracy although the later SB lathe spindles were superfinished to a very high standard and the lathe is in very good condition. Adjusting the tailstock this way seemed to compensate for a lot of inherent machine errors although only if nothing is touched once the above has been achieved.

Everything was moving so nicely along at this point or so I thought...

To be continued.
Attachments
7.jpg
Last edited by Carrdo on Thu Apr 08, 2021 7:39 pm, edited 1 time in total.

User avatar
Carrdo
Posts: 1234
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo » Thu Apr 08, 2021 5:21 pm

Continuing with the "fix".

I knew that to machine the remaining flange and spigot surfaces dead concentric and square, nothing could now be touched or altered. I first had to remove the drive dog but now there was nothing to drive the arbor blank except if I made an independent drive.

So with my convoluted thinking I made what is shown in the photo. The pulley on the arbor was made originally with a drive fit on a 3/4" motor shaft. I reamed it out and made a crude lap from a wooden dowel and some fine valve grinding paste to give a free running fit on the arbor shank. The pulley set screw had a brass pad to prevent it marking the arbor shank when tightened.

The rest of the setup was cobbled together from what I had but it involved days of trial and work out every possible problem as it arose.

Finally, to slip the pulley over the arbor shank, the tailstock barrel was carefully backed off while making certain that I did not turn or let the arbor slip off the headstock live centre or move the arbor in any way. That was when Murphy stepped in and to my horror I had a wobble!

Well, I had just proven the second line of the thread " nothing could now be touched or altered".

What to do? One should always have a Plan B and that was fix the "fix".

To be continued.
Attachments
8.jpg

User avatar
Carrdo
Posts: 1234
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo » Thu Apr 08, 2021 6:00 pm

The fix to the " fix" turned out to be Adam Booth and his Abom79 Youtube videos.

Whenever he needed to machine, centre and have run true a short piece of partly machined stock, he would set the work up in the 4 jaw with copper shims and then proceed to tap the piece true both on diameter and axially.

I thought yeah you can get the work to run somewhat true but not to the degree I wanted.

Anyway, I tried his method and it worked! See photo No. 9

I held the shank of the arbor for about 1/2" deep in the jaws of the 4 jaw with thin copper pieces. Adam uses much thicker copper shims as his lathes are much bigger. The chuck jaws were then tightened quite snugly and the tapping began.

Copper is an interesting material as it is so ductile. Even with the thin shims, the tapping of the stock will swage the copper so the work can move minutely but still maintain jaw pressure/grip on the work.

It is an iterative procedure.

I first indicated the work dead true at the 4 jaw chuck end and then ran the indicator along the top of the arbor blank shank and then checked the flange runout tapping against any runout in both directions. After about 3 iterations (and on the last iteration only kiss tapping the work), the 0.0001" indicator needle only vibrated without moving indicating that I was dead true both axially and on concentricity.

The rest was just nerves and concentration. I used a freshly ground HSS raked tool, ground and then honed with a diamond lap and took off a maximum of only 0.002" total per pass meaning I had to make over 15 passes to complete the machining expecting all of the time that the tool might dig in or some other disaster would strike because of the huge overhang out from the chuck but it didn't. The final passes consisted of alternatively taking shaving cuts on the inner face of the mounting flange, the spigot diameter and finally the end face of the spigot to have everything on size, square and concentric.

The moral to the story - do it right the first time and start with a proper length blank. Would have saved 90% of the time and effort I expended.

PS: The parting tool shown in photo 9 was only used as an under cutting tool to cut a recess at the spigot/flange interface as machined into the original mounting arbor. I turned the lathe spindle by hand for this operation.
Attachments
9.jpg
10.jpg

User avatar
Carrdo
Posts: 1234
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo » Sun Apr 11, 2021 5:41 pm

The last act - locating and drilling the new arbor for the four metric mounting screws.

The mounting screw size on the scope is M4 x 0.7mm x 16mm long. The original slotted head mounting screws were replaced with some high quality metric alloy socket head cap screws.

The three jaw chuck to rotary table adaptor was made decades ago and was the most challenging piece of metal I ever machined. The rotary table end has a metric thread and the chuck end has a 1-1/2-8 TPI as used on the 9" SB.

As we are drilling clearance holes here in the flange of the new arbor and as both the new and the original arbor flanges are exactly the same diameter, one can use the method shown in photo 13. Everything is aided by the use of the eye loupe and good lighting.

Photo 14 shows the overall setup used. I am employing one of my new (and best) three jaw and drill holding chucks. The mounting holes were first spotted and drilled undersize just in case.

Be sure to remove any backlash in the rotary table before starting and lock the rotary table when drilling. Also, ensure that the arbor shank is securely held in the 3 jaw without the jaws marring in any way the work. As before, copper strips are best. Test the chuck grip by trying to turn the arbor. And finally, since the 3 jaw chuck is mated to the rotary table by screw threads in this case, ensure these threads are fully tightened and stay that way during drilling - ask me how I know and why I was so glad I started with undersize drilling. After that little adventure, I held the 3 jaw chuck body in one hand turning it backwards while drilling so the chuck was locked down on the rotary table at all times.

If anything can move or turn, it will so be prepared.
Attachments
11 Centering the Rotary Table.jpg
12 The Three Jaw Chuck to the Rotary Table Adaptor.jpg
13 How the Screw Hole Radial Offset in the MT4 Arbor was Picked Up.jpg
14 The Setup Used to Locate Space and Drill the New Arbor Mounting Screw Holes.jpg
15 The New Arbor Attached to the Body of the Centering Microscope.jpg
16 The Centering Microscope Set Up in the Spindle of the Milling Machine.jpg

Post Reply