Machining Setup's with Few Comments

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Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

The right angle attachment is now mounted on the Millrite quill. It is all a very, very close fit. I struggled to get it on as the attachment is so heavy and it had to be aligned perfectly square in all directions before it would even think about mating with the quill. Not shown is the thick piece of board I put on the mill table to protect it if the whole mess had decided to drop.

After just tightening the two take up bolts, everything locked together solid even without slitting the liner piece but I will do that just to be safe.

I am very happy as to how it turned out in the end.
Attachments
555 The Right Angle Attachment Mounted on the Millrite Quill.jpg
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Harold_V
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Re: Machining Setup's with Few Comments

Post by Harold_V »

It is my opinion that you need not slit the bushing (although it would do no harm). That would be particularly true if it is a snug fit. I use thin walled bushings routinely for holding bastard sizes in collets. I rarely split the bushing, although I also try for a reasonably thin wall. On one the size of yours, I suspect that the resulting thickness won't be a problem.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

Thanks Harold. The fit achieved seems to hold the right angle attachment very, very securely to the quill of the mill although I will really only prove this with repeated use.
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Bill Shields
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Re: Machining Setup's with Few Comments

Post by Bill Shields »

So the big question is how tough is it to rotate to square it up with the table axes?

Can you move it by hand twist or is it a thump with a soft hammer operation?
Too many things going on to bother listing them.
Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

Bill,

When the right angle clamping bolts are loose, one can thump the right angle attachment with your fist and it will rotate slightly. But when the clamping bolts are tightened and the spindle drawbar is taken up, it is like the right angle attachment is welded to the quill. It will not turn even when hitting it with a small soft face hammer.
TimTheGrim
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Re: Machining Setup's with Few Comments

Post by TimTheGrim »

Mine is a different brand than yours. On mine the unpainted side bosses were accurate to the collet bore and equal.
I have my vise mounted and trammed so I touch off the fixed jaw, move half the distance and then place the 90 deg.
Attachment In the vise and then with the assistance of the knee and quill get it mounted and almost tight.

I have some nice 5/8 die set pins so I put one in a collet and check with an indicator before final tightening.

Most recently I used it to swing a radius to match a receiver on a sight rail.

Image

These are a great asset for your mill. Have fun with it.
Illigitimi non Carborundum
'96 Birmingham mill, Enco 13x40 GH and Craftsman 6x18 lathes, Reid 2C surface grinder. Duro Bandsaw and lots of tooling from 30+ years in the machining trades and 15+ years in refinery units. Now retired
Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

Trying to finish what turned out to be a 7 year project previously described on this thread staring on June 19, 2018 (page 5).

This is one of the few times I use CNC for an operation (actually I don't, I go over to Richard's shop and he used his shop built CNC milling machine to do this operation for me). This was to produce the "Napoleon's Hat" curve for the replacement scriber carriers found on a Starrett 354 6 " height gauge.

From my hand sketches Richard first produced a 2D CAD drawing and from that he produced about 15 lines of code to have the machine produce the curve.

To test out the program he first ran a test piece as seen in the first photo. Home (0,0,0) was made the top of the curve with the cutter at about 1/2" above the blank. As it was vitally important to have the cutter at the exact centre of the blank, we ran several test cuts initially and from the results adjusted the table of the mill manually until a square set against the blank indicated that the exit tail points on each side of the blank were exactly in line (under magnification).

When the blank curve was centred, it was replaced with (up to this point) the machined first scriber carrier. A new 3/16" diameter two flute carbide end mill was used to make all of the cuts. The blank was made from mild steel but the scriber carriers themselves were made out of Starrett gauge stock which is a much tougher alloy steel even in the annealed state. Richard used a conservative horizontal in feed of 0.010" per pass until the full curve developed, then the in feed was stopped and the cutter advanced in a 0.005" depth of cut per pass until it cut to full depth (about 0.270").

With me, it was just step back and watch.

The final results are shown in the last photo. They look really good. One can't tell the original from the replacement, all the curves align perfectly.
Attachments
556 Test Piece CNC Machining.jpg
557 CNC Milling the First Scriber Carrier .jpg
558 CNC Milling the Napoleons Hat Curve on the First Scriber Carrier.jpg
559 CNC Milling the Napoleons Hat Curve on the Second Scriber Carrier.jpg
560 The Overall CNC Milling Setup.jpg
561 The Original with the Two New Scriber Carrier Pieces.jpg
Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

A delicate chamfer setup and grinding operation which was the very last operation left to do.

The scriber carrier end chamfers are 45 degrees by 1/32" wide. This gives a grinding depth from touch off of only 0.0155". The grinding space is very tight so, eventually, I came up with the setup shown (not the first setup tried). Everything has to be set truly square here and not canted in any direction so make certain everything is checked and checked again. If anything is out, you will see it.

The last photo shows the new scriber carrier installed on the Starrett 6" height gauge. I don't think anyone can tell the difference from an original OEM manufactured part.
Attachments
564 A Delicate Chamfer Setup and Grinding Operation.jpg
565 A Delicate Chamfer Setup and Grinding Operation.jpg
566 A Delicate Chamfer Setup and Grinding Operation.jpg
567 The New Scriber Carrier Installed on the Second New Starrett 354 Height Gauge.jpg
RET
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Re: Machining Setup's with Few Comments

Post by RET »

Hi,

Don is meticulous in his work. Everything has to be exactly right.

In the CNC pictures, the first one shows the 1/2" wide test piece before we went and made a CAD drawing so we could modify the hat curve because the hat was a little too wide on top to be right. With the drawing, we were able to modify the code so the curve was right. This isn't always easy because the "G" code position numbers have to be right to 5 decimal places where the two curves meet.

Because of the "G" code, the path that the cutter follows is always the same, but we used the X axis dial, incrementing a few thousandths at a time to move the table so that the hat shoulders were at precisely the same height. Once Don was happy with that, we used the Y axis dial to move the part in so that the top of the hat was fully developed (the flat spot on top was just eliminated).

We did this first on the 1/8" thick test piece, and when that was right, the test piece was replaced with the first good part which is a little over 1/4" thick. We first made a shallow cut and used that to get the part positioned properly using the same steps we had done with the test piece. Once the table was in the right place, we made successive passes, downfeeding 5 thousandths each time until the cutter was cutting full depth.

We were very cautious in doing this because Don had already done an incredible amount of work on the two parts and the last thing we needed to do was have the cutter grab and move the vise or move the part in the vise. With the combination of climb milling and the 3/16" carbide cutter the finish on the part is very good.

I asked Don how he had made the rectangular through slot in the part since it is perfectly done. He said that he used his bandsaw to remove most of the material and then slitting saws to get the finish and accuracy he needed inside.

My comments cover the CNC part only since I felt that a little more explanation might help.

Richard Trounce.
Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

Third time lucky! Another little project which turned into a machining nightmare!

This time the project involved making a new, smaller internal part for a UK David Brown floating and adjustable reamer the S1, the smallest one made in a series (range 3/4"-13/16").

I don't know how and where I got this tool as it has been laying around in the workshop for probably 40 years. I have never used it as it was missing the cutting blades which, recently, I was able to locate a source in the UK which had them for a "reasonable" price. I purchased the last two sets available for the S1, the more expensive carbide insert type.

David Brown floating reamers can still be found used and are advertised by a few UK based tool suppliers but they are outrageously expensive to buy new (and the cutting blades also). Think 500 pounds for one (with a spare set of blades)!

The floating reamer which I have is new and obviously had never been used. When the cutting blades arrived in the mail, I thought, finally, I am able to put the reamer to use. Not so!

The internal diamond shaped piece which controls the blades stick out and gives the reamer its floating properties would not fit the shallow slots machined into the cutting blades sent as it appeared to be for the next larger size reamer in the series. Now I knew why it had never been used.

The reamer has been made to a very high standard. Everything is hardened and ground probably to "tenths" all over.

All that I had to do was to make a new diamond shaped piece to fit the blade slots.

to be continued.
Attachments
569 The David Brown Floating Adjustable Reamer Partially Disassembled with the Two Purchased Sets of Carbide Insert Cutting Blades.jpg
570 The David Brown Floating Adjustable Reamer Fully Disassembled.jpg
571 The 1946 Patent for this Reamer Assigned to David Brown.jpg
572 The Original Diamond Shaped Part Which Needed to be Remade (rear) and My First Failed Attempt at This (in front).jpg
Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

Actually, what you see in the last photo of the last post was the second attempt to reproduce the part. On my first go around, I quickly got to the point where no further machining was possible and the partially machined blank flew into the scrap bin.

As Richard says thinking about how to do something before one starts is the most important first step.

On a small part like this, the rule is to do the inside machining first. This consists of a slightly elongated 1/8" dia. slot which sets the reamer float. But how much float? I chose 0.010" total float. Why?

The width of the cutting blade slots is 0.200" exactly. If one has to machine a 0.125" wide slot (which was the dia. of the ground centre pin - actually it miked to 0.1248") and one has 0.010" float, the length of the slot elongation is 0.135". As the slot elongation is in the direction of the width of the part, this leaves (0.200" - 0.135")/2 or just 1/32" transverse wall thickness which I considered thin enough.

To start, machine a true and square rectangle blank (7/16" long by 1/4" wide by 1/8" thick) the best you can on all 4 sides and on thickness. This is because the layout proceeds from this and it has to be as accurate as you can make it. The blank material which I used was Starrett gauge stock as it is a tough steel which is wear resistant and it can be hardened with minimal distortion.

Layout the centre of the elongated slot in the exact centre of the blank and also its extremities. The blank was set up in an endwise position between the vise jaws of the mill as then I could use the table stops on the mill to limit the length of the transverse slot. I used my eye loupe and good lighting to "pick up" the layout lines as close as I could. Pre drill with a # 30 drill (0.120") a centre hole and then follow this with a 1/8" dia. end mill full depth to elongate this hole in one pass (very slowly and carefully) using the mill's table stops. The blank was set on a truly parallel mild steel spacer which one could mill into. I also found one of my 1/8" HSS end mills to be a few tenths undersize which was what I ended up using.

I only go into this level of detail as this is what is needed in this case. The result was the ground centre pin was a very firm shakeless slide fit in the finished slot end to end.

What is equally important with this part is the included angle on the diamond ends. I was lucky I had an original part from which I could take all measurements as this turned out to be 54.5 degrees. This unique angle has to be maintained exactly as it forces the two cutting blades to be exactly 180 degrees apart when everything is assembled. How do I know this? That is how the second failed part came to be as shown in the photos.

to be continued.
Attachments
573 Centering the Blank to the Layout Lines.jpg
574 Milling the Slightly Elongated Central Slot.jpg
575 After Milling the Slightly Elongated Central Slot.jpg
Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

At this point I decided it was time to make a proper sketch of the finished part from all of my scribblings. I keep records like this not because I will ever need them again, but as a reminder of how to do things as I forget a lot as time passes.

Next was to layout and machine the tapered sides of the diamond. This was done as shown in the accompanying photos. Not that it was all that accurate but it would become that way in the checking process - a process that is known as the German method. Machine and then check your work at each and every step to verify that it is correct before proceeding further. This is where the initial accuracy of the rectangle pays off as it is used to set the tapered external shape as best one can.

to be continued.
Attachments
576 Laying Out the External Diamend Shape.jpg
577 Setting the Layout Line as Horizontal as Possible.jpg
579 After Milling one End of the Blank .jpg
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