Machining Setup's with Few Comments

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NP317
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Re: Machining Setup's with Few Comments

Post by NP317 »

An example of a spider allowing extreme work on my (former) Atlas 12" lathe:
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Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

Back to my most favourite subject of grinding the "third facet" on a 11/32" diameter HSS two flute end mill on the surface grinder. This is also known as gashing an end mill or giving it centre relief.

Please note that all of the following relates to two flute end mill third facet grinding only. Four flute end mills are ground differently as are six flute end mills, etc. I will get into this in the future.

As I have stated several times previously in this thread, no end mill will cut for long without getting into this operation. All of the readily available commercial end mill grinding fixtures are really not designed for this operation - they are really only designed to grind the primary and secondary relief angles on the end mill cutting edges. But one can add a very simple additional setup so they will. The only problem is, the setup is a bit slow. Commercial T&C grinders have all of the additional rotational, nodding and angle movements built right into the machine so one can do this operation almost instantly.

But first to give an explanation of what is the "third facet" on a 2 flute end mill. See my rough sketch in the first photo and the actual ground facet on a commercial end mill as seen in the second photo.

The third facet is needed on an end mill to remove metal ahead of the end mill's cutting edges so they can cut. In addition, the third facet is there to provide centre relief on the end mill which lowers the centre of the end mill to below the cutting edges to prevent any rubbing at the centre point.

On a centre cutting end mill, all of the facets and relief angles come to a true point at the centre of the end mill but with a non centre cutting end mill, the metal at the centre is removed or relieved. 95% of what we do, is done with a non centre cutting end mill.

To see how the commercial bodies do it, I first studied a new Cleveland 3/8" diameter HSS centre cutting end mill as I figured, if anyone, they truly know what they are doing. The Cleveland end mill is beautifully ground all over with perfect geometric facets and relief angles. Measuring the third facet with a vernier protractor, I came up with the angles shown in the sketch. It was obvious after studying this end mill, that the third facet had been ground with a straight wheel having a very sharp 90 degree corner.

I also became aware, after some reflection, the smaller the end mill diameter, the steeper the third facet angle is ground. The third facet is ground at a steeper angle (for end mills under 5/8" - 1/2" diameter) than the commercial end mill sharpening fixtures allow for as the front bevel on my unit is machined to 30 degrees for the secondary cutting edge clearance grinding and the 3/8" diameter Cleveland end mill third facet was ground 48 degrees . On the Cleveland end mill, the upper edge of the third facet is 90 degrees to the two cutting edges and ends at exactly at the centre point. Being ground on a circular curved surface, the facet appears to tilt down and away towards the periphery of the end mill which, in fact, it does. Hence, what appears to be an odd angle isn't odd at all - it is perfect geometric grinding.

The third photo shows the additional bits and pieces necessary to grind the third facet to commercial standards. For the trial cuts seen in the fourth photo, I set the third facet angle to 45 degrees (with the end mill fixture clamped to the small angle plate with the large toolmakers clamp) as the end of this end mill had been badly ground so just as a test... Also, I was going to grind slightly past centre to produce the necessary centre relief.

I did not show here how the end mill cutting edges had first been aligned square using the special Washburn end mill aligning fixture (which has been described and shown earlier in this thread). After this initial operation and the 45 degree angle was established, the commercial end mill grinding fixture barrel was advanced 6 clicks (the end mill turned 90 degrees) and then a further click (15 degrees).

Ensure that the grinding wheel has a truly square corner, touch of a third facet surface, index 180 degrees, traverse the table, repeat the operation and slowly advance the wheel in small increments towards the centre of the end mill while feeding down in 0.0005" or 0.001" increments. You will slowly see the third facet grow and move towards the centre. Using good lighting and an eye loupe, one can easily see when all facets intersect at the centre if one proceeds slowly and carefully. I went slightly beyond centre to produce some centre relief.

The actual grinding itself, took all of 10 minutes (while being extra careful) as preparation is everything.

The results speak for themselves (photo 5 and 6). I used a 150 grit white aluminum oxide wheel (I got them cheap on Kijiji) with no burning of the metal at all grinding dry but the wheels are dedicated solely to end mill grinding. I do have a straight 120 grit CBN wheel but haven'd tied it out to date.
Attachments
146 My Rough Sketch of the Third Facet (shaded) on a Two Flute HSS End Mill.jpg
147 An Actual Third Facet on a Commercial Two Flute End Mill.jpg
148 All of the Bits and Pieces Necessary for Grinding the Third Facet on My Surface Grinder.jpg
150 The Setup Used to Grind the Third Facet.jpg
151 The End of the End Mill After Grinding the Third Facet.jpg
153 The End Mill after Grinding the Cutting Edge Primary and Secondary Clearance Angles and the Third Facet.jpg
Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

A group of two flute HSS end mills sharpened by the latest method. They look professional.
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154 A Group of Two Flute HSS End Mills Sharpened by the Latest Method.jpg
Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

Now here is something which you don't see too often. Ultra thin toolmakers foil. It is only 0.0003" thick.

It was given to me by a toolmaker who, unfortunately, is no longer with us.

It is so delicate, I am unable to remove it from the roll without it tearing. Perhaps some of you, if you know better, can enlighten me as to how to unroll and handle it better. And some of the ways it can be used.

All I can think of to get it to lay flat is to wet it with my fingers and then roll it out on a flat surface with a wallpaper seam roller.

In the photo I show a strip of 0.001" thick feeler gauge stock for comparison and that is delicate enough to handle without kinking.

I have used small pieces of it as "shim" on the surface grinder but what other uses does it have...?
Attachments
515 Ultra Thin Toolmakers Foil.jpg
Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

1 " wide abrasive belt sanding belts - the abrasive belt splice/joint fails with time usually after a year or two of use.

Can they be re-glued and after re-glueing will they fail again?

I have a number of these belts purchased over the years. Even new, the belt splice seems to fail with time even when not used.

Checking on the net, this seems to be a universal problem with these abrasive belts even for professionals. The abrasive belt manufacturers don't seem to be particularly helpful in this regard saying only buy the number of belts you will use up in a year or so. The belt splicing techniques they use employ specialized machinery and generally their belt splicing techniques are guarded as trade secrets.

I checked a number of woodworking and metal working sites and it seems everything under the sun has be tried both by us home shop machinist types and by professional metal workers with very mixed results at best. The re-glued belts usually fail again at the splice after a short period of use.

The requirements of an abrasive belt splice have three major requirements, making it a difficult situation.

1. The belt splice has to be strong and remain strong under load (tension). On my metal belt sander, the belt is under strong tension at all times to prevent it slipping off the tracking pulleys when belt sanding and to have the belt track properly.

2. The belt splice and glue has to remain flexible under speed. My belt sander runs at 3600 rpm and the belt splice is continually flexing over the quite small tracking pulleys at this speed.

3. The belt splice and glue has to be heat resistant under the above conditions at all times due to the heat being generated by the abrasive action of the belt itself on the work piece.

To add to the confusion, here is how I tackled the problem.

The first photo shows a typical 1" wide abrasive belt which I have and the splice from a belt which has failed. If one just pulls on the belt itself, it will fail at the splice as it has been sitting in the workshop for about 10 years unused.

The first operation to re-splice a failed joint belt was to remove any traces of the existing adhesive. The best chemical I found for this was perchloroethylene or commercial spot remover. In Canada PCE is now either restricted or banned all together due to its cancer causing effects. So be warned. The bottle I have was from something which I had from decades ago. Acetone or lacquer thinner were both less effective.

Next was to scarify the ends of the abrasive belt in order to produce a slightly rough surface to which the new glue would adhere better. I just used some coarse sandpaper and a sanding block. You don't have to overdo it.

I usually don't mention or endorse any commercial products but I found this. Scotch brand bi directional filament tape as seen in photo 520. It is only 0.0075" thick and I had to buy the large roll seen. It is expensive. Just cut off an oversize piece which will be used as the joint splice. This tape comes with one side having an adhesive glue.

DAP Weldwood contact cement, the original. This is a rubberized high strength contact cement. It also is very expensive. I just bought the 3 oz brush on container as I didn't know if it would work or not. One can purchase a pint or quart of this cement for virtually the same price.

Both of these products can be purchased on line, but for us in Canada, neither product is available domestically so they have to be brought in from the USA so add shipping to an already expensive item.
Attachments
517 One Inch Wide Abrasive Belt and Splice.jpg
518 Removing All Traces of Existing Splice Glue.jpg
519 Scarifying Each End of the Abrasive Belt.jpg
520 Special Bi-Directional Filament Tape Which is Only Eight Thousands of an Inch Thick.jpg
521 Special Rubberized Contact Cement.jpg
Last edited by Carrdo on Fri Oct 22, 2021 5:13 pm, edited 5 times in total.
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Re: Machining Setup's with Few Comments

Post by Carrdo »

The reason why this particular contact cement was chosen (after evaluating many of them) was, it is rubberized so it remains flexible at all times and has a quite high temperature rating both of which are very necessary. It also has a very high rating in tension.

Next, the contact cement is applied (brushed on to) to the ends of the abrasive belt and to the glued side of the bi-directional filament tape. After applying the glue, the parts must remain un-contacted for a minimum of 15 minutes (and up to 2 hours) before assembly. Just follow the directions given.

After a minimum of 15 minutes, the pre glued ends of the abrasive belt are set together on top of a piece of wax paper and aligned as seen in the first two photos and the filament splice is rolled over the joint (glue side to glue side) with a wallpaper seam roller. It can be a sticky operation.

Next is the clamping operation. After rolling, carefully set a second piece of wax paper on the remaining side of the spliced joint and then place a thin wide wooden strip on top of the wax paper on each side. Clamp the assembly carefully in your bench vise as seen in the third photo and leave it there clamped for at least 24 hours. Support the free end of the abrasive belt also.

Then remove the glued belt splice and let it rest for a further three days minimum (I let it rest for a week) to allow the contact cement to develop full cure strength. Trim away any excess splice material with scissors.

The belt can then be reinstalled on your belt sanding machine as seen in the last photo. I have only run the belt for a total of 5 minutes so far but the new splice still looks and works perfectly. We shall see what happens with time. This particular belt has been used for the past 5 years and still works fine for everything I do.

All of the above may just be a pyrrhic victory due to the cost and investigative time involved, as abrasive belts are relatively cheap but I just can't stand to throw something new away just like that.
Attachments
522 Glue Applied Ends of the Abrasive Belt are Aligned and Set Together on the Glued Filament Tape Then Rolling out the Tape.jpg
523 After Rolling to Keep Everything in Place.jpg
524 (Long Term) Clamping After Applying New Glue to the Back of the Abrasive Belt and Bi-Directional Filament Tape.jpg
525 The Re-glued Belt Re-installed and Running.jpg
Last edited by Carrdo on Fri Oct 22, 2021 5:21 pm, edited 3 times in total.
Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

Small drill and small end mill extensions.

Many times I have encountered situations where I have to drill or mill next to a shoulder and the drill or end mill cannot reach the part due to interference from the spindle or quill of the mill and/or the part holding device itself.

In such situations, one must use an extension to complete the operation.

These are quite simple to make but with the small work I often encounter, correct methods have to be used. In the first photo, a 1/4" dia. CR straight rod is held in a collet in the lathe. The extension is for a 1/16" dia. two flute HSS end mill having a 1/8" dia. body.

Carefully face, centre drill, undersize drill, bore and finish ream the central hole which is 1" deep in this case. The secret is to have very sharp cutting tools and to drill slowly with lubricant and clear chips frequently. After centre drilling, I stage drilled the hole first with a sharp 3/32" dia. drill, followed by a sharp 7/64" dia. drill, followed by boring with the miniature boring bit to 0.122" dia., 1/2" deep and then final 1/8" dia. reaming to full depth. A 4-40 NC set screw drilled and tapped 1/4" from the end of the extension bar completed the job.

The last photo shows a number of drill and end mill extensions made over the years for operations which could not have been done any other way.
Attachments
530 After Drilling Boring and Reaming the End Mill Extension.jpg
531 End Mill Extension to Machine Part with Other Drill Extensions Made Over the Years.jpg
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Bill Shields
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Re: Machining Setup's with Few Comments

Post by Bill Shields »

I make extensions in a similar manner but found an easy way to hold the bit in place...

Loctite.
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Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

Fun with small, square hole single tooth broaches made from water hardening drill rod.

By small, I mean a 1/8" square hole or smaller.

In a pinch these are not hard to make but they are definitely single use only.

To form the undercut on the broach, which is very important, set the angle of the lathe's compound between 10-15 degrees as seen in the second photo. Also, note the extremely long angle round nose undercutting tool made from a very thin HSS parting blade.

After forming the broach, it is hardened all over. I do not temper these broaches.

The results can bee seen in the second last photo. While the results were not perfect, they would do the job which I needed to be done.

Some observations.

Yes, they are single use only because if you try to use them again, see the last photo. I pushed these two broaches to the limit and one collapsed into a pretzel and the other snapped off, perhaps because of the way they were heat treated but...

The thin steel strip is mild steel 1/8" thick while the broad steel strip is mild CR steel 3/16" thick. From my experience, the maximum mild steel thickness should be no greater than 1/8" for this type of broach.

Make the business end of the broach (the pilot round end and square cutting section) no longer than necessary to pass through the material thickness. There is a tremendous pressing force on the broach and the pretzel was the result of a too long square length on one of the broaches.

The pilot hole drilled in the mild steel was 0.002" larger than the square section on the broach and no lubricant was used.
Attachments
526 Milling the Seven Sixtyfourth Inch Square End of the Single Tooth Broach.jpg
528 Forming the Undercut on the Single Tooth Square Broach.jpg
529 Two of the Shop Made Single Tooth Square Push Broaches.jpg
530 After Broaching.jpg
531 They are Single Use Only or This Will Happen.jpg
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Bill Shields
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Re: Machining Setup's with Few Comments

Post by Bill Shields »

I have made them from drill rod

Made square as you show in sounded

Then tipped the milling head to undercut..or shoved a shim under the spindex unit

Then hardened.

Good for multiple cuts in brass
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Carrdo
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Re: Machining Setup's with Few Comments

Post by Carrdo »

An end grinding setup in the lathe to produce a hollow ground (the cutting edge) end on a HSS single tooth 7/64" square hole broach. It is not the easiest way to broach through a 3/32" thick piece of CR steel in this case but when there are few alternatives.

One has to be very careful to align the broach dead square and centred on the slightly oversized drilled hole for the broach. As well, the workpiece must be fully supported underneath as it can bend quite easily with the pressing pressure. I used a well known ratchet type arbor press to do the pressing.

One can also make up a miniature HSS slotting cutter for the spindle of your mill if it has a lever type quill (need also a rotary table).

I am thinking should I invest the $$$ needed for a commercial rotary broach as one can get square precision ground HSS broach's from 1/8" down to 1/16" square in 1/64" increments. These would be great for my model work but a very big $$$ investment and one has to be aware that there are some limitations even with such equipment on what can be broached and do I really need (can Justify) such fancy equipment.
Attachments
532 Hollow Grinding the End of a New HSS Single Tooth Square Hole Broach.jpg
112 The Part Machined Rotary Throttle Handle with Sketch and the New HSS Single Tooth Broach.jpg
Last edited by Carrdo on Fri Oct 29, 2021 9:16 pm, edited 1 time in total.
jcfx
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Re: Machining Setup's with Few Comments

Post by jcfx »

Carrdo wrote: Sun May 30, 2021 9:40 am Now here is something which you don't see too often. Ultra thin toolmakers foil. It is only 0.0003" thick.

It was given to me by a toolmaker who, unfortunately, is no longer with us.

It is so delicate, I am unable to remove it from the roll without it tearing. Perhaps some of you, if you know better, can enlighten me as to how to unroll and handle it better. And some of the ways it can be used.

All I can think of to get it to lay flat is to wet it with my fingers and then roll it out on a flat surface with a wallpaper seam roller.

In the photo I show a strip of 0.001" thick feeler gauge stock for comparison and that is delicate enough to handle without kinking.

I have used small pieces of it as "shim" on the surface grinder but what other uses does it have...?
It doesn't look as thin as gold ( brass ) leafing, which is extremely thin since I don't see your pieces exhibit the
"static cling " look that leaafing does. When I did use leafing I used a combination of a very soft sable brush and my breath to lift
the leaf to transfer to the pre glued surface.
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