Machining Setup's with Few Comments

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Carrdo
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Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

A low profile tee slot clamp made to a design by Harold Hall.

Recently, I had occasion to machine some locomotive parts which required one of these to be made. There are many ingeneous designs for low profile tee slot clamps on the net for home workshop use as well as numerous commercial products available which may or may not be suitable.

Initially, I made up something along this line also but after having reviewed what is out there, I saw much better ideas than what I had come up with.

Some of the best designs, in my opinion, are those of Harold Hall, a UK model engineer and writer of many technical workshop publications and books. On Youtube search for Low Profile Clamps Five Designs. The one which I made is the third in the series. I do not have the plans for it so I just "eyeballed" it.

As most of this is a milling and drilling job, ensure that you use sharp cutters and have the stock is well clamped. My low profile clamp was made longer than the standard design so I used two commercial set screws instead of a cap screw on the clamp body. I made the clamp piece end angles 15 degrees. Also, to avoid marring the rotary table tee slot bottom surface, I placed a 0.005" thick shim piece, seen in the first photo, down in the rotary table tee slot first for the ends of the set screws to bear against when tightening them down.

The rotary table was set up as shown in order to finish machine the deep slot(s) in the part(s). I pre-machined as much of the slot(s) as possible using a conventional side tooth saw which produces a flat bottom slot. However, I needed to finish the slot(s) having a convex circular bottom, hence the large diameter woodruff cutter seen in the last photo. This cutter will operate very close to the surface of the rotary table and the setup has to allow for a significant portion of three sides of the part to be free of any obstacles where the cutter will traverse (approx.120 degrees rotation). Always something new and different.

Most of the clamping force will be provided by the top clamps but the low profile tee slot clamp is necessary to locate and hold the part's curved face against the center dummy "wheel". This also ensures that the part will be oriented truly radial. I will be taking very light cuts with the new cutter to ensure the cutting force is minimal. I do not want anything to move once it is in place and clamped. I have invested a lot of time and effort in these parts to get them to this stage and not without incident due to me not paying enough attention to the above.

I am not going to describe any of this again to the live steam boys, so unless they read this, they will just see the final slotting operation and not how I got there.
Attachments
442 A Harold Hall Tee Slot Low Profile Clamp Disassembled.jpg
443 The Assembled Tee Slot Low Profile Clamp.jpg
444 The Setup on the Rotary Table to Hold and Locate the Part.jpg
445 The Part to be Finish Slotted Located and Oriented on the Rotary Table.jpg
446 The Complete Clamping Locating Assembly Utilizing the Low Profile Clamp.jpg
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

The actual machining operation with the above setup.
Attachments
353 The Final Deep Slotting Operation.jpg
354 Afer Final Slotting.jpg
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

Cross drilling in miniature.

Cross drilling employing commercial drill bushings is a standard machining operation but when it involves really miniature parts, this may be another story. The smallest cross drilling which I have done successfully is on a 3/32" dia. rod using a #67 drill which had to be a specified distance from the end of the rod.

Preparation is everything here.

The first photo is all of the bits and pieces needed. The miniature long cotter pin is 1/32" dia. The miniature drill bushing was made from a piece of 3/32" dia. stock held in a collet. If you do not have collets of this size, turn a piece of 3/16" dia. rod held in your 3 jaw down to a 3/32" dia. OD exactly. Then centre drill the end with a sharp #000 centre drill and finish with a #67 drill held in a quality drill chuck in the lathe's tailstock. Cut off the drill bushing blank and face both ends square.

One also need a quality drill chuck for the cross drilling operation. I use a 0-1/8" capacity Albrecht. Costly, but very high quality and accurate holding ability.

Also, one has to make an accurate (truly parallel edges) support spacer for the rod to be cross drilled which is slightly thinner than the 3/32" dia. rod. Mine was 0.070" thick but a piece of 5/64 " thick stock would have been even better. Not shown, but needed, are a pair of tweezers to handle all of the tiny bits. If something falls on the floor and rolls away, you are going to have a job finding it.

The drilling setup is shown in the second photo. Set the drill bushing slightly further from the end of the rod than needed. One can drill through slightly into the support piece or tap it back so that the drill, upon breakthrough, just misses it. Ensure everything is bedded and square before drilling. Use the drill bushing to align the drill. These miniature drills are very flexible so a slight misalignment doesn't harm them. Peck drill and clear chips frequently. Employ a very light down feed especially when breaking through the 3/32" dia. rod. Drilling speed was of necessity very low for such a small drill. After drilling, return the 3/32" dia. rod to the lathe and face the end of the rod to the finished length from the end of the rod to the centre of the cross hole.

The third photo is my jar of custom shop made drill bushings for every possible job encountered so far.

What was all of this miniature cross drilling for? See the last photo.
Attachments
447 All of the Bits and Pieces Needed.jpg
448 The Setup for Miniature Cross Drilling.jpg
449 Jar of Custom Made Drill Bushings for Every Possible Job.jpg
735 The Leaf Spring End Hangers Installed with Locking Cotter Pins.jpg
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

Another shop issue which is taking far too much of my time and energy - HSS end mill gashing.

I just cannot operate in the shop without having razor sharp cutting tools - I never have and never will. As I have stated before, probably up to 75% of the problems I have in the (home) shop, related to milling, are from employing end mills which really need to be much sharper than they are.

Most people would just buy HSS end mills, use them until they were dull and then throw them away particularly if they are from offshore. I have over the years accumulated boxes of them of all sizes and types, mostly good American ones. I won't throw them away simply because they are dull but I need to have a practical way to sharpen them. Fortunately, I have a surface grinder which, while not ideal, can be used for this purpose; however, there are many practical problems which first need to be overcome.

To date, I have only been successful with two flute HSS end mills. Carbide end mills need CBN or diamond wheels for sharpening which are really expensive and my usage of carbide doesn't justify their cost (at least up to now). Also, I only sharpen the ends of the end mills and not the spiral peripheral cutting edges. This leaves the end mill as a surfacing cutter only but that is fine as many of my operations are just that.

Just to do the above there are still many practical problems to overcome. Chief among these is end mill gashing as no end mill will cut for long without getting into this operation. Why this is so I have dealt with elsewhere on this thread.

Many commercial end mill grinding fixtures for surface grinders exist but they all have the same problems - you cannot gash an end mill using them. Also, aligning the end mill cutting edges truly square to the grinding wheel is a by guess and by golly operation and to really sharpen the cutting edges of any end mill properly, they need to be truly square to the edge or corner of the grinding wheel. The Washburn aligning fixture (also described earlier in this thread) is the only practical way I know of to achieve this alignment and it is not easy to make. The first photo shows how it is used in the surface grinder in conjunction with a well known commercial end mill sharpening fixture. Good lighting and the eye loupe barely seen in the photo are essential. The photo shows how the cutting edges of a 1/4" dia. two flute HSS end mill are aligned.

To be continued.
Attachments
112 Aligning the Cutting Edges Square on a One Quarter Inch Diameter Two Flute HSS End Mill.jpg
Carrdo
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Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

To actually sharpen the end of a two flute HSS end mill, the centre section of the end mill has to be relieved or ground away. I call this the gashing operation. It is not the way an end mill is gashed commercially using a purpose built tool and cutter grinder but since few of us have such fancy equipment, we need to modify the commercial procedure a bit to suit our needs.

The problem is if an end mill is not gashed, the centre relief found on a non centre cutting end mill is soon lost due to repeated sharpening of the ends of the end mill. Once this happens, the end mill will no longer cut and a way has to be found to restore the centre relief.

One point, centre relief gashing will make all centre cutting end mills non centre cutting but since 99.5% of all end milling which I do doesn't need such an end mill, I keep the few centre cutting end mills which I have separate for these rare occasions.

The first photo shows how I modified a standard bench grinder for this purpose. A purpose built end mill holder seen in the photo was also made to hold end mills from the smallest up to 1/2" diameter. A standard 1/16" thick reinforced cutoff wheel with large diameter relieved wheel flanges is mounted in the bench grinder. The way the setup is nothing is left to chance and all side and/or bending forces on the thin wheel are eliminated.

Experienced T&C grinder operators can gash an end mill by hand but I can't and I don't recommend it.

An end mill is securely mounted in the holder and gently moved forward between the guides and rocked to produce the gash or centre relief slot. The slot itself does not have to be very deep (only a 1/32" - 1/16" deep) as the process can be repeated many times as the end of the end mill is re-sharpened on its end. The slot is also angled slightly as seen in the second last photo.

For smaller end mills (less than 3/8" dia.) a 1/16" thick reinforced cutoff wheel will work but it removes a lot of the cutting edge on the end mill. Much thinner (0.035" thick) large diameter reinforced cutoff wheels can be purchased commercially as seen in the last photo. I made the special large diameter relieved wheel flanges for these wheels so that only the outer 1/2" depth or so of wheel remains exposed since they are so thin. They can be used either in the surface grinder or with the bench grinder. The miniature Dremel cutoff wheel seen in the last photo also, I will try it with the Quorn T&C grinder which I have but I haven't yet made the special holder it needs.

The above represents a lot of precise machining work but since I will never need to buy another end mill again... I am retired and trading time for $$$. After gashing on the bench grinder, the 1/4" dia. end mill was sharpened in the SG using a standard dressed 46 grit straight white wheel as seen in the previous post's single photo. I can tell you the cutting edge of the end mill is now razor sharp on the end. In the UK one would say this end mill is now really a slot drill but it will produce a beautiful fine surface finish much like a single point fly cutter.

One final practical point. With the centre of the end mill now relieved or removed, the edge or corner of the surface grinder wheel does not have to grind precisely to the centre of the end mill making the primary and secondary cutting edge grinding operations much easier to do.
Attachments
113 The Bench Grinder Table and End Mill Holder for Gashing a Two Flute HSS One Quarter Inch Dia. End Mill.jpg
114 The End Mill Gashing Operation on the Bench Grinder.jpg
115 Two End Mills Gashed by this Method.jpg
343 The Very Thin Reinforced Resinold Bond Cutoff Wheels Used in End Mill Gashing.jpg
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

The bandsaw blade silver soldering fixture which I use to make up or repair my bandsaw blade stock. It was made to a design by Harry Hawkins who was a past president of TSME.

In my 14" Delta metal bandsaw, I use mostly 1/2" wide DoAll Dart high carbon steel blades bought in 100 foot rolls.

After cutting or shearing a piece of bandsaw blade to length, just square up the ends on a belt sander past any kinks or bends. Then place both open ends of the bandsaw blade in the fixture and clamp it leaving a 0.002" wide end gap. I do this by eye but one could use a 0.002" thick feeler gauge to set the gap. Just ensure that both ends of the blade are in line.

Flux, heat the ends of the blade to a bright orange red with the propane torch from underneath the blade and then add a touch of silver solder just enough to fill the gap. If you add to much it will have to be filed away afterwards. Then let the soldered joint partially cool and then dump it in hot water for a while to remove any residual flux scale and thats it. The entire setup consisting of fluxing and silver soldering can easily be done in 30 seconds.

The body of the fixture is a 6" by 2" by 1/4" thick piece of cut down structural steel channel as shown. The 4 bandsaw blade aligning pins are in line and are set to accommodate 1/2" wide blade material but can be altered for other blade widths.The upper blade clamp is spring loaded.

It is so simple, effective and easy to use.

One bit of general band sawing advice learned through experience is, do not over tension the blade when band sawing (just use enough tension to do the job) and after finishing release the blade tension. When the blade gets dull and you start using a lot of force to produce the cut, often the blade will fail through fatigue and once this starts to happen, the blade will soon fail again if it is re joined. It will also happen a lot sooner if you leave the blade fully tensioned after each use.
Attachments
451 Bandsaw Blade Silver Soldering Fixture (after H. Hawkins).jpg
452 After Silver Soldering.jpg
Mr Ron
Posts: 2126
Joined: Tue Dec 22, 2009 12:36 pm
Location: Vancleave, Mississippi

Re: Machining Setup's with Few Comments

Post by Mr Ron »

What alloy of silver solder do you use?
Mr.Ron from South Mississippi
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

Pretty much any high silver content silver solder, the same types as when silver soldering copper model locomotive boilers. Either thin strip or small dia. rod (1/32" or 1/16" dia.). Just looked in my "scrap" silver solder box and am reading on one Easy Flo 45 no cadmium and on another Silvaloy A 45 non cadmium.

I forgot but with Easy Flo there is Easy Flo 35 and Easy Flo 45. One of them forms a good fillet which is good for model locomotive boilers and fittings but you don't want it for this application.
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

Continuing with the struggle to sharpen all of my end mills on the surface grinder (SG) and with the various other fixtures which I have either bought or made to date.

This thread deals only with sharpening the ends of my HSS end mills and not the spiral cutting edges which involves another type of fixturing which I have but have not used to date.

This has become an all out battle and I am determined that I am going to win it (at some yet to be determined cost).

From the easiest to the most difficult type of end mill to sharpen. I will stick to two and four flute end mills as these are the most common although I have end mills having up to 10 flutes. As the number of flutes increases on an end mill, the difficulty in sharpening the end mill end teeth increases due to the smaller space between adjacent flutes and teeth.

The first photo shows a near new four flute end mill having centre relief provided by the end mill manufacturer. It is not that difficult to sharpen such an end mill on the SG utilizing a commercial end mill sharpening fixture as one only has to sharpen the primary and the secondary clearance angles or facets. This is what is seen on many videos describing end mill sharpening.

But what happens when the centre relief on the end mill disappears with repeated sharpening? If one wants to keep using the end mill, one has to get into what is known as the "gashing" operation which will restore the centre relief but not the way as seen in the first photo.

Next is shown a variety of two flute end mills all of which have "centre relief" but not in the same way as shown with the four flute end mill. You will say that they don't have any centre relief as they are all centre cutting two flute end mills but they do - it is what I call "the third facet" which is ground at right angles to the cutting edges on the end mill. If you look at any new, two flute centre cutting end mill, you will see that the third facets are ground such that, at the centre of the end mill, they exactly come to or form a point which is the centre relief.

Producing this third facet as stated above is very difficult to do without having a high quality tool and cutter grinder and even having a good SG it is a step up in difficulty.

Another step up in difficulty is size. The smaller the end mill of whatever type, the more difficult it becomes to sharpen as everything becomes more critical and fussy to do the grinding correctly.

The last photo of a four flute end mill is one which I have deliberately destroyed on its end. It has no centre relief, it has no cutting teeth and it is small (1/4" dia.). It is the challenge which is going to test my methodology to the limit.

Preparation is everything here. In the last photo you will see the commercial end mill grinding fixture used, the aluminum angle spacer piece, the grinding wheel and the eye loupe used. Also good lighting is essential and I mean it as things have to be aligned to the best your eyes can see with and without magnification.

The grinding wheel first. I use a 120 grit open bond straight wheel when grinding HSS end mills. More commonly, a cup wheel is employed and there are advantages to using one but I don't as I have gotten used to the devil I know. I only grind in 0.0005" or 0.001" feed increments so there is not an issue with burning the HSS. This wheel produces a very fine keen cutting edge. The traditional test of any machine tool cutting edge is, can you cut the hairs on the back of your hand with the finished cutting edge and with this wheel I can. Don't scrape too hard as it is like using a keen razor blade.

This grinding wheel is dedicated to sharpening HSS only and is not used for any other purpose. It is critical to have a sharp 90 degree corner on the wheel at all times so the wheel is diamond dressed on its periphery and slightly up one side closest to the operator for about 1/8" all at the same time.

With any commercial end mill holder/sharpener, a critical feature is the indexing must be very positive without any shake or slop so buy a recognized brand. Even so, I had a problem with this American make one as in some places the indexing was "mushy" until I discovered that the collet end cap was binding slightly against the body of the unit in places, so buyer beware.

What does the tapered aluminum spacer piece do? It is tapered 2 degrees and it is essential if one is using a straight wheel to do the sharpening. They don't tell you this on any of the internet videos on end mill sharpening.

The end mill is first held in the sharpener fixture (on mine it is done by tightening the end cap on the bottom of of the fixture to the 5C collet threads - very fiddly as this has to be done with the sharpener fixture held up side down and the cap partially tightened so that it grips the end mill but not fully tight so one can still turn the end mill by hand) and a tooth is aligned square to the edge of the grinding wheel.

The above is easy to say and not so easy to do.This is where the eye loupe comes in. If you do it by eye only, it is a guess and by golly operation. More about this later.

Once a tooth has been aligned square to the grinding wheel, the two degree tapered spacer is then inserted between the fixture and the magnetic chuck back rail. I will show a photo of this later. The smaller end of the taper points to the LHS on the magnetic chuck when you are facing the SG.

This angles the wheel very slightly so that it grinds at a slight angle. Why, because if you don't do this, the square corner of the grinding wheel will touch the edge of the adjacent or next end mill tooth on a four flute end mill and the cutting edges of a two flute end mill when grinding the third facet on a two flute end mill. If this happens, I can tell you this is the end of the end mill as I have destroyed dozens of end mills this way. If you don't believe me, just try it...

There is much more to the technique so stay tuned.

PS: The caption in the second photo should read various size two flute end mills having "apparentely" no centre relief. I am not perfect.
Attachments
132 A Four Flute HSS End Mill Having Centre Relief.jpg
133 Various Size Two Flute End Mills Having No Centre Relief.jpg
134 A Small Ground Away Four Flute HSS End Mill with No Centre Relief or End Teeth.jpg
125 The Start of the Setup on the Surface Grinder.jpg
Last edited by Carrdo on Mon Dec 07, 2020 11:38 pm, edited 6 times in total.
pete
Posts: 2518
Joined: Tue Feb 10, 2009 6:04 am

Re: Machining Setup's with Few Comments

Post by pete »

Many thanks for taking the time for this Carrdo. This board really should have a "like" button though.
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

To continue, the sketch shows how the grinding fixture and an end mill is presented to the corner of the grinding wheel at a slight angle. The sketch shows the gashing or the third facet grinding of a two flute end mill. The shaded part of the end mill is the primary relief facet having the cutting edge. The angles shown in the sketch are a bit exaggerated to show the operation more clearly.

One can see that the grinding wheel grinds deeper towards the centre of the end mill but still clears the cutting edge of the end mill which is so important. It also shows why having a truly square corner and keeping it that way on the grinding wheel is very important.

To grind the third facet, one starts at the outer edge of the end mill or half way into the radius or centre of the end mill and slowly advances the grinding wheel towards the centre while also deepening the cut in very small depth and in feed increments of 0.0005" or 0.001". Whatever one does on one side, the fixture is immediately indexed 180 degrees (for a two flute end mill and 90 degrees for a four flute end mill) to make exactly the same cut on the opposite side or the next facet.

As one moves closer and closer to the centre of the end mill the third facets grow until they meet at a point in the centre. This is easier to say than do as always there is the danger that one will in feed a little to far and the edge of the grinding wheel will touch the cutting edge. This is where good lighting and the eye loupe come in to know exactly where the outer edge of the grinding wheel really is. Unfortunately, as the grinding wheel outer edge approaches the centre of the end mill, everything becomes more and more obscure. I can only tell, in the final stages of the grind, what has happened after the grinding wheel has made the pass and the SG table is traversed to show the last cut. So at the end, one has to be very careful and only take very small cuts to see how far the wheel has ground down towards the cutting edge. The rule of how far to go, ideally, on the last cut, is the wheel edge runs from the centre of the end mill down the cutting edge to just about half the radius of the end mill and stops before the the scalloped part of the cutting edge (the flute) which extends from the tip of the end mill.

All of the above is easier to show than to describe but just look at a new end mill and you will see this.

To be continued.
Attachments
140 My Sketch Showing How the End Mill Grinding Fixture and End Mill is Presented to the Corner of the Grinding Wheel at a Slight Angle.jpg
Carrdo
Posts: 1444
Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Re: Machining Setup's with Few Comments

Post by Carrdo »

One thing which I did not discuss with the 1/4" diameter challenge 4 flute end mill was how the butchered end mill was initially aligned?

Usually, I use the Washburn fixture which I made to align an end mill tooth square to the grinding wheel (see photo # 1) but in this case since all of the end teeth on the end mill had been ground away, this was not possible.

Simply put, I did it by comparison. I took a similar size 4 flute end mill and aligned it in the Washburn fixture noting the rotated position of the spiral at the end cutting edge. Then, I rotated the butchered end mill via its spiral cutting edge to exactly the same rotational position as the end mill in the Washburn fixture. I then drew a fine line across the end of the butchered end mill to simulate a tooth position to give the starting-alignment point for grinding. A bit crude but quite effective.

The last photos show the various grinding stages and setups used throughout the end mill grinding operations. In this case, I am showing a 3/4" diameter 4 flute end mill first as this shows better detail in the photos. I always start the grinding operations with the secondary relief angle if the end of the end mill needs more than a touch up.

This is followed by the actual results for the butchered 1/4" dia. 4 flute end mill but they are not quite as clear.

To be continued.
Attachments
126 Aligning a Cutting Edge on a Three Quarter Inch Diamater Four Flute End Mill Using the Washburn Aligning Fixture.jpg
127 Using the Commercial End Mill Grinding Fixture to Grind the End Mill Secondary Angle.jpg
128 The Two Degree Tapered Spacer Piece Needed when Grinding a Four Flute End Mill with a Straight Wheel.jpg
135 Stage One Grinding-Grinding the Secondary Relief Angle.jpg
136 Stage Two Grinding-Grinding the Primary Relief Angle.jpg
137 The End Mill After Grinding the Secondary and the Primary Relief Angles.jpg
Last edited by Carrdo on Wed Dec 09, 2020 12:34 am, edited 1 time in total.
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