Tips and tricks in machine tool practice

Jeremy Suter
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Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Fri Dec 24, 2021 9:32 pm

Stephan.wintner wrote:Jeremy, I was thinking about the turning technique below - using a steel rod with a hole to produce a radius. You state that a 4mm diameter hole will produce an 8mm diameter ball end, or 4mm radius.

I'm thinking the resulting surface is actually an elliptical shape, and the chord of the surface would be 4mm. Which works out to approximating a 2.8 mm radius (4 * sin45) - is there something I've overlooked? I assume you hold the steel tool such that the circular edge of the hole contacts the work all around.

Stephan

Hi Stephen
I never thought about the maths, but when the 90 degree angle on the cutting edge stops cutting, its before it reaches an equal angle on both sides of the cutting edge. It stops cutting and more polishes.

I have just spent the afternoon doing it to check it works and show how its done.

Drilling a piece of silver steel with a 4mm hole and squared off with approx. .75mm flat edge.
IMG_6857.JPG

I have tapered the outer side so I can see where it is on the brass to be turned
IMG_6856.JPG

A piece of 8mm Brass in the chuck. Always start by rounding the end with a file first.
IMG_6863.JPG

IMG_6864.JPG

Lathe spinning and hand tool pressed against brass. Keep rear of the toll moving in a cone shape style with the cutting edge pressed hard against the brass rod.
IMG_6866.JPG

The black line across the rod is 4mm from the end.
IMG_6865.JPG

Keep on going as before working to that line
IMG_6867.JPG

Notice the marks on the cutter where I have fallen off the rod and hit the chuck as it needs some pressure.
when the cutting edge meets the bar all the way round the cutting edge you should have an equal radius.
IMG_6868.JPG

I had to put the cutter back in the lathe and refaced the cutting edge. I didn't hardened the tool and should have. It definitely needs to be for brass.
IMG_6870.JPG

Looking at the end you can see how much still needs removing so work the cutter for the centre to the outer edge.
IMG_6869.JPG

Just finished and polished the length and ball of the rod with emery.
IMG_6872.JPG

Putting the cutter back on the end to polish to a shine to show what's been cut.
Then measured from the end to where the curve starts. measuring the shiny end.
I have had to pose this picture as I used the pin on the other end of the callipers to measure.
IMG_6873.JPG

With a bit of effort I could go most of the way round to form a sphere.
IMG_6874.JPG
IMG_6875.JPG
IMG_6877.JPG

Measured across the diagonal not across.
IMG_6876.JPG

The tool is a bit scratched from where I fell off the ball and hit the chuck I also had to reface it 4 times.
IMG_6878.JPG

I have just cleaned up the lathe and thought I would just check again. 7.98mm
IMG_6880[1].JPG
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Tips and tricks in machine tool practice viewtopic.php?f=132&t=6350

Stephan.wintner
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Re: Tips and tricks in machine tool practice

Postby Stephan.wintner » Sat Dec 25, 2021 7:04 pm

Cheers Jeremy. I'm going to try that out when my lathe arrives. I'm still puzzled - there's something I'm missing about the math & geometry but it clearly works. I may have a go in my 3d CAD to try and see what I'm missing.

Stephan

Jeremy Suter
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Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Sat Dec 25, 2021 11:04 pm

Stephan.wintner wrote:Cheers Jeremy. I'm going to try that out when my lathe arrives. I'm still puzzled - there's something I'm missing about the math & geometry but it clearly works. I may have a go in my 3d CAD to try and see what I'm missing.

Stephan

Its not the maths your looking at but the angle of the cutting edge to the circle when the angle nears the equal point it stops cutting on the inside and starts wanting to cut on the outside edge It probably works the other way round on a larger radius curve but I have never tried.
Tips and tricks in machine tool practice viewtopic.php?f=132&t=6350

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Hardwicke
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Re: Tips and tricks in machine tool practice

Postby Hardwicke » Tue Dec 28, 2021 8:10 pm

I was about to try the wheel form tool today but found my mounting block won't hold such a small tool. Which block do you recommend? Myford ML10
20211228_200525.jpg
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Hardwicke
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Re: Tips and tricks in machine tool practice

Postby Hardwicke » Tue Dec 28, 2021 8:15 pm

I did turn down the flange on a wagon wheel as a test. Straight plain cut tool.
20211228_175825.jpg

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Jeremy Suter
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Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Tue Dec 28, 2021 10:49 pm

Hardwicke wrote:I was about to try the wheel form tool today but found my mounting block won't hold such a small tool. Which block do you recommend? Myford ML10


I can't say I recommend any block. I always mount my tools in a Adjustable Quick Change Tool Post, but looking at your pictures It might be easier just to block it up with some shim steel under the tool the Society Flangeway gauge works quite well for this. Or even fit it in the rear tool post upside down as its adjustable, although I would not recommend that for a first go.

Myford do make a very nice quick change tool post which will fit the ML10 . Not cheap but well worth the money in the end. For small tools I do block them up or out so the tool sits under the tightening screws.
IMG_6927.JPG

The holders are adjustable for height with the screw at the back and are available separately.

you can see a piece of filler metal to push the cutter under the screws its not fixed tight and will slip out. before use.
IMG_6928.JPG
IMG_6929.JPG
IMG_6930[1].JPG
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Tips and tricks in machine tool practice viewtopic.php?f=132&t=6350

Terry Bendall
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Re: Tips and tricks in machine tool practice

Postby Terry Bendall » Wed Dec 29, 2021 2:31 pm

Hardwicke wrote:I was about to try the wheel form tool today but found my mounting block won't hold such a small tool.


Jeremy Suter wrote:looking at your pictures It might be easier just to block it up with some shim steel under the tool


For those without the luxury of an adjustable tool post, using some packing under the tool is the standard way of bringing the tip up to what is called centre height - the horizontal center line of the lathe spindle. I have a four way tool post for my Cowells lathe and the picture below shows the packing under the tools although slighly out of focus since the picture was intended to show the use of a form tool. The packing can be of any convenient thickness.

Using a form tool is a good way of starting to turn a sphere or a dome which can then be finished off with the tube that Jeremy showed earlier in this post.

Terry Bendall
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Hardwicke
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Re: Tips and tricks in machine tool practice

Postby Hardwicke » Thu Dec 30, 2021 11:50 am

I had hoped it would fit in this cradle/boat. Alas, it doesn't.
20211230_114236.jpg
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stephenfreeman
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Re: Tips and tricks in machine tool practice

Postby stephenfreeman » Thu Dec 30, 2021 3:46 pm

Went over to to quick change post years ago, still got the original tool holder, which I don't use, it takes half-inch tools (don't have any now) whereas the Quick change are smaller.

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Tim V
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Re: Tips and tricks in machine tool practice

Postby Tim V » Thu Dec 30, 2021 6:58 pm

Quick change tool holder, you won't look back. I see there are some offers at RDG.
https://www.rdgtools.co.uk/acatalog/Qui ... yford.html
Tim V
(Not all railways in Somerset went to Dorset)

BrianW
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Re: Tips and tricks in machine tool practice

Postby BrianW » Fri Dec 31, 2021 6:44 pm

I have one of these https://www.warco.co.uk/quick-change-to ... results=10 on my Warco lathe.
They are marketed as suitable for Myford 7. I find it sturdy with accurate repeatablility when changing toolholders.

Specification quotes 10mm capacity, but it takes up to 1/2" square toolbits (below).
323QCTP0_5toolbit.JPG


Red toolbit is 10mm square.
325QCTPfitted.JPG


Main block is 58mm square overall by 37mm high.

BrianW
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Hardwicke
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Re: Tips and tricks in machine tool practice

Postby Hardwicke » Fri Dec 31, 2021 8:43 pm

Here's the wheel holder/collet.
20211231_202847.jpg

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20211231_202832.jpg

20211231_202721.jpg

20211231_202614.jpg

20211231_202528.jpg

20211231_202459.jpg
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David Knight
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Re: Tips and tricks in machine tool practice

Postby David Knight » Fri Dec 31, 2021 9:17 pm

FWIW here is a link to the site that features this item.

https://www.fohrmann.com/en/wheel-holding-fixture.html

By strange co-incidence I had been trying to remember the name of this company as a link had been posted some time back, by Ivan IIRC, and I remembered they had some very interesting tooling.

Cheers,

David

Jeremy Suter
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Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Sat Jan 01, 2022 1:07 am

Mike
Looking at the picture of your wheel in the arbour you might want to put a washer or 3 in to space out the wheel from the Knurled Nut as they are about the same size and the Form Toll will want to cut into it when you are profiling. Or Turn a bit off it first.
Tips and tricks in machine tool practice viewtopic.php?f=132&t=6350

Terry Bendall
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Re: Tips and tricks in machine tool practice

Postby Terry Bendall » Sat Jan 01, 2022 8:35 am

An interesting device which would be possible to make without much difficulty. It still requires a three jaw chuck which is accurate and true or needs to be held in a collect chuck or a four jaw chuck.

Jeremy Suter wrote:you might want to put a washer or 3 in to space out the wheel from the Knurled Nut


Or turn up a simple spacer - basically a thick washer which may be more accurate.

Terry Bendall

Jeremy Suter
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Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Fri Apr 08, 2022 7:14 am

Turning a Dome in 7mm scale for a Stanier 262t which has a tapered boiler and will go for casting.

Two things to note.
. A tapered boiler is a cone and its lying on its side so the base is parallel to the track.
. That means the angle of the fly cut is twice the angle of the cone.

The dome I am doing is sitting on a centre line diameter of 36mm at an angle of 3.6o and a cone taper of 1.8o.
dome.jpg


So the first job is fly cut the base. Setting the fly cutter to an 17.5mm radius. Slightly less than the centre diameter
IMG_7038.JPG


The brass bar to be cut is set to the angle of the total incline of the boiler 3.6o .The left hand side closest to the cutter so the bar is cut at the 3.6o angle with a parallel cut.
IMG_7059.JPG


The bar is fly cut to 17.5mm radius, parallel cut.
IMG_7057.JPG


Now I have altered the angle of bar to be cut to 1.8o to do the taper.
Which is not possible without allot of altering of the cutter radius.
IMG_7043.JPG


I have replaced the fly cutter with a taper cutter set at 1.8o.
IMG_7060.JPG


This takes several cuts at the same time. So I will slowly drive the bar across the cutter.
IMG_7044.JPG

IMG_7061.JPG


Once all the way in so that the 18mm radius is at the centre line of the bar.
IMG_7062.JPG


This leaves small lines where each cut does not meet the one in front.
IMG_7046.JPG


To remove the lines on the base I shunt the blade along slightly.
IMG_7064.JPG


Then run it in again to the same 18mm centre line point. This takes out the cut lines.
IMG_7049.JPG


Any lines left can be removed with emery paper easily.
IMG_7051.JPG


Just sowing it sitting on the cutter to show cut angle.
IMG_7050.JPG
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Tips and tricks in machine tool practice viewtopic.php?f=132&t=6350

Jeremy Suter
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Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Fri Apr 08, 2022 2:08 pm

Moving on to the top of the Dome.
I have replaced the tool post and set the bar in the chuck to form the basic shape in the dome.
IMG_7067.JPG


I'll miss out the mounting the spigot and parting off as this has been covered in earlier posts. (Or I forgot about photographing that bit).

Now mounted in the cross slide for the flare to be done. The base whatever the shape will follow the guide.
IMG_7068.JPG


Not the best picture to show that the cutter is cutting in the right place. It has started cutting the top of the boiler on one the right hand side.
IMG_7069.JPG


The flare is fully done now and the angle its set at can be clearly be seen.
IMG_7071.JPG


Now with a bit of filling and polishing the base is cleaned up ready to set the height of the dome.
With this the dome is basically done
IMG_7072.JPG


This is done by slim cuts passing the cutter backward and forwards until the centre height is slightly higher than the 7.19mm the finished dome needs to be.
IMG_7074.JPG


The next step I need to form the Radius on he top its about a 6 inch radius. So will have to be done by eye using the side of a flat cutter rather than the point.
IMG_7098.JPG


This is mounted in the tool post leaning backwards father than forward.
IMG_7078.JPG


Starting at the outer edge then moving in slightly and changing the angle so I can cut the net section and so on done several times until I am satisfied with the curve and polished with a emery board for a smooth curve.
IMG_7077.JPG

IMG_7076.JPG


When finished I need to smooth off and make all flow together.
IMG_7080.JPG

IMG_7081.JPG


Top now done. I have used large file to round off he corners and smoothed with fine emery. The sides are also tapered and the flare tightened from the original ball cutter that did the flare.
IMG_7082.JPG


Then final job on the dome is to put the rivet detail on starting at the top of the boiler. I need to put 6 pop marks in equally spaced. Using the index wheel on the back of the spindle and a drill to make the pop marks in the front resting in a guide so that the same position is found when I rotate the dome by 60o 6 times.
IMG_7083.JPG


Once pop marked they can be drilled out .45mm.
IMG_7084.JPG


All drilled out they are then filled with 45mm brass wire.
IMG_7085.JPG


Soldered in position from below.
IMG_7086.JPG


Then filled back using a ring around the top so all are the same height.
IMG_7087.JPG


When all the same height the back needs to be trimmed flush.
IMG_7088.JPG

IMG_7089.JPG

IMG_7090.JPG


Now the dome is finished and slotted onto a piece of sheet rolled to represent the tapered boiler. and a snug fit all the way round
IMG_7092.JPG

IMG_7104.JPG

IMG_7101.JPG
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Terry Bendall
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Re: Tips and tricks in machine tool practice

Postby Terry Bendall » Sat Apr 09, 2022 7:22 am

Jeremy Suter wrote:Now mounted in the cross slide for the flare to be done. The base whatever the shape will follow the guide.


Lots of useful information Jeremy. Please could you explain how the holding device shown in the second picture works? Do you rotate the dome by hand against the cutter with the spring keeping things firm? What is the purpoose of the thin brass rod?

Thank you

Terry Bendall

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Will L
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Re: Tips and tricks in machine tool practice

Postby Will L » Sat Apr 09, 2022 10:44 am

Terry Bendall wrote:
Jeremy Suter wrote:Now mounted in the cross slide for the flare to be done. The base whatever the shape will follow the guide.


Lots of useful information Jeremy. Please could you explain how the holding device shown in the second picture works? Do you rotate the dome by hand against the cutter with the spring keeping things firm? What is the purpoose of the thin brass rod?

Thank you

Terry Bendall

Terry I think you'll find Jeremy explained this one in the very first post on this topic 5 pages back
viewtopic.php?f=132&t=6350#p67156

Jeremy Suter
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Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Sat Apr 09, 2022 12:53 pm

Terry Bendall wrote:
Jeremy Suter wrote:Now mounted in the cross slide for the flare to be done. The base whatever the shape will follow the guide.


Lots of useful information Jeremy. Please could you explain how the holding device shown in the second picture works? Do you rotate the dome by hand against the cutter with the spring keeping things firm? What is the purpose of the thin brass rod?

Thank you

Terry Bendall

As Will points out I have shown this jig before. But a few close ups of the jig and another description always helps.

The Jig is sitting in the back tool post of the lathe without any work in. The centre line of the chuck is in line with the centre line of both rods in the jig.
There are two rods running through the jig . The one on the right is to mount the brass Chimney or Dome , and is 1/8 inch steel. There is a brass handle at the back and a spring between the handle and the body.
IMG_7132.JPG

The second on the left is a 2mm brass tube with a 1mm nickel silver wire slotted in and folded over at right angle thus producing a shelf for the rim of the item to be machined to sit on. The fold in nickel wire sits in a groove in the brass tube to keep it steady although the screw that can be seen underneath is holding both the brass tube and the nickel wire in position. It has also been pushed slightly away from the steel rod as the last Dome I did was sitting slightly off the end of the nickel wire.
IMG_7133.JPG

Here it is out of the tool post and upside down where the 10BA Streel screw that holds the brass rod in place can be seen.
IMG_7129.JPG

Showing this picture again to show where to start with the cutting.
Set the ball cutter up to the work at the top of the lowest part of the rim which is sitting on the guide. The brass handle depressing the spring so that it does not interfere with the rear of the guide rod and can be still rotated. With thumb on the top of the dome switch on, the chuck rotates clockwise. Using the handle at the back slowly twist the dome anti clockwise it will move away from the cutter as the dome is rotated following the guide. Once all the way round move the dome 3 - 5 thou up and start again.
IMG_7068.JPG

After several revolutions it will look like this. At the end the back will show some ware where it has been running on the guide which is why the guide is made of nickel rather than steel. So when doing the the body of the dome there will be a little bit to come off the rim. A steel guide would cut the back at the same time as the ball is cutting the front.
IMG_7069.JPG

At this point a small amount is taken off the rim first.
IMG_7070.JPG
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Tips and tricks in machine tool practice viewtopic.php?f=132&t=6350

Jeremy Suter
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Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Sat Apr 09, 2022 2:43 pm

Making PETTER Bearings

Most of the time when building locos I use the standard ones supplied by whoever but occasionally I find the generally supplied ones will not fit.
This is such a time. I built this loco 25 years ago from scratch using a pantograph milling machine to cut out the parts at a 2:1 ratio and designed to take Slaters horn blocks. Now I am asked to do the same loco in 4mm scale an NSR 062t New L. So without doing any more plastic patterns or etching I can use the original patterns and reduce on the pantograph milling machine to 4mm by changing the ratio to 3.5: 1.
img20210414_09132176.jpg

As I am not going to alter the original plastic patterns I made just cut the chassis frames to 4mm scale. The horn guide gaps are 4.4mm wide which do not equate to any commercial bearings.
IMG_6127.JPG


So I need to make some.
I copied this Jig from Dick Petter of our area group who sadly died last year.

Note the pin on the side and the clamping nut on the bottom.
IMG_6989.JPG

Note the three holes and the pin in the top and the tightening nut on the left hand end.
IMG_6990.JPG

here it is split down to the component parts.
IMG_7134.JPG


Its a very neat little device that can be mounted in the lathe.
IMG_6994.JPG

Or in the milling machine
IMG_7011.JPG

First of all I will cut some blanks in cholphos ( free turning Phosphor bronze) that is 1/4 inch bar cut to 1/8th inch deep with a 3.2mm hole in the centre 3.2 as against 1/8th means they will not need reaming to allow the axle to spin freely.
Cholphos set in the collet drilled. faced and parted off. I also need a blank top hat bearing with a 4.4mm outside diameter with a 1/4 inch step.
IMG_6974.JPG

With a pile of blanks and a control item I can set up the jig in the milling machine the saw blade is 40mm x 0.7mm thick same thickness as the chassis frames, and is set up against the control bearing.
IMG_7004.JPG

Now with a blank added and clamped in place by the nut on the top. The pin on the top is moved to the front hole which tilts the bearing to the right and I run the saw past it.
IMG_7009.JPG

Now I move the pin to the back hole and the bearing tilts to the left so I run the saw past it again.
IMG_7008.JPG

All I have to do now untighten the nut on the bottom pull the pin in the side out rotate by 180o and repeat.
IMG_7010.JPG

The slots in the bearings look like this, and allow the axlebox to rock in the horn guide.
IMG_7002 (2).JPG

IMG_7013.JPG

Bearings done compensation still to be thought about. beam or sprung
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Tips and tricks in machine tool practice viewtopic.php?f=132&t=6350

Terry Bendall
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Re: Tips and tricks in machine tool practice

Postby Terry Bendall » Sun Apr 10, 2022 8:41 am

Jeremy Suter wrote:As Will points out I have shown this jig before.


Thanks Jeremy. Clearly I was not paying attention earlier. :(

The bearing jig is very neat.

Terry Bendall

John Palmer
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Re: Tips and tricks in machine tool practice

Postby John Palmer » Mon Apr 11, 2022 10:12 am

Two more fascinating sequences. Thank you, Jeremy; most enlightening.

Quite a bit of work must have gone into the taper cutter, which I assume was custom made to provide the requisite 1.8 degree taper. A couple of questions:

1. How did you make/obtain the cutter itself? Looks as though it might have been adapted from a parting tool.
2. When cutting the 1.8 degree taper, how did you establish that you had reached an 18mm diameter at the centre point of the workpiece – was that purely by prior calculation of how far you had to index in?

On the jig for machining the bearings, I note that the mount for the bearings is in two parts, upper and lower. Is that to permit substitution of different components to suit different bores of the particular bearings being machined?

Jeremy Suter
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Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Mon Apr 11, 2022 9:44 pm

John Palmer wrote:Quite a bit of work must have gone into the taper cutter, which I assume was custom made to provide the requisite 1.8 degree taper. A couple of questions:


The taper cutter was made for the job out of a block of steel from my scrap box. Just set it up in the lathe and turned a 1.8o taper on it, so that the centre was 33.5mm diameter then drilled taped and a base screwed on.
After the that I milled out a 1/8th deep slot to fit a piece of 3/16th tool steel in. Then milled the rest of the quarter out to fit a clamp. (Although I didn't go deep enough first time and had to reset it ang go a little deeper which worked in my favour as it was not level and gave resting point for the clamp to lever on).
Clamped a piece of 3/16th mild steel in then re-turned it to bring the excess on the clamp to the same diameter. as the body.
IMG_7136.JPG


1. How did you make/obtain the cutter itself? Looks as though it might have been adapted from a parting tool.


The cutting edge was made from a piece or 3/16th square tool steel.
IMG_7143.JPG

Ground at a unknown angle to allow enough relief when cutting.
IMG_7144.JPG

But the blade is on the wrong side of the quarter. I wanted the body behind it not the clamp. So a groove had to be ground in the front face with a slitting disc to give relief to the cutting edge, then run that groove along the edge of a carborundum stone to sharpen.
IMG_7137.JPG

The slots in the cutting edge were put in with a slitting disc to allow relief on the length of the cutting edge. It would have had allot of chatter without them. ( diagonal lines across the base of the dome.)
IMG_7060.JPG


2. When cutting the 1.8 degree taper, how did you establish that you had reached an 18mm diameter at the centre point of the workpiece – was that purely by prior calculation of how far you had to index in?


I measured where the 36mm Diameter is on the cutter and stopped when it was approximately in the middle of the base. I usually use a plastic disc cut to the right diameter for checking.
IMG_7145.JPG


On the jig for machining the bearings, I note that the mount for the bearings is in two parts, upper and lower. Is that to permit substitution of different components to suit different bores of the particular bearings being machined?


Correct. Different axle sizes require a different mount.
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John Palmer
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Re: Tips and tricks in machine tool practice

Postby John Palmer » Wed Apr 13, 2022 12:35 pm

Thanks, Jeremy.

Confirmed my impression that a lot of grinding work must have been necessary on the cutting tool itself, as it appears that the cross section of the tool steel has been nearly halved. Even if bulk of this was done on a grinding wheel, I presume that the finishing work had to be done on the mill or lathe with suitable precautions to keep the grit particles away - if nothing else this would seem to have been necessary for the grooving, which I take it was done with a suitable disc mounted on an arbour.

Even measurement of where the cutter is cutting a 36mm diameter isn't straightforward, as allowance has to be made for the amount by which the cutter projects above the surface of the coned mount. Aids like that plastic disc gauge become very useful in those circumstances.

Impressive stuff!


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