Tips and tricks in machine tool practice

Daddyman
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Re: Tips and tricks in machine tool practice

Postby Daddyman » Tue Dec 27, 2022 4:27 pm

Jeremy Suter wrote:Hi David
It had to be done.
When you look at photos of these the spring need to look a little more ornate than those supplied.

1468d Inside Gateshead shed I'm doing 1463 which has different pipe work arrangement for the Westinghouse pump, In fact there seem to be quite a few varying arrangements of the pipe work among the class.


Nicely done, Jeremy!

Yes, there are a few different routings for the W/h piping. A couple of locos had only two coal rails too.

Are you going to be painting it? If so, note how the cab roof is black, and ends at a white line just at the lower edge of the curve into the cab sides. It's easily missed, as there is often a glint coming off the curve, but your photo of 1468 shows it clearly.

Jeremy Suter
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Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Fri Jan 27, 2023 7:49 pm

The Tennant 1463 class now painted

Halfords etch primer, Phoenix LNER Darlington Apple Green and Humbrol Satin Black thinned with Rustins Cellulose thinners, lined with mixture of bow pen and HMRS transfers.
Varnished with MAD Clear Lacquer sprayed neat not thinned . Just needs coal and glazing
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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 Feb 25, 2023 4:01 pm

Correcting badly drilled crankpin holes in Gibson wheels


I have been given back one of my railmotor chassis for completion and the first thing I have done is to strip down what has been done so far. The wheels have had the crank pin holes drilled and all are in different places so the first job is to correct them.
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To do this I need to be able to set the wheel in a position so that the wheel can be drilled and then changed for the next in the same position.
Using a steel block with an axle slotted in and two holes either side, one to hold the wheel in place the other as relief for the drill. The axle has been reduced from 1/8 th to 3.1mm so that the wheel is still a tight fit but the axle hole is not stretched. The clamping hole has been tapped 12ba and a bush has been made to slot neatly between the spokes and hold the wheel in the correct position.
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The wheel fits neatly in place the boss on the back of the wheels keeps the tyre level.
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The jig is fitted in the pillar drill on an adjustable table.
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The drill has a small amount coming out of the chuck to reduce any wander and lowering the drill slowly makes sure I cut a new hole rather than follow the old one.
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once drilled the wheel can be changed for the next without adjusting the table.
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All four were done with a 1.2mm drill but two of them the old hole was still visible so I re-drilled those two with a i.6mm drill.
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Now I have four wheels with larger holes than required for the crankpins. Bushes need to be made.
This is done from 32nd brass rod
Centre drilled with a 0.5mm centre drill.
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Then drill down 6mm with a 0.7mm drill a bit of spit on the small drill help to lubricate and stop the snapping.
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Once drilled I will now tap the hole 14ba a spot of clock oil will help lubricate the tap.
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Now I need to turn the outer part of the bush to fit the holes in the wheel, so for the two 1.4mm holes I turn the outer to 1.45 and try and fit them in then emery paper to reduce to fit they need to be a tight fit in the wheel and some Loctite will be needed.
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The rim is next at 1.8mm.
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Ready to be parted off.
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Now the wheels with a 1.6mm hole I do exactly the same but as this is going onto a Walschealts valve gear chassis there is some extra forces on the rear axle and have decided to go belt an braces on this by keying the bush for the rear axle so the lager bushes have worked in my favour.
So before parting off fully I have fitted the bar in the milling machine and am going to mill a 0.3mm slot so that I can key the bush in the wheel. These small solid carbide milling cutters are remarkably robust and have not broke one yet they go down to 0.1mm on 4mm shank.
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Now fitted and pinned and locktited with .3mm brass wire.
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Steel 14ba screws fitted. I only have the one size but easy to shorten just need to make threaded bushes to hold the coupling rods in place as there is so little room for the pin behind the slide bars.
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Last edited by Jeremy Suter on Sat Feb 25, 2023 10:14 pm, edited 1 time in total.
Tips and tricks in machine tool practice viewtopic.php?f=132&t=6350

DougN
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Re: Tips and tricks in machine tool practice

Postby DougN » Sat Feb 25, 2023 8:06 pm

Dare I say "wow" that is fantastic. The crank pin holes are one thing I dread as I have heard some Alan Gibson wheels need to be drilled. I really like your jig and the idea of making one if I ever end up with some wheels that do need drilling really appeals! Now that I have a unimat that I could do all these things on.

Thanks for the explanation and photos!
Doug
Still not doing enough modelling

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grovenor-2685
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Re: Tips and tricks in machine tool practice

Postby grovenor-2685 » Sat Feb 25, 2023 9:54 pm

Jeremy Suter wrote:Steel 13ba screws fitted.

Is this a typo? Since you tapped 14ba. Or am I missing something?
Regards
Keith
Grovenor Sidings

Jeremy Suter
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Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Sat Feb 25, 2023 10:12 pm

grovenor-2685 wrote:
Jeremy Suter wrote:Steel 13ba screws fitted.

Is this a typo? Since you tapped 14ba. Or am I missing something?

Hi Keith
Yes its a typo but 14 ba screws fitted now original edited to read correctly
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 Feb 26, 2023 9:20 am

A very neat idea :)

Jeremy Suter wrote:a bit of spit on the small drill help to lubricate and stop the snapping.


Alternatively some thin lubricating oil such as 3 in 1 or withdraw the drill to clear the swarf or use the clock oil.

Jeremy Suter wrote:Once drilled I will now tap the hole 14ba a spot of clock oil will help lubricate the tap.


What Jermy did not mention is that the lathe (I assume) would be tuned by hand not under power. The same technique can be used in other situations to make sure that the tap feeds in "square" to the work. Some very light pressure is needed to get the tap started but once this is done the action of cutting the thread should drew the tap into the work. It may be necessary to turn the lathe backwards to clear the swarf, as would be done when cutting a thread with the work held in a vice.

Terry Bendall

Jeremy Suter
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Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Sun Feb 26, 2023 10:03 am

grovenor-2685 wrote:
Jeremy Suter wrote:Steel 13ba screws fitted.

Is this a typo? Since you tapped 14ba. Or am I missing something?

Hi Keith
Yes its a typo 14 ba screws fitted now original edited to read correctly
Tips and tricks in machine tool practice viewtopic.php?f=132&t=6350

bevis
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Re: Tips and tricks in machine tool practice

Postby bevis » Sun Feb 26, 2023 11:36 am

Agree with DougN. Brilliantly simple way of solving this issue. Thanks for sharing it.

Jeremy Suter
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Joined: Tue Apr 14, 2009 6:56 pm

Re: Tips and tricks in machine tool practice

Postby Jeremy Suter » Sun Jun 11, 2023 10:41 pm

Here is another wheel conversion job


The 3'6" wheels for Bamburgh need to look finer and thinner. It has been suggested that the Gibson 3'8" bogie wheels should be reduced to 3'6" so they have finer rims. The wheels also need to be thinned from 2mm to about 1.75mm Light railway wheels are much lighter than main line engines.

Because I need to thin the width down on these wheels it will not be possible to reduce the 3'8" tyres to 3'6" so the other option is to make the 3'6" tyres fit the 3'8" centres and the reason is I will loose the lip on the front of the wheels.

This is a picture of what I need to do to make the small tyres fit the larger centre and thin the tyre down to keep a lip at the front.
The shaded parts are to be removed.
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This job is being done using collets in the Myford lathe. I have fitted an ER25 Collet holder and check that it running correctly.
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As the tyre is tapered I need to check that it is running perpendicular using the dial gauge.
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Because when I tighten the collet holder it moves the tyre closer to the holder I need to make sure all the tyres are in the same place when I start to take out the inside. To do this I mark the collet holder an arrow. I put a paint dot on the cap for this sort of job when I bought it.
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Some of the Gibson tyres are very hard to remove from the centre so I destroyed the smaller centres and cut the larger tyres off.
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Tyre fitted in the Collet.
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I will be using a Boring bar to remove metal from the centre of the tyre.
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Now to cut where I want to I need to start or finish the cutter in the same place each time so that the recess for the tyres match each other so I need to know the backlash on the cross slide and the I already know its 3 thou but to check I use the dial indicator on the back of the boring bar.
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The pen written numbers are where I need to turn the handle to when going into the tyre and the 05 is how where I need finish when I am cutting the depth I need to cut although the arrow should be facing the camera as I am cutting the inside of the tyre.
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Tyre being cut.
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Once cut the inside need to be cleaned with 800grit emery paper held in forceps clamp and also the sharp corner needs softening so the centre cam be pushed in without damage.
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To do the front I have moved it to the Step Collet on the watchmakers lathe.
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The finished tyre on right
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When the insert is fitted it is slightly proud at the back and can be removed in the watchmakers lathe as well.
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and again the front needs to be taken back so that a etched front with crankpin position can be added.
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Left are original right have new centres.
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The last thing is to check the wheels concentricity from the centre hole, using a tapered axle with the tyre slotted on and the dial indicator to check the hole is still central. I did have a couple of failures which is the reason I cut the larger tyres rather than just push the centres out which were the failures.
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Next job is to make new shorter axles.
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