JowettTalk

A few useful additions have been made to the Jowett Health and Beauty Salon including a trolley for the gas bottles and Digital Readouts for the milling machine and Lathe.




After spending a couple of weeks learning all I could about measurement on lathes and mills, speaking with UK suppliers and looking at helpful DRO websites, I was leaning towards building my own as prices were in excess of £800 per machine. I came close to following an open source project that used available scales (capacitive, optical and magnetic) that connected to a small box of tricks that would revitalise my long lost electronic skills. This connected to a smart phone or tablet and was driven by the open source apps.

However, after scouring the world for suitable scales to fit my machines that did not seem to be available in the UK, I started dealing with a firm in northern China. I had primed myself on shipping and customs as I thought this might be a problem, but it was not. I was amazed at the quality of Engish communication and helpfullness. What is more, the advice received got me to buy the best (1 micron) optical units with 5 times the resolution of those commonly available. I had discounted optical scales because they were only available in 50mm increments in UK and US that meant they would stick out all over the place. This company cut the units to my exact (1mm) measurements. They included covers, brackets and other hardware all in the price. What is more the display units were so good and at a good price I decided not to waste my time building my own. So all up I got the kit for quarter the price with 5 times the resolution.

It has taken some time to design how to fit them to acheive minimum loss of travel, best ergonomics and ability to still use carriage locks. The milling machine was used to make the attachment blocks to the z-axis on the mill and the x and y axis on the lathe.

However, now I might be able to measure within eight one hundred thousanths of inch or two thousanth of mm. Investigations are continuing on how good it will be. This is a new ball park for me!

This was all prompted by the need to check out the blocks I had welded and rebore the cylinders. It will also help with the set-up of the carburettor jig.

Finished the DRO on the lathe today, making up the cover for the compound slide and anchoring all the cables.
Also sealed all the covers on lathe and mill with clear silicone to keep the oil out.
The Gallery album has more detail of the installation.
You have to get the scale and the transducer so that the runout is less than 4 thou or .1mm in 3 axes. This is relatively easy if the fixing points for both end of the scale and the fixing point for the transducer are milled surfaces. I had to make up pads with set screws for levelling for the long x axis on the lathe which has over 480mm of travel. It took me a couple of days of trial and error to get the scale parallel, level and square with .1mm in 480mm using the dial guage on two axes and a set square with a strong light behind it. Then the same with the transducer!

The X axis transducer had a complex set of adjustable brackets.

The lathe Y axis has one milled surface that the scale could attach to but the slide lock had to be redesigned and replaced by a set screw that can be adjusted with a spanner.
The transducer required a pad for adjustment in three dimensions!
Also added a stop to prevent the tailstock crashing into the cover.


This shows the access holes on the compound slide cover for slide lock and the rotation lock and angle viewing cutout.

So now I have to learn how to use my new toys.
The problem I am trying to solve is how to align the throttle spindles on the carburettors. The only face that can be used is the base of the carb and in many carbs this is distorted. Before fixing to the right angle on the mill bed this face was filed flat. Usually a part of the throttle bore is not worn as it is covered by the plate end so this was used for alignment by placing a new spindle into it . This gave a sliding fit with no play. A collet of the correct diameter was put into the quill and the spindle was inserted into it whilst the carb was still loosely clamped.

This gave a rough alignment but tightening the carb onto the right angle would move it slightly so the mill bed was moved to compensate.

The shaft was then blued and the alignment adjusted in the x and y axis using the DRO to get even scouring all around the circumference of the spindle. So as to check vertical alignment this check was done at the bottom and top of the blued spindle.




However, I was still not happy that this would align the carb vertically such that the worn bush (now at the bottom) was in the correct place. The length of the unworn part of the housing is not really long enough to ensure this.

So now plan B (using a centre finder), with a plan C (fitting the butterfly) also to be tried today. The aim is to compare alignments using my highly accurate DRO. Preliminary accuracy is estimated to about 20-50 microns as that is what made a difference with the blueing method. Note it seems to be possible to resolve within 1 or 2 microns, but I have yet to see how repeatable that is.

However, plan B required me to learn which centre finding method was appropriate, so last night I did some research on home machinist

This sent me to a great set of MIT videos, the first one being Machining Skills 1: here.
Duration 40:32
1) Basic
2) Layout Techniques
3) Basic Tools: Drill Press, Band Saw, Belt Sander & Grinder
4) Locating and Drilling Holes
5) Tapping Holes

Machining Skills 2..
Duration 57:33
1) Basic 2
2) Drilling Holes
3) Special Drills for Plastics and Hard or Abrasive Materials
4) Drill Press Limitations
5) Bandsaw
6) Suitable Speeds, Feeds and Materials
7) Bandsaw Setup
Using the Drill Press Vise

Machining Skills 3..
Duration 30:02
1) Basic 3
2) Good Practice - Clean Up
3) Small Belt Sander Configurations
4) Grinder Operations and Materials
5) Deburring and Buffing
6) Finishing Techniques

Machining Skills 4, Milling Machine 1.
Duration 50:33
1 Milling Machine 1 Layout & Use; what the different parts do
2 Quill Feed Allows you to move tool up and down
3 Axis Handfeed Feed/Crank on Axis with Dials to adjust the Bed
4 Gibb Locks Holds/Locks Bed to Saddle & Saddle to Knee and Knee to Body of Machine Locking Ring Adjustments
5 Power Feed Attached to one or more of the Axes Forward/Reverse Knob and Variable Speeed Control
6 Digital Readouts Measure position of Axes to 0.001" or in mm
7 Milling Machine Set-Up Squaring the Head Square=Z-zxis of head [Quill] is perpendicular to axis of Bed
8 Squaring the Vise Adjusting the vice so back [stationary] jaw of vice is parallel to bed Machine Safety, Protocol, & Shop Safety
9 Milling Machine Accessories & Workholding Techniques
Milling Machine Tools
Drill Chuck-drilling & reaming
Boreing Head-more precise cutting to 0.0002"
Fly Cutter-used to square up a part [4 teeth and 1 single tooth]
End Mill-shank type milling cutter
Collett Chucks-holds End Mills
Saws-used to make deep narrow slots-installed on an arbor
Reamers-used to smooth out inside of drilled holes
Edge Finder & Center Finder-used to locate punches or holes on a milled part
Boreing Tool-Used on a shank head to bore holes

Machining Skills 5, Milling Machine 2
Duration 1:03:33
1 Milling Machine
2 Square and Hex Collett Blocks-used to hold/clamp parts to machine features on 4 and 6 sides of a part, respectively 2 V Blocks Holding parts to machine features into parts and end of parts
3 Hold-down Clamps Used to hold large or irregularly shaped parts
4 Using Angle Blocks Used to hold materials to machine features not perpendicular on a part
5 Drill Press Vice Used to hold a part to machine a feature @ 45? angle and other positions/angles Also used with angle blocks to hold parts
6 Lathe Chuck With Vise Used to hold parts in the milling machine; not accurate method, but quick/convenient
7 Double Sided Tape Used to hold a part in a vice securely without distortion
8 Squaring High Aspect Ratio Parts Used to hold a part to be machined securely and squared
9 Right Angle Attachment A right angle gear box to mill features in an end of a larger/slender part that is clamped in the vice.
10 Slitting Saw A saw blade that is used to cut slots/slits/features in a part Can also be used with a right angle attachment
11 Rotary Table A bench/table attached to the bed of the machine used to machine circular parts, grooves, circles, segments
Dial indicator and Co-Axe indicator uses to square/center the Table to the Y axes
12 5 C Collett Indexer Used to hold
Colletts and position parts in up to 24 positions for various milling features

Machining Skills 6, Milling Machine 3
Duration 46:33
1 Milling Machine 3 Squaring a part, maching all surfaces so they are flat and perpendicular to one another and nominally to the part that will be milled; removing burrs
2 Squaring a Plate Squaring the sides of a part/plate to the dimensions of the finished milled part; remove burrs
3 Using the Edgefinder Used to locate the edge of a part relative to the spindle of the machine
4 Drilling Holes Drill press used to drill holes in parts; center drill milling and other drill bits; setting depth stop

Machining Skills 7, Milling Machine 4
Duration 45:33
1 Reaming Holes Reamer is used to make a drilled hole larger and smoother within 2/10000" of it's diameter
2 Boring Holes A Boring Head is used for making very accurate holes; also used on a quill producing more accurate holes
3 Milling a Slot End Mills used to mill slots in a piece
4 Milling a Shoulder Conventional & Climb Milling

A shoulder or step milled into a piece.
Conventional Milling-part is fed against the motion of the tool; best for rough cuts
Climb Milling-Part is being fed along with direction or rotation of the tool; better surface finish cuts

5 Cleaning the Machine

Very important in the use of milling machine; chips, dust, etc.. Needs to be cleaned Only a brush or vacuum should be used. Air should never be used; this risks blowing chips into machine and possibly damaging it Most accidents in a machine shop happen when bringing parts to a machine or when the machine is being cleaned

Machining Skills 8, Lathe 1
Duration 45:02
1 The Lathe Components @ Set-Up Axes and Feeds
2 Turning Tools
3 Turning and Facing
4 Cutting Off a Part

Machining Skills 9,Lathe 2
Duration 47:33
1 Tapping
2 Boring
3 Knurling
4 Cutting Tapers with the Compound
5 Turning Shafts Use of live center
6 Single Point Thread Turning

Machining Skills 10, Lathe 3
Duration 34:32
1 Lathe Chuck
2 Lathe Arbors
3 Turning Between Centers
4 Face Plate Irregular Shapes
5 Face Plate Thin Materials

Keith

If you add a circular location that is a good fit in the choke tube to your angle plate,

Edge find on one side zero the readout edge find on the opposite side then half the reading will give you the centre line of the choke tube.
now all you have to do is clamp the carb onto the angle plate as your photograph, align the existing holes with the best fit spindle that you have, then ream,
I would put the worn hole at the top to machine first, any minor miss alingement is now immaterial as you have determined the centre line from the location.

Hope this helps

Steve

Thanks Steve,
Just come up from the garage where I completed the task before reading your post.
So this is what happened this afternoon.
I first altered the right angle so that I could insert the butterfly to align the throttle spindle.

I also solved the rotation problem by having parallel bars supporting the only other alignment surface, that is where the float chamber fits. This might not have been exact but checking with a precision 7mm bar as a throttle spindle and the new throttle spindle itself did seem to concur.

This was further checked by using the dimple on the new spindle to align using the DRO and then moving the spindle up and down in the collet with some blue on it.
Then the butterfly was inserted and fully closed with a further bluing to confirm alignment.

One thing I noticed when locking the saddle and bed prior to drilling was that both moved slightly around .030mm or less. First one way when tightening a lock and then the other when tightening the other lock. So this had to be taken into account and minimized.

After drilling I had some fun seeing if I could measure the diameter of the hole with and edge finder, and two verniers before reaming the hole to the desired size.

This was new exercise for me after viewing the MIT videos and reading my DRO manual. So I am not sure how accurate my edge finding was. I seem to be able to repeat measure to better than 40 microns. I will need a few more days to confirm this though as errors and movements can creep in all over the place.
It needs some statistical analysis.
Then the press was used to push in the bearings.


Before fitting the new spindle and butterfly.



Whenever fitting the butterfly I always check to see if light will go through and thus completely shut off any air.

Having slept on it, I think Steve's idea of a bar inserted into the barrel might be good for repeatability as I have a few carbs to do. So now need to find some suitable bar to turn down and try out my new toys on the lathe!

Once the bar is made for a sliding fit, a hole where the spindle should go through a diameter (could measure as Steve suggests but will use the V block method for centering a bar) will act as a locator. The hole will be aligned vertically and can be semi-permanently bolted to the right angle. Then the carb will be slipped on and rotated to align the spindle holes with the hole in the bar. The carb can then be bolted to the right angle. One problem may be the variability in the distance between the carb base and the throttle hole as some bases will have been refaced.

The hole in the bar will have to have one or two removeable sleeves as the alignment hole needs to be 7mm with the rebored hole 9mm. This would require the bar to be a cylinder so that the sleeves can be removed after alignment. I will have a go next week with another carb to see how laborious the current method is. It should be a lot quicker the second time.

I will also check out that problem when locking the bed and saddle. Perhaps some wear needs to be taken up in the gibs. I like the use of the dead mallet in this video.
https://www.youtube.com/watch?v=XHMS9FBBsx4

I completed the two carbs last night by replacing a choke spindle and inserting bushes that I had made from tube that I went out to buy. After some careful measuring again, the hole was opened up with a drill, then reamed to get a tight fit of the bush and tight fit of the spindle. Then the bushes were reamed to get a sliding fit.
I also painted all the parts that needed painting and buffed up the bodies and parts with a very fine brass brush. I then struggled with assembling the choke mechanism and will have to look at the before pictures to figure out how it all goes together.

As an interlude I did some measuring tests between my Moore and Right micrometer, a small and a large vernier and the DRO edge finder. As I said previously, this really neeeds to be analysed statistically. It also needs different people to try as each will have a different touch and different capabilities of reproducing that touch. I can see now why electrical, ultrasonic or laser technology has superceeded the finger in gauging distance. Below 1 thou and things get quite hit and miss and, with the DRO being able to resolve down to 4/100th of that, the variance can be startling (but perhaps not significant). The micrometer can be read to 1/10000th inch and the verniers resolve to 5/10000th inch. As I said before, I think the edge finder could be read with a lot of practice and sensitive fingers to 16/10000th or 40 microns when measuring a length. You have to read two edges when comparing a length and I think my fingers can read to about 20 microns on the edge finder. It would be interesting to see how accurate one who reads Braille can do! Note I am not saying here that everyone can use each instrument to consistently measure that accurately. The key thing is to relax and touch lightly to get consistent measurement. Alegedly human fingers can measure 13 nanometers!
Tomorrow will try with the dial guage, but now off to rugby. This video suggests a mechanical edge finder doing the transition should find within .5 thou, 5/10000th inch or 12.5microns

https://www.youtube.com/watch?v=f0od-cp_9dg

I thought I would do some measurement experiments today and then set up the gibs on the mill. I first used the edge finder on the ground parallel bar to measure its width. After some practising I did ten passes on each edge to see what the spread of repeatability was.
The edge finder goes through three phases. As you move in with it out of balance the two cylinders gradually reduce in out of balance and you can guess when they are in balance and read the DRO (Digital Read Out). Then you move a bit further and the finder kicks out as the edge is grabbed and friction kicks it out of balance, you can take a DRO reading here also, then you move back (of course first taking up the backlash in the thread) and take another DRO reading when the finder goes back to being in balance. I used the magnifying glass to accentuate the transition. The three readings give you a spread between transitions which depends on your ability to move slowly and consistently and your reaction time to the change. After practicing I got this down to less than 100/100000 inch. That is of course 1 thou, but I am able to move the bed by just 100000th of an inch if I am careful.



The important point here is the edge is where you detect the return back to balance, not the other two readings.
So then I tried ten times to find the edge and recorded these readings.
+.00000, +.00015, +.00007, +.00011, +.00023, +.00027, +.00011, +.00007, +.00015, +.00011,
Then I moved to the other side of the ground bar and got these readings.
+1.05271, +1.05279, +1.05283, +1.05252, +1.05350, +1.05291, +1.05252, +1.05275, +1.05244, +1.05255.
So the differences are
.00000, +.00008, +.00012, -.00019, +.00079, +.00020, -.00019, +.00004, -.00027, -.00016,
Those statisticians amongst you may be able to get a standard deviation and midpoint for that lot. I guess I could try Excel!

I then tried the dial indicator attached to the collet and recorded this set of readings when attempting to bring the indicator back to the same point. There might be a bit of parallax error in some of these readings and with more care I could make it more accurate.
+.00000, +.00007, +.00027, +.00007, +.00000, +.00007, +.00007, +.00015, +.00003, +.00011, +.00007,

My conclusion here is that the DTI is excellent at finding the edge, but is not much help centering the chuck over a point unless I devise some way of rotating through 180 degrees with consistency. But I think I can probably get to 1/10000inch consistently by taking say 5 readings and discounting the highest and lowest and averaging the other 3.


I then moved onto adjusting the gibs, trying to get a balance between ease of movement and stability. The DTI was placed against the angle plate and the bed was rocked to see if there was any movement. I managed to get it to less than 1/10000inch.

This is one of the two gib adjusters.