2015 POTD Thread Archive

I barely crimped one edge of the wrist pin hole in the rod, light press fit in the piston. I dabbed some loctite in the rod's end, then pressed the pin through with a small c clamp. Got in it's final location with a tiny brass drift and a scrap of steel for a mallet. Then a douse in carb cleaner, and some paste wax to buff it out. Not a difficult, or long project, but immensely satisfying when my brother asked where I found it, and I replied that I made it. His wife had seen the pictures of it's production, but was stunned at the finish (I like shiny), and the weight. All I used was a piece of 3/4" 1018 CRS and a small piece of shafting from the small parts junk bin. Polished up starting at 400 grit, finished with 1000 grit paper.
 
Had a play this afternoon .. at making a fluted knob as I intend to make several out of aluminium with steel inserts incorporating a free moving shouldered stand off washer .
They are to replace missing cover closers that screw on threads poking out of access covers and also to replace several small " Wing nuts " that I'm finding increasingly difficult to work due to loosing sensitivity in my finger tips because of type two diabetes.

To get the flutes I used a simple high quality 1/4 shanked wood router spade blade in my lathe , making seven light passes on the aluminium bar I'd turned down at one end so it will easily fit the boring bar holder on my QCTP.

Getting the spacing's for the flutes was done using a 6 " diameter motorcycle engine timing disk that is marked off in degrees , mounted on a threaded bar I'd put in th back end of the aluminium bar. Then using a single loop of thin stainless steel wire I hung a 2 foot long thread made into a pendulum using three 19 mm nuts for the weight. Hung off the threaded bar so it was one and a half thread pitches from ( almost touching ) the timing disk.

As first flute cut at bottom dead centre ( BDC ) , loosen the clamp screws rotate 40 degree second tighten the clamp screws , rotate to 80 third .. 80 through top dead centre to 40 degrees make fourth and so on till I almost made it right round then i noticed some thing .. can you spot the deliberate mistake and work out how it happened .

The timing disk has an 8 mm centre hole :-
( I might end up putting an 8 mm holed double sided bush in here and use an Allen key set screw to hold it in place )

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The hastily modified end product.:-
Well we all have to learn somewhere yet still make a few mistakes

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So did you see where it went wrong & why ?

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So did you see where it went wrong & why ?
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Given the way the wheel is marked I guess an error is easily made. I count 8 flutes where you should have 9 (360/40). I suppose you gained or loss 20 degrees somewhere?
Before I had a rotary table and mill I wrapped a piece of masking tape around the back of my lathe chuck and marked off 5 degree increments using dividers and added a pointer off the headstock. You work with what you have. Using the timing disk was being resourceful. Good work.
 
jmhoying said:
I made a storage rack for R8 accessories for my Bridgeport clone mill.
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Very nice job all around. Too big? No way.

If I understand the design correctly, the 1" rods slip into the receivers (bolted to the mill). I would be concerned that, over time, vibration might cause the rack to work it's way out of the receivers. I would implement some sort of positive mechanical retainer at the joint. Maybe weld a nut onto the OD of each receiver (drill & tap thru) for setscrews or even thumb screws. Better safe than sorry.
 
mws said:
Given the way the wheel is marked I guess an error is easily made. I count 8 flutes where you should have 9 (360/40). I suppose you gained or loss 20 degrees somewhere?
Before I had a rotary table and mill I wrapped a piece of masking tape around the back of my lathe chuck and marked off 5 degree increments using dividers and added a pointer off the headstock. You work with what you have. Using the timing disk was being resourceful. Good work.
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You hit on the head fair & square with the timing disk , it's marked in 90 degree quadrants marked in a contra puntal cadence ( I think that's how it is termed :rolleyes: ?) .

If you look a bit more carefully you can see the two thicker ridges , as soon as I'd finished making the first one incorrectly I thought I'd better be a lot more careful .
Then I realised so long as I actually made the flutes @ 40 degrees it would work out giving a second flute that would be cut at 60 degrees .

Now I'll be making a cut off stub with the turned down spigot end so I can add an 8 mm thread rod to enable me to screw on as many more new pieces of aluminium bar as I need to make all the rest of the knobs . That should save me wasting a lot of expensive metal .
 
I had to repair the 400 mm wide cut hand propelled rotary electric mower because my wife Alison decided to try modify it by trimming the lawn's edge with it where the edge runs on to a concrete block step edge. Result a bent blade and the shredding the seven groove drive belt .
I found a supplier of these multi groove belts on line & ordered one ......cost about $ 5 USD .

Getting the blade back to a usable state & resharpened was a doddle ....I stood on it whilst it was laid on the grass, it balanced beautifully once I'd done that & resharpened it with a hand file .

As I was taking the motor & drive shaft housing out the plastic over body I noticed that the drive spindle for the blade was not parallel to the motor drive shaft . The housing had become strained & distorted over a years regular use & my wife's modification attempt , I decided further investigation was needed .
Using the lathe I turned up an aluminium mandrel with a counter bored end to fit over the top end of the drive blade shaft to enable me to knock it out of its bearing without damaging the shaft's end so I could undo the motor mounting screws which were hiding under it .

I tried using very hot water to soften the plastic housing and a block of wood with two " F" type ratchet clamps to bend the mounting carcass back past where it would be true and give it a few fractions of an inch more back bending so when it cooled it would reset back to being true. That didn't work it went back to the distorted form again.

This called for drastic measures.
I packed the housing underneath so the outer edges were parallel to my bench and slipped the " F" clamps on again, gave them a bit of tension then got out the gas blow torch. Six or seven quick wafts of an intensely hot flame on the casing at it's weakest part saw the casing soften and the clamps loosen, so I gave each clamp another tightening action and left things to cool whilst I played elsewhere.

On removing the clamps and slipping some turned up test bars in the shaft holes I was delighted to find that they had reset to being about 2 degrees splayed outwards from true. On reassembling everything and putting on the new drive belt it was heartening to find that the outwards splay was still evident ..that should take care of it getting warm for the next year or two . The rear garden pocket handkerchief sized lawn got a celebratory hair cut .
 
I started with a chunk of cast ally from a muffin tin.
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After heaps of chips I had faced both ends, turned down the middle to a spot on 53.27mm dia to cut a thread to fit the diagonal of the finder scope.
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:headache: It was supposed to be bored and then threaded to fit this
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All my other diagonals have the thread inside not outside, that will teach me to double/triple check.
Oh well, plenty more muffings to choose from and I eventually ended up with this.
Both ends internally threaded 1.0 mm pitch.
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With a bit of 50mm dia threaded tube it all screwed up very nicely.
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extropic said:
Very nice job all around. Too big? No way.

If I understand the design correctly, the 1" rods slip into the receivers (bolted to the mill). I would be concerned that, over time, vibration might cause the rack to work it's way out of the receivers. I would implement some sort of positive mechanical retainer at the joint. Maybe weld a nut onto the OD of each receiver (drill & tap thru) for setscrews or even thumb screws. Better safe than sorry.
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Yes, I have plans for that. The receiver has a thick enough wall for me to put in a set screw or two.

Jack
 
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