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Old 11-13-2017, 10:22 AM   #91
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$50 for postage, that's crazy! Sorry about that. Isn't their some sort of industrial supplier in Australia like McMaster-Carr? Even $3.50 a piece seems like a bit much. As for size, 3/0 in the piston rod only leaves you 1/16" on a side, perhaps that is enough. Make sure the pin is in the very center of the shaft and the cross head is reamed for a very close fit to the piston rod.

David


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Old 11-13-2017, 11:53 AM   #92
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Hi David,if the pins are 1/8 at the bigger end and 2" long i can use the bottom section to give me about a 4.0 or the top end to me about a 3.0.I think i would orefer to use 1 slightly larger pin than 2 smaller ones.I also bought some 3/32
rollpins.I have pinned them 2mm for the moment to check the stroke is central to the cylinder.May need to adjust but i am awaiting endmills to finish the cylinders before i do anything else


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Old 11-13-2017, 02:41 PM   #93
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I guess you could use 1 larger pin instead of two smaller pins. But, something to consider, is that the entire weight of the locomotive and the train is bearing on the cross head to piston rod connection. With one pin per cross head instead of two, this weight bears even harder on the hole through the cross head. The socket in the cross head for the piston rod has a very thin wall. One large hole might start to elongate with time. There must have been reason for our friend Marty to specify two pins per cross head. I'm sure you will make the right choice for yourself.

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Old 11-13-2017, 03:47 PM   #94
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Baz,

Ok, it is a UK supplier, but that shouldn't cause a problem.

For small steel and brass taper pins (metric), try these

http://www.proopsbrothers.com/assort...1159-430-p.asp

It is also worth immersing yourself in the website, I always find lots of other small things that I want. They do really cheap brass wire brushes for fitting onto a pigtail, great for removing dirt and debris without doing further damage.

Imperial taper pin reamers, had mine a long time and no problems, great price for a full set

http://www.tracytools.com/taper-pin-...t-hss-1-16-1-4

or if you want metric reamers, but only individual

http://www.tracytools.com/taper-pin-reamer

Again, always a good read if you are after odd cutting tools.

Even though the pins are metric and the reamers are imperial, I have never had trouble fitting them together at these small sizes, metric is 1 in 50, imperial is 1 in 48


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Old 11-14-2017, 04:06 AM   #95
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Thanks John ,i have ordered 100 small taper pins for about $15 posted
I only have a reamer for the largest size but for that price i can afford a couple more smaller reamers.Will also get 4 at 1/8 local for $3.50 each and that
should cover me.
Yes David i have thought about the load on the pins so i dont know which way to go yet.I followed the drawing for the cross head and machined the collar on the end which leaves me less room for 2 pins,also thought about pining at 90o
with one vertical if i can get them out.All to be concidered in the near future
Meanwhile after a few days in the shed with the outside temp in the mid 30s
and the shed getting up over 40oc i have almost finished the screw reversing
gear. Just used an M6 s/s rod,made the wheel etc.Finish is a little better than my average.Click image for larger version

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Old 11-14-2017, 10:47 AM   #96
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Nice work on the reversing screw, looks good!

If and when you pin the cross head, I suggest that you try to put the large end of the pins in the upward direction, so, if anything was to ever loosen, the pin(s) do not fall out. I put both of my pins in such a way that they can also be removed with out too much trouble. They are installed at about 45 degrees from vertical. This made for a crazy set up to drill for the pins, attached is a photo of the set up.

The adjustable parallel was used to make sure the cross head was pushing hard on the piston rod before drilling. This was drilled as an assembly to make sure everything was lined up well.

David
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Old 11-14-2017, 12:45 PM   #97
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Nice set up for drilling for the taper pins.I still have to remove some matl from
the end of the piston rods to centralise the piston this may cause a problem with opening up the 2mm holes for say a 3mm taper pin.With the lever arms
i remember from the dim and distant past it was good practice to drill and tap at 90o for a grub screw to hold in posn for drilling and fitting the taper pin
Not practical for the cross head but i realize i need to clamp down or bottom the rod before drilling Will all come out in the wash
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Old 11-14-2017, 12:55 PM   #98
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Just noticed that on you reversing screw the 3 bearing blocks are milled much deeper than 1/8" that my drawing shows.Much more positive guide for the 2 fixed and 1 moving block. Also like your small wheel bit more shape than mine
Once i get mine up to a certain stage i may remake some items for improvement.Also toying wit the idea of single point screwcutting a new 2 start
screw. Would have to make a tap also,cant see how i could cut a 2 start 1/4" internal thread single point. How did you do it ?
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Old 11-14-2017, 02:42 PM   #99
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Yes, the nut for the reverser screw was a challange! I ground a piece of 1/4" HSS into a miniature boring bar. (Much "quality time" spent in front of the grinding wheel.) The "boring bar" had the end ground such that it had a 60 degree cutter on the end to make the thread. No photos of this right now, but, I may post one later today. Before making the thread in the reverser nut block, I did a "practice" run on a simple round piece of brass just to prove to myself that I could actually make this thing!

The reverser wheel is modeled after the plastic hand wheels on my little Unimat 3! I really like the shape and feel of them, so the reverser got one made of steel. I still use my little Unimat for many of the small parts. It's so much easier to fee what you are doing on a small machine. I can also get the RPMs up much higher on my Unimat. The Unimat is also handy for a miniature high speed drill press.

David
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Old 11-14-2017, 10:17 PM   #100
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I have a sieg C4 lathe and then got a bought a cheap sc3 to to mod up
Main advantage of the small lathe is you can reverse the lead screw thru
the tumbler gears so can cut a left hand thread.May try making a tap from
silver steel just for the excersise.If i can make a tap the i can make a short length of 2 start thread..The drw shows 1/8 silver steel pins pressed into the brass sliding block but there is not much depth did you have any problems
I have in mind to make top hat pins and press into the reach rod
Meanwhile i have reposted my thread on the small sieg and mods you
might find it interesting.Are you going to start posting your own threads ??


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