Elmer 25 Build

[lellasone]

Hi All,

A friend (who might jump in at some point) and I are are going to build a wobbler together. We'll each make 2 of our respective parts and then get together some time next month to do the assembly. This is both of our first build so it should be an adventure .

To kick things off here's a 3D printed prototype of the engine. It's missing the oil hole by the flywheel shaft but is otherwise complete.

A few questions for anyone who's got a second:

• A lot of the builds seem to use an angled grub screw rather than the piston + setscrew arrangement, is that just a fabrication thing, or are their problems with method in the diagram.
• Should the pivot pin also have a lubricating hole like the one for the flywheel shaft?

 

[lellasone]

Well it's been a good long time since this was posted, but I do now have the first part to show! The frames (2+ a spare) are finished, except for the oiling hole. The pivot pins are also done, but I may end up re-making those.

One question I have is what people think of 5-40 threads these days? I'm debating between switching everything over to M3/4-40, or getting some 5-40 taps/dies. Do you think it's worth getting the specialized tooling?

 

[minh-thanh]

Hi !

A few questions for anyone who's got a second:

• A lot of the builds seem to use an angled grub screw rather than the piston + setscrew arrangement, is that just a fabrication thing, or are their problems with method in the diagram.
• Should the pivot pin also have a lubricating hole like the one for the flywheel shaft?

One question I have is what people think of 5-40 threads these days? I'm debating between switching everything over to M3/4-40, or getting some 5-40 taps/dies. Do you think it's worth getting the specialized tooling?

Answer your questions the way I would do :
Do what you feel like and want, Use tools that are readily available and easy to find, as long as it suits the design you are building.

 

[stanstocker]

Well it's been a good long time since this was posted, but I do now have the first part to show! The frames (2+ a spare) are finished, except for the oiling hole. The pivot pins are also done, but I may end up re-making those.

One question I have is what people think of 5-40 threads these days? I'm debating between switching everything over to M3/4-40, or getting some 5-40 taps/dies. Do you think it's worth getting the specialized tooling?

I think 5-40 is one of those weird screw sizes that involves a trade off to replace with metric. A standard M3 - 0.5 screw will have the correct diameter but will also have notably finer threads which may be an issue in aluminum. An M4 screw is quite a bit larger than a 5-40 screw in diameter so fits and clearances can require attention, although the roughly 36 TPI of an M4 standard screw is likely just a wee bit stronger than 40 TPI of the 5-40.

4-40 may let you get a more scale like head and nut size on a model at the expense of weaker hardware and weaker threads in aluminum.

Model engineering has all sorts of oddities that come up. Given the cost of all the tooling for machines and the number of taps and dies we end up buying getting a set of 5-40 taps and an adjustable round die on 5-40 seemed like a minor expense compared to always having to mark up drawings and remembering to change clearance hole dimensions as well as the hole to be threaded. Maybe I'm just lazy. PM Research has 5-40 taps for $6.50 and dies for $15.00. Even the posh chromium super deluxe taps for aluminum are around $15 from MSC. MSC also sells three piece sets in 5-40 for around $20.

It's worth buying good taps and dies, with reasonable care it's rare to break one and unless you are dealing with materials that are tough or have inclusions they rarely get dull in a small home shop. Line up well, clear your chips, use the right lubricant when you can, when you don't have the perfect lube at least use a decent one

 

[krypto]

If you want to thread a 1/8" rod you use a 5-40 die. That's handy! It's also a nice size for model work and why you see this old thread size in old plans.

 

[Richard Hed]

I think 5-40 is one of those weird screw sizes that involves a trade off to replace with metric. A standard M3 - 0.5 screw will have the correct diameter but will also have notably finer threads which may be an issue in aluminum. An M4 screw is quite a bit larger than a 5-40 screw in diameter so fits and clearances can require attention, although the roughly 36 TPI of an M4 standard screw is likely just a wee bit stronger than 40 TPI of the 5-40.

4-40 may let you get a more scale like head and nut size on a model at the expense of weaker hardware and weaker threads in aluminum.

Model engineering has all sorts of oddities that come up. Given the cost of all the tooling for machines and the number of taps and dies we end up buying getting a set of 5-40 taps and an adjustable round die on 5-40 seemed like a minor expense compared to always having to mark up drawings and remembering to change clearance hole dimensions as well as the hole to be threaded. Maybe I'm just lazy. PM Research has 5-40 taps for $6.50 and dies for $15.00. Even the posh chromium super deluxe taps for aluminum are around $15 from MSC. MSC also sells three piece sets in 5-40 for around $20.

It's worth buying good taps and dies, with reasonable care it's rare to break one and unless you are dealing with materials that are tough or have inclusions they rarely get dull in a small home shop. Line up well, clear your chips, use the right lubricant when you can, when you don't have the perfect lube at least use a decent one

try this jplace for lower cost but quality stuff: Victor Machinery - Metalworking tools and supplies

Also, 5-40, I believe is 1/8th "

I've gotten to the point that most threading that can be done with a die, I end up doing on the lathe, even small threads as invariably I don't have the right die. If i have the die, I use it, but if not, then set up the lathe. For threads in holes, however, I use taps for small holes and for large enough ones to put on tbhe lathe, which almost invariably would cost a fortune for4 the tap but bigg enough to cut on the lathe, that's where I go.

 

[lellasone]

Okay, thanks everyone for the thoughts, this is awesome! I think I'll go ahead with getting 5-40 gear at least the next few projects.

@Richard Hed Thanks for the link. Any chance you've used there reamers? those rates also seem pretty good.

 

[Richard Hed]

Okay, thanks everyone for the thoughts, this is awesome! I think I'll go ahead with getting 5-40 gear at least the next few projects.

@Richard Hed Thanks for the link. Any chance you've used there reamers? those rates also seem pretty good.

I have about 500 pounds of reamers. Don't need any. They are for sale, want some? I see you live in Chicago. If you are interested, I'm selling unused ones for half price of what Shars sells them for plus shippiong. It would be worth while if you got a lot of them as then I could send them USPS for a one package price to anywhere in US

I also have very good but used ones that I will sell for 1/3 price of Shars. also the well used ones for 1/4, used but still good. Then of course, there are ones I will sell by the pound, rust and generally too well used but if you have a sharpener, they would be fine to regrind.

Ah, but before I obtained my 500 Lbs of tshem, I did indeed buy some from Shars, and they are fine quality. Victors, I use for buyiong left hand taps, drills and RH taps. I lookt at their jprices last nite and I thimpfk their prices have gone up since I last bought about 3 years ago. Didn't look at the reamer prices.