Advice Needed on Bearing Block

[Troutsqueezer]

Howdy,

I am in the process of making Elmer's #44 Open Column Twin. This will be my second engine and it's a step up as far learning new techniques. It's slow going but so far so good. Currently, I am working on the brass bearing blocks for the crankshaft. As you can see in the pic, there is a radius that needs to be cut on the top of the bearing. I've been thinking about the best way to do this but haven't come up with any good ideas. I have a new RT that I haven't used yet but even with that I'm not sure how it could be used without putting a radius in the wrong places. Should I get my files out and start with the elbow grease?

Thanks for any advice.

-trout

 

[Blogwitch]

Trout,

I think this is a job where you need to say 'do I just want it done, or shall I learn a lot from it and set the machine up to carry out the job'.

If you just want to get it done, get a couple of steel washers or small discs turned to the correct size, and superglue one to each side of the job, clamp in a vice and file it down to shape, using the washers as patterns to file down to. It would be much easier to do if the hole was already in there, you could then use a bolt to hold the washers in place.

You can use an RT to do the job, but it would be a two step process using the tip of the cutter to get your sharp internal corner. Do one side, then turn around and do the other 'square' corner, or reposition the other cutting edge to be on the hole centreline.


Blogs

 

[Troutsqueezer]

Thanks Blogwitch, especially for taking the time to draw it out. I never thought about flipping the RT to vertical position! I do want to do it the right way. I plan on making a number of Elmer's engines mainly to learn machining techniques so I can eventually make that larger scale hit and miss IC engine. Who knows, maybe a small locomotive is in my future too.

-trout

 

[mklotz]

Elmer's designs, among others, make frequent use of this style of rounded bearing cap. I prefer to do these by making incremental cuts to form the profile and then using a fine file or small vertical belt sander to smooth the final shape.

I did enough of them that I wrote a program to generate the incremental cutting chart needed as a function of the bearing cap measurements.

I never put the program on my webpage since I felt it was just too specialized to have any general interest.

If you're interested in pursuing this approach, I'll be happy to send you a copy of the program.

 

[Troutsqueezer]

Elmer's designs, among others, make frequent use of this style of rounded bearing cap. I prefer to do these by making incremental cuts to form the profile and then using a fine file or small vertical belt sander to smooth the final shape.

I did enough of them that I wrote a program to generate the incremental cutting chart needed as a function of the bearing cap measurements.

I never put the program on my webpage since I felt it was just too specialized to have any general interest.

If you're interested in pursuing this approach, I'll be happy to send you a copy of the program.

Sent PM. Thanks Marv.

-T

 

[mklotz]

Sent program. Enjoy.

 

[Jasonb]

I usually do then as Blog's says with filing buttons. Easier if you leave the shaping until the hole has been bored.

If you have a 3 axis DRO they have a button that will give the incremental cuts.

Jason

 

[MikeR C]

So, I'm confused. I have made several sets of bearing caps like this and just used a corner rounding endmill ???

 

[Troutsqueezer]

So, I'm confused. I have made several sets of bearing caps like this and just used a corner rounding endmill ???

I didn't realize these even existed. It makes sense, just like a wood routing bit, only for metal. As time goes on and my tooling inventory grows, I may include several of these. Thanks for the idea Mike.

I wish there were a machinist tool supplier near me so I could run down there and pick one up but alas, I'd have to buy one off the Internet and pay for shipping.

There also is the point of view that it would be good to learn how to perform this task using what I have on hand and I would like to try both Blogwitch and Marv's methods. I'm looking to gain experience on my first builds and plan to try as many BKM's (Best Known Methods) as I can, including yours at some future point.

-trout

 

[joe d]

It makes sense, just like a wood routing bit, only for metal.

-trout

Trout: I've had some success using carbide router bits in the mill for shaping aluminium. Never tried it on brass of ferrous, though. Your mileage may vary!

Joe

 

[Jasonb]

So, I'm confused. I have made several sets of bearing caps like this and just used a corner rounding endmill ???

As the centre of the circle is usually on the split line and you need some metal left for the bolts, its seldon a 1/4 circle so a corner rounding cutter does not give the correct profile.

Jason

 

[doc1955]

Here is a link to how I did this task.
http://www.homemodelenginemachinist.com/index.php?topic=7576.msg80729#msg80729

 

[MikeR C]

OK, I didn't mean to sound condescending, I thought I was missing something.

http://www.harveytool.com/products/...ategory_id=1&gclid=CN_3tLDTk58CFRD7agod4EM2jQ

I have several of the 2 flute with about a 1/16" radius (but I didn't pay any where close to this) and an assortment of the larger ones I found in a pawn shop.
They are easily made and if you find the larger ones, easy to resharpen.
I completely understand what you mean by doing a job with what you have on hand, I have a finite budget for my hobbies
If I didn't all my engines would be made on a Fadal unless I used my turning center and the boring parts would be done by my shop foreman!!!
I'll go back to being quiet
MikeR C

 

[Troutsqueezer]

Didn't take it that way at all, Mike. I appreciate the input and learned something.

-T

 

[Troutsqueezer]

Here is a link to how I did this task.
http://www.homemodelenginemachinist.com/index.php?topic=7576.msg80729#msg80729

I just came back in the house after a couple of hours out in the shed filing the radius on the bearing and saw this. I never would have thought to use a flycutter type tool or boring head with a custom shaped tool bit. I copied and pasted that pic into my database for future reference.

I fit a couple of washers onto the bearings to use as guides and it seems to be working well. Tomorrow night I should have them finished.

-Trout

 

[bearcar1]

Trout: I've had some success using carbide router bits in the mill for shaping aluminium. Never tried it on brass of ferrous, though. Your mileage may vary!

Joe

I too ventured to try carbide cutters for woodworking and was successful in my attempts both in brass and aluminum. Very light cuts of about .005" were made and the finish was excellent. I don't think I would wish to do so on a regular basis but for a onesy-twosey type of job, if I did not have the proper tooling, I'd do it again. Caution is the name of the game and safety glasses are a MUST. Now I'm headed to the shop to see what it is I can get myself into.

BC1
Jim

 

[Troutsqueezer]

Turns out the 'ol tried and true file can be underestimated. I put in a couple of washers with a bolt and nut and filed around them to get the arc I needed. Those threads posted on here about using files, maintaining files, etc. did not go unnoticed. I know, this isn't much of an achievement in the scheme of things but, baby steps. So important for that good foundation, huh?

-Trout

 

[shred]

Looks great. Never underestimate the file (or belt sander) and some filing buttons.

I've acquired a couple corner-rounding bits that I like to use for blinging, but they're annoyingly expensive.

 

[zeeprogrammer]

I put in a couple of washers with a bolt and nut and filed around them to get the arc I needed.

Great tip! Washer as a template. I would have just had a go and been disappointed. I'm always looking for these little gems (that many people might not even think about).

filing buttons...I've seen at least a half dozen references to that in the last couple of weeks...I need to go learn...

 

[duckman]

Just make a "D" end mill with the radius ground in with relief on the back side . You can make virtually any shape you want JMHO