Reamer

[Cross Slide]

I bought a set of plans for building a model steam engine. The whole project uses all round, Square, and flat CRS and Brass. That is what got me interested in it. As I have most of the supplies already. After looking over and reading the plans I found that I need a 1” Reamer for the Cylinder Bore. I looked into a 1” reamer and found that the shank is 3/4”. My biggest chuck is 5/8”. 

What are my options for getting the bore of the cylinder to spec if I can’t get a reamer that fits my chuck? The design of the cylinder is also a blind hole. 

Trevor

[Dr Stan]

Turn down the shank of the reamer or bore the hole.

[Cross Slide]

(01-10-2021, 12:32 AM)Dr Stan Wrote: Turn down the shank of the reamer or bore the hole.

That’s good to know. I didn’t realize I could turn the shank down. For some reason I thought it would be hardened.

As for boring the cylinder out, my boring bars suck. I haven’t had any luck getting a good finish with them yet. Definitely wouldn’t be a good enough finish for a cylinder and piston. 

But I will try turning the shank down.

Trevor

[TomG]

Boring would be the prefered method for a cylinder bore, over reaming. The hole will be more consistent, and should have a better surface finish. Get yourself the type of bar that uses square HSS tool bits and grind the bit just as you would grind it for turning. Get the biggest bar you can for rigidity, probably 3/4' for a 1" bore, and take some practice runs to get the technique down. My guess is you were probably using pre-ground carbide boring bars, which are tough to get a good finish with. Also make sure you aren't using low carbon steel for the cylinder. You'll never get a good finish with that.

Tom

[Dr Stan]

Leave enough material in the hole so you can hone it to finished size.  A wheel cylinder hone should be a perfect fit.  Use kerosene or diesel fuel as a cutting fluid.

Would it be possible to alter the design so you would have a through hole that would be covered with a plate in assembly?  A though hole is a lot easier to machine than one with a bottom.

[Cross Slide]

(01-10-2021, 10:40 AM)Ok TomG Wrote: Boring would be the prefered method for a cylinder bore, over reaming. The hole will be more consistent, and should have a better surface finish. Get yourself the type of bar that uses square HSS tool bits and grind the bit just as you would grind it for turning. Get the biggest bar you can for rigidity, probably 3/4' for a 1" bore, and take some practice runs to get the technique down. My guess is you were probably using pre-ground carbide boring bars, which are tough to get a good finish with. Also make sure you aren't using low carbon steel for the cylinder. You'll never get a good finish with that.

Tom

Tom. 
These are what I have for boring bars. They are just cheap ones. 
   

The plans call for the Cylinder to be machined out of Cold Rolled Steel Bar Stock
I have a piece of Cold Rolled Steel. But I’m not sure if it is 1018 or 1045. I’m leaning towards 1018. 
In the plans it says “Use one size under, drill to the correct depth for the cylinder bore, and finish off with a 1 inch reamer. Polish the boar using scotch pad and a hand drill motor.”
A Brake Cylinder Hone should work fine for that as well, and I have one of those. 
The plans call for the piston to be machined out of Brass. They say “Machine the piston slightly oversized. Polish the piston until it fits down the cylinder bore. 

Trevor

[Cross Slide]

(01-10-2021, 11:15 AM)Dr Stan Wrote: Leave enough material in the hole so you can hone it to finished size.  A wheel cylinder hone should be a perfect fit.  Use kerosene or diesel fuel as a cutting fluid.

Would it be possible to alter the design so you would have a through hole that would be covered with a plate in assembly?  A though hole is a lot easier to machine than one with a bottom.

Stan. 

I’m not sure if it would be possible to cut the back off the cylinder and make it a bolt on or not. I will need to study the plans and see if it could be done. 
But that is a good point. It would be easier to machine it right through instead of bottoming out. 
I will try machining it as the plans specify first. I want to see if I can do it as called for first. If it doesn’t work out it’s just a bit of material wasted. 

Trevor

[TomG]

(01-10-2021, 12:06 PM)Cross Slide Wrote:

(01-10-2021, 10:40 AM)Ok TomG Wrote: Boring would be the prefered method for a cylinder bore, over reaming. The hole will be more consistent, and should have a better surface finish. Get yourself the type of bar that uses square HSS tool bits and grind the bit just as you would grind it for turning. Get the biggest bar you can for rigidity, probably 3/4' for a 1" bore, and take some practice runs to get the technique down. My guess is you were probably using pre-ground carbide boring bars, which are tough to get a good finish with. Also make sure you aren't using low carbon steel for the cylinder. You'll never get a good finish with that.

Tom

Tom. 
These are what I have for boring bars. They are just cheap ones. 


The plans call for the Cylinder to be machined out of Cold Rolled Steel Bar Stock
I have a piece of Cold Rolled Steel. But I’m not sure if it is 1018 or 1045. I’m leaning towards 1018. 
In the plans it says “Use one size under, drill to the correct depth for the cylinder bore, and finish off with a 1 inch reamer. Polish the boar using scotch pad and a hand drill motor.”
A Brake Cylinder Hone should work fine for that as well, and I have one of those. 
The plans call for the piston to be machined out of Brass. They say “Machine the piston slightly oversized. Polish the piston until it fits down the cylinder bore. 

Trevor

Toss those aside and get one of these: https://www.travers.com/double-end-borin...2-590-003/

You'll also need to get something besides 1018. Your best bet would be one of the leaded sissy steels, such as 12L14.

Tom

[Dr Stan]

(01-10-2021, 12:45 PM) "TomG Wrote: Toss those aside and get one of these: https://www.travers.com/double-end-borin...2-590-003/

You'll also need to get something besides 1018. Your best bet would be one of the leaded sissy steels, such as 12L14.

Tom

Excellent suggestions.

[f350ca]

I use those cheap carbide boring bars, but they take a lot of grinding and honing to get them to cut.