Boring Problem

[Bastelmike]

For an actual project I need a part as shown in the pic. Don't know yet what's the best method to manufacture the horizontal bores. These bores will carry bearings later. The opposing bores should be well aligned for the shafts and they should be pretty well parallel too.

The part is welded steel, bore dia. is ~1.4" and the opposing bores are ~11" apart.

I have a horizontal mill without and a vertical (Bridgeport Clone) mill with DRO.

Any good ideas how to machine it ?

Mike

 

[PeterB]

It depends on the size. If it's small then make it from one piece.

 

[metal_magician]

Try drilling and reaming the holes in one shot depending on your tolerances, that may be good enough. If they are super tight and depending on the travel of your horizontal mills tables Y axis, do the before mentioned and then make a boring bar that has two cutters that you can set to take your final cut. Indicate your part parallel and perp to the table. Indicate the center of your reamed holes. Insert your double cutter through the holes and into the spindle and receiver of your horz mill. Set your mill the the center of the indicated holes, and feed the y axis to take the cut. Think of using it as a mini boring mill. Hope this helps!

 

[metal_magician]

Oh, And you should have some dial indicators set on the mill to give you reference! Just a thought

 

[Tin Falcon]

Do a Google search on line or inline boring. It is a technique used for large machinery such as front end loaders etc to bore and re-bore for bushings etc.

What size lathe do you have mount the part(s) to the lathe . mount the boring bar between centers and bore that way. you may need to make a jig to help with alignment and repeatability.
I would machine the holes to 1.125 to 1.25 before assembly.

make one edge straight and use that as your reference plane or line.
Or use you center hole as a reference. may work better.

You will need some room to do this. Like 24" of z axis.

is this for a model project ?? Kind of big.


Tin

 

[lensman57]

Hi,

I only do very small scale model engineering but given that you have 1.25" holes to bore or drill that are 11" apart then I guess that you'd have to drill and bore these holes individually as I don't think the distance between them would allow you to bore them in one go.
you need to establish a datum to work from then the centers of the holes could be indicated and marked out and then drilled and bored using a good boring head, I think your bridgeport should have enough Z travel to do this.

Very interesting problem.

Regards,

A.G

 

[MuellerNick]

As long as the base plate is flat, parallel and perpendicular, you can use any side as reference. If it is not, make it fit your specs.
Drill the holes in separate ops, referencing with an edge finder.

Nick

 

[Darren English]

Make the corner posts seperate from the base.

Finish the bores to the correct size.

Insert a rod through the bores to align them. Then you can weld them to the base.

If you do not want to weld them screw thru from the base.

 

[Tin Falcon]

Another option is to bore out the squares to size then put shafts through to align the holes then silver solder in place. welding is likely to pull the pieces in all sorts of directions. it can be done but very careful tack on opposite sides. You will need to keep the heat and stresses as equal as possible.
Tin

 

[Darren English]

That's a very good point Tin

 

[Tin Falcon]

Another down side of aligning with rods is cost . ball park figure about $50 for a couple feet of inch and a half 12L14 from mcmaster carr..
Daren English was typing at the same time I was. so a little crossed posts there.

you cold silver solder or super glue to get the alignment then drill and tap for bolts to get strength .
Tin

 

[kvom]

It looks as if he has an axle shaft going through the holes, so using it as an alignment tool makes sense.

I would drill bore the holes using the BP and DRO as close as possible leaving a slip fit for the bearings. Then use the axle for alignment and secure the bearings with green Loctite. The bores do not have to completely precise as the loctite can fill reasonably large gaps.

Trying to keep alignment with screws is iffy IMO.

 

[lensman57]

It looks as if he has an axle shaft going through the holes, so using it as an alignment tool makes sense.

I would drill bore the holes using the BP and DRO as close as possible leaving a slip fit for the bearings. Then use the axle for alignment and secure the bearings with green Loctite. The bores do not have to completely precise as the loctite can fill reasonably large gaps.

Trying to keep alignment with screws is iffy IMO.

Hi,

I agree with you, the axels could be indicated and the height noted using a height gauge and some short home made jacks and repeated for the other side and then the loctite would do the rest.

Regards,

A.G

 

[Bastelmike]

Do a Google search on line or inline boring. It is a technique used for large machinery such as front end loaders etc to bore and re-bore for bushings etc.

What size lathe do you have mount the part(s) to the lathe . mount the boring bar between centers and bore that way. you may need to make a jig to help with alignment and repeatability.
I would machine the holes to 1.125 to 1.25 before assembly.

make one edge straight and use that as your reference plane or line.
Or use you center hole as a reference. may work better.

You will need some room to do this. Like 24" of z axis.

is this for a model project ?? Kind of big.


Tin

Hello Tin and everyone,

thank You for a lot of ideas.

I have a 15x40 lathe, but I don't like to use it for this job. I think I am better off with the horiz. mill and a long boring bar. I can machine both set of bores in one setup, so they should be parallel.
And the mill has external support bearing, IMO it's better suited for this than a lathe. Wish I had a horiz. boring mill with rotary table

Just have to make a long MT5 boring bar.

My projects are usually a bit bigger, one reason prob that among some friends who do metalwork, I got the larger machines.
These parts are going to become truck frames for a garden railway a friend of mine is building. They will look a bit more complicated than the sketch but in the sketch you see everything that has to be machined with some precision.
The railway will use a gas engine now, maybe later a steamer...?
I know no one except from internet who has built such a large steam locomotive, so I expect problems with it

Okay, think I am going to do it with a long boring bar and the h-mill in one setup.

Thanks for your ideas.

Mike

 

[Bastelmike]

Make the corner posts seperate from the base.

Finish the bores to the correct size.

Insert a rod through the bores to align them. Then you can weld them to the base.

If you do not want to weld them screw thru from the base.

As for welding, I'm afraid alignment is gone after welding. You always have warp during welding.
I plan to predrill the corner posts before, but not large holes, maybe 20mm.

Mike

 

[kvom]

Sounds like 15" gauge, pretty huge for a garden railway. That being the case, the need for super precision is lessened.

 

[MuellerNick]

I think I am better off with the horiz. mill and a long boring bar.

Almost 300 mm long and about 35 mm in diameter? I already hear the chatter and squeak over here.


Nick

 

[Bastelmike]

Sounds like 15" gauge, pretty huge for a garden railway. That being the case, the need for super precision is lessened.

Oh no, not 15" gauge; 7 1/4" gauge. Scale 1:8

We don't have CAD model finished yet, but I've measured several drawings from full size standard locomotives and the distance from bearing cover to bearing cover is more than 2000mm. With 1:8 You get more than 10" in model size.
For standard gauge I have several drawings of wheel sets; length of the shaft is in every drawing >2100mm.

But You are prob right it doesn't need super precision
Mike

 

[Bastelmike]

Almost 300 mm long and about 35 mm in diameter? I already hear the chatter and squeak over here.


Nick

Why Nick?

With the boring bar supported by the external arbor support, I don't see the problem. I have several long arbors for that mill, Ø16-40mm and they are longer than 300mm if You measure their length from the end of the taper.

This method is also used on horizontal boring mills, and these boring bars are sometimes more than 2m long; the bars don't have 200mm diameter.

I have abandoned this idea for other reasons now, not for chatter.

Mike

 

[MuellerNick]

With the boring bar supported by the external arbor support,

Ah, OK. I didn't think complicated enough. You make a boring bar with adjustable cutters, then have fun getting it into the pre-drilled holes, slip on the arbor, break your neck adjusting the boring bar's cutters. And do that twice.

Pre-drill the holes, weld on the 4 blocks, clamp the plate flat on the table, mill the outer sides of the blocks with the vertical spindle for reference, switch to horizontal, find references with the edge finder and use a boring head.

Takes less time than making a boring bar.


Nick