question on boaring

[chrispare]

When useing a boaring head and bar, is it better to use the mill or the lathe??
And should I be ueing a fast speed or slow?
I am using aluminum right now but will also be using cast.

thanks chris

 

[kvom]

I get better results on the lathe. With a boring head you are more limited both as to RPM and plunge rate/rev.

 

[steamer]

I'm with KVOM. I am more comfortable boring with a lathe to a tight tolerance than with a boring head....It may be just me...as I know people who prefer otherwise...

If it gets the hole in the right place to the right size....it's the right way for you.

Dave

 

[stevehuckss396]

I perfer the mill. I get a better finish and less taper in the mill. Maybe because of the auto feed in the mill. I also like it because I can press in my liners in engine blocks and then finish bore them and not have to worry about the liner changing shape when i'm done.

Works for me.

 

[jpeter]

Regarding speed, rpm, google for a surface feet per minute chart. You'll find a chart that'll tell you what rpm to set your spindle for the type of material, cutting tool material and diameter of hole your boring or rod your turning. Follow the chart and your tools will work much better and last much longer. This is especially important when milling cuz the tools are so expensive and hard to sharpen.

 

[hammers-n-nails]

its been my experience that when boring in the mill with a boring head the limiting factor for speed is the rigidity of the machine, because the tool i not balanced. i have a large mill and i feel good at about 100-150 rpm regardless of diameter/sfpm.

 

[jpeter]

Before I retired the shop where I worked had a 1/2 dozen lathes to use, 3 Clausings, a SB heavy 10 and a 16 inch Monarch. They all were tired. We also had a BP mill and a Lagun vertical mill. I found boring cylinders on the Lagun got me the best job. The BP did a good job too. I always got a taper boring in the lathes. Since I retired though I got a used Sheldon 11 inch lathe for my home shop and it bores dead nuts. So when I choose between my BP and lathe I usually choose the lathe. It's true too the boring head in the mill makes it out of balance. That fact alone points me to the lathe.

 

[Loose nut]

Boring heads on round column mill/drills don't alwasy work very well, the head can't be clamped down firm enough and it tends to oscillate back and forth a bit ruining the hole (I learnewd this the hard way).

On the square column mills, like the RF 45 type, boring heads work much better. I can bore a hole very nicely on mine.

 

[GWRdriver]

If it gets the hole in the right place to the right size....it's the right way for you. - Dave

That's what it really boils down to isn't it. Since I get about equal accuracy from both my lathe and mill I tend to let the job dictate which machine I use. Some jobs are easier to set up on the mill, some jobs are easier to set up in the lathe, although for the past several years it seems the balance of boring jobs has tipped in the direction of the mill. Also, quite a few years ago I spent the money to buy a good US-made boring head and when I dial up .0005", it will give me .0005"!

 

[MachineTom]

It more depends on the job your doing, than the Mill vs Lathe decision. If boring a 1/2" hole in a 2"D round, it would be silly to use a mill, If its a 3" hole in a 10" plate most home lathes will not fit the piece to begin with.

A cylinder CI 2.5" sq and 5" long, really rough tapered cored hole, mounted on the mill and used a extra long .750 EM to clean out the bore, followed by a 1" EM from each end, since it was already in the mill, I figured use the boring head to get to final size 1.250, a 6" solid carbide bit should do it, the job was done, but the finish was awlful, 5" was just too deep for the 1/2D boring bar, the 5/8 bar was too short. The lathe would have been the better choice in this case.

 

[Tin Falcon]

When using a boring head and bar, is it better to use the mill or the lathe??

Boring bars are used for either mill or lathe.
boring heads are used on mills only!

And should I be using a fast speed or slow?

Get yourself a feed and speed chart and post near your machines.
speed is dependent on
1) material
2) diameter of in this case the hole you are boring
3) the cutting tool material .HSS is run slower than carbides.
4) if you are finishing generally a low feed rate and relatively high speed.

I am using aluminum right now but will also be using cast.

other factors are boring bar diameter and tool geometry a little radius and a well honed tool will do wonders for surface finish.
the boring bar should not stick behold the boring head or tool holder more than 3x diameter for steel and 7x if you are using solid carbide.
Like others have said a boring bar speed is limited to how well it is balanced.
Tin

 

[Antman]

Hi Guys,
Haven’t posted for a while, just haven’t felt verbose recently.
I needed to bore 47mm with a 42mm shoulder about 20mm deep for a rotab I’m trying to make. Held a 25mm plate in the 4-jaw in the lathe, drilled with my biggest 16mm MT2 tang drill bit in the tailstock and opened up the hole with my home made boring bar that takes a round 4mm HSS tool. The finish was lousy, I think due to the problem of holding the tool for sharpening. When the hole was big enough, I started to ponder a better way. How I eventually achieved a decently accurate bore with an ok finish was to use a 50 degree HSS tool I made for dovetails in the shaper and cut the far side of the bore, reversing normal lathe rotation and feeding towards the chuck with an extra idler gear in an extra quadrant I made myself. Being a Newby to machining I wonder if what I did is acceptable practice?

Ant