Posts: 375
Threads: 53
Joined: Jun 2013
Location: Jonesborough, TN
11-06-2014, 09:23 AM
(This post was last modified: 11-06-2014, 09:24 AM by chucketn.)
I'm trying to make a between centers boring bar to use for boring the Sparey Dividing Head I've cast.
I'm not having much luck. I have drilled the centers in the ends twice, and when the bar is mounted between centers, I get .003" to .005" runout on the bar.The first time I cut the centers I used a flange type ER32 collet chuck that I made. I know it has .003" runout. I tried again with my 4 jaw independent chuck and got the same runout when mounted between centers.
The bar I'm using is from a platform roller on a treadmill. Lathe is an 10 year old Micromark 7x14.
Any ideas where I'm going wrong?
Chuck
Micromark 7x14 Lathe, X2 Mill , old Green 4x6 bandsaw
The difficult takes me a while, the impossible takes a little longer.
Posts: 240
Threads: 30
Joined: Mar 2014
Location: Planeta Rica, Colombia
My guess is to start at the beginning. Is your tailstock aligned with the headstock?
JScott, proud to be a member of MetalworkingFun Forum since Mar 2014.
Posts: 375
Threads: 53
Joined: Jun 2013
Location: Jonesborough, TN
(11-06-2014, 09:38 AM)JScott Wrote: My guess is to start at the beginning. Is your tailstock aligned with the headstock?
That is where I'll start.
Chuck
Micromark 7x14 Lathe, X2 Mill , old Green 4x6 bandsaw
The difficult takes me a while, the impossible takes a little longer.
Posts: 3,003
Threads: 51
Joined: Apr 2012
Location: Ontario
Does it matter if there is runout?
Free advice is worth exactly what you payed for it.
Greg
Posts: 375
Threads: 53
Joined: Jun 2013
Location: Jonesborough, TN
(11-06-2014, 09:59 AM)f350ca Wrote: Does it matter if there is runout?
I don't know, to be honest! Does it?
Chuck
Micromark 7x14 Lathe, X2 Mill , old Green 4x6 bandsaw
The difficult takes me a while, the impossible takes a little longer.
Posts: 3,003
Threads: 51
Joined: Apr 2012
Location: Ontario
Just to make sure we're on the same page. Is this a bar that carries the cutter between the headstock and tail while the part being bored is mounted to the carnage?
If so runout shouldn't matter, your offsetting the cutter (effectively creating runout) to bore the hole.
Free advice is worth exactly what you payed for it.
Greg
Posts: 7
Threads: 0
Joined: Jul 2013
Location: UK
It matters not a jot
The tool bit is excentric anyway , the tool tip care not if the bar dose not run true , it will still follow a circular path thus bore a true hole
There was a design that used a sliding dovetail arangmet to make the bar wobble this was to provide a fine adjustment of the cutter
Stuart
Lordedmond, proud to be a member of MetalworkingFun Forum since Jul 2013.
Posts: 1,827
Threads: 51
Joined: Apr 2012
Location: Oklahoma
I agree with Greg if the cutter is mounted in the bar between centers and the part on the carriage the runout that you have doesn't matter, because the cutter is stationary in one spot between the centers
DA
dallen, proud to be a member of MetalworkingFun Forum since Apr 2012.
If life seems normal, your not going fast enough! 
Posts: 8,854
Threads: 318
Joined: Feb 2012
Location: Arizona/Minnesota
Yup, what Greg, Stuart and David said.
Ed
Posts: 375
Threads: 53
Joined: Jun 2013
Location: Jonesborough, TN
11-06-2014, 11:54 AM
(This post was last modified: 11-06-2014, 11:57 AM by chucketn.)
Whew! It finally makes séance! Thanks for all the input.
Next decision is whether to make the spindle, and bore the hole to fit, or bore the head and turn the spindle to fit.
Chuck
edited to correct speeling
Micromark 7x14 Lathe, X2 Mill , old Green 4x6 bandsaw
The difficult takes me a while, the impossible takes a little longer.
