Floating Reamer holder verse rigid.

[xr650rRider]

The centers were used to true the bar but it doesn't mean your center is true in the spindle, unless you turn a new one and use it.

 

[DShortt]

The centers were used to true the bar but it doesn't mean your center is true in the spindle, unless you turn a new one and use it.

And if you move the tailstock, then what?

Plenty of ways to chase one's tail if you're up for the exercise.

 

[xr650rRider]

And if you move the tailstock, then what?

Plenty of ways to chase one's tail if you're up for the exercise.

Mine is aligned, if yours is that bad, may be time for some maintenance. Normal practice to turn a center in your machine and then it's aligned with spindle. When you put a center in your tailstock, you have a true reference to align to.

 

[DShortt]

Mine is aligned, if yours is that bad, may be time for some maintenance.

Yours is aligned across the entire bed length within .0001", which is what everyone touts when indicating a bore?

OK then.

 

[xr650rRider]

Yours is aligned across the entire bed length within .0001", which is what everyone touts when indicating a bore?

OK then.

I don't have a reamer that long.

 

[DShortt]

I don't have a reamer that long.

So you indicate the position of your tailstock to the exact same location on the bed every time? And your tailstock remains within alignment along it's entire travel?

Or if you've a different method of indicating perfect alignment when boring a chamber then please enlighten me. I'll consider anything if it works.

I've lots of questions about ridged holders. Just looking for answers.

 

[xr650rRider]

So you indicate the position of your tailstock to the exact same location on the bed every time? And your tailstock remains within alignment along it's entire travel?

Or if you've a different method of indicating perfect alignment when boring a chamber then please enlighten me. I'll consider anything if it works.

I've lots of questions about ridged holders. Just looking for answers.

I have a barrel thru-flush, so I do position my carriage in same place every time. My tailstock always hits the bump stop on back of carriage, so yes, it's in a repeatable position. My tailstock alignment is deadnuts side to side and I'm low in front .0003" over 12" test bar. It remains the same over 4" tailstock travel.

If you get the gist of what Bruce Thom and others are doing is cutting a reamer holder with spindle held tool. Using the tailstock to advance the holder results in a perfectly true reamer holder. Scribe mark it and re-insert in the same position everytime you use it and you have an aligned reamer holder.

 

[DShortt]

I have a barrel thru-flush, so I do position my carriage in same place every time. My tailstock always hits the bump stop on back of carriage, so yes, it's in a repeatable position. My tailstock alignment is deadnuts side to side and I'm low in front .0003" over 12" test bar. It remains the same over 4" tailstock travel.

If you get the gist of what Bruce Thom and others are doing is cutting a reamer holder with spindle held tool. Using the tailstock to advance the holder results in a perfectly true reamer holder. Scribe mark it and re-insert in the same position everytime you use it and you have an aligned reamer holder.

I wasn't aware that a tailstock could even move over 4" of travel under load with only 0003" of deflection. I've learned something this evening.

Color me skeptical.

 

[INTJ]

I have been watching Bruce set up a lathe (new Kingston HJ-1100) in my shop to cut chambers his way with a rigid reamer holder. It takes a long time with leveling and aligning everything.

After watching him do it I would be confident chambering that way. I could easily see doing all to .25" or .3" of a chamber, and then going to a pusher for the final part if you really wanted to make sure everything was as good as possible. Most chambers wouldn't need the pusher.

However, it takes a heavy lathe. The HJ-1100 weighs 3500 lbs. It takes a good chuck. In this case a D1-6 8" Bison Set True. And then of course you need to bore the reamer hole from the chuck to the tailstock. Bruce swapped on a collet chuck for that.

I will soon have to chamber three 416 Barrett barrels for ELR rifles. The blanks are 42" long with 1.8" diameter shanks. They are long enough to fit through the headstock on the HJ-1100 and make use of the spider that Bruce has. I think the HJ-1100 will be a better choice then the PM 1440 GT for these barrels.

The biggest issue that I see with a floating reamer holder is that even with a good one like the JGS, it doesn't always align right. Almost always, when I start a new chamber the pilot is slight off center. I fiddle with it until the reamer pilot goes straight in before I start cutting. I'll bet with Bruce's method the pilot is always aligned with the hole.

 

[boltfluter]

First thing I would do with any PTG ground rod is put it on some good v blocks and check it for run out. Mine is crap, to say the least! If running a reamer ridged, your set up better be "dead nuts" or now your reamer just became a nice boring bar! Good luck, your gonna need it. Not saying it can't be done, just not with the hobby lathes that most smiths run. Happy reaming!
Paul

 

[Dusty Stevens]

I have been watching Bruce set up a lathe (new Kingston HJ-1100) in my shop to cut chambers his way with a rigid reamer holder. It takes a long time with leveling and aligning everything.

After watching him do it I would be confident chambering that way. I could easily see doing all to .25" or .3" of a chamber, and then going to a pusher for the final part if you really wanted to make sure everything was as good as possible. Most chambers wouldn't need the pusher.

However, it takes a heavy lathe. The HJ-1100 weighs 3500 lbs. It takes a good chuck. In this case a D1-6 8" Bison Set True. And then of course you need to bore the reamer hole from the chuck to the tailstock. Bruce swapped on a collet chuck for that.

I will soon have to chamber three 416 Barrett barrels for ELR rifles. The blanks are 42" long with 1.8" diameter shanks. They are long enough to fit through the headstock on the HJ-1100 and make use of the spider that Bruce has. I think the HJ-1100 will be a better choice then the PM 1440 GT for these barrels.

The biggest issue that I see with a floating reamer holder is that even with a good one like the JGS, it doesn't always align right. Almost always, when I start a new chamber the pilot is slight off center. I fiddle with it until the reamer pilot goes straight in before I start cutting. I'll bet with Bruce's method the pilot is always aligned with the hole.

Make sure your shop has very good climate control

 

[INTJ]

First thing I would do with any PTG ground rod is put it on some good v blocks and check it for run out. Mine is crap, to say the least! If running a reamer ridged, your set up better be "dead nuts" or now your reamer just became a nice boring bar! Good luck, your gonna need it. Not saying it can't be done, just not with the hobby lathes that most smiths run. Happy reaming!
Paul

Bruce aligned and indicated things I had never heard anyone even talk about. The lathe is a step above a typical Taiwan built lathe, and it is heavy and stable. Add to that Bruce has been cutting excellent chambers this way for a long time.

That said, I agree that setting a lathe up this way is isn't for hobbyists........

 

[ridgeway]

My PTG rods come in handy sizing up bushings after pre boring to make sure it's a good fit.

 

[xr650rRider]

Make sure your shop has very good climate control

Chasing millionths

 

[Dusty Stevens]

Chasing millionths

It matters for thousandths when you go from 50 to 80 degrees i assure you. When chambering solid thousandths matter

 

[xr650rRider]

It matters for thousandths when you go from 50 to 80 degrees i assure you. When chambering solid thousandths matter

Bearings should be seizing across the globe.

 

[Dusty Stevens]

Bearings should be seizing across the globe.

Bearings have an oil wedge clearance

 

[tobnpr]

It matters for thousandths when you go from 50 to 80 degrees i assure you. When chambering solid thousandths matter

Thermal expansion coefficient of 4140= 6.78 microns per degree (at least according to the table I checked).
6.78 x 30=203.4 microns, = two tenths.

Unless my math is wrong, of course ...

 

[Alex Wheeler]

This stuff is starting to sound complicated.

 

[Trophied]

And different bearings have different built in clearances for different temperature service.