update: rigid reamer holder

[LVLAaron]

What's the tolerance of the reamer mfg's shank? I bet you'll find that you'll need multiple rigid holders if you want a fit as good as you made on your initial holder.

If I were to attempt this I'd be looking for a high quality straight shank er collet chuck. Then I'd mount a solid block where my tool post goes and bore that with the boring bar mounted in the lathe chuck. Bore it with about a .001 interference fit and shrink it in.

You'd be relying on the quality of the collet chuck and collets you purchase but the reamer would be held solid and you could feed it in with the compound to have a good feel of how it's cutting.

Check out the couple of threads @dustin_drews posted recently. He did exactly that.

 

[Tucker65]

Check out the couple of threads @dustin_drews posted recently. He did exactly that.

I saw that thread and his adjustable ball and socket for aligning the reamer.

I was just wondering about the tolerance in the reamer shanks and how that might effect what you're trying to accomplish with your experiment. I actually measured a few reamer shanks and found almost .001 difference in the shank diameter in the handful that I measured. I would imagine if you had that much clearance and put an indicator on the tip of the reamer you'd get quite a bit of movement whet you tighten your set screw. As good as yours fits now it still might even have some measurable movement, especially when about measuring in tenths.

Lots of ways to get a chamber cut into a barrel and as long as it's cut straight, and on size, I like seeing how others are doing it. With the rigid holding though I'd just be worried about turning my reamer into a boring bar. Your chamber might not have any measurable run-out but it is actually the size you want it to be.

 

[TaperPin]

Great results. Bravo!

 

[boltfluter]

I saw that thread and his adjustable ball and socket for aligning the reamer.

I was just wondering about the tolerance in the reamer shanks and how that might effect what you're trying to accomplish with your experiment. I actually measured a few reamer shanks and found almost .001 difference in the shank diameter in the handful that I measured. I would imagine if you had that much clearance and put an indicator on the tip of the reamer you'd get quite a bit of movement whet you tighten your set screw. As good as yours fits now it still might even have some measurable movement, especially when about measuring in tenths.

Lots of ways to get a chamber cut into a barrel and as long as it's cut straight, and on size, I like seeing how others are doing it. With the rigid holding though I'd just be worried about turning my reamer into a boring bar. Your chamber might not have any measurable run-out but it is actually the size you want it to be.

Spot on Tucker! A rigid set-up with a reamer is just begging to become a boring bar. Not saying it can't be done, but just be aware of how many ways it can go wrong. Carry on gents, great discussion.
Paul

 

[AccelR8]

Kinda funny seeing this thread come back around because yesterday I was looking through a drawer of lathe tooling and there was a JT to MT arbor I had bought 20-some years ago for, well, something I guess. Never used it.

I don’t chamber many barrels but this might be useful for other things I do. Also things we do at work, one infrequent job in particular that presents certain challenges.

 

[LVLAaron]

Don't forget that "rigid" is sort of a misnomer with this setup. It's a rigid holder.. but the tailstock shaft has play in it. It's small, but exists.

To be fair to the debate, floaters aren't perfect either. They can get away from you if you don't monitor what they're doing.

 

[xr650rRider]

Don't forget that "rigid" is sort of a misnomer with this setup. It's a rigid holder.. but the tailstock shaft has play in it. It's small, but exists.

To be fair to the debate, floaters aren't perfect either. They can get away from you if you don't monitor what they're doing.

I believe Bruce Thom said it in first video. Alignment and rigidity is basic good machining practice. Floater is a crutch for bad alignment.

 

[ricco1949]

TOOL POST BLOCK:

I used a bored tool post block for the first barrels I chambered.....recommended by my chambering mentor to be able to use the DRO when chambering.

I bored to the size of my largest reamer and dealt with varying sized reamers by shimming the block and/or varying the torque on the block holder bolts to get as close as possible on vertical.

A more critical problem I encountered was the bored hole went out of alignment when I tightened the cross slide gib. I fixed that by boring a larger hole in the block, gluing in a plug and reboring a new concentric hole.

Eventually I tired of adjusting the block.

I resorted to a Gretan reamer holder held in a tool post MT holder. I merely dial in the dead center using the cross slide for horizontal, the tool post for vertical and let the Gretan holder take of axial alignment.


The block worked well when new but there were just too many variables to work around.

If I ever tried it again I'd use a 1 inch boring bar holder with a plug and bore it. Full axial and radial adjustment would then be available.

I pre taper bore and have never experienced any chatter with either setup.

 

[LVLAaron]

TOOL POST BLOCK:

I used a bored tool post block for the first barrels I chambered.....recommended by my chambering mentor to be able to use the DRO when chambering.

I bored to the size of my largest reamer and dealt with varying sized reamers by shimming the block and/or varying the torque on the block holder bolts to get as close as possible on vertical.

A more critical problem I encountered was the bored hole went out of alignment when I tightened the cross slide gib. I fixed that by boring a larger hole in the block, gluing in a plug and reboring a new concentric hole.

Eventually I tired of adjusting the block.

I resorted to a Gretan reamer holder held in a tool post MT holder. I merely dial in the dead center using the cross slide for horizontal, the tool post for vertical and let the Gretan holder take of axial alignment.


The block worked well when new but there were View attachment 1498247just too many variables to work around.

If I ever tried it again I'd use a 1 inch boring bar holder with a plug and bore it. Full axial and radial adjustment would then be available.

I pre taper bore and have never experienced any chatter with either setup.View attachment 1498248

Thanks for sharing that. This is why I like to start and participate in these threads. Lots of smart stuff out that that people never share.


I was thinking... take the design of the adjustable rigid holder that @dustin_drews built, but mount it as a solid tool post (removing the compound).


I have an MT3 tool holder... I need to do a test chamber with the carriage to see how I like it before I commit to building something like that, however.

 

[xr650rRider]

Now for the buzz kill. Can you see it on the target? In one of Eric Cortina's video's with Gordy, he said he used the $265,000 8 or 9 axis machining center. Cut a sacrificial tool holder for the reaming operation that would be perfectly aligned with the spindle. Barrel was dialed in dead nuts, reaming was thru gun drilling where barrel rotated one direction and reamer the other. Said chamber was perfect and he did several barrels. He said they shot good but no better than ones that had been chambered by simpler methods.

Now some of what he said was inferred and I don't have the full details on how he/his machinist actually performed the operations.

Video is linked in this thread

 

[LVLAaron]

Probably not, but some guys like to talk about about how their version of something is the best. Marketing and self-promotion. When in reality, it's just a setup that works best for the guy with the tools he has.

 

[Jonnyofalltrades]

All of this talk of aligning lathes, and only one guy mentions a level!
You don't need the level to get your lathe horizontal, you need it to get your lathe straight. This doesn't apply to bench top lathes, but any lathe of reasonable size will have multiple jackbolts at either end. Two precision levels on the carriage, 90 degrees from each other. Run from end to end, tweaking jackbolts until neither level shows displacement. (That’s the Cole's Notes version).
By doing this first, many of those misaligned headstocks and crooked tailstock rams are suddenly bang on.
Machine tool maintenance is my day job.

 

[PatMiles]

^^^^What Johnny said!!^^^^

 

[xr650rRider]

All of this talk of aligning lathes, and only one guy mentions a level!

That was a prerequisite when this started.

 

[Jonnyofalltrades]

That was a prerequisite when this started.

I have just had so many situations where guys complained about crooked lathes, and the machine was twisted, humbacked, etc.
One guy was convinced that his tailstock was way too high, so pulled the spacer from under it and surface ground it. The lathe wasn't straight, and had a swayback. His tailstock was fine, until he ruined it.

 

[LVLAaron]

Well... Mine is straight, to the exact tenth within 9.5 inches.

 

[Greg Y]

Try pushing a reamer with the tailstock and a dead center and see what happens....I think you'll be pleasantly surprised.

 

[critter68]

Can someone provide a link for purchasing the "blanks" used, ie MT-Jacobs adapter, etc....I need a MT#4. I haven't been able to find inexpensive and not hardened. Thanks

 

[LVLAaron]

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

Or... you have a lathe.. Make one

 

[critter68]

Yeah those are spendy. UR talked about less than 20 bucks. I found Victor Machinery Exchange website and they are cheap but out of stock. Thanks Aaron