# ER32 in the 4 jaw



## epanzella (Mar 18, 2020)

Just finished yesterday's project. I occasionally need to make shafts for RC plane motors that turn from 10K to 20K rpm. They have to be accurate to a few tenths and need to be swapped end for end for finish machining. I made a Viper knock-off chambering fixture a few years ago for machining rifle barrels that worked out really well for me so I decided to make a mini version for doing things that spin. I like the range of ER32 collets so I picked up a collet chuck with a straight shank so I could dial it in axially and radially. Haven't machined anything with it yet but I dialed in some long dowel pins to a few tenths along their length without much trouble.  I used the same 1/2x20 threads as my chambering fixture so I wouldn't have to make another set of brass tipped bolts. I made it with 8 flats so I could have the bolts between the chuck jaws or lined up with them. It doesn't seem to make much difference which way I mount it. Of course I can use this without the collet chuck as well for other stuff like chambering pistol barrels.


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## DavidR8 (Mar 18, 2020)

Nice work! 
I’d be terrified of those bolts spinning around though. 


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## Ulma Doctor (Mar 18, 2020)

DavidR8 said:


> Nice work!
> I’d be terrified of those bolts spinning around though.
> Sent from my iPhone using Tapatalk


The bolts are something to be acutely aware of, but you don’t be overly fearful of the set up. Just keep arms, hands, and clothes away from the mayhem and you will be just fine.


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## Ulma Doctor (Mar 18, 2020)

Nice work!!! @epanzella


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## ErichKeane (Mar 18, 2020)

Nice!  I've been considering making one of those Viper-clones for a barrel threading project I have to do.  Yours seems shorter than I typically see these (typically seem to be ~7 inches long?), so I'm curious how effective you find this on longer barrels?  Or are you only doing shorter ones?

I've got a 3ft long headstock, so a headstock-side spider doesn't work for me  :/


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## epanzella (Mar 18, 2020)

ErichKeane said:


> Nice!  I've been considering making one of those Viper-clones for a barrel threading project I have to do.  Yours seems shorter than I typically see these (typically seem to be ~7 inches long?), so I'm curious how effective you find this on longer barrels?  Or are you only doing shorter ones?
> 
> I've got a 3ft long headstock, so a headstock-side spider doesn't work for me  :/


The unit in this post is a mini-version of the viper knock-off I made a few years ago which is for full sized for rifle barrels.  My headstock needs a 24+ barrel to use the outboard spider which works OK with blanks but not on barrels that have been finished to shorter lengths. The big one works great so I have high hopes for it's little brother. Below is a pic of the full size one I made about 2 years ago.


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## ErichKeane (Mar 18, 2020)

Ooh, thats great!  That is almost exactly what I was thinking of making (right down to brass epoxied onto the bolts, and the flats for the 4 jaw!).  I'm stuck in a bit of an 'analysis paralysis' on mine.  I was thinking 7 or 8" long, and I know the Viper is 4" diameter (with a 1.5" passthrough), which looks about what you went with?


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## epanzella (Mar 18, 2020)

ErichKeane said:


> Ooh, thats great!  That is almost exactly what I was thinking of making (right down to brass epoxied onto the bolts, and the flats for the 4 jaw!).  I'm stuck in a bit of an 'analysis paralysis' on mine.  I was thinking 7 or 8" long, and I know the Viper is 4" diameter (with a 1.5" passthrough), which looks about what you went with?


The brass tips have 5/16 studs leading to a 3/8 shoulder. They were pressed into the bolts and then machined true. I don't know if epoxy would hold.


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## DavidR8 (Mar 18, 2020)

epanzella said:


> The brass tips have 5/16 studs leading to a 3/8 shoulder. They were pressed into the bolts and then machined true. I don't know if epoxy would hold.


Thanks for that detail, I was wondering how they were made.


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## Aukai (Mar 18, 2020)

Ulma Doctor said:


> The bolts are something to be acutely aware of, but you don’t be overly fearful of the set up. Just keep arms, hands, and clothes away from the mayhem and you will be just fine.


Mayhem, I've seen his work on TV, he'll spoil your whole day.....


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## ErichKeane (Mar 18, 2020)

epanzella said:


> The brass tips have 5/16 studs leading to a 3/8 shoulder. They were pressed into the bolts and then machined true. I don't know if epoxy would hold.


Ah, neat!  Thanks for the details!  My initial plan was to thread them and tap the bolt, but pressing them into the bolts seems like a better solution!  My other thought was to use brass bolts, but that seems expensive.


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## epanzella (Mar 18, 2020)

DavidR8 said:


> Nice work!
> I’d be terrified of those bolts spinning around though.


I hear that! The brass tipped bolts are too long for this small fixture but I need that length for the larger fixture and didn't feel like making a whole nuther set of bolts.  I'm not too worried because they're spinning close to the jaws that I have to avoid anyway. I saw a guy that painted his jaws orange so he could see them, maybe I'll do the same with the bolts. Thx 4 da hedzup!


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## DavidR8 (Mar 18, 2020)

epanzella said:


> I hear that! The brass tipped bolts are too long for this small fixture but I need that length for the larger fixture and didn't feel like making a whole nuther set of bolts.  I'm not too worried because they're spinning close to the jaws that I have to avoid anyway. I saw a guy that painted his jaws orange so he could see them, maybe I'll do the same with the bolts. Thx 4 da hedzup!


Thanks mate!


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## mksj (Mar 19, 2020)

You can hold in the brass tips with a little red Loctite. Interesting approach to the alignment issues sometimes seen. Was there consideration of something like the Shar's ER-40  set-tru style chuck? I often do very close in work to the chuck and prefer to use a collet system with nothing to catch my fingers/hands. I previously tried an ER-40 collet in my 4J but not really happy with that setup so made my own Set-True ER-40 chuck.


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## epanzella (Mar 19, 2020)

mksj said:


> You can hold in the brass tips with a little red Loctite. Interesting approach to the alignment issues sometimes seen. Was there consideration of something like the Shar's ER-40  set-tru style chuck? I often do very close in work to the chuck and prefer to use a collet system with nothing to catch my fingers/hands. I previously tried an ER-40 collet in my 4J but not really happy with that setup so made my own Set-True ER-40 chuck.


As far as I know, that collet chuck can be adjusted radially but not axially. I see various solutions to this problem that are really expensive but that's not for me.  I'm not a machinist. I'm not even a hobby machinist. I build rifles and Radio controlled planes. I repair and modify my trucks and boat as required. I'm a guy that builds stuff and fixes stuff. I make tools and parts to build stuff and fix stuff. This is why I have my machines and I try to make whatever I need rather than spending a pile of money. The ER32 chuck cost $20 and the hunk of aluminum was free.


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