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Trying to use a small precision chuck in a tail stock. How to hold it dead center?

Laverda

Cast Iron
Joined
Mar 24, 2014
Location
Riverside County, CA
I recently bought a Llambrich precision chuck and a Royal sensitive drill feed for it. The first job I have for it will be in a lathe. The lathe tail stock is MT4 and the sensitive drill feed is 1/2" diameter. I will be using a very small drill (#78 - .016") and need it dead center in the tail stock. Holding the drill feed in a chuck does not get it perfectly centered. So I considered using a MT4 to 1/2" collet but there is no way to get a draw bar in the collet to hold it.

So how do you hold a 1/2" shaft in a MT4 taper that will get it as close to center as possible? I would prefer to drill the hole in the lathe after all the other turning is done on the part and not have to move it to a different machine.
 
First adjust/fix your tailstock. If a decent chuck in the tailstock doesn't hold 'on centre' there's a problem. The thing I don't get with these 'sensitive drill feeds' is they actually de-sensitise your feel. Personally I use a true-running pin-vice whose bore I lapped to a nice smooth sliding fit on a dedicated pin I hold in the 1/2" drill chuck .. fine down to # 80.
 
Get an adjustable drill holder from a small screw machine. Typically they have a 5/8" shank to mount in the turret and an 1/2" or larger female bore for the tool. Replace the shank with something that fits your tailstock (or a non-precision drill chuck held in your tailstock). Put the precision chuck in the adjustable part of the drill holder. Put the drill or a small dowel pin in the precision chuck, adjust the drill holder to the headstock spindle axis and tighten up the drill holder.
I said "get an adjustable drill holder". You can probably make one in less time than it takes to buy one and get it delivered. Two small flat plates, one with a tapped hole near each end, the other with somewhat oversize bolt clearance holes in matching locations. One plate has something you can grab with your tailstock. The other plate has a receiver (nice bored or reamed hole with setscrew, eh?) for the shank of your precision chuck.
 
I have a small ER Chuck with a 3 mt prong for the tailstock, but the tailstock needs calibration before use, same would apply to a drill chuck,.
The tailstock spindle needs to be bang on.
You could through drill the tailstock spindle, I have a cheap wood lathe that’s through drilled, can’t see why not, it’s enough for a long drill to be poked through, but 8mm is the max, enough for a drawbar I reckon?
Mark
 
Get an adjustable drill holder from a small screw machine. Typically they have a 5/8" shank to mount in the turret and an 1/2" or larger female bore for the tool. Replace the shank with something that fits your tailstock (or a non-precision drill chuck held in your tailstock). Put the precision chuck in the adjustable part of the drill holder. Put the drill or a small dowel pin in the precision chuck, adjust the drill holder to the headstock spindle axis and tighten up the drill holder.
I said "get an adjustable drill holder". You can probably make one in less time than it takes to buy one and get it delivered. Two small flat plates, one with a tapped hole near each end, the other with somewhat oversize bolt clearance holes in matching locations. One plate has something you can grab with your tailstock. The other plate has a receiver (nice bored or reamed hole with setscrew, eh?) for the shank of your precision chuck.
You can get a 4MT tanged shank with an ER collet chuck on the end. Get one that takes ER collets big enough to hold a 5/8" tool (ER-25, 32 or 40) and get the appropriate 5/8" collet. Or you can get a 4MT X 5/8" end mill holder. Then get a (preferably new condition) 5/8" shank floating tool holder with a front end that has a 1/2" bore with a set screw. Hardinge, Brown & Sharpe, Somma and "no-name" made such tools and they are often found on eBay.

Stick the collet chuck or end mill holder in your tailstock and make a mark on both the tailstock ram and collet chuck, maybe at 12:00, so you can always insert the chuck in the same orientation. Then mount the floating tool holder in the collet chuck or end mill holder with the set screw and the two adjusting screws in a convenient location. Turn a short piece of metal held in the lathe chuck to .500" and use that to get the 1/2" bore of the tool holder adjusted to center. Leave the floating tool holder in the 4MT tool forever and dedicate it to use with your sensitive drill holder.


https://www.ebay.com/itm/224459288529?hash=item3442d0efd1:g:YAkAAOSweC5fj2CZ&amdata=enc:AQAIAAAA4OsJkFM6VncOKnsuObEM9oZLBhuguj9sXGVg1r9ozpDklxU3neNRKKfvkue4Ggp9FTtup87E5S+2J+oPDtonmOGD+jG4L7U5wXfEziJCs4+BFXtnyyFhX2Zj8cuagM6YL8li24+FqHojOjJDWWfo6tUJeh9WKSjnxJb/99VOr3tbyvud8ZQZftc9wPNH2Zn+ye23Gi11o7OwNwwWrei4iZmExpO7IZD5ImTLAf9Dvh+a3Errb0AIakD/Im7dph5o/HnzunWOTPSNpZTAvj55QuGWnNw02hZ7aJVPH5UX8rW8|tkp:Bk9SR6jczeWBYw (ER25 5/8" collet)

https://www.ebay.com/itm/225493202149?hash=item34807134e5:g:3AgAAOSwLiNjQnDa&amdata=enc:AQAIAAAA4FSvMVw+kWJAm8ID35nJWHn423S7CHbUtMN8oO3A2GU9IRPRBXKfVKhydS5WN9CyCKLNA67aFPLQW3g0z/6+QMiMSuGi1ydpVDYEvulsGRc4XV3SeZw0WbJl9eto/76oRLOwubCPBNAGfL9z4u7vzKyTvIL/qCwe+4lB9q8mz7Z39qYew260tP15U346Wn4NQz+wWz6EpDqtO7Te0DnrRWO7kw1Vx7xDDODWtFKFgbs/AgqSRDl7T0n/U+NXatwhRfyzu7ueVodzk3UN2EyhHi1TJyu2es7yD5msgWbO7Hwv|tkp:Bk9SR7z2heWBYw (Get the MTA4-ER25)

Or get an end mill holder with MT4 tanged shank and 5/8" bore.


These are floating tool holders for drills, not taps.


Larry
 
Don't forget to eat your weetie's takes a lot of strength to feed that drill in without pre drilling it.
 








 
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