I need an unusual faceplate, or something else

[KentRigby]

Hi,

I bought a Seig C3 lathe to play around with and convert to a CNC lathe. It has a 4" faceplate with a three hole pattern and an MT4 spindle bore. But all of my existing chucks have 1" or 1.125" x 8 TPI female threads. I have been searching for a faceplate I can bolt on that has a male 1" or 1'125" x 8 TPI thread so I can attach my existing chucks. I'm not finding anything that will work.

Does anyone have any suggestions of
1) where I can buy such a faceplace, or
2) some other way to be able to attach my threaded chucks.

Thanks,
Kent

Update: I've attached some pictures of what I have been using (a Craftsman 101 with a threaded spindle), the chucks I hope to be able to use, and the faceplate on the Sieg lathe. I hope that helps to clarify things.

 

[ChazzC]

Hi,

I bought a Seig C3 lathe to play around with and convert to a CNC lathe. It has a 4" faceplate with a three hole pattern and an MT4 spindle bore. But all of my existing chucks have 1" or 1.125" x 8 TPI female threads. I have been searching for a faceplate I can bolt on that has a male 1" or 1'125" x 8 TPI thread so I can attach my existing chucks. I'm not finding anything that will work.

Does anyone have any suggestions of
1) where I can buy such a faceplace, or
2) some other way to be able to attach my threaded chucks.

Thanks,
Kent

Please ignore my original post, I didn’t read your post correctly.

You want a backplate with either a 1”-8 or 1-1/8”-8 mount that can be fixed to the C3 3 & 4 hole spindle: everything I am familiar with goes the other way, allowing a flat-back chuck/faceplate to mount on a threaded spindle. The other adapter I have used just allows a threaded-back chuck to fit a different threaded spindle.

I’ll keep looking.

 

[markba633csi]

You mean the spindle has a 4" flange with 3 hole pattern? And you don't currently have any chuck that fits it, correct?
This would fit but still would not accommodate your existing chucks unless they have removable backplates:

Adapter, 4" Lathe Chuck 2426

Lathe Chuck Backplate Adapters 2426 Compatible with 4" 3-Jaw Lathe Chuck on Mini Lathes; Use with Chucks with a 70 mm Registration Recess Diameter; Wo...

littlemachineshop.com

AFAIK no one makes a flange mount to male thread spindle adapter- such an arrangement would be less than ideal
Ideally you want the chuck as close to the headstock as practicable with a minimum of adapters

 

[Uglydog]

Any thought of using an MT4 shank from a used up drill, fixing a plate and turning it so it's centered?
If you went this way. I'd only use it with a live center.

Daryl
MN

 

[homebrewed]

LMS sells compatible 3 jaw and 4 jaw chucks. A plain faceplate is around half the price for a chuck, but a bolt-on chuck will provide better all-around performance. The price for a purpose-made adapter, if one is even available, likely would be comparable to a chuck anyway. Low demand = high price

The incremental cost if combined with a CNC conversion is relatively minor. Something to consider.

 

[ChazzC]

I have not been able to find anything like what you are looking for. You can try calling Little Machine Shop - they are always helpful, even if it is something that they don't have they will tell you who does.

However, I'm afraid that the only solution is to make (or have made) the adapter. I have an MT3 arbor that is threaded 3/4-16 that I have used on my 7 x 16 Mini-Lathe but only for work that is close to the headstock. I have not found any MT4 threaded arbors (and can't find the MT3 one I have listed, either).

ABM Tools has blank MT4 arbors threaded for a drawbar, so you could cut you own 1"-8 threads (max size of the blanks), but while the drawbar would keep the arbor secure in the spindle, as @markba633csi says, such an arrangement would not be ideal (to say the least). Also, using a threaded-mount chuck for a CNC lathe would limit the usability (no back-side tool bits).

I think your best bet is to get new chucks & faceplates. BTW, what you are referring to as the "faceplate" on you SIEG lathe is the Spindle Mounting Plate; this is a faceplate that would fit your lathe:


Here is a dimensioned drawing of your spindle (PDF attached); per the drawing is MT3, not MT4:

 

[OTmachine]

Any thought of using an MT4 shank from a used up drill, fixing a plate and turning it so it's centered?
If you went this way. I'd only use it with a live center.

Daryl
MN

And since drill shanks are soft, you could drill and tap for a draw bar.