Fitting A Qctp

R

ronboult

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My new Sieg Runmaster 13 x 40 lathe has a rotating 4way toolpost as standard (Pic 1). I wish to mount a new QCTP which requires a straight 16mm shaft.

IMG_2659.jpg

Unfortunately the post on which the supplied TP is mounted has a 25mm boss at the bottom of the 16mm threaded section (Pic2) which will have to be machined away down to the top of the topslide.

IMG_2660.jpg
Underneath the topslide there is further enlarged boss to stop the toolpost pulling through with a locating roll pin to stop the post rotating when tightening the locking nut (Pic3).

IMG_2661.jpg

I need to remove the post for machining. I have drilled out the roll pin but can't easily decide whether the post is a threaded insert or an interference friction fit. That is do I have to unscrew the post or press it out on a press? From the marks on the underside I am pretty sure it is a press fit but I don't want to chance breaking the topslide if it is threaded!

I am sure I have seen a similar toolpost Q somewhere on the Web but a search has failed to find it.
Has any body seen a similar set up and can offer advice?
 
Although I can't offer any help on how to remove your threaded post as I never had experience doing so, my 8x14 mini lathe had a similar post. The QCTP tool post (from Lathemaster) I got for it was made/modded specifically for the lathe so I did not have to deal with machining down that boss.

The QCTP came bored out to fit over it. Not sure of your tool post has enough meat to bore out the bottom but if the tool post I had was bored out, possibly yours can too.


On the left is the bored out AXA tool post (China), on the right is an unmodified AXA tool post (DTM)
IMG_5429.jpg
 
Hi Will
Thanks for the info. I have purchased a Phase II BXA from USA and it is transit. Whether I can bore it out to fit will have to wait until it arrives. My inclination is still to make a "normal" 5/8 post. I still wish for a Dorian which I will purchase when funds are available and the Dorian will then just drop on when I get it .

Still finding my way round my new lathe, cleaning and adjusting. http://www.hobby-machinist.com/threads/new-sieg-runmaster-330x1000-lathe.35198/

More photos to follow.
Ron
 
Does the parts breakdown for your lathe show the post? If so, it will probably show whether it is threaded or not. If it isn't threaded it should be a simple job with an arbor or hydraulic press. As long as you support the top slide table close to the post I should think the risk of damage would be low.

I agree with you that it would be wiser to alter the post rather than the body of the tool post itself.
 
Hi mikey
Thanks for the suggestion.
I had already checked the part breakdown in the manual. Unfortunately the manual is Chinese and out of date. The topside shown in the manual has a Tnut like many USA machines. I think mine is made for the European market as I believe this type of toolpost is more common there. I have closely examined the top of the post where it exits the topside and can see no signs of a thread. That and in conjunction with the indents on the underneath disks suggests it is pressed in.
Ron
 
Yeah, I wouldn't want to bore out my Dorian QCTP like that. It doesn't make sense for that post to be threaded in but who knows. Most of the installs I see like this people just bore out the tool post. I did come across one video (not that great of a video) showing that the post was just a friction fit. But it's a completely different lathe. Hope you get it figured out.

It's too bad you wouldn't be able to make use of the Dorian's QCTP locking feature but I've only ever needed to use it once anyway so no big deal. And if for some reason you end up having to bore out the tool post, looks like there's room but I'm not for sure, I've never disassembled mine yet. I never really looked closely to see what those center parts are but I have an idea.


Img_1031.jpg
 
ronboult said:
a locating roll pin to stop the post rotating when tightening the locking nut
can't easily decide whether the post is a threaded insert or an interference friction fit.
I am pretty sure it is a press fit
Click to expand...

Hi
I think it is a press fit, try taping the shaft with a soft hammer.
 
I agree with tapping with a brass "adjuster" that whole toolpost looks suspiciously like the one on my Chinese mach from Sumore. Mine tapped out very easily.
 
Went out and refreshed my memory re: mounting my qc post .Rather than machining the original "bolt" I just bought an appropriate one at hardware store and modified the head as necessary. Kept the old one in case needed. FYI, I had a lot of tool chatter and hash marked finish when I began using it. Discovered the qc body was bearing on the compound only near the center ..near the bolt?...and was rocking in use. Machine or grind the lower surface of the qc body so that the center area is slightly recessed, leaving 1/4 to 1/8 bearing surface near the edges. World of difference !!
 
Hi
I agree make a new bolt & keep the old one in case it is needed.
 
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