New QCTP a tad too big ..maching it down perhaps

[Round in circles]

New QCTP a tad too big ..machining it down perhaps

Well the title gives the game away . I've lashed out ,spent the rent & beer money to buy a $200 (ish ) dollar two face QCTP.

I turned the 1/4 " off each side of the anchor bolts retaining flat plate nut down to get the centre mounting bolt arrangement to slide in & out the top slide like a dream . The bolt is way too big for my "Tee " nuts as it totally fills the top of the inverted " channel on the top slide .


On mounting the actual QCTP and putting in a 5/8 shanked tool in a holder I became aware that the piston that locks the tool holder was showing about 1/2 " of piston face above the top edge of the holder when the holder & tool were set for the correct cutting height . The holder is still fully contained on the main QCTP block with about 5/16" of the base of the block showing clear below the cutting tool holder in this current position so I'm not worried that it may be tilted or about to tilt right now .

I ran a test cut ..it works well but I'm a bit concerned that there may be wear /movement developing in the future . Is is a sound idea to turn or have someone mill off the bottom 5/16 of the QCTP block to lower it and thus enable the tool holder to be raised and fully cover the piston face or should I not bother about it ?

When I ordered the QCTP over the phone I gave them distance from a new dead center set in the headstock spindle to the flat of the bed which is 5 & 5/16 " . The suppliers said , " In that case you'll need the mid sized QCTP then" , & that's what they supplied & I paid for .

 

[Jim2]

Hmmm. . . . I've only just entered the wonderful world of QCTP recently myself, but it does sound like your toolpost is too large. I'm not sure what options you might have since you've modified the tee nut? Maybe it's not too late to exchange for a smaller one?

Maybe post up a picture, so you can get some better input.

Jim

 

[mce5802]

What size lathe do you have? I'm assuming it's a bxa size holder if it has a 5/8 slot in the holders.....which is good for 10"-15" swing. I recently made a mistake in the other direction, having to put a 1" riser block under my toolpost. I knew when I ordered it that I'd have to do this, but what I didn't realize was the post is too small for the size of the compound, it's hard to get up close to the chuck. Guess they size em the way they do for a reason. The better ones are made of tool steel too so would be tough to machine without carbide tooling. Maybe you might think about getting the next size smaller (AXA maybe, depending on your lathe swing) and selling your current one on eBay. I'm sure someone's looking for one.

 

[Round in circles]

Thanks lads,
I don't really want to fleabay the QCTP as I've also got a shed load of new tooling for the tool holders , I'd like as not have to take a massive hit on the resale price as well :nono:, :roflmao:.


I think that the QCTP sold to me is the correct size for a modern 10 " swing lathe , heck the lantern tool post had only just been invented when my 74 yr old old pensioner lathe was made :lmao:.
The top slide mount top face does indeed seem to sit quite high compared to a modern lathe.

When I posted the help request I hadn't tried to see if it is hardened but suspected it might be . earlier tonight i tested it with
a brand new 2nd cut file , it just skidded off the corner of it so that answers that part of my question like a sledge hammer on my thumbs . It's either a quality carbon steel for the QCTP & tool holders or case hardened mild steel .

I do have the tipped tools to cut it but at 12 mm to tear off it could be a very long job plus the whole reason I'm changing the older four way block tool holder is that there is a tendency for the thing to rotate a few degrees over a couple of hours of actually turning , especially if I'm trying to take down corners and it becomes a smidgin clonky as it hits /taps the corners .
Once I've got rid of the majority of any corner it settles down and stays put ....... Well most of the time . :lmao:

I guess I will now go and see what a specialist engineering company very local to me will charge to precision grind off the unwanted part ..at least it should still be square & true with the gear they have in their workshop as it may be the cheapest option in the long run..

 

[schor]

I would go back to the place you bought it from and tell them they sold you the wrong one, you really want an axa size for your lathe.

 

[kd4gij]

I would agree that an AXA is a better fit for older 10" and 12" lathe. But he said is has alot of 5/8" tooling it that won't fit a standerd AXA tool holder. I would use the BXA-200 tool post as is.

A picture of your lathe with the tool post mounted would help.

 

[schor]

I would agree that an AXA is a better fit for older 10" and 12" lathe. But he said is has alot of 5/8" tooling it that won't fit a standerd AXA tool holder. I would use the BXA-200 tool post as is.

A picture of your lathe with the tool post mounted would help.

Ah, yes the 5/8" tooling.

Throw the toolpost in the 4jaw, indicate it true and turn it down would be my method.

 

[Jim2]

Possibly a bit unconventional, but perhaps toss your compound aside and fabricate your own riser block in its place? That way you'll have a more rigid setup, and maintain a higher level of adjustability w/ your toolpost. The compound is really only used for threading and the occasional taper. . . . Well, it's a thought anyway.

Jim

 

[roadie33]

Ah, yes the 5/8" tooling.

Throw the toolpost in the 4jaw, indicate it true and turn it down would be my method.

^^^
What Steve said.
That would be the easiest way with some good Carbide tooling.

 

[Round in circles]

The mono block I have at present that I can turn things with ( but it rotates a tad occasionally ) it sits on a precision ground bright steel spacer .


The 74 yr old pensioner with the modern QCTP mounted .


Part of the piston showing at the top edge of the tool holder , cutting tool is at the right cutting height .


Line up view of the new QCTP .
Note the excess I can take off at the bottom of the block but as it is hardened or quality steel it may have to be precision ground off ..... Professionally .
I reckon 1/2 " off the bottom face will allow the piston to be sufficently covered to stop any wear forming over time & there still be plenty of travel for the tool holders to sit well on the keyway .