Just finished my QCTP.

[websterz]

Nothing new under the sun, but here's my take on the QCTP anyway. I started out with a 2" cube of 12L14 which turned into the post body. The cam is a piece of 303 stainless round I had knocking around the shop, and the center post is 3/4" drill rod. 1/4" drill rod was used for the handle, and 1/2" for the 2 pistons. Here it is all fitted together:



Here is a view showing the parts spread out a bit:



My solution to the problem of keeping the pistons from falling out is shown here. I drilled holes up from the underside of the body that bisect the piston holes. 8-32 setscrews hold short lengths of 1/8" drill rod in place. Each piston is cross drilled with a 3/16" hole to allow it plenty of movement while still being trapped in the hole by the pin:




The tool holder shown is just a quick test piece I made from a scrap of 7075 so I could check the function of the post. Future holders will be made from steel for extra mass and rigidity. A test with the parting tool shows the setup to be extremely rigid. I am a happy camper. It took me 3 days of on and off work to build, probably 10-12 hours total. I apologize for the less-than-stellar pics. My wife has the camera in her car and I was forced to use my cell.  I will get some video of it later on this week (if I get my camera back that is  ).

[jamoni]

So the cam was turned with an eccentric, right?  Are all the sliding surfaces hardened?

[websterz]

So the cam was turned with an eccentric, right?  Are all the sliding surfaces hardened?

I did all the lathe work in my 4 jaw chuck. I didn't measure the cam offset, I fly by the seat of my pants a lot.  Checking it just now there looks to be about .048" offset.

I don't plan to harden the post...12L14 probably won't respond too well to heat treatment. This goes on my 7x12 lathe so it's not a high use production environment.  It will likely outlive the lathe.

One change I may make is to replace the 1/2" round pistons with rectangular ones (or at least larger round ones) for better contact. If the tool holder's not fairly centered it wants to cant a bit when I lock it down.

[Bernd]

Nice fly-by-the-seat tooling.   

I've always figured it was complicated making one of those holders. I do have one on my Logan, but need more holders for it. In order to make those I need a dovetail cutter. Just to many excuses to use for procrastination on making one. Perhaps on the next tool order. 

Bernd

[NickG]

Nice work Websterz. This is on my list of projects but keeps getting pushed down. It's still on there because I can't afford to buy one but different models keep jumping in the way! I think what's putting me off is the number of holders I'll need! 

Great job though. I can't see the need for hardening either really.

Nick

[websterz]

I suggest making a tool holder first, then building the tool post to fit it. The reason being you need to make sure your dovetail cutter is small enough to cut the female dovetail in the holder. I went the wrong way and made the post with my fancy inserted dovetail cutter that I made last year. It did a bang-up job on the post but I made the male dovetail narrower than the OD of my cutter so using it for the holders was impossible. Luckily I found a resharpened 60* cutter in my stuff that was small enough. It was no longer 60* though, closer to 55*. I dressed the toolpost with it so that the angles match. I don't plan on using holders other than the ones I make so the angle isn't critical...it just has to be consistent.

[NickG]

Thanks, i've got  a normal 45 degree one that's definitely small enough, I know they are not supposed to be as good as the dovetail won't be quite as strong but it should do the trick.

[Rob.Wilson]

GREAT JOB websterz 

Looks like it will give you good service for life    nice one 


Regerds Rob

[websterz]

GREAT JOB websterz 

Looks like it will give you good service for life    nice one 


Regerds Rob

Thanks Rob! 


I tried it out yesterday for the first time. Normally I like to do all of my parting off with a rear mounted toolpost, so I thought that would be a good test for rigidity. My usual shop work consists of lots of 9/16" 4140 round stock. It's not uncommon for me to make 100 parting cuts a day on my (heavily modified) 7x12 lathe. I ran 50 parts in just under 2 hours with the same old parting tool, but mounted in the "normal" position using my new QCTP. Rigidity was excellent and the cutter stayed on center throughout the course of the job. I noted that I need a little extra clearance between the back side of the holder and the sliding face of the toolpost, as there was a bit of binding when I removed and replaced the holder to test repeatability. The holder is a trial piece made from 7075 with the intention of using steel in the future. If the aluminum holds up under repeated use (and I expect it to) I may forgo the steel and stay with aluminum for it's ease of machining. I will be reworking the pistons before I am finished tweaking the post. The small round pistons don't have enough bearing surface for my liking and I will replace them with much larger rectangular ones that should provide a more even pressure.

[chuck foster]

great looking QCTP 

i have thought about making one but thought it would be next to impossible........................but you have give me the incentive to give it a try 

so i might be bugging you with some questions 

chuck 

[websterz]

great looking QCTP 

i have thought about making one but thought it would be next to impossible........................but you have give me the incentive to give it a try 

so i might be bugging you with some questions 

chuck 

Chuck, this thing was easy as can be. Really, there's NO reason why you can't build it! I just placed an order for all the stuff I need to do hot bluing in my shop. I can't wait to start finishing everything in the shop a glossy black!! 

Fire away with the questions...I'm ready!

[ksor]

Hi

Really nice peace of work  !

[websterz]

Hi

Really nice peace of work  !

Thanks ksor! Here's a pic of my morning project. Making toolholders is addictive!   I would have kept going but I ran out of 3/4" brass for the height adjusting nuts and had to order some more. I have 3 more feet of material set aside for making holders. That will give me a total of 21 assorted tool holders that fit this post. I plan to cut the dovetail and drill/tap the adjusting screw hole and leave them like that for future use. It will be nice to have blanks on hand for those odd jobs that need a special tool.

[Bernd]

I was going to send you my address and ask if you'd donate the un-used ones to me but I guess not, huh? 

Nice job.

Bernd

[websterz]

I finally got out to the shop today and made the new pistons for my QCTP. The 1/2" round ones didn't have enough surface area and the toolholders tended to cant to one side or the other depending on how high the holder sat on the post. Here is a new piston next to the old one:



The rectangular ones are 1" x 1/2" and contact the full height of the toolholder preventing tilt. I will get pics of the post in situ tomorrow (if I get any shop time in). The biggest advantage to making the post and holders, aside from the cost of commercially made ones, is that I can tailor each holder to sit halfway down the side of the toolpost when the cutter is on center. This way I can maintain full contact with the pistons at all times which makes things much more rigid.

I also took my old 2 piece plinth off and replaced it with a shorter, solid steel version. That got the toolpost down to a more workable height and reduced chatter considerably. A couple of packages arrived in the mail today. One was a handful of 2 inch long 3/8-16 cap screws, one of which now secures the post to the lathe. The other was a foot long piece of 3/4" brass. Now I can make more height adjusters and finish cutting my spare toolholders.