Yup, the title says it all. I need a machinist to drill and tap a redding T-7 toolhead from 7/8-14 to 1-1/4-12.
I saw one done some years ago and there was sufficient meat to handle it. I have several uses for this but have no equipment nor talent to accomplish it.
I'm pretty sure this is where the machinists of the gun folk hang out...There is one brand new tool head, perfectly flat on the bottom, with 7 holes. It appears to be iron or steel. It certainly isn't aluminum.
Would be nice if a machinist started up a vendor thread. ;)
The problem is going to be that the toolhead is more than likely hardened requiring the use of carbide tooling, which is simple enough for the boring part but carbide taps are expensive and easy to break or necessitating the use of a faceplate and 7 setups to complete. A quick test with a file will tell you how hard.Quote:
Originally Posted by AbitNutz
I think your best bet would be to find a small cnc shop with thread milling capability that can do this job on a vmc.
But yet it's not. Just simple cast iron, very easy to machine, in fact the carbon in the cast iron acts as a lubricant as anyone who has ever drilled cast iron will tell you.Quote:
Originally Posted by akajun
If it's cast it's an easy job, just find someone who can set it up to drill on center of the existing holes. With the right guidance an apprentice could do it.
Any machine shop can do that.... Its just the cost involved on doing it on a CNC...
Yep! If the OP had a thousand of them it would be fairly cheap :)Quote:
Originally Posted by M.A.D
I might be able to help you.
Listening :)
The thread size might be the sole issue. Also unlike bolt holes in a farm inplement you want the tapped holes pretty darned straight :-). IT CAN be done on say a Bridgeport but guiding the tap PERFECTLY straight is the issue, we have ways of doing that
Having run a cnc mill for decades (out of the cnc trade now) I can tell you that a thread milling process will do the NICEST job. The thread will be perfectly aligned to whatever you want it aligned to, and to location within a few .001"
I would try to get ahold of this guy, and have pictures of the whole project ready to send him. I have never talked to him but watching his vids he seems to be an OK guy.
https://www.nyccnc.com/how-to-machin...er-fusion-360/
He is into gun stuff, and the G code for that thread size has future value, not a difficult part to write a program for.
Over the years since I started in the machinist trade I have done and seen a lot of "heck yea this is an easy job" especially involving threads.
(long story)
One shop where I worked we machined the hydraulic cylinder for the Abrams tanks....very involved cnc program, took 8-12 hours of cnc time to machine one, lots of deep drilled holes 1/8" or so in diameter....8-10" deep. One supervisor got "sold" on a tapping head mounted on an articulated arm...the arm kept the tap square, an air motor ran the tap in and out. The idea was to run the cnc making parts, and have the operator tap the tapped holes in the parts while the machine was running. Pushes some cycle time over to the secondary operation....can give you more parts per shift. So "Bob" goes to town on these parts with a 7/16-14 tap, each end has like 12 holes...he does not bolt that parts DOWN to the table top on the machine. He does a whole months worth of parts, more then 20 of them...24 holes each. Then they hit inspection.....oops the tapped holes are in at all kinds of angles, the inspector dug out several 7/16-14 gauges and you could see a few degrees of angle to each hole compared to the others. So they had to go to Cadillac Gauge (the customer who supplied AM general with the part) and have them approve a heli coil process, they tested a part to destruction and approved it. All 20 parts with 24 holes each had to be setup, holes bored on location, tapped, and heli coils installed.
Bigger taps especially can be challenging to control while applying rotation with a tap wrench or a crescent wrench...it CAN be done...but it is tougher than it looks.
One COULD bore all the holes to location on the mill, then setup the part in a decent sized lathe on a faceplate, indicate the holes in, then single point thread each hole.
Bill
I'd say the hardest part would be to tap a straight, clean thread. If the ram was removed, the base and turret could be mounted (assembled) on the table with clamps and setup blocks.
Locate the center of any hole you like and use the detent on the press to index each one. Clamp, bore, tap, un-clamp. Turn the turret till the next hole clicks in. Repeat.
I dont agree with this notion. If you have this set up on your lathe and drill and then bore the hole, it will be completely concentric with the tailstock of the lathe.
All taps have a counter sink on the end which is set up to prevent this problem. You'd lube the hole with cutting fluid, put some on the tap, insert the tap into the hole as far as it would go, then move the tailstock up with a regular tungsten point it it to engage the tap. Lock down the tailstock, lock the headstock so it can't turn and then put some pressure on the tap with the ram of the tailstock.
Now, get a wrench and start to turn the tap into the work. At the same time, keep the pressure on the rear of the tap by advancing the tailstock wheel. It's easier if a second person keeps pressure on the tap. If you work at it like this, it's hard to see how your tapped hole won't be perfect. Back in the old days, people did some pretty amazing work on manual lathes. Outfitted the Armed Forced for 4 wars before CNC came on the scene. Not faster, but cheaper!
Sometime ago I threw out a project to this forum to see if I could find a machinist to convert a Redding T-7 Toolhead from 7/8-14 to 1-1/4-12. Little did I know how big a job this would be. Also, little did I know how great and talented the people really are who frequent these forums.
The gentleman that contacted me goes by the name KADADOG. His work was impeccable, his speed on getting it done make the Star Ship Enterprise look like it was tied to an intergalactic stump.
I can't say enough good things about him or how he rescued me and my project. The truth is, this project could have turned out to be a nightmare if the wrong guy hand got a hold of it.
So again, my thanks to KADADOG and these forums. If anyone needs some custom machine work done and he is willing to do it, I wouldn't hesitate.
Maybe Don will chime in and tell us how he did it...
It all sounds good...to use more precise terms if you bore the hole the hole will end up aligned with the Z axis of the lathe...the tailstock being exactly aligned with the Z axis is a different issue.Quote:
Originally Posted by Zbench
Sure you can shove the tailstock center into the center in the back of the tap, but then you need to turn the tap..which is a large one...takes quite a bit of torque...while cranking the tailstock quill at the same time....and when we are done we want it all within .001 :-). Once it is setup, why not just bore the thread with a single point tool ??
Bill
My issue with the lathe-boring method would be having to setup 7 times. There are ways to simplify it but a lathe (IMO) isn't the best machine for a job like this.
Same method, do it in the mill then. I just don't think a few .001 either way is going to blow up the apple cart. Are your shellholders lapped to that degree of accuracy? How about the top of the ram? I think sometimes "theory" gets bound up and overcomes "reality". Sounds like the OP got the job done. I'd be willing to bet that Don didn't use a CNC to do it though.
I am not old, but am 52 and it seems that button pushers are the norm and manual work may be falling by. 30 years ago, you could walk into a decent machine shop with a small job and usually have it done well on manual lathes, mills and surface grinders. Now, if you walk into a machine shop the first thing they want to do is write a program for a 1 off job, gets expensive in a hurry. Are we starting to loose the art of manual machine work? I have seen so many things that were completely perfect come off of manual machines, sure it is a pain when things get complex but not understanding the basics of manual machining to me seems like a big downfall.
I am not a machinist, but was learning from a darn good one at one point before he passed. He fabricated all of the repair parts for a GE lighting special products facility. I really miss watching him work. His personal home shop was amazing. He loaded and cast commercially in his spare time and even made a few moulds that we shot in some very obscure rifles he owned. He made some beautiful paper patch moulds over the years. Right before he passed his shop burnt down, lost some of the prettiest rolling block and falling block rifles I ever got to shoot. He machined and built a 22LR Gattling gun that was so much fun.
Zbench is right on about the tolerance. Look at how much shell and the shell holder are able to float in the ram. Even +/- .010" probably wouldn't hurt anything.
My point exactly. People forget when using a tap, that the minor diameter of the hole does indeed rub on the groove valleys of the tap. Unless you are really inept, it can't get that far off in practical use. Plus, since it's cast iron, the chips quickly break, not like mild steel. Tapping cast iron is one of the easiest things in the world to tap. Not boring a car cylinder here.
Quote:
Originally Posted by JSnover