Thread: Rotary Table questons

Hi Stuart,

Following the project with interest, just curious, what is "PCD" ?

Regards
Ray

Pitch circle diameter.
A series of holes on a certain diameter. In this case the dia is a little over a drill size less than the size of the bore and the number of holes is a little more than will fit on that circumference.

Bore 45, aiming for 43 so I can clean it up a little and its my first try
15/64 drill, call it 5.953.
circle diameter= 37.047
circumference = 116.38
circumference/drill=19.55
call it 20
Not sure if I should start with a small drill then open it out, but I'm going to try straight to size with a stub drill and see how it goes.

Stuart

I should add. You can do all the maths on this and position each hole manually or if you have DRO press a few buttons on the DRO then zero the axis, drill a hole, press "next hole" button, zero axis, drill hole, repeat until at the end with any luck at all the center falls out.

Well its done.
I set it up with a wiggler point then checked it with the coaxial indicator. It said I was 0.123mm out.
Problem one is you have to enter an end angle or the DRO does work. I thought it would assume "20 holes equal pitch" but it doesn't. So end angle = 342. Problem two is stub drills wont go through 50mm, so i had to go around twice, once with a stub and again with a normal drill. Problem three the center caught the drill as it fell as there isn't enough room for it to fall clear of the hole. Easy fixed just leave a little on the last how, but I do have a scrape on my brand new drill shank :'(.
Took 45 minutes machine time, and about 2 hours in total, the next one will be a lot faster.

Stuart

Is there a reason why you didnt machine it in the lathe.

Hi pc,
I don't have the best selection of small boring bars that are long enough. Although I'm sure I could have managed, it was more about getting some practice using PCD which I might need to use later in the build.

Stuart

Originally Posted by pipeclay

Is there a reason why you didnt machine it in the lathe.

Why waist it if you don't need to? Drilling and boring it out would have turned it into a pile of swarf, now he has the off cut to use on something else.

Stuart
Came out great.
I didn't think it would have come out so easy. Usually with steel the drill will run into the next hole unless you leave a bit between holes, which then makes it hard to get the piece out if it's thick. I suppose with the cast being brittle helped out a lot.

I see you have the DRO worked out, I bet you are now one of the DRO converted people that will be telling everyone else you don't how you did without it.
Unless you are doing the different functions every day you will need to keep the book handy.
I find having the 2 different brand DRO's gets me mixed up even more when doing different programs. Never had this problem so much, when I only had the Meister's.

Dave

The second one didnt come out so well but it only took 35 minutes from starting setup to hitting the center out. I didn't use the stub drill so had a little more wandering.

Just finished boring out the first one. I bored it to 45.38mm then carefully bored out the extra 0.38mm. oops lol

I must say the DRO does make life easy. I know it's possible to do PCD manually, but I cant imagen doing it. I'm used to g code so it will take awhile to work out whats different and whats not. I must say the end angle is a pain.

For to try some HSS on the taper.

Stuart

Ok I'm just about there. I have about 0.004" slop on the taper. how much do I need to take off the face? I think according to daves math its 0.0162, sound about right?
Stuart

The taper is 8 to 1 so I think you are spot on.
Have you used a bit of emery on the taper to get a really smooth surface? I would wrap it around a piece of steel or wood so it stays strait.

If you keep getting through your projects this quick you will list will be done in no time.lol


Dave

It feels pretty good as is but I was going to ask if that was a good idea or a bad one.
I've got it down to no slop but just a little rock which is where I think I want to be. The cams will pull it down, they cant stop it slopping. I'll try the faceplate tomorrow as it has the tightest taper. maybe blue it up just to see how close I got.
I think things might slow down a little after that as I have to start making T nuts etc before I can continue. I'll bore the pin holes using the rotary table instead of PCD as I think it will be more accurate. The mounting holes I will do PCD.

I'm sure I'll find an excuse to stop and move onto something else soon who knows, the vernier for the lathe tailstock might turn up tomorrow lol

Stuart

T nuts are going to slow you down after this?

I wouldn't bother boring the holes and just drill them. I just had a look at the ones in my lathe and they have only been drilled from factory. I think they are like that so they have a bit of wiggle room, same with the cam lock holes.

Dave

T nuts will slow me down, not stop me lol but it will end up being a couple of hours work in them. Still don't have a gas torch for blacking

oops I forgot, I have an endmill that should do the pin holes. Around 16mm from memory, just need a pilot hole first.
The camloc holes I'll have to bore if I am going to match the standard size locks. I'm pretty sure I dont have anything that size. I'll check again in the morning.

Stuart

Originally Posted by Stustoys

It feels pretty good as is but I was going to ask if that was a good idea or a bad one.
Stuart

If you don't use a bit of emery or an oil stone to knock off the little highs to make it really smooth, the face plate, chucks etc will wear them down over time and then you will have a loose fit. Remounting it to take a skim off the face latter down the track will be a big pain in the ar*e.
It really matters on this job because a small amount off the tapper makes a big difference.
When I remachined the chuck and face plate that I bought off ebay I did this, and have never had a problem with the fit from wear. As for fit I like mine to sit off the the face about 1 or 2 thou and then the cam locks pull it up.

Dave

I'll give it a polish first thing. Then get out the blue and some shims.

Stuart

Going to have to get myself a pc for the shed.