marking out pcd's

I have the clarke cl430 lathe, and still learning how to make things.

would like to get some more chucks from arceuro but they are different pcd to my lathe.

with limited equipment how do i mark out the pcd i need for other chucks?

i need to mark out 108, 84 and 66mm. clarke is 115mm

I did make one backing plate using 1" ali rd i got the clarke one's marked out then bolted it on and turned it match head on lathe.

then marked out the 108mm and drilled it but was slightly out.

managed to be able to use it as was on 4 jaw independant.

but wont get away with it for other chuck's i want.

cheers

Usually you need to turn a register on the backplate to locate the chuck radially. This should be a light press fit so the chuck clicks into place. Locate the chuck on the backplate and spot through the bolt holes with a drill that just fits them. Remove chuck and drill holes either clearance or tapping size depending on how you want to hold it. No need to mark out a PCD as such.

Did you machine a register / step in the backplate that then keys into the back of the chuck.?

Don't get me wrong it's nice and good practice to get the holes spot-on but the 2 keyed together will allow for some slight leeway in the holes matching exactly.

Nick

Edit :- I see I posted at the same time as John.

Edited By Nick_G on 17/03/2015 08:21:11

i cant get to holes on other chuck once i place it on backplate as it bolts from back.

or am i missing something?

like i say still learning.

or do i mark out holes then drill them slightly oversize, after turning register?

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I recently mounted a chuck onto a backplate. A different kind of packplate but the principle is the same.

I did make a video of the process here. **LINK** I however cheated with the PCD's and used a DRO. But I am sure it would have been OK without providing the register was a good snug fit.

The bit that shows the register is at about 8 mins in.

Nick

will look at that at home ta.

can't open it on works comp.

sounds like what i have done wrong is drill holes to fit second chuck, before turning register.

because have had to make register slightly under size.

> sounds like what i have done wrong is drill holes to fit second chuck, before turning register.

If its anything like the usual backplate, you will have plenty of spare metal to play with.

The whole thing depends on the register being accurate, for good balance as well as accuracy.

You can turn off the register you have made and start over without losing anything but a bit of pride

Fit the backplate to the spindle and turn the face smooth. Remove the studs from the chuck and turn a register that is the closest shake-free fit you can get in the back of the chuck.

Put the studs back in and enlarge the holes enough that you can fit the chuck without any of the studs rubbing on the sides of the holes - this is so that the register is the only thing that locates the chuck.

Job done.

Normally you would use a sharp point to draw a circle at the right PCD for the stud holes. There are lots of ways to index or mark out the locations for the holes, but as they need to be clearance their exact position is not critical.

Neil

am using some 6" x 1" ali rd stock as cant find backplate right size od of chuck is 133 mm.

marking out holes to fit backplate to lathe aren't prob cos if slightly out when i turn od to right size it comes out right.

so if i am reading things right, get first 3 holes right , i then need to turn female register, turn it over and turn male register to fit other chuck?

then i need to find way of getting holes for new chuck in right place.

Man thing is that the male register needs to be turned with the backplate fitted to the spindle. 1" is plenty of metal to play with, my 4" backplate is 1/2" thick and though the 'flywheel effect' is useful it doesn't need to be thicker than the 1/4" flange it is attached to. You could let an alloy backplate have a bit more meat in it.

How many studs in the chuck and do you know the PCD (pitch circle diameter) of the holes?

If its three, scribe a circle the diameter of the PCD with the backplate on the spindle, set a pair of dividers to the radius of this circle and step around it making six marks (remember drawing hexagons this way when you were at school?) Drill every other mark.

Another way, crude but effective, is to take the studs out of the chuck, and place a sheet of paper over the back. Rub with pencil or grubby fingers and you should be able to get an impression of the outline of the chuck and the fixing holes. <sensitive souls look away now> Carefully mark the centres of the fixing holes and use this as a template when setting out the holes on the backplate, with care it should be accurate enough as they are clearance holes.

I used this method to set out the holes for this cylinder head, as I scrapped thr first one after I had spotted through the locations and tapped the block.

Neil

most of chucks are 3 hole but the 4 jaw i have is 4 hole.

A simple and accurate method for drilling the holes in the backplate. No DROs (really) no rotary table , no marking out and no filing, but you do need a bench drill. Firstly, as discussed, initially turn an accurate register on the backplate.

Take a length of, say, 10mm studding, nuts, and a couple of pieces of steel plate or large washers with a 10mm hole. Grip the studding tightly in the chuck and using one washer below the jaws and one below the central hole in the drill table lightly tighten a nut up from beneath. The chuck is now lightly clamped, backside uppermost, on the drill table. Determine the appropriate tapping size drill for the threaded fixing holes in the chuck and insert into the drill chuck. Now position the 3-jaw chuck by rotating it and swivelling the table on the drill column until one of the chuck fixing holes is aligned with the drill. Quicker to do than to describe. Now firmly tighten the bottom nut so that the chuck is tight to the table and ensure the drill remains aligned with the hole. Place the backplate on the chuck and clamp it in place with a nut and washer on the upper protrusion of the studding. Now drill through until the drill just breaks through the backplate. Remove the backplate and using some wooden packing on the back of the chuck body drill the backplate hole clearance size. Remove the packing, deburr the hole if necessary and then using the appropriate fixing screw attach the backplate to the chuck with one of the other fixing holes, not that one aligned with the drill. Repeat the process as above, then again for the final hole. Dismantle all, clear the swarf from the screw holes and checking again for no burrs finally re-assemble. If you have a milling machine or a tailstock drill pad for the lathe then drill the clearance holes thereon, no messing about with packing. Ideally it would be better to make a stud of appropriate length with a short thread at each end so that the chuck jaws grip on a plain shank but studding will suffice if well tightened.

Probably quicker to do than to type about.

Michael

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Better dig-out those old geometry books !!

... It's a simple matter to construct a right angle, using dividers.

MichaelG.

Or set the dividers to 1.414 x radius.

Neil

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... ish.

http://apod.nasa.gov/htmltest/gifcity/sqrt2.1mil

... Construction by Euclidean Geometry is so much more elegant.

MichaelG.

Edited By Michael Gilligan on 17/03/2015 15:25:30

Edited By Michael Gilligan on 17/03/2015 15:36:41

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'Naughtyboy'

Where abouts in the country are you.??

Maybe somebody can help you with this.??

Nick

i am in wf15 nr leeds yorks

If its a front fixing chuck eg one where the bolts go right through then make a transfer punch. Just a bit of bar that is a snug fit in the hole, turn a point on it probably get away without hardening. Place chuck on register, punch in one hole and give it a tap. Drill and tap this punch mark and put chuck back onto register and retain with one screw, repeat for opposite hole and then do the other two.

If its back fixing eg threaded hole in the chuck and screws come through the backplate then use transfer studs. Take a bit of studding or thread some rod to fit the threads in the chuck, cut 3 or 4 bits and again turn a point on them. Screw them into the chuck threaded holes points facing out so they are just proud of the back, place chuck on register and give it a tap with a soft hammer. Teh pointed studs will have marked the hole positions

Good advice by Neil and a couple of others, turn the register the critical bit. Reading between the lines your not bolting aluminium as a sandwich to chuck and back plate, if so forget it?

Easy way and mentioned this before, no need to faff about with anything else other than a driller!

Remove jaws from chuck and clean off face.

Place chuck upside down then double check fit of back plate then remove.

Line up any of the three tapped holes with same drill size looking for deflection. No need to clamp. Drop back on the backing plate without moving anything.

Drill through back plate then redrill again clearance or dead on size, most are M10 so 10mm fine.

Line up next hole as above, this time bolt backing plate to chuck then drill through tapping size.

Remove bolt and back plate then line up last hole. Drop back plate on bolting down then drill through.

The only thing that can go wrong is user moving the chuck out of alignment. To do all above looking around 15 mins.

There are lot's of ways (variations on a theme) of doing this but the one I use is as follows..

As Neil says - turn your register - and initially try to get a very good fit on the chuck - no movement

Then mount a faceplate true on the cross-slide and bolt your chuck (facing outwards) to it with a bolt (or threaded rod) through the chuck centre. Install your drill chuck in the lathe mandrel, together with a bit that is a close fit into one of the chucks mounting holes. Juggle the chuck around on the angle plate till the drill will just enter one of the chuck's mounting holes. Once the drill enters the hole smoothly (use the saddle movement to test it) tighten up the chuck's through bolt.

Change the 'aligning' drill bit for a centre drill and place the back plate onto the back of the chuck and clamp it (I use a large G clamp). Start the hole with the centre drill and then change it for a 'clearance' bit (e.g. a drill size that is a clearance size for the tapped bolt hole you just lined up with). Carefully drill into the back plate till you are almost through it. Unclamp the back plate and finish drilling through it in the drill press. I will admit that I didn't last time around - I did it all in the lathe but was very careful not to drill into the tapped hole

Then it's easy. Rotate the back plate - use the new hole to bolt the back plate to the chuck and centre/clearance drill the second hole - BEING VERY CAREFUL NOT TO DISTURB THE CHUCK. Unbolt the first hole, rotate the back plate again, bolt 1 & 2 holes up - and drill the third hole.

Now you can just leave it like this and it should be good.

However, I like to mount the back plate onto the lathe and take just a 'smidgen' off the register - enough to allow a slight adjustment. I then bolt the chuck on (but lightly) and test it with some 12mm silver steel gripped in the jaws - just tapping it true against a DTI. Then I tighten the back plate bolts fully and test again. Obviously a 3J may not be true on other material sizes but I know that it should be fairly good in at least that one spot.

Hope this all makes sense. It's easier to do than explain.

You will need a fairly large angle plate to do it like this but they are very useful items to have on the lathe anyway...

Regards,

IanT

Gordon Bennett what a load of faffing about, if half you lot worked for me I'd sack you in a heart beat. [ no smiley ]

Turn register to a good fit, screw 3 cup point allen grub screws into the threaded holes on the chuck cup side out. Just leave enough so it sits on the register and you can remove the screws with a pair of snipe nosed pliers.

Sit backplate onto the chuck supported on a wooden block and whack the back plate.

Once removed you now have 3 small circles made from the cup heads, mark out the centre and drill clearance holes to suit.

Takes 16 times longer to type than do.