Stuart 10v cylinder Cover PCD on warco DRO

tried many times now to get the PCD function on warco D60-70 dro to work when creating the hole pattern for the Stuart 10v cyclinder covers.

Even put the gasket down to see how the first to holes lined up and spot on but tend to drift on the 3rd hole and then the last 2 are no where near.

followed YouTube ... done little machine shop calculator and all looks ok but holes do not match.

I am doing a bolt circle on a 1.125 inch pcd...5 holes...starting angle 0 ending 360 (which seems to be correct when watching you tube vids). Centre on zero bang in the Centre of cover plate.

enclosed a photo.

Edited By Matt Homer 1 on 01/08/2017 23:19:35

Edited By Matt Homer 1 on 01/08/2017 23:20:20

Most DROs need you to enter the start angle eg zero and the angle of the last hole 288deg in this case (360-72)

I think you'll find it easier to use the cover as your drilling jig , use transfer punches through the holes already drilled to pop your hole centres, if you don't have any make one out of hardened & tempered silver steel, IIRC mine was an offcut of 2.5mm. I have sets of transfer punches but they are too long for such a small cylinder hence making one about 2" long.

​George.

Looking closer Georges method may be better as the holes in the cover do not look equally spaced, the lower two being further apart so DRO won't compensate for that.

Don't you just dial up 6 holes starting at 0 and ending at 360 ?

regards Martin

Not tried it that way Martin but sounds like it would do the same thing with hole 1 & 6 being in the same place. Will stick a sharpie in the mill and give it a go.

Though entering the right number of holes can be handy if not drilling every one as it makes it a bit easier to keep track of where you are especially if there is more than one ring of holes on a part.

Looks like X-axis backlash issues to me.

Check that the doodah that moves your read head hasn't come loose.

Neil

It does mean you can't really make mistakes in calculating and inputing the final hole angle though.

regards Martin

Hi Matt,

I find the easiest way for holes on a PCD is to use my DRO as the X and Y axis count guides but also use the formula in the Zeus booklet, which covers from 3holes through to 12 holes, though of course they all must be equally spaced.

I am just in the process of finishing a Stuart S50 and used this method very successfully for both ends of the cylinder.

Mike

Matt,

Looking at your photo reveals the possibility of two faults. (But be aware that the measurements may be distorted because the photo is tilted. As it could be an optical illusion, and you should check the real objects.)

Bearing in mind that the measurements are approximate, it looks as if:

• the gasket has the holes cut correctly at 72 degrees each, but the diameter was off centre.
• the cylinder head was correctly centred, but the angles are wrong for 5 evenly spaced holes. I'd guess that the angle between holes was somehow set at 67.5 degrees rather than 72 degrees, leaving 90 degrees between the first and last holes.

I often make mistakes doing this kind of work. Now I always rehearse on a bit of wood or cardboard before cutting metal, and check it carefully.

Dave

Just checked mine. I could also get odd numbers to be produced if I didnt press the enter button ( just continue to scroll down ) on every step.

So centre over part and press X - 0 enter, Y - 0 enter then scroll down to dia 1.125 enter etc

Setting start angle to 0 and finish at 360 produced the required shape. First move was 0.5624 on X

What was interesting was that when in PCD function and setting 0.0000 axis (first step) if you move the table, the display remains as 0.0000 and 0.0000

Brilliant response ...thanks very much.

Going to try JasonB's theory first with the DRO as that now makes sense...start zero and finish on 288.

cheers

Matt

ASF had similar odd results trying Martin's method

1st attempt 50mm PCD, 6 holes start/stop at zero and all went well with 5 equally spaced holes and ending back on the first hole

2nd attempt start at 20deg finish at 20deg as if the PCD is not on x or y axis, first hole went to right place but all the others stay at zero/zero as I scroll through the hold numbers?

Mat as I mentioned earlier stick a felt pen in your mill and just make a dot to check things until you have sorted things out. Neil's suggestion of a loose bracket giving wrong readings in one direction would also cause problems as the table moves more than the scale shows

So the second version should be start at 20 finish at 380 ?

You presumably have asked it to space 6 holes along an arc starting at 20 deg and ending at 20 deg which has zero length so all the holes will be on top of each other.

regards Martin

PS I always have to do a test run through when I do it too as I don't do many pitch circles.

Edited By Martin Kyte on 02/08/2017 13:58:12

I'll give that a try later numbers make sense, just spending too much time following the trackers from riders in a race across Europe - two leaders are close to the 3rd checkpoint with less than 10km between them after almost 2000km of racing picking different routes

Ok sorted....start 72 degrees end on 360 degrees and hole pattern correct.

Learning all the time ! except bust a cheap carbon tap off in the cylinder LOL

Many Thanks for the replies and advice.

Matt