There are a number of options. It all comes down to what tooling and equipment you have access to. For example if you have CAD and a printer you can print off a 1:1 drawing and use that as a template. A rotary table is good for spot drilling and then drilling cylinder caps or templates. Transfer punches are also useful for marking out for drilling from an existing part. Scoring a groove in marking out dye on a piece of metal in the lathe can be used for a PCD prior to marking out the hole positions, You will get more help if you make you question less general and more specific regarding what you are wanting to do.

I would suggest the cylinder caps have to be done before the cylinders if you are matching one to the other, you can't usually do it the other way round for example.

Martin C

Depends on what equipment and how cack-handed you are.

A rotary table makes the cylinders easy, and though my DRO doesn't do PCDs automagically, it reduces the chance of mistakes.

I use paper templates but make sure your printer is accurate and circles aren't ovals. Print a big circle and measure it. Another problem with templates is are likely to slip; I glue mine down but beware of the glue softening the paper and allowing it to stretch. Avoid wet glues!

When I did my first mini-lathe only engine – no DRO, rotary table, mill, or other fancy gear – I superglued the end caps precisely in position on the cylinder, blued the end with a felt tip, carefully marked out with a compass and centre-popped the holes. Then I wigglered the pops under my pillar drill and tap-drilled the caps through and into the cylinder. Drilling both parts in one go means mistakes don't matter because everything lines up. Despite double checking I made a small a mistake at one end, and the holes only line up in one of six positions – doesn't matter.

The superglue is released by boiling or heating gently with a blowlamp: a blowlamp is faster. An alternative is to mark out, drill and tap two holes and bolt together instead of gluing. I prefer glue. Old glue can be scraped off and cleaned with Nail Varnish remover.

I've never tried the traditional method. Secure each item on the mill, centre pop the first hole, calculate the PCD coordinates with paper and pencil (or cheat with a published table), zero the mill on the first hole, drill it, and then dial-up the other PCD coordinates one by one, and drill again. Do the same for each object, and they should fit together. Real men do this without marking out, but I'd be happier to mark the job up and eyeball it before drilling because I'm clumsy and mistakes like not allowing for backlash are punished severely!

Another job that's easy after doing it a few times.

Dave

If you are going to stick with manual marking out then best get the right tools, a pair of dividers is what's needed to mark out not callipers be they firm leg or digital.

I suggest you tackle the Front (top) cover first as that is less critical than the back (lower) one. And go about it like this

1. Blue the face that mates to the cylinder, this means any scribed lines won't be seen.

2. Put cover blued side out in the 3-jaw and using a ctr or spotting drill put a small dimple in the middle. Remove from lathe

3. Set dividers to 9/16" (half PCD) and use them to scribe a circle using the just drilled ctr hole to locate one leg, When setting don't do it from the end of the rule, locate one leg in the 1" engraved line of the rule and then set the other leg to the 1 9/16" position.

4. Take a dot punch and make a small dimple with that somewhere on the scribed 1 1/8" circle, inspect with magnifying glass and adjust if needed.

5. Set dividers to just under 17mm and then with one leg in the punch mark scribe two arcs one either side, now move divider to where the arcs cross the PCD circle and strike another two arcs. Then move again and strike an arc that should cross the PCD circle at the same point as the last arc, if not adjust dividers and repeat until you have 5 equally spaced arcs.

6. Dot Punch the remaining 4 hole positions, check with glass and then go round with centre punch to make a deeper mark.

7. Drill all 5 holes tapping size.

8 Locate cover on correct end of cylinder, lining up the holes so two are parallel to port face and clamp in position.

9. Hold clamped parts in mill or drill and drill one tapping size hole into cylinder using the cover to guide it's position.

10. Mark cover so you know which way to put it back on then unclamp from cylinder and enlarge the hole you just used as a guide to clearance size.

11. Tap hole in cylinder, preferably using some form of tapping guide or guide with the drill/mill.

12. Use one of the supplied screws to fix cover back onto cylinder and then repeat drilling, enlarging and tapping sequence for each of the remaining holes.