Did a bit more on my little Stuart 10V today. One of the next bits i want to do is drill the cylinder, cylinder base and cylinder head. Effectively 5 holed flange, on a 28odd pcd... Ideally, i'd have a little rotary table, or a mill with DRO, but lacking either of them. I have the Myford and drill press, and have a diving head in its box(never been use, and dont know how) Any bright ideas on how I could drill accurately? I could use the base and cap to spot through to drill the cylinder. The usual 2mm clearance on bolt holes wont quite cut the mustard on this job Could I somehow use the dividing head bolted on the drill bed? (table tilts/rotates etc) I did look at some of the budget rotary tables, but not convinced myself to buy one just for this.
Direct index it off the spindle gear on the lathe. ML7/ML10 has 25 teeth and super7 has 30, both divisible by 5. Mark the pcd then use a tool to cross off the 5 points for centre-punching.
Super7, so that works... so put a scribe in the tool post, mark out the pcd, then just scribe across using the cross slide, with the spindle indexed on the gear...?
Print it out to scale with crosses instead of holes, stick it on and prick punch through. Have you a milling/vertical slide? Put it on that and pick up the centre. Coordinate drill using the dials. You can construct a pentagon using just a straight edge and compasses if printing is not an option. For stuff like this, if you did not have the right gear, you can print out or buy the biggest protractor you can find and fix it in the end of the spindle with a pointer. If it is an strange number of divisions, print out a circle divided into that number.
If the part will run true in the chuck just black up the face and scribe a circle then index 6 teeth 5 times and nick across the scribed circle with a tool.
Went with this method in the end...worked a treat. Perhaps a little unorthodox, who knows. But it worked.
that's probably the most accurate way to do it on a lathe.......turn the diving head round 90 degrees and you'll be cutting gears next
