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| Deep hole drilling 101 on lathe? |
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| PekkaNF:
--- Quote from: Jonny on July 04, 2014, 11:10:57 AM ---How deep are these holes and diameter. Various ways to do it with normal twist drills accurately. --- End quote --- Hi. I'm having no problem until 5xD. There is 7xD carbide trough cooled drills, but now I need some holes min 10xD. With trough cooled drill. NO PECK DRILLING. Have to go in one go. Material is 1.7225. 42CrMo4. 4142 on a good day, but I have mostly 36NICrMo16, 1.6773, 1050. Now I admit that it does not sound much, but give war a change! With industrial machines, industrial drills and industrial prices. My next drill to break is bit over 40€ a piece on sale. I would be really happy to hear how others have done this. shaddr3 here is making probably slightly longer and smoother hole on slightly easier mater (least I hope). Pekka |
| vintageandclassicrepairs:
Hi All, Regarding a high pressure pump what about using the motor and pump from a domestic oil burner, They have a built in bypass pressure control valve ???? Just a thought John |
| shaddr3:
My maximum depth hole is 35.5xD BLIND, and my minimum depth hole is 16xD BLIND in 6061 Aluminum hex bar. Going to be difficult to center the hex but I plan on using 6 point socket with three set screws to hold the material in a steady center with roller finger bearings. Measured my material and play in socket, found .005 so .0025 on each edge, may shim three sides. Machine a small groove in the socket for the finger bearings. Smoothness isn't so much as important as straightness but I don't have strict tolerances. My hole is a water passage, with 2xD holes drilled perpendicular joining the passage. My blind deep hole just needs a 7/16" NPT thread on bore entry. |
| Jonny:
Pekka ive only done it a few times for production items. From memory 170mm long x finished 12mm dia hole, no runout permissible using a Colchester 50" Triumpth, about 30 off. Last time a one off on Harrison 140 12 years ago, two holes parallel 1/2" through and a 5/8" through with M28.5x 1.25 screwcut lower down. All need to be parallel. Extend a finishing reamer and a slightly smaller drill by brazing or silver soldering. Normal hss decent twist drill. May have used a centre drill but cant guarantee, just drill in with coolant around 8.5+mm dia as far as you can get think about 5mm max depth before pulling out to clear swarf. Any further heat gets in to the part gradually getting worse and worse coolant or not. So dril a little, remove and repeat. At this point with flimsy machine or out of square you may need to bore out to next drill used so it centres. No boring out on both machines here just went on to larger extended drill and ploughed all the way through, often drawing drill out to clear swarf and that's the key. Dropped speed to around 60rpm plenty of coolant and reamed out to final size, no boring nothing. 170mm long took about 22 mins job done, hard part is the initial smaller hole. 1/2" and 5/8" silver steel poking through showed runout of 0.03mm, I was half expecting 3mm. Material shouldn't be a problem. |
| PekkaNF:
--- Quote from: Jonny on July 07, 2014, 12:12:41 PM ---..... Extend a finishing reamer and a slightly smaller drill by brazing or silver soldering. Normal hss decent twist drill. May have used a centre drill but cant guarantee, just drill in with coolant around 8.5+mm dia as far as you can get think about 5mm max depth before pulling out to clear swarf. Any further heat gets in to the part gradually getting worse and worse coolant or not. So dril a little, remove and repeat. ..... Material shouldn't be a problem. --- End quote --- This material is problem. Wonderful for shafts, turns easy with carbide inserts (real ones, indian/chinese will break), compared to this one 42 CrMo4 (Moc 410) is soft and really nice. I may need to resort that. This is hardened and tempered, approx.1000 N/mm2 of tensile strength. I measured some I had (took them work, they have a hardness tester): 25 mm 365 HB -> n. 1220 N/mm2 20 mm 342 HB 16 mm 206 HB -> n. 700 N/mm2 This will not drill with HSS and even HSSCO5 is very marginal. See: http://www.acerosboehler.com.ar/english/files/downloads/V155DE.pdf Because this is work hardening and hard peck drilling will not work. You have to make hole on one go. Sawrf is long, most of the time it is one long continous swarf until you speed up over 100 m/min (carbide insert). I have dried. Dormer HSS A002 10mm dia will last one or few holes max. 66 mm deep. D8mm Dormer HSCO (A777) 425 rpm is a bit better, but both will break if stopped even once (peck drilling). I may need to resort lower strength material. But it has it's own set of problems. I know there is are different steels on same spesification and I know there is just right steel which will do and machine well, but I can't buy few 6 m bars of as a private customer, should buy few tons of it and have a company. Not much progress on this front yet, but I have a lead of small amount of nearly ideal steel bars AND I might get ex industrial small drilling unit with pneumatic 700N feed on reasonable price. ER 20 collet though....no trough coolant on that one. Pekka |
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