What kind of tip facet should I expect?
Colin Whittaker | 19/06/2017 11:17:13 |
155 forum posts 18 photos | It's only cost me a few dollars so it's no big deal ... I decided to buy some spot drills for use in making accurately located holes in brass for a clock. The set of Chinese bits that arrived from AliExpress do not come to a conical point as I would expect. From one side the bit does come to a point but when rotated 90 degrees there is now a large flat profile that doesn't look as though it will deliver the wanted hole precision. Who's confused about what a spotting drill should do/look like? Me and/or the Chinese supplier? Thanks, Colin |
JasonB | 19/06/2017 11:20:24 |
![]() 25215 forum posts 3105 photos 1 articles | All mine have a straight bit between the two ends much like you get on a twist drill, depending on make the size of this does vary. |
JasonB | 19/06/2017 11:40:14 |
![]() 25215 forum posts 3105 photos 1 articles | On the left is an unbranded Chinese one (actually it may be Interstate) on the right a branded keo one that I got from MSC and that is the make I buy now as they cut better. Keo one probably cost more than a whole set from Aliexpress but if you want precision you need to buy decent things. |
John Flack | 19/06/2017 13:29:59 |
171 forum posts | I have in the past purchased c/drills from Drill Services these range from O to 4/O the smallest having a tip of 0.010". I paid about a fiver then,but being double ended halves the cost. No ides how this compares with info above John |
Colin Whittaker | 19/06/2017 14:08:01 |
155 forum posts 18 photos | Sounds like I do have the real thing. Thanks for the intelligent answers to my stupid question. I guess I'd better give my supplier some positive feedback. Cheers, Colin |
ChrisB | 19/06/2017 14:59:05 |
671 forum posts 212 photos | The Dormer stub drills I have all end up with a pointed tip with almost no web. Compared to a stub drill a normal twist drill has a much larger web. |
Mike | 19/06/2017 15:02:34 |
![]() 713 forum posts 6 photos | I've always used centre drills rather than spot drills. When both ends are no longer capable of being sharpened, you are left with a useful cylindrical bit of HSS which can be ground into other tools. Yes, I am stingy! My chart lists 12 drills, from sizes 00 to 10 (0.125 to 1 inch, although sizes 0 to 4 will perform most tasks in my workshop. |
I.M. OUTAHERE | 19/06/2017 18:47:19 |
1468 forum posts 3 photos | I have a nice carbide spotting drill , split point geometry , well that was until i dropped it on the concrete floor chipping the point 😭 . While i'm here and as i will eventually get around to fixing that spotting drill i am interested in everyones thoughts as to the type of grind i put on it with my T&C . Split point ? Four facet ? Ian. |
Neil Wyatt | 20/06/2017 19:35:37 |
![]() 19226 forum posts 749 photos 86 articles | Expect an article on web thinning in the next MEW. As far as I can see Jason's better drill has the web thinned, perhaps the other drill could be ground to match. Spotting drills are a use for broken jobber's drills, as long as they haven't bent. Neil |
JasonB | 20/06/2017 19:52:11 |
![]() 25215 forum posts 3105 photos 1 articles | Keo site says their spot drills have a constant thickness thin web that does not require web thinning if sharpend Edited By JasonB on 20/06/2017 19:55:55 |
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