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| bogstandard:
Darren, We all have our own little ideas of getting things done in the shop, so you do it how you want to. There are no hard and fast rules, so if it suits you, DO IT. It is always a good idea to have interchangeability, I have done it between my lathe and RT on the mill. It works for me. John |
| Stilldrillin:
Good thinking, and blummin well done Darren! :thumbup: :clap: :clap: :clap: |
| raynerd:
Hey Darren, I`ve viewed this topic many times over the last few weeks as I have been concentrating on my workshop and machines and getting everything running as I want it before I go any further with engine builds etc. I have decided to make a QCTP like this and just have a couple of questions. I`m going to be using a round bar of steel rather than a block like you did, only because that is the scrap I found and was given free from the scrap heap! 1. Can I ask about your off centre bore in the main body of the tool post, was this simply to give more clearence when the two sides where taken down to size? I guess if it had been central, once the centre spigot and cam were fitted it would have got near to the edge of the dovetails/sides right? 2. Also, most QCTP have two sides each dovetailed to accept a holder when needed for turning or facing, so a side on the left and a side on the front. I noticed that you have cut flats on two sides but only dovetailed one. Is there any reason you didn`t put a dovetail on the second side so as to gain to working faces? 3. The dovetails themselfs are 60deg or did you use 55deg because of your cutting tool - either way, I mentioned a 60deg dovetail in my latest thread here: http://madmodder.net/index.php?topic=1731.msg17115#new and Jonny gave a reason why it may be more suitable to use 45deg dovetails. I`ll be honest that I`m still not 100% sure why I would have to be more accurate cutting 60deg dovetails than 45deg dovetails but if this is the case, do you think the 45deg would be more suitable? Anyway, hope you can help. I wasn`t a member on here when you posted this thread so just wanted to say nice job and hope mine turns out as well. I`d be chuffed if it did! |
| Darren:
--- Quote from: craynerd on September 06, 2009, 08:23:48 PM ---Hey Darren, I`ve viewed this topic many times over the last few weeks --- End quote --- Really....., well you don't seem to have understood it very well cos most of what you wrote is wrong......... :whip: Most of the answers to your q's are in the posts, have another read, slowly this time, and come back with anything you are still unsure of and I'll only be too happy to help.. :thumbup: |
| NickG:
Chris, I think the following is right but somebody please correct me if I'm wrong! On the accuracy thing, I think Jonny is right in that you would need to be more accurate machining the 60 deg dovetails. Pythag tells you that with a 60 deg dovetail, say if you make the dovetail 1mm too wide (exaggerated for purposes of explaination) that will allow the holder to move 1 x tan60 outwards, i.e. 1.73mm. With a 45 deg dovetail, 1mm deviation would allow the thing to move out 1mm, since tan45 = 1. Also, Jonny mentioned repeatability. When you clamp the holder up with the 60 deg dovetail the variation on how far it pushes outwards is likely to be greater as a smaller component of the force is acting directly inwards. As he said, difficult to explain, will try to knock up a CAD sketch for you tonight if you are still struggling. Although it never occurred to me before, 45 deg would be better. Nick |
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