Here is a list of all the postings Andrew Williams 1 has made in our forums. Click on a thread name to jump to the thread.
|Thread: Boring problem|
Again thank you all for helpful comments. I have just done the thing that I should have done earlier and fixed a 200 mm long piece of 50 x 10 bar in a tool holder and mounted it parallel to the lathe bed with a clock in contact reading to 0.01mm. At 150 mm from the centre of the tool holder pushing on the bar as hard as I can with a thumb gives a maximum deflection of 0.025mm whereas at 40mm I can only manage 0.01mm deflection when pushing the bar with a spanner. A small movement of the carriage either way with the rack hand wheel does not give a defection Exceeding 0.002mm (the slightest deflection on the dial). So the conclusion? The lathe is in pretty good nick, try a boring tool upside down and cut on the rear of the hole, use a solid a tool as possible and, whenever possible use an hss tool newly sharpened rather than an insert tool. This latter point will no doubt raise eyebrows among some but my recent work using a tangential tool holder with an hss tool (plus the completion after a long gestation period of a decent tool grinder) has convinced me to ditch the chips for much work.
Thank you for the responses. As I guessed it is just a matter of a bit of play here, a bit of flexibility there and learning to live with it. The problem is that I have always had in mind a conversation with one of the elite of the model engineering world at, I think, the last open day held by Myford in Nottingham. He was firmly of the opinion that, with proper adjustment of the lathe then the problem would not arise.
This may well be a common effect on a light lathe (ML7 with little wear) but on boring a hole the tool always takes an extra cut when withdrawing it from a hole. The size of the cut is somewhat unpredictable so making boring a rather hit and miss affair. Am I missing a trick or is it a matter of tightening up gib strips etc?
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