Carl Wilson
Member
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- 1,957
- Location
- Moray
My Harrison M250 lathe has not been used in anger in about 18 months, due to my recently completed VFD and DRO fits.
The lathe will be central to the efforts surrounding my Harrison Mill refurbishment. Hence I decided to check the set up of the machine and specifically to ensure that it was turning parallel.
I chucked a piece of 25mm diameter steel with a 100mm protrusion. A light cut of about 0.05mm was taken. This showed all was not well. Measurement indicated a taper of 0.056mm, smaller at the headstock end.
I started to adjust the machine level to effect a correction. I couldn't seem to nail the problem down. Subsequent test cuts showed an error that kept altering. I suspected that the saddle might be part of the problem. I indicated it to see if there was any lift or play.
Though the saddle "felt" alright, I found that there was 4 thou or 0.1mm lift at both head and tailstock ends of the apron side. I adjusted this out carefully. The manual gives the procedure. The central M8 SHCS is slackened and then the outer portion is rotated anti clockwise. Small increments are all that are required. The manual gives a figure of 30 degrees rotation to take up 0.1mm.
Having made the appropriate adjustments, the saddle felt positive - free to move with a just perceptible drag and no tight spots. The DTI showed that the lift was now near non-existent.
Further test cuts were much more successful. Adjusting the level now made sensible and appropriate changes to the taper. The discrepancy is down to 0.002mm over about 100mm length. I'm going to stop at that.
Here is a picture of the test piece.
The lathe will be central to the efforts surrounding my Harrison Mill refurbishment. Hence I decided to check the set up of the machine and specifically to ensure that it was turning parallel.
I chucked a piece of 25mm diameter steel with a 100mm protrusion. A light cut of about 0.05mm was taken. This showed all was not well. Measurement indicated a taper of 0.056mm, smaller at the headstock end.
I started to adjust the machine level to effect a correction. I couldn't seem to nail the problem down. Subsequent test cuts showed an error that kept altering. I suspected that the saddle might be part of the problem. I indicated it to see if there was any lift or play.
Though the saddle "felt" alright, I found that there was 4 thou or 0.1mm lift at both head and tailstock ends of the apron side. I adjusted this out carefully. The manual gives the procedure. The central M8 SHCS is slackened and then the outer portion is rotated anti clockwise. Small increments are all that are required. The manual gives a figure of 30 degrees rotation to take up 0.1mm.
Having made the appropriate adjustments, the saddle felt positive - free to move with a just perceptible drag and no tight spots. The DTI showed that the lift was now near non-existent.
Further test cuts were much more successful. Adjusting the level now made sensible and appropriate changes to the taper. The discrepancy is down to 0.002mm over about 100mm length. I'm going to stop at that.
Here is a picture of the test piece.