Hi Guys,

No doubt some of you will remember this thread from some time ago ! And my attempts to get reasonably accurate measurements of the blade speed.

Bandsaw blade speed.

Well here I am some months on and deciding to try and reduce the blade speed. I had thought that if I could increase the size of the gear on the hub of the bottom driven wheel I could reduce the speed to within the range needed for cutting mild steel plate. Well I am only partially successful !

I found that the biggest toothed pulley that I could fit was 90 mm diameter, restricted by a tapered steel reinforcing rib behind the bottom wheel. Ringed in red in the picture.

a28-01-2018-003.jpg

So having decided on the largest toothed pulley that I could fit, I next had to work out what size belt I needed in order to drive it.
I ended up calculating that I would need a 150XLO37 belt. 10 mm wide with a 5.08 mm tooth spacing. So I bought both items. The pulley was an aluminium one made by Dunlop, of all people ! I thought they only made tyres, apparently not. They make a very wide range of toothed aluminium pulleys and drive belts. Anyway these are the two items that I bought.

25-10-2018-001.JPG 25-10-2018-002.JPG 25-10-2018-003.jpg

As can be seen the pulley needs machining to suit the existing bottom wheel on the bandsaw. Machining the pulley created some interesting machining problems. My Myford lathe only has a four inch three jaw chuck ! I could have used the six inch four jaw independent one but it would have been a little more awkward since the new pulley had a 15 mm tooth width and an overall thickness of 1" inch
(25 mm). I would have needed jaw protection and various packings, which after playing about with, I wasn't happy. Too many bits !

Quite some time ago I had purchased a set of soft jaws for the Pratt Burnard four inch chuck and they had sat in the draw, unused.
Since I had them I decided to use them. But I didn't want to carve most of them away just to hold this pulley. I'd seen a video where a chap had drilled and tapped the jaws on his chuck to fit sacrificial blocks to hold the workpiece. So I thought, why not do the same.

27-10-2018-001.JPG
These are the soft jaws ! You can see where I've marked the centre of the jaws so that I know how much stick out I have got to account for.

27-10-2018-002.JPG 27-10-2018-004.JPG 27-10-2018-005.JPG 27-10-2018-006.JPG
I marked out the position for the 5 mm hole, 18 mm deep in one jaw using a vice stop, then drilled all three, and tapped them M6. Those screws are 15 mm long.

27-10-2018-007.JPG
I used a piece of 1" inch diameter aluminium bar, drilled 6 mm, and parted off three 15 mm thick pieces. The piece of yellow strapping tape was used because the bar was not truly round.

27-10-2018-012.JPG
This is a family picture of the components of my modification to the new soft jaws. From left to right.
The new jaw, the alloy piece, below that, the M6 Allen cap screw and washer. Then another alloy piece.

27-10-2018-014.JPG 27-10-2018-013.jpg
This is the finished set ready for use, with the alloy pieces fastened to the jaws with the M6 cap screws. I could have used countersunk head screws but too lazy to look for them.

Part two coming up !
Attached Images




Read the full thread at metalworkforums.com...