D G Williams
Active Member
Thank you for that, Jim. I used a carbide insert tool but I will try HSS - I got a nice little set from Arc Euro Trade recently - and I'll be lavish with the cutting oil.
David.
David.
Bogie Springing
- Thread starter Susie
- Start date
Susie
Western Thunderer
Hi David,
I was going to try to get a photo of the tool I use, but haven't got round to it. Essentially it is a standard right hand knife tool, in HSS. The form tools themselves are high carbon steel (silver steel). With the depth of cut that most modellers use there is no need for any back rake on the tool (going from the tip of the tool along the length of the blank) just top rake, and side and front clearance.
The popularity with carbide inserts seems to be entirely due to people not knowing how to sharpen HSS, and the ease of replacing the tip when it is broken. Of the three types of cutter, carbon steel (silver steel or gauge plate) can be made the sharpest, then HSS with carbide coming a very poor third. Carbide has the advantage when turning cast iron, but it cannot stand intermittent cuts without breaking, as it is so brittle.
The cutting fluid I use is Rocol RTD liquid, which comes in a squeezy bottle and lasts ages. It can be got from RS components, stock number 239-4852. This can also be used when tapping holes or using a die.
When turning silver steel, one needs to keep the speed down, about 230 rpm for 1 inch bar using HSS, and about half that when using one cutter to make another. Also a low speed is needed when using the form tool, even on brass, as the length of cut is considerable. With a standard lathe tool, the length of cut might be 20 to 50 thou: the form tool's is 375!
As a bit of a plug, if anyone is near Royston, Herts., there is a model engineers 'class' one Saturday a month in one of the schools' workshops. There are facilities for turning (Colchester and Boxford lathes), horizontal and vertical milling, shaping, surface grinding, and also welding and brazing. PM me if interested.
Susie
I was going to try to get a photo of the tool I use, but haven't got round to it. Essentially it is a standard right hand knife tool, in HSS. The form tools themselves are high carbon steel (silver steel). With the depth of cut that most modellers use there is no need for any back rake on the tool (going from the tip of the tool along the length of the blank) just top rake, and side and front clearance.
The popularity with carbide inserts seems to be entirely due to people not knowing how to sharpen HSS, and the ease of replacing the tip when it is broken. Of the three types of cutter, carbon steel (silver steel or gauge plate) can be made the sharpest, then HSS with carbide coming a very poor third. Carbide has the advantage when turning cast iron, but it cannot stand intermittent cuts without breaking, as it is so brittle.
The cutting fluid I use is Rocol RTD liquid, which comes in a squeezy bottle and lasts ages. It can be got from RS components, stock number 239-4852. This can also be used when tapping holes or using a die.
When turning silver steel, one needs to keep the speed down, about 230 rpm for 1 inch bar using HSS, and about half that when using one cutter to make another. Also a low speed is needed when using the form tool, even on brass, as the length of cut is considerable. With a standard lathe tool, the length of cut might be 20 to 50 thou: the form tool's is 375!
As a bit of a plug, if anyone is near Royston, Herts., there is a model engineers 'class' one Saturday a month in one of the schools' workshops. There are facilities for turning (Colchester and Boxford lathes), horizontal and vertical milling, shaping, surface grinding, and also welding and brazing. PM me if interested.
Susie
D G Williams
Active Member
Thank you Susie -
That is very helpful, lots of useful information - much appreciated. Keeping the speed down to get a fine finish is the opposite of what is usual! Looks like I'm going to have to remember how use the back-gear ...
David.
JimG
Western Thunderer
D G Williams
Active Member
Thanks - I hadn't thought of that!
David
David
D G Williams
Active Member
That sounds nasty! Hope you get it sorted.
David