Pete F
25th Jul 2016, 03:13 PM
I have a parting tool holder to suit insert tool holders, like this one. https://www.machineryhouse.com.au/L028
The issue with the above tool holder is that the holder for the parting tool blade then sits in an AXA tool holder, which goes in the QCTP ie it's a holder within a holder. The end result is it hangs out a long way from the toolpost and I noticed this was causing torque on the whole top slide when parting difficult materials.
I thought I could do better, so designed and made a tool holder that slides straight in to the QCTP and results in the parting thrust going straight down to the supporting way. I'll include a number of photos in case anyone wants to copy it. Everything is as compact as I dared to make it, with some overlap in features, and things like counterbores as thin as I dared to go. Function over form, and features are often asymmetric.
This the disassembled components. The dovetail is quite fussy to get exactly right. I cut one and it was fine, but it was toward the end of the travel of my QCTP handle. I preferred it to be toward the start of it so re-cut it. I could have left it, but was worried it may wear further as I use this holder a lot and it's not hardened. No biggie, I cut another, and the dovetail cutter I made the other week went through this steel like a hot knife through butter.
363496
This is the assembled unit. I didn't have many short 5 mm cap screws, and most of mine are longer. There's a very slight variation in head height as they're from different sources and I can see in the counterbores. I'll get some more (slightly longer) at some stage, but these are just fine for now.
363497
This is a close-up of the top part of the holder. The design is based on the original, but is a lot more compact. Also (hopefully) slightly less, well, crap than the original. The double bevels pull the blade in and down as the cap screws are tightened. That was also a bit fussy to get just right. All bevels are 45 degrees and I used a commercial cutter for them.
363498
Mounted in the QCTP
363499
The end result. This was parted at high speed (around 1500-2000 rpm) but that's faster than I'd normally use. I use cutting oil to lubricate the sides of the tool and it produces just too much smoke with a big cut like this and oil. I wanted to give it a hard time and see if I could crash it. I can't recall the type of steel, I know it's neither 1020 nor free turning, as both of them produce an excellent, almost mirror like, finish. It was a short I had in the scrap box and I just took the parted off piece and placed it on top.
363500
About the only other thing I can think of for anyone else making this, is the grub screw in these holders is M10 x 1. It makes sense to use a metric fine thread but I didn't notice and set up for a standard M10 (1.5 mm pitch). By shear coincidence I accidentally picked up a wrong tap and started tapping it as M10 x 1. I have marked that tap box now, as it's in the same series of manufacturer as all my standard taps, whereas my M10 is from another company. I thought something was wrong as the tap felt blunt. In fact the tapping drill size for that tap is 9.0 and not the 8.5 mm I used. As it turned out I can't seem to find any M10 x 1 grub screws that are long enough for this application, so I went back to standard M10. Lucky for me I realised early enough and there was no real harm done. Once the height is set and locked down it doesn't make any difference anyway. I used a straight knurl for the adjuster, as it should be for something that is turned only. A bit of turning etiquette there :wink:
All in all I'm very happy with the results and it's noticeably more rigid than the previous arrangement.
Edit: Unrelated, but I just noticed when reviewing the photos to see if they uploaded ok, that in the fourth photo you can see the thrust bearing I put under my QCTP nut. I thought it may help to reduce the friction when tightening the toolpost, and does indeed seem to make a marginal difference. I don't change my toolpost angle more often than I absolutely need to, but may eventually put a handle on this nut. We'll see. I thought the experiment was worth the price of admission for a cheap Chinese thrust bearing.
The issue with the above tool holder is that the holder for the parting tool blade then sits in an AXA tool holder, which goes in the QCTP ie it's a holder within a holder. The end result is it hangs out a long way from the toolpost and I noticed this was causing torque on the whole top slide when parting difficult materials.
I thought I could do better, so designed and made a tool holder that slides straight in to the QCTP and results in the parting thrust going straight down to the supporting way. I'll include a number of photos in case anyone wants to copy it. Everything is as compact as I dared to make it, with some overlap in features, and things like counterbores as thin as I dared to go. Function over form, and features are often asymmetric.
This the disassembled components. The dovetail is quite fussy to get exactly right. I cut one and it was fine, but it was toward the end of the travel of my QCTP handle. I preferred it to be toward the start of it so re-cut it. I could have left it, but was worried it may wear further as I use this holder a lot and it's not hardened. No biggie, I cut another, and the dovetail cutter I made the other week went through this steel like a hot knife through butter.
363496
This is the assembled unit. I didn't have many short 5 mm cap screws, and most of mine are longer. There's a very slight variation in head height as they're from different sources and I can see in the counterbores. I'll get some more (slightly longer) at some stage, but these are just fine for now.
363497
This is a close-up of the top part of the holder. The design is based on the original, but is a lot more compact. Also (hopefully) slightly less, well, crap than the original. The double bevels pull the blade in and down as the cap screws are tightened. That was also a bit fussy to get just right. All bevels are 45 degrees and I used a commercial cutter for them.
363498
Mounted in the QCTP
363499
The end result. This was parted at high speed (around 1500-2000 rpm) but that's faster than I'd normally use. I use cutting oil to lubricate the sides of the tool and it produces just too much smoke with a big cut like this and oil. I wanted to give it a hard time and see if I could crash it. I can't recall the type of steel, I know it's neither 1020 nor free turning, as both of them produce an excellent, almost mirror like, finish. It was a short I had in the scrap box and I just took the parted off piece and placed it on top.
363500
About the only other thing I can think of for anyone else making this, is the grub screw in these holders is M10 x 1. It makes sense to use a metric fine thread but I didn't notice and set up for a standard M10 (1.5 mm pitch). By shear coincidence I accidentally picked up a wrong tap and started tapping it as M10 x 1. I have marked that tap box now, as it's in the same series of manufacturer as all my standard taps, whereas my M10 is from another company. I thought something was wrong as the tap felt blunt. In fact the tapping drill size for that tap is 9.0 and not the 8.5 mm I used. As it turned out I can't seem to find any M10 x 1 grub screws that are long enough for this application, so I went back to standard M10. Lucky for me I realised early enough and there was no real harm done. Once the height is set and locked down it doesn't make any difference anyway. I used a straight knurl for the adjuster, as it should be for something that is turned only. A bit of turning etiquette there :wink:
All in all I'm very happy with the results and it's noticeably more rigid than the previous arrangement.
Edit: Unrelated, but I just noticed when reviewing the photos to see if they uploaded ok, that in the fourth photo you can see the thrust bearing I put under my QCTP nut. I thought it may help to reduce the friction when tightening the toolpost, and does indeed seem to make a marginal difference. I don't change my toolpost angle more often than I absolutely need to, but may eventually put a handle on this nut. We'll see. I thought the experiment was worth the price of admission for a cheap Chinese thrust bearing.