Thread: Slitting Saw Operation

Use a 6mm end mill to full depth and move left to right to width.
You could also use a 6.4 to full width and depth and then run a 6.5 to finish.
Would be a last resort to use the slitting saw,not the best way or preffered way to do it.

If you dont have the appropriate cutters you are welcome to borrow them off me,or you can use my mill and do it yourself if you are unable to use the mill you have,we are both in the west and not that far apart.

Pipeclay,
As usual, your replies are prompt and pertinent.

I considered the 6 mm endmill approach, but it just 'looked' too small.
The flutes only cover about 10 mm depth, (desired is 10.17).
This meant there would be some rubbing of the endmill shank, excessive when machining across the shoulder on the bush (would require 18 mm depth).
Perhaps I need to look for a long-length endmill.

I completed the job this morning.
I moved the cutter the full amount, 1.75 mm, then did cuts of 1 mm to depth.
Repeat for other side.
The 1.75 mm is more than half the 3 mm saw width and I think this gives more even wear on the saw teeth.
Result looks functional, and seems to fit the broach correctly.
A first broaching operation will be attempted later today.

For any future broaching bushes, I will look closely at the endmill approach.

Thanks for the offer on the tooling, but I am OK for now.
Happy machining,
John.

How big a flange did you put on the bush,a 25 mm OD flange would of done.
Did you end up with steps at the base of the bush or did you file them.

Hi John,
I have never heard of an endmill cutter of 6mm dia and having the flutes only 10mm long (deep). Do you have special endmill cutters for your vertical mill? Have I understood what you wrote?
If you have to do this job again I recomend the use of a Slotting Drill (it is not a drill) which is used in the milling machine. A slotting drill is a two fluted endmill that is true to width/diameter.
If you want to cut a slot and use a four fluted endmill cutter, using it to cut an accurate slot without moving the cutter sideways, you are doomed to failure.
Only a two fluted cutter will cut to size to form a slot. The slotting cutter is used by taking multiple cuts until you are down to required depth. A cutter of 6.5mm should be readily available. I have cut 0.125" slots to a depth of 5/8" (16mm) x 7/8" (22mm) long using my lathe. These slots were perfectly accurate to size with no marks on the side of the slots. The parts were for the valve gear on my 5" gauge steam loco. The steel bar for the parts was held in the toolpost. The cutter was made of TC and had straight flutes with a 1/32" radius on the end corners. The speed used was 2150rpm.

If you try and use a four flute cutter, the cutter will spring sideways and the finished job is ruined. The slot will be at least 0.010" wider and the sides will be ragged and rough.
Wishing you all the very best on your loco, they are great fun

Kody

If you are getting ragged and rough and oversize results with an End Mill there might possably be something wrong in your technique.

Pipeclay,
The flange on the bush is 27 mm diameter - just leftover from a previous job.

I do not understand your question on steps at the base of the bush.
My bush has only one shoulder, for the top flange.
I do not have steps, machined or filed.

For the slot, the slitting saw produced a nice sharp square bottom.
There were 3 cuts to depth, 3 mm wide in middle, then 1.75 mm wide each side.

Kody,
My only 6 mm endmill was part of a set purchased from EMCO in Sydney.
- no markings ( Indian ?),
- parallel shank 6 mm diameter,
- 55 mm long,
- 13 mm cutting depth flute (previous comment made without actually looking, sorry),
- 4 teeth.

I have a couple of mill bits I purchased for wood-working.
Two straight TC flutes.
Is this the type you suggested ?
If not, where can I get some ?

We hope to have our electric loco operational at the Blue Mountain Railway Society track, Blaxland, in March.

Update,
Successfully cut a keyway into a sandwich pulley of steel/aluminium.
Initial depth inadequate, so had to re-do with two extra shims (PVC !).
Initial fit to key stock (branded USA) was too narrow - had to file width.

Learnt a lot about how to use (misuse) an arbor press.
Must improve technique to ensure broach is always vertical, could have been a disaster !

Happy machining,
John.

The steps I am reffering to would of been at the bottom of the slot cut with the slitting saw,Ive never seen it done without there being a slight step at the bottom of the slot.
Next time if possable when you make shims try and use steel the Pvc will squash under load.
Did you purchase a single pass broach.
You can purchase Slot Drills from any Engineering supply outlet.
If you make more bushes in the future to suit your broaches work on a SMALLER head size will make it a lot easier on your tooling.

John how long did you make the Bush.

Pipeclay,
The broach came with a 1 mm shim.
It is Chinese HSS Grade B1 with 15 teeth.
First broached without shim, then with shim.
Tried fit with keystock, keyway was slightly narrow and not deep enough.

Redid with 2 PVC shims, each 0.25 mm to get depth.
Filed width (carefully) to fit.
Note that depth in the axle could have been too shallow.
I need to check keyway standards.

The bush is 42 mm long.

I think PVC for shim is OK as the compression strength is reasonably high and there is a substantial area guiding the broach.
Note that this is a one-use shim.

Happy machining,
John.

"If you want to cut a slot and use a four fluted endmill cutter, using it to cut an accurate slot without moving the cutter sideways, you are doomed to failure."

I found this out the hard way Kody. I tried to cut a 10mm slot in some RHS with a 4 flute endmill. The resulting 'slot' looked like a meandering river.

In the end, I used a smaller mill to work on each side of the slot, creeping up on 10mm. The slot was off center by the end though, but didnt matter for my job. It did get me thinking about how to slot to centre in one crack though - is this what you use 2 flute end mills for?

Brendan

Did you attempt to cut a captivated slot in RHS or were you coming in from the end.

Was the end mill you were using a centre cutting end mill?
If not, that definately is at least 1 of your problems,slot drills are designed for numerous functions but 1 of there main ones is to cut captivated slots.

Drilled two 10mm holes then tried to join them with an end mill. Was 3mm RHS.

I cant recall whether it was centre cutting or not. I have little milling experience. I do know however that it was a p!ss poor slot that resulted. If 2 flute mills are good for slotting then thats great to know for future reference.

It would appear to me without seeing the Item that there might of been something amiss in the set up,either the work holding method,the ridgidity of the mill or possably the Cutter.
Was the End Mill a Fine Spiral or a Corse Spiral.